texts: Is 'stacking' engines a viable way to maximize efficiency?

texts:
Suppose we have $n$ carnot engines connected together labelled as $C_1,C_2...C_n$, now suppose we feed an energy of $E_1$ into $C_1$, now by the second law of thermodynamics, it must be that efficiency can't be $1$ , so some heat is dumped to environment, let's say we 'direct' the heat dump $E_2$ into $C_2$, and we keep doing this procedure till we reach the $n-1th$ engine. Now, the heat dump of this engine into n+1th engine must be very small in magnitude ( say we have enough engines such that this happens), then this if we look at the at the total efficiency of the process:
$$ e= \frac{Q_{in-sys} - Q_{out-sys}  }{Q_{in-sys} }$$
The question I have is how to achieve the step where we direct the heat loss from the $ith$ engine to the $i+1th$ engine. If there was a way to do that I Think this would be a viable method for maximizing heat engnine output.


texts:
I haven't found a text that explains the PID controller in simple words. I know the theory: that it calculates the derivative and the proportional gain and the integral etc, but I need to know in reality what is the output of each function and each combination of functions.

For example, starting with the proportional: it sends an input that is proportional to the error recorded. So if the error is 5 V, does it do $\frac{1}{2}\cdot5\text{ V}$ to diminish it? or $\frac{1}{5}\cdot5\text{ V}$? or $-\frac{1}{5}\cdot5\text{ V}$ or what? I don't understand.

As for the derivative, it monitors the derivative across a specific time? And then does what? Also, what if there is a noise/disturbance at the begining, so the PID controller will not have normal use rates of change to compare? Same with integral. Can you point me to a good resource or explain me please?


texts: Show thread feature as thread symbol in Solidworks drawing

texts:
I have a SolidWorks part with a thread feature as shown below.

Is it possible to show the same as thread symbol in corresponding Solidworks drawing


texts: Force in a member of the loaded overhead sign truss

texts:
I was solving problems from the Meriam and Kraige Engineering Mechanics Statics vol-1 and I couldn't get the correct way through this problem.

The question is to find out the force in member $DK$ of the loaded overhead sign truss.

My attempt

I tried eliminating member NM,FG,GT,HI.i tried using the method of section but any section passing through DK is of more than 3 members.

Please suggest how to approach this problem.Thanks.


texts: How do I 'fuse' together two different kinds of data to get a final result?

texts:
I am building a robot (2 powered wheels and one ball bearing). The problem is that I can't seem to make it drive straight. I literally find it impossible, I have been trying for weeks.

Currently I am able to rely on rotations (of both motors) or the gyro readings(I also have two gyros, each near the two tyres)

Is there a way I can fuse those together, giving me a more accurate way to determine which motor I need to speed up?

My motors accept a value from 0-900 (although the speed should be determined by me and not fixed). Also if an algorithm exists, I'd like some directions of what I'd need to swap if I make the motors go backwards.


texts:
I'm an engineering coop at a vibrations consultant. I was given a graph plotting a series of applied frequencies against a floor's acceleration response to them. I was asked to find the natural frequency and damping ratio, but I haven't been able to find the damping ratio. I've taken a course in vibrations, but we were always given more about the scenario (mass of the object, spring constant, etc.). I've asked him to at least give me a starting point, but he's refused.

My boss also asked me to find the theory behind how the damping ratio is determined empirically. All the resources I've found online either reiterate what I already learned in my courses, or are so advanced that I can't even begin to understand them.

My questions are: how is the damping ratio determined empirically, and what is the general way to solve this problem?

For context, my vibrations course focused on 1 DOF systems, teaching the basics behind damping ratio, natural frequency, and general vibrations. We did questions about base excitation and rotating imbalances in machinery.


texts:
I'm working on building a 3D Zoetrope like the Disney Zoetrope in this video. The part that has me stumped is the bearing. I bought a lazy susan bearing but it's a bit loud, doesn't have any mount options, and doesn't spin as freely as I'd like.

I also see turntable bearings that seem like essentially the same thing but with better mounting options. My worry with those is their size. I have a 4 foot platter and most bearings are quite small, which is why I went with the lazy susan bearing at 24" diameter.

Thrust bearings have also come up but the ones I've seen don't have any mount options. They seem constructed exactly as I need them with the bearings being sandwiched vertically (top to bottom), instead of horizontally between an outer and inner ring.

I've also been reading that certain ball bearings have a a radial and/or angular thrust capacity. And that this may provide the rotation I need, though again the mounting options seem really limited for a turning table.

I've been googling for days and seem to have a mental block. I don't know how I would stabilize a 4 foot platter if the bearing is small and centered, like the turntable bearings I found. So, what kind of bearing would be best for this? How would I mount it (if its not super obvious)?

I'm thinking of using a pulley to drive the zoetrope, though I'd prefer a direct connection with the motor drive shaft in the middle of the platter.


texts: Why is there a moment at the cross section end when you cut a body?

texts:
I just started mechanics of materials, and it seems that my knowledge from statics has gotten rusty over the summer. But there was a  new concept introduced in the first example problem today.

There was a horizontal bar connected to a wall (fixed support). I understand that with a fixed support, there are horizontal and vertical reaction forces and a moment as well. However, when the professor cut the horizontal bar to calculate the internal loadings, he drew vectors for vertical and horizontal forces AND a moment. Since I didn't use this approach in statics, I don't get the reasoning behind adding a vector for the moment when the body is cross sectioned. Can someone explain to me why a moment is added at the newly cut end?


texts: What constructive solid geometry CAD programs can accurately model and simulate structural rope, cable, pulleys, and dynamic motion elements?

texts:
It seems that flexible objects just don't model well in many popular constructive solid geometry (CSG) CAD programs. Most CSG modelers seem to assume exclusively rigid bodies with sharply defined and constrained motions. Actually having fully dynamic unconstrained components seems mind-blowingly out of scope.

For example, there is a "collapsing string toy" from decades ago, that seems to be far beyond the ability of most CSG CAD to model and then dynamically simulate:

Google image search: collapsing string toy  (also known as a "thumb puppet")

https://www.google.com/search?tbm=isch&q=collapsing+string+toy

It is similarly exceptionally difficult for most CSG modeling software to accurately model and simulate the motion of a solid rectangular cube supported by two eye bolts, attached to two compound block and tackle rope pulleys.

It is very limiting for a mechanical engineer to be locked into such an inflexible and rigid understanding of modeling.

So, what CSG modeling software is actually capable of simulating such dynamic complexity of motion?


texts: Pouring copper onto another copper block

texts: When pouring copper onto another copper block and I want to have a good solid welding of the poured copper onto the block, do I need to use a flux? Or, if the block is freshly cleaned and free of most oxidation, would that be enough?


texts:
This is probably very well explained but I'm lacking the terminology knowledge and that's keeping me from finding the information I need.

I have a frame to which I need to attach a weight carrying arm. The arm will need to rotate vertically (1 degree of freedom) but will not be doing complete turns thus a bearing is overkill. The arm has a rectangular profile which is hollow inside, so I was planning to weld 2 small pieces of sheet metal to the frame that will form a bracket inside of which the arm will fit then drill a hole and put a bolt through but I'm afraid that due to the vertical rocking motion the bolt will quickly come loose.

What would be the proper solution in this case?


texts: Shouldn't enthalpies be equal in isentropic process?

texts:
I have some questions about the enthalpies between two points during an isentropic process in a nozzle. By doing the energy balance between the two points, one gets:

$h_1 + \frac{v_1^2}{2}+gz_1=h_2+\frac{v_2^2}{2}+gz_2$

If one neglects the potential energy and assuming that the velocity at the inlet is 0, one ends up with this:

$h_1 =h_2+\frac{v_2^2}{2}$

This is the part that raises some questions. If the process is isentropic, it means that the entropy doesn't change and therefore there is no heat added (or vice-versa) to the flow. But wouldn't that make $h_1 = h_2$?

My guess is that because $h = u + Pv$, the Pv term is the one that makes them different, considering that the flow energy (Pv) is different. But this would make $u_1 = u_2$. Is this true?

And if this is true, why don't we just use the following relation:

$P_1v_1=P_2v_2+\frac{v_2^2}{2}$

At this point, one can't really define $Cp$ or $k=Cp/Cv$, which would lead to the well-known isentropic flow equations. Am I getting something wrong? Can anyone help me to understand this? Thank you!


texts: How do I manually shape this heating element?

texts:
I have here a heating element that broke when it was used to ramp a furnace to 750 C, breaking at 740. The element had previously been used for higher temperatures and appears that it may have possibly shorted. The shape of the element is custom, as well as the furnace, and so we had a custom element machined with a specific wind, but this new element is straight. I have few tools and am limited in buying tools; So, whats the best way I can give the coil this shape? Some things to consider:

The previous coil broke at what appears to be a weak point. It's possible that it shorted, but its also possible that it just gave out. Therefore, with shaping it, there needs to be as few of strained points as possible.
It needs to remain planar, which is our largest problem right now. I attempted to curl it around a cylinder, and it now spirals upward (we have more coil if we need to start over.) If it doesn't remain planar, shorting will be likely.
When we attempted to spiral around a cylinder, it gives a good general shape, but will generally expand after releasing tension.

Below are two photos of what we are dealing with. The poorly coiled lustrous one is the new, and the burnt black piece in the ceramic is the old.


texts:
I'm building a mechanical system using GIM for university purpose.
I have to position the sliding point in (X=0.320, Y=0.320*tan(25°)). This point have to be accurate to study the cinematics (PICTURE 1).
GIM allow only to insert the distance of the sliding point from the extremes of the bar. the value of the distance is 0.320/cos(25°)=0.353081...
The problem is that I can't insert the function but just the numerical distance. This create an miscroscopic error when I find speed and acceleration.

How can I fix it? Can I insert the distance using a function? or defining the X,Y coordinates to avoid mistakes?
PS: sorry for my english
THANKS


texts: How do generators in space transmit/ deposit energy back to Earth?

texts:
I've read about the idea of putting solar panels in space, or the already used electrodynamic tethers which gain energy as they move through Earth's magnetic field.

The question I have is:

How do you get the generated energy back to Earth?


texts: Why 0.2% of strain is considered while taking proof stress?

texts: When a material does not show a distinct yield point then 0.2% of strain is considered and a line is drawn parallel to the elastic line and the corresponding stress is called proof stress. My question is why are they taking 0.2% of strain? Is that an assumption and does it differ with materials


texts: Which K-factor (metal bending) is defined first, ANSI or DIN?

texts:
Description
We had been through several issues with K-factor handling of two teams due to the same name assigned by different standards.
ANSI and DIN has defined the same term for the same purpose. However they defined different reference points, so there is a serious ambiguation: K-factor (ANSI), K-factor (DIN)
Expected behavior from the latter institute would be it should have chosen some different name for the "their" K-factor; like L-factor or M-factor (who cares?).
Question
I'm trying to find out the responsible institute that defined the same term without doing a research and caused the confusion. I couldn't get any helpful documents from the internet. Where can I find which K-factor is declared first?


texts: What is relationship between dislocation width and interfacial and elastic energy?

texts: Let us say I have a defined dislocation width,now how would the interfacial energy and elastic energy vary when the dislocation width is more or less.I feel having a wider dislocation would mean bonds being more stretched so higher elastic energy(since more is the deviation from the equilibrium position).However my book(Mechanical Metallurgy by G.E.Dieter) says that wider dislocation implies less elastic energy.(A contradiction).Also I am totally clueless about the analogy between dislocation width and interfacial energy.


texts: Which dimensions of columns supporting flat slabs do not require a punching shear check (according to ACI code)?


texts: Adding a lubricant to an already lubricious material, how is CoF affected?

texts:
I have a dry film moly-graphite lubricant (CoF=.075) and a lubricious CVD coating (CoF=.05).

The CoF of each of these lubricious materials was determined using the same ASME standardized test.

The standardized test consists of:  a plain steel object is coated in the lubricant to be tested; it is placed on a plain steel plate;   the plate is slowly tilted until the object starts to slide; the angle at which sliding occurs determines the CoF (a lower angle correpsonds to a lower CoF).

If I used both the coating and the lubricant together, would that lower the CoF further?

I.E. If I took the steel test object, and I coated it with the CVD coating, then on top of that I applied the dry-film moly-graphite lubricant, would that combination have a lower CoF than either material alone?

If yes, How much? If no, Why not?

This seems like a relatively straight forward question, but I've yet to get a clear answer from anyone.  Most people seem to drag other variables into the problem statement, but I'd like to know, all other variables remaining equal, can we answer this question - or is it truly impossible?

The following assumptions apply:

The only variable that changes between tests is the lubricant used.  All other factors remain exactly the same in each test. E.g. surface finish, temperature, interface load, materials being tested, etc. all remain exactly the same between tests.
The CVD coating is permanent and non-removable.  The moly-lubricant can be applied over the CVD coating and/or to the other part; either way is perfectly acceptable, so whichever scenario allows you to answer the question is fine by me.

PS:

This question was triggered by a problem I ran into at work.

It's not a homework assignment - I've been out of school for almost a decade now :)

It started off as a simple question that no one in the office could answer, so I turned to the internet, because I'm a curious george.

So far, my attempts for help on other internet sites have been met mostly with hostility and wild assumptions about the problem that were not stated in the get go.

I got one answer here so far, and I realized some assumptions regarding outside factors were being made that I didn't anticipate, so I revised the question to clarify what assumptions should apply in any attempt to answer the question.

I just want to know, if all other factors remain exactly the same, what effect to expect from adding a lubricant to an already extremely lubricious material.


texts:
I would like to make an ice cream machine for home use. That is a mixing bowl which can be stored in the freezer over night and then keeps cold long enough to freeze the ingredients while mixing them.

At first I thought I would just wrap a mixing bowl in commercial cooling packs, but apparently, in the hard shell cooling packs, they often simply use water. Now I would like to come up with a more fancy design.

My idea would be to get a long copper pipe and bend it around my cooling bowl. After bending, it would be like a long spiral around the bowl. At one end, I would plug it shut, then it's filled with water and with a bit of air left, the other end is plugged.

Would the pressure from freezing water be enough to unbend the copper?
Do you have ideas on fastening the copper spiral?


texts: Questions about the level flight lift equation

texts:
In level unaccelerated flight we have relation
$$
W=L=\frac{1}{2}\rho\cdot V_{stall}^2\cdot S\cdot C_{l,max}
$$
taken from book Daniel P Raymer "Aircraft Design: A Conceptual Approach" equation (5.5) at page 85.

The question is: why does this formula use $C_{l,max}$ and not $C_{l,min}$? In fact in the case that the $C_l$ in use is not $C_{l,max}$, and the speed is little more than $V_{stall}$ (valued for $C_{l,max}$), it happens that the lift is not enough and stall happens on aircraft anyway. If using $C_{l,min}$ the calculation is more cautious.


texts:
I m going to find the shear stress at section n-n .
So , shear stress in beam has formula of τ = V(A)(y) / It, where y = distance from the centroid of particular area to neutral axis

I get the correct $I$ (second moment of inertia), but I'm having problem of finding the shear stress at $A$.

$V$ (shear force) is a constant 40 kN from 0 m to 0.4 m (in my SFD diagram).
For $A_y$, I have $100\times10^{-3}\cdot12\times10^{-3}\cdot(94-50)\times10^{-3} = 5.28\times10^{-5}\text{ mm}^4$

Is my Area (green coloured part) correct ?

so $\tau = \dfrac{40\times10^3\cdot5.28\times10^{-5}}{5553152 \cdot 12\times10^{-3}} = 3.81\times10^{-6}$, but the given ans is $15.85\times10^6$

Does the section n-n mean when we cut off the beam at n-n , the side view of n-n look like in the diagram?

EDIT: sorry , it should be τ = V(A)(y) / It , where y = distance from the centorid of particular area to neutral axis

EDIT: How  to  get  the 21.05 Mpa ?  I only  get  the  15.8Mpa  after  correction.... $$\tau$$ = (40x10^3)(5.28x10^-5)/ [(5553152x10^-12)(24x10^-3)] = (15.8x10^6)MPa


texts: How do you name rods to fix several parallel metallical plates in mechanical devices?

texts:
In many mechanical devices, especial old ones, like clocks, the design is used, where two or more parallel planes fixed and all moving parts are placed in between.
In this case planes are fixed with metallic rods like this

What is the term for them?
Is this just "threaded rod" or "stud"?
https://en.wikipedia.org/wiki/Threaded_rod

Real world example


texts: How thick is it reasonable for the walls of a steel gas pipeline to be?

texts:
The TurkStream project site claims the gas pipeline will use pipes made from 39 millimeters of high-quality carbon manganese steel with additional plastic coatings on both sides. Yes, they claim 39 millimeters (roughly 1,54 inches) of steel walls - that's a whole lot of steel! For comparison, the M41 Walker Bulldog light tank had only 38 mm of armor plating.

Is such wall thickness realistic for an industrial gas pipeline? Why would you need that much steel for a gas pipeline?


texts: Why do baseball pitching machines have wheels stacked instead of side by side?

texts:
I was working on a project where I have to launch a ball. The current design has two wheels that are side by side with the ball going between them. I noticed that in almost every commercial ball launcher, the wheels are stacked on top of one another rather than side by side.

I don't understand what advantage this has over my current system. It seems a lot more accurate and precise, but I don't see why.


texts: Suppose that you have a bar of length 2 meters. This bar is along the x-axis. At x=0 there is a pin support. Also, at x=1 meter there is a pin support. A forceof magnitude 50Newtons is applied along the x-axis or along the axis of the bar at x=2 meters. What are the reactions at the supports?


texts: How do I spec out a thermoelectric cooler?

texts:
I want to build a small ice cannon that uses pressurized air (either through an air compressor or a CO2 cartridge) to shoot small ice pellets at my coworkers. I plan to use a thermoelectric cooler to freeze the water but I don't understand how to spec it.
For example, what are the key parameters of this product that will let me know if the cooler will achieve what I'm hoping it to?

Thermoelectric Cooler - 40x40mm
COM-10080 In Fritzing Library
Description: Thermoelectric coolers (TEC or Peltier) create a temperature differential on each side. One side gets hot and the other
side gets cool. Therefore, they can be used to either warm something
up or cool something down, depending on which side you use. You can
also take advantage of a temperature differential to generate
electricity. The thermal tape listed below works very well to attach
heat sinks to the hot side.
This Peltier works very well as long as you remove the heat from the
hot side. After turning on the device, the hot side will heat quickly,
the cold side will cool quickly. If you do not remove the heat from
the hot side (with a heat sink or other device), the Peltier will
quickly reach stasis and do nothing. We recommend using an old
computer CPU heatsink or other block of metal to pull heat from the
hot side. We were able to use a computer power supply and CPU heatsink
to make the cold side so uncomfortable we could not hold our finger to
it.
Features:

40 x 40 x 3.6mm
lmax - 7A
Umax - 15.4V
Qcmax - 62.2W
Tmax - 69C
1.7 Ohm resistance
127 thermocouples
Max Operating Temp: 180°C
Min Operating Temp: -50°C

If I want to freeze 10 mL of water from room temperature within a certain time period, how would I spec out the cooler? What are the base equations that govern how long it takes to freeze the water?


texts: How do multiple enphase microinverters stay synced to the grid?

texts: In a prior question it was established that any string or microinverter that is grid tied must put out sinusodial power. But there is also the task of being in sync with the grid. It seems from apperances that task for a single string inverter is far simpler than for an arrary of 28 microinverters on a 10kwh solar system to stay in step with each other let alone the grid. I can only imagine the analog nightmare of trying to cue 28 phonographs to play the same lp in unison and with variations in drive components and lp pressings. So what is the microinverter problem and solution to this symphonic nightmare of phase variance?


texts: Charger for lead-calcium battery circuit

texts: I post it because I want to know if anyone of you see any error in this circuit made in proteus 8.6. I accept any observation, this circuit provide 12v of output and 3 modes of charging fast(15 A), medium(10 A) and slow(5 A).


texts: Could air-launched space planes reach escape velocities?

texts:
Rockets like the Ariane 5 weigh hundreds of tons, but with about 85% of that weight being fuel, the payload fraction is only about 3% (~10-20 tons).

Virgin Galactic is building suborbital space planes, mostly for tourism purposes. They fly at about Mach 4, too slow to escape earth.

Now, I wonder if an air-launched spacecraft in the next 20 years realistically could really fly us to the moon - that is, could they reach escape velocities?

As side question in case they can: Would they be more or less fuel efficient than standard rockets such as the Saturn V? How much payload would be realistically being transportable?


texts: Why vertical wind turbine don't be half covered

texts:
I think it would be more efficient for a vertical wind turbine to have a covered funnel about half of it

Something like this figure

It would protected the turbine from opposite wind and also redirect another half wind to the correct side. It should increase overall efficiency

Are there any problem of this model so it not being used?


texts: The underlying library FreeCAD uses to manipulate STEP file format and format conversion

texts:
I am looking for answers to the following questions concerning FreeCAD from someone who is familiar with implementation of FreeCAD :

Which library FreeCAD uses to parse STEP file format?
Which library FreeCAD uses to convert file of STEP format to Obj format?
Is it possible (or how hard is it) to use the above mentioned libraries as standalone libraries in other projects. I have checked some options, but they are all proprietary software.
If one has many files of STEP format that need to be converted to Obj format, is it possible to write a script to call FreeCAD to do it in a batch.


texts:
I'm trying to find online the derivation for the 2 parameter margules equation but cant find it anywhere.

basically need to prove
$$
\frac{d}{dn1} (x_{1}x_{2}(A_{21}x_{1} + A_{12}x_{2})) = x_2^2(A_{12} + 2(A_{21}-A_{12})x_{1})
$$

but everytime I try just end up with a page full of rubbish. I've searched online for the derivation but cant find it anywhere.

EDIT: the A values are functions of temperature only and can be considered constants


texts: Can hydraulics be used with a squarish piston?

texts: I'm designing a custom part that needs an active shock absorber and space is restricted. I most likely won't be able to use a stock absorber and was thinking, can two squarish tubes be made tight enough?


texts: How to convert solid part to shell part in Abaqus?

texts:
I want to compare the same model with solid shape and shell shape,
since my model is big, I am wondering if there is a way to convert the solid part into a shell in Abaqus easily without creating a new model from the beginning?

Please help me resolve this problem
Thank you very much..


texts: Required torque to move 6000kg at 27.77m/s

texts:
I'm trying to find the required Newton or Nm of torque to move 6000 kg up a grade at 100 km/h.

I'm trying to work out the closest suited engine platform to do the job while been efficient, durable,cost effective and most of all required torque.

Mass: 6000 kg
Speed: 27.77 m/s = 100 km/h
Grade: 7° = 12%
Wheel size: 830 mm


texts: What is the hardware called that can step a lever N degrees upon manual force?

texts:
I'm trying to build a step stool that has a rotating chair back that will rotate from top position (e.g. chair) into bottom position (e.g. step stool). I do not want a free rotation of the chair back so I want to avoid it slamming on the floor. I've been looking for a bearing that acts as a mechanical stepper to click every 15 degrees with enough force requirement to stop the chair back from falling to the ground without force being applied (other than gravity).

I've been searching google for a while now and cannot figure out what this part would be called.


texts: I'm working on an FEA model and my mesher uses a "Marching Voxel method" I'm wondering what the relationship is between mesh size and computation time is? I.e. if I half the mesh size (1mm to 0.5mm) is the computation time for the tighter resolution doubled? quadrupled? eight times longer?


texts:
Dyna Beads are a brand of small ceramic beads that are claimed to have a balancing effect on vehicle tires. Here is a video showing them in action.

How do these work? What are the physical principles involved?


texts: Entrainers to distill MTBE from Methanol? - Chemical Engineering Question

texts: What have you found to be some effective entrainers to distill MTBE from Methanol, given the azeotropic conditions at 67%. I have tried to simulate 1-butanol, as well as ethanol, and numerous other components although have come up short in distilling with high purity.


texts: Block Diagram using Integrator (Linear Systems Theory - Hespanha)

texts:
This

Not sure what to do. At first I ignored what is said about using an integrator and drew the block diagram of the system, which looked a little complicated. So now, using just integrators I am stuck. If we try just taking the first system

x'1 = x1 + 4u

if we want to us an integrator, where y' = u, how can we ever draw this while satisfying the previous equation?

EDIT: Actually I think I got your hint. Is my system correct ?


texts: Rated flow in the following is in conjunction with the rated lift meaning it can lift 15 meters at flow of 12 Liter/ minutes from a well? But what if its sucking water from the water company with existing flow rate. So the total flow rate is additive and is more than 12L/ minute, right?  Or wrong? I plan to buy this pump and it confused me for days.


texts:
I'm trying to make a gear to mesh with a motor shaft that I bought online, but it doesn't give any information about the pitch or diameter. When I measured the diameter and pitch of the motor shaft, it doesn't seem to conform to anything metric or imperial. So I just guesstimated how big the teeth should be and how spaced apart they should be and designed a gear from scratch. I 3D printed some test gears to see how they mesh, fine tuned it, then printed a full size gear. The teeth appear to mesh very well, but its very very loud, which I am predicting is due to the two gear pitches being different.

After a bit of research, I figured using a gear generator would be much more accurate. I generated the gear based off of the circular pitch (tooth size). Now I've narrowed the correct tooth size down to 3.2mm $\pm$ 0.2mm. But I don't know if this will work any smoother than my original. I don't want to waste a huge 12+ hour print on a gear that wont mesh well. What kind of tolerances do I need for proper meshing? Will 3D printing even provide enough resolution for a quiet and smooth fit? I am using an Ultimaker 2 by the way. I appreciate any insight I can get.


texts: Which is the best tutorial on Oldham's Coupling?

texts: I am a sophomore in mechanical engineering and am unable to understand the purpose and functioning of Oldham's Coupling.


texts: How to determine minimal wall thickness for a rectangular pressure vessel?

texts: I know this is a basic question but google only gives formulas for more "rounded" shapes. How to calculate the minimal thickness for a flat wall knowing tensile strength of the material and the maximum pressure difference between two sides?


texts: How to find yield strength and Young Modulus from S-S curve

texts:
I have a S-S curve and am not sure how to find yield strength from it as when I did 0.2% strain (0.002 * strain at fracture) I get a small number that plots close to (0,0)?
For young modulus, I am not sure where to take the values as it’s not a completely straight line?
Are there any other methods here please?


texts: I have a circulation tank that runs a piping loop out and back in with a motor pump on it to keep fluid constantly agitated in it.  I want to add an inlet to the tank, so I can fill it without pouring liquid into it.  The way the line is set up, I have an option to fit the inlet between the tank and the motor pump.  And, I will need a priming pump to get fluid to the normal motor pump that's inline with the circulation tank.  Will a priming pump push past the circulation pump if I leave the priming pump on (if both are on, if just the one is on)?  Will the circulation pump pull through the priming pump if the priming pump is off? I think the way this will work is I use the priming pump until the line is filled with new fluid then turn it off and use the circulation pump to fill the rest of the tank.  I am worried that if one of two pumps in series is off, flow will be stopped altogether.  Are there any other possible problems I should consider when running pumps in series?


texts:
This is my first question here. I am having trouble finding the 2nd moment of area of a ring with a thickness 't' and radius 'r'. I seem to be a factor of 2 out.

What I do is I consider an area like a piece of pie, and say that this is dA. I believe

$$dA=r*t*dθ$$

where r is the radius, t is the thickness and dθ is the small angle over which dA is encompassed. Then I integrate with respect to area:

$$\int r^2 dA$$
$$\int_0^{2\pi} r^2 * r*t*d\theta$$
$$\int_0^{2\pi} r^3*t*d\theta$$
$$2\pi*r^3*t$$

which is a factor of 2 out.
Any help would be appreciated
Thanks
Matt


texts: Suitable tube materials for making a light-weight, heavy-load bearing structure

texts:
I am looking to build a detachable hammock stand structure for camping. I was originally thinking about making one out of PVC but I am in the UK and it isn’t cost effective as it looks like it needs to be imported. I am therefore looking for alternative materials that are durable enough to bear a heavy load (up to two adults) but are light enough to carry when detached.

Any suggestions? I have been looking at polycarbonate tubes but I am unsure if it would be rigid enough with weight pulling on it and what diameter the tube would have to be. Any ideas are greatly appreciated!


texts: Some tight-coiled springs are made so that they are already under tension - how are they manufactured?


texts: Heat Loss through a run of insulated piping

texts: I've been racking my head around calculating the amount of heat loss still water will experience through a run of insulated piping. The water in the tank is maintained at roughly 550°F saturated, and a standpipe measures the water level some distance away. However, most of the example problems and literature I can find assume some movement of water through the piping, and here, we know the water will be still. I'm assuming this needs to be setup in a way that we can equate the Qin to be equal to Qout, with Qout being losses due to radiation and convection, and we should be able to find the temperature at the end of the pipe if we know all of the other parammeters, but I'm not sure how to setup my Qin. Any ideas? Thank you in advance.


texts: Reconfiguring a Safe to only need Four turns

texts:
I'm not sure if this is an appropriate place to ask this, but I figure the worst that's going to happen is my question will just get closed, so here we go.

I just got my first home defense handgun, a Glock 19 gen 4, and I was wanting to store it within my combination safe. I timed myself at roughly 25 seconds to open the safe and retrieve the gun. This is fast, however, I was wondering if I could make it faster.

Normally you would need to turn the dial like this(Please note i don't count the first 4 turns because that should be muscle memory when opening a safe anyway):

4 times to the left, and end on the first number
3 times to the right, and end on the second number
2 times to the left and end on the third number
1 time to the right and end on 0. (This last step seems to be universal)

What I would like to do is reconfigure my safe to do something like:

4 times to the left, and end on the first number
1 time to the right, and end on the second number
1 time to the left, and end on the third number
1 time to the right and end on 0.

I'm essentially cutting out the extra turns of the tumbler. The concept seems solid, and I can indeed make it to the back of the safe tumbler to see the internals.

My question is, is it possible to change not only the combination, but the way the combination is entered, and skip additional turns? The only downside I can see to this is by overriding the functionality of the safe, I may be decreasing the number of permutations for the combination. I can live with that if it means cutting down the retrieval time of my gun to around 5 seconds, which my concept will likely do.

Is this possible?


texts:
A recent news item featured this photo of a WW2 bomb being prepared for detonation.

Can anyone identify the purpose of the large widget sitting on the bomb? it's got a lot of cooling fins on it, and there appears to be fan on the right hand side. There's also what looks like an earthing cable in the foreground and what might be a power cable in the background, so my guess is that its either a heater, or a cooler.

I'm aware that some explosives are inert when cooled sufficiently, so maybe it's an attempt to freeze the bomb to make it safe. I'm also aware that some early bombs could be made safe by injecting steam into them which would melt the explosive and allow it to be poured out, so maybe it's some form so steam injector?

But I'm just guessing. Does anyone know what it really is and what it's supposed to do?


texts: Is there an industry consensus standard for storing sensor data?

texts:
I would like to know what standard(s) may exist for formatting log data from sensors that record information such as:

temperature
pressure
humidity
vibration
acceleration vector
magnetic field vector
location vector (ex: GPS)
etc.

I have been an end-user of SCADA software products which record various data fields for each stream of log data it receives into a MySQL database. However, I have never looked into determining how exactly that data was stored. I would like to know if there exists an industry consensus standard for storing sensor data that facilitates information interchange. For example, the Internet Engineering Task Force (IETF) publishes documents called "RFCs" for the purpose of standardizing implementations of commonly used protocols like IMAP (email), TLS (secure web browsing).
For example, such a standard might indicate to me the best practices for:

formatting units of measurement (ex: degF vs. °F)
formatting of timestamps of each measurement (ex: ISO-8601)
file format type (CSV files vs. SQL database)
delimiters for measurement data (ex: , in .csv files)
indicating origin and license of data (ex: end device owner/operator, equipment tag number, CC RDFa tags)
encrypting measurements (esp. in a way compatible with sudden power-loss, ex: DTLS)

While researching this question I noticed that the IETF says the Internet of Things (IoT) is a topic of study for several of its working groups. Its definition of IoT is

The Internet of Things is the network of physical objects or "things"
embedded with electronics, software, sensors, actuators, and
connectivity to enable objects to exchange data with the manufacturer,
operator and/or other connected devices.

However, I did not find any IETF standards document describing standard methods for storing log data. Is there an ISA standard covering methods for logging data? I really like their ISA 5.1 standard for P&ID symbols, "Instrumentation Symbols and Identification".
Thank you for any direction you may provide.

Edit-Update (2021-02-02)
After several months of off-and-on research, the closest standard that defines what I was looking for is the Semantic Sensor Network (SSN) Ontology published by the W3C. It is an expanded version of the Sensor, Observation, Sample, and Actuator (SOSA) Ontology. It is capable of associating metadata about an observation (i.e. units, time, location, site-specific names, relationships to other entities in a data collection hierarchy) in an RDF graph data structure. RDF graphs can be "serialized" into JSON (specifically, JSON-LD). The JSON graph data can be formatted using the JSON lines specification so each observation can be appended to a newline-delimited log file in a streaming fashion. Because the logs are machine-readable, an appropriate software package could later import the readings into a database or whatever a user requires.
Search results aren't clear whether SSN will become an industry-standard for general encoding of sensor information but it seems to me the best method for storing sensor data in a self-documenting way. For now, I'm happy to have discovered the method of recording measurements + metadata as an RDF graph using the SSN ontology, serializing the graph as as JSON-LD, and formatting the JSON-LD as JSON Lines that are streamed and appended to a continuously growing log file.


texts: P&ID questions on reports, connection, etc

texts:
Good day to all of you. I got some questions in my mind regarding on P&ID:

In electrical, symbol will have their own default reference name for example "Motor" will use "M" , while for wire they will have "N" for "neutral". So in P&ID they will have specific naming for pipe lines and also instrumentation lines. Can i have, this instrumentation lines reference as "Signal Line 1" or better stay as "Software Link"?

For reports wise, is it necessary to separate between Pipe and Instrumentation Line? For example, Pipe would have Pipe connection report while Signal Line would have Signal Line connection report? How about their BOM report?

3.Do Instrumentation Line should have the same details as Pipe Line ? Is the information suitable and sufficient?

Name
Brand
Model
Spec
Service
Insulation Type
Insulation Thickness
Size/Gauge
Order No
Supplier
Remarks
Length

Based on the diagram, how the connection report should be for Signal 01 and pipeline 01?

For pipeline 01
"pipeline 01 connected to IND001 via Signal 01 & T003 connected to T004 via pipeline 01?".
For Signal 01
"Signal 01 connected to IND001"?

Is this symbol generally used in P&ID as to link to another pipe?


texts:
I want to build a home automation system by hooking up various sensors (e.g., passive IR motion sensors, magnetic door contact switches, vibration detectors, etc.) around the house to detect things then send the sensor signals to a central command center / control station.

PIR Motion Sensor

I want to do this wirelessly and solderlessly with a budget of roughly $10 per sensor. So, for example, I could hook up a breadboard circuit that receives the sensor signal and sends it to a Wifi network.

Is there a simple circuit component or IC that can convert the analog sensor signal to a wireless signal then transmit that signal to the network via wifi without, say, hooking up an entire microprocessor (e.g., Raspberry Pi) to each sensor? A Raspberry Pi for each sensor would blow my budget.

I'm looking to install a simple component part in, say, a solderless breadboard circuit at the sensor level. Then read all the signals off the network at the control station using a Raspberry Pi or laptop.

What kind of components and configuration would anyone here recommend?

Edit 1

Apparently, a USB wireless adapter or a network adapter might be the component I'm looking for. But would it be possible to build up a separate breadboard circuit for each sensor and pipe all the signals to the wifi network? If so, how? I want to keep my budget to about $10 per sensor.

USB Wireless Adaptor

Edit 2

I found this article which reflects what I'm trying to do with the sensor. But it says nothing about a wireless (analog-to-digital) conversion.

PIR Motion Sensor Schematic

Breadboard Hookup

Edit 3

I like the suggested ESP8266 chip described here. (Could this really be $ 5-10 per sensor?)

ESP8266 chip

Breadboard configuration

Schematic


texts: How to calculate flow rate of water through a pipe?

texts:
If a water pipe is 15 mm diameter and the water pressure is 3 bar, assuming the pipe is open ended, is it possible to calculate the flow rate or water velocity in the pipe?

Most of the calculations I have found appear to need 2 of these: diameter, flow rate, velocity.

So more specifically can you calculate flow rate or velocity from water pressure and pipe diameter?


texts: Obtaining the correct flat plate turbulent boundary layer thickness in a CFD simulation

texts:
I used a commercial CFD software to simulate incompressible turbulent flow of air over a flat plate.  I setup a 2D domain 1.5m long in the x direction and .2m in the y direction.  The boundary conditions are as follows:

Left side (x=0): is a velocity inlet
u = 100m/s
$\nabla p\cdot n = 0$

Right side (x=1.5) is a pressure outlet
$p = 0$ Pa
$\nabla u\cdot n = 0$

Bottom Side (y=0) is a wall boundary
u=0m/s
$\nabla p\cdot n = 0$

Top Side (y=0.2) is a symmetry boundary

For turbulence, I enabled a $k-\omega$SST model and prescribed turbulent intensity of 5% and a viscosity ratio $\frac{\mu_t}{\mu}=10$ at the inlet.  My program automatically sets conditions at all other boundaries automatically.

My mesh consists of 300 quadrilateral elements in the x-direction and 100 quadrilateral elements in the y-direction.  To ensure that the mesh is sufficiently refined to capture the boundary layer, I biased the mesh so that the elements connected to the wall boundary are 4000 times smaller than the elements connected to the symmetry boundary (i.e. the elements connected to the wall boundary are approximately $4*10^{-6}$m )

With a time step of 0.01s, I ran my simulation up to 30s to ensure a steady state was achieved.  In the end, I was surprised to find that my boundary layer thicknesses $\delta$ were smaller than the well-known 1/7 power law, given by:

$$\frac{\delta}{x} = \frac{0.16}{(Re_x)^{\frac{1}{7}}}$$

where $\frac{u x}{\nu}$, where $x$ is the horizontal distance from the beginning of the plate, and $\nu$ is the kinematic viscosity.

I thought that I should be able to achieve a close match to this 1/7 power law with my simulation independently of how I choose the turbulent conditions at the inlet.  But my boundary layer ended up being almost 30% smaller than the 1/7th power law all across the plate and I'm not entirely sure why.  Is there a minimum turbulent viscosity ratio and turbulent intensity required to achieve 1/7th power law?


texts: I am trying to create an op amp based negative voltage regulator

texts:
I am trying to find simulate an op amp based linear regulator negative voltage regulator circuit.
I have done the circuit for positive voltages, but does not know how to do it for negative voltage. Anyone could help me?  I dont know how to connect the op amp.
I have included a screenshot of my simulation


texts: What tests are made in an Ingress Protection to verify that no water entered the enclosure?

texts: I am asking this question on what tests are made to to verify that no water has penetrated the waterproof enclosure during an Ingress Protection test.  I have researched tests online and most often this is done simply by a visual inspection.  Is a visual inspection an acceptable method as it could be very subjective if a small amount of water penetrates.  Another method which I could think of is to weigh the item before and after the test and verify that no water has seeped in but this method would require a high accuracy scale which I do not have at my disposal. Can someone please suggest another method or if a visual inspection is considered enough by the industry?


texts: How would measuring the number of photons on a finite number of pulses break coherence of a weak coherent laser source in COW QKD protocol

texts:
I' m trying to understand attacks on Quantum key distribution protocols. In the COW QKD protocol, pulses from Alice are passed through an asymmetric
coupler and a fraction 'T' of the photons are sent to generate key, and the remaining fraction '1 − T' is sent into an interferometer to monitor coherence of consecutive pulses. In one of the references "Zero-Error Attacks and Detection Statistics in the Coherent One-Way Protocol for Quantum Cryptography"by Gisin et al. I came across the sentence:

  If any two non-empty pulses are coherent and all pulses are equidistant, any attempt of measuring the number of photons on a finite number of pulses breaks some coherence and contributes to errors.

which I'm unable to understand.


texts:
why can't remove the Image frequency using a band-pass filter?
I've been asked to search for the reason why we can't use BPF (band-pass filter) in order to remove the effects of the Image frequency?
I've searched but couldn't find anything useful about it.
I would be glad if you could help me.


texts: Any industry convention for Carbon / fiberglass mold color?

texts:
I was wondering if there is a specific color that will add some benefit to a carbon / fiberglass mold
Maybe help identify problem spots without resin or easier to see in general?


texts:
I am trying to understand the difference between Latches and Flip-Flops, as an example: RS-Latch and RS-Flip-Flop. In my lecture script the only difference is that latches are level triggered and Flip-Flops are edge triggered, so far now problem.

In one task we had to build an RS-Flip-Flop with Nor gates, could someone give me an example of it? Because in the Solutions there is a picture of an RS-Latch (the one you can see on wikipedia), but latches are edge-triggered, so we can't build an Flip-Flop by using just two nor gates, can we?

Thanks in advance.


texts: Does turbulent river flow classify as uniform?

texts:
I found this meme in a facebook group on engineering concepts:

I selected A (steady and uniform). In selecting A I assumed the width of the river to remain constant along its path and no parameters change with time.

But why steady? Velocity doesn't change with time. It's steady.

But why uniform? We get the same volume across any cross section because width of stream doesn't change.

I think people who selected any other option are confusing laminar with turbulent flow. This has nothing to do with it if you made the correct assumptions.

Is my selection (A) and justification for it correct?


texts: Cube vertex/corner blending/fillet algorithm

texts:
I created fillets/blending for a cube corner in 3 cases.

For the first case, the 3 radius are equal. The blending surface is a sphere patch.

For the second case, two radius are smaller than the third. The blending surface is a torus patch.

But for the third case, one radius is smaller than the other two. I cannot figure out the algorithm generating the blending patch. I did a lot of search for papers on surface/edge blending, but didn't find the algorithm for this case. Are there any document or paper on the algorithm for this case?

Could someone give me some hint?

The STEP and picture files for the three cases are attached.


texts: Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

texts:
I have been wondering if there are certain media (for instance glass, air, foam, etc.) which are peculiar given their chemical composition and/or structure allowing them to filter out mechanical waves (examples include: sound, vibrations) of high or low frequencies. Do these exist? Could I please have some examples?

The less abstract example: I tend to notice the bass of the music booming over from the car next to me when I am stopped at a red light. I do not know if this is due simply to the amplitude of those low frequency components or whether there is mechanical filtering at play (suppressing the higher frequencies). This is the source of inspiration for asking my question.


texts:
I have a Statics assignment which I don't seem to fully understand.

Here is the full assignment:

For the first question I have tried making several tables with Areas of each parts and the centre of gravity for each recognizable shape (triangle, square, circle, quarter circle, half circle). The problem is I don't understand how to piece it together. The figure doesn't have an xy axis (should it have one?).

I have made these calculations for the areas so far:

This is what I don't fully understand, how should one make use of this table. I have stumbled upon several tables which some contain the area A and coordinates x and y and others with only the area A and coordinate z. Which one to use? Here is an example:


texts: Strange simulink error. Professor & TA don't know. Any Ideas?

texts:
I am currently working on developing a simulation for a restricted UAV, and I’m having some issues with Simulink while doing this. I have my mathematical equations which have been approved by my professor, but while I’m trying to simulate the system I am running into strange issues. Moreover, neither my professor nor my TA can figure out what is causing this issue, despite multiple private sessions to troubleshoot. If anyone can shed some light on the issue it would be highly appreciated.

Firstly, the equation I’ve modeled on Simulink is this:

My Simulink block diagram is above. Input 1 Is Fb+Ff which, in this scenario = 6.8. Input 2 is theta which = 0.

I have annotated the values that should be and are at each of the nodes before the summing junction. In this section of the block diagram the theoretical value and the simulation agree.

The problem comes in the more complex half of the diagram. The graph I am validating should look like this.

There is an initial rise and then oscillations about a non-zero number. Obviously, my graph will be ideal so oscillations will not persist like they do in the graph above.
My final graph is this…

Where the y-axis is elevation angle in degrees and the x-axis is in seconds. Obviously these two graphs are in no way similar. In an attempt to analyze where I could have made an error in my block diagram, I analyzed the behavior at each node.

Immediately after the cos block to the lower right I get oscillating behavior

Immediately after the summing junction and gain (1/0.91) I get:

The above bears a resemblance to the graph I’m validating against.

After the first integrator, however, I get this.

Adding the two graphs together, should I not be getting a graph that rises and then oscillates about a non-zero number?

Have I made a mistake in my block diagram somewhere?

The only value I’m allowed to change is the gain marked De.

At this point I am starting to hit a wall and really need some insight on this. Surely this cant be something wrong with the Simulink source code.

Nothing I do gets me anywhere near the validation graph. Can someone please point me in the right direction or let me know if you see any errors?

Any insight is highly appreciated, thank you for reading.

Should you want to view the Simulink file for further analysis, it is available for download here: https://ufile.io/08aqv However please note that the attached file is my entire Simulink project. The circuit reference in the question above is contained in the subsystem "elevation".


texts: Where water goes in split air conditioner system in "dry" mode?

texts:
In split air conditioners, there are two tubes connecting the indoor unit and the outdoor unit. According to the generic schematics I find online (like this one), they are part of the closed circuit for coolant gas.
But most systems have a "dry" function that removes moisture from air. Where does the water goes, if there is no water/air connection between the indoor and the outdoor units? Or the tubes function is different from what the drawing shows, and there is indeed a water line, then how the coolant flows between the indoor and outdoor units?
PS: I could use a "heat-pump" tag here.


texts: Is this alternate grounding practice practically implementable?

texts:
While grounding power sockets in modular prefabricated steel buildings (see Light Gauge Steel Frame Technology), can we just connect the ground wire to the steel frame of the building itself? as the entire frame is grounded. Would that eliminate the need of other systems required for grounding?
No one can actually “touch” the steel frame, if you’ve concerns about the entire structure being on live power. There are layers of insulation: rock wool between the panels of the steel frame, then OSB boards or thermopine, then entire structure is covered with water proof membrane, then cladded with steel, and on the inside there’s thermopine and wood/paint on cement sheet.
Can someone tell me how can I get to know if such practices are allowed in the US? Which local authority to contact?


texts: What's the difference of using different state-space forms for solving eigenvalue problem?

texts:
I have a set of equations of motion describing a planetary gear train of 18 DoF (sun, 3 planets, carrier and ring), they have the general form of:

$$\mathbf{M{\ddot q}+{\Omega_c}G{\dot q}+{Kq}=F(t)}$$

$K$: stiffness symmetrical matrix
$M$: Mass symmetrical matrix
$G$: Gyroscopic skew symmetrical matrix
$\Omega_c$: angular speed
$F$: excitation
$q$: generalized coordinates

While trying to solve the eigenvalue problem with Matlab, I noticed there´s a whole bunch of ways to represent the equations in state space form and I don´t understand what the main difference is, or which one I should use, since when calculating I get different results in the eigenvectors.

But for the free vibrations I have the equation without damping:

$$\mathbf{M{\ddot q}+{Kq}=0}$$
1.
and to solve the standard eigenvalue problem of:

$$\mathbf {\omega^2M\phi_i-{K}\phi_i=0}$$
I use the Matlab code:

[v,D]=eig(K,M)
root=sqrt(D)
natural_frq=root/(2*pi)

which gives me all real natural frequencies and eigenvector per frequency.

2.
I also tried calculating them in the form of:
$$\mathbf{{\dot x}=Ax+Bu}$$

$$ \begin{bmatrix} \mathbf{\dot q} \\ \mathbf{\ddot q} \end{bmatrix} = \begin{bmatrix} \mathbf{0} & \mathbf{I} \\ \mathbf{-M^{-1}{K}} & \mathbf{-M^{-1}{G}} \end{bmatrix} \begin{bmatrix} \mathbf{ q} \\ \mathbf{\dot q} \end{bmatrix}+ \begin{bmatrix} \mathbf{0} \\ \mathbf{-M^{-1}} \end{bmatrix}u$$

and by using:

[v,D]=eig(A)

I get similar results but in complex numbers (there´s no need for the square root), so with some extra code I choose only the imaginary parts and select the positive values of the eigenvalues vector, which instead of 18 elements is now 36. The frequencies I get with this method against the first ones are paractically the same, but the eigenvectors are not, they are also complex and the results don´t look correct.

3.
Then there's another state space form:

$$ \begin{bmatrix} \mathbf{I} & \mathbf{0} \\ \mathbf{0} & \mathbf{M} \end{bmatrix} \begin{bmatrix} \mathbf{\dot q} \\ \mathbf{\ddot q} \end{bmatrix} +  \begin{bmatrix} \mathbf{0} & \mathbf{-I} \\ \mathbf{K} & \mathbf{G} \end{bmatrix}\begin{bmatrix} \mathbf{ q} \\ \mathbf{\dot q} \end{bmatrix} = 0$$

If I use the code:
    [v,D]=eig(-B,A)
I get similar results as the last method, I'm not sure which form of state space this form is, I would guess it's $$A{\dot x} = -Bu$$.

The main question is that I don't know which is the best solution to my problem and why I get complex frequencies in the second method, if my angular speed $$\Omega_c$$ is zero, all damping terms should also go to zero and thus not affect the system results , right?

EDIT: why do I get very different values when calculating the eigenvectors through the standard eigenproblem form $$\mathbf {\omega^2M\phi_i-{K}\phi_i=0}$$ and with the state space?


texts:
I'm building a rotary inverted pendulum to demonstrate reinforcement learning principles, however I have little experience with mechatronics. I will be building something similar to this.

However instead of plastic I will be using 10 mm aluminum tubes. The arm (horizontal) will be about 150mm long and the pendulum (vertical) will be about 150mm to 200mm with a little weight at the end (a few hundered grams).

So I have started my construction but the problem I have now is choosing a motor. I started looking through sparkfun and some chinese stores for motors until I realised that I have no idea what type or how powerful of a motor I need.

In order to avoid the complex calculations, I was hoping someone could give me a ball park estimation of the torque I would need, and the best type of motor for this application (stepper or a classic DC motor) considering my setup?


texts: Calculating the load torque on a turbine pump

texts:
How is the load torque on a turbine pump handled. Generally, with motors, there is a load attached to the shaft which resists the output torque of the motor however, with a pump increasing the flow rate of water, I assume the water should act as a smaller load.
Currently, I am calculating this load torque using the approach of a point load at the end of a cantilever beam. I know in a more realistic sense, the water would be a distributed load but I am going for a simplistic answer and I'm wondering if this is a valid approach to calculating this load.


texts: What is a good reason if the data from analysis and measurement does not give a good agreement?

texts:
Currently I am doing a comparison results between analytical results and measurement results, I compare stress and strain values in 32 specified locations, unfortunately I found that there are some locations does not give a good agreement.
and my professor want me to think about the reason, instead of modifying the model,
does anyone come up with an idea about a good reason for this problem?
Thank you
Cindy


texts: Is it possible to replicate a motorcycle engine cylinder head?

texts: Is it possible to create a mold of an aluminium motorcycle cylinder head so that you can create an exact replica with melted aluminium?


texts: I'm using a torque wrench whose unit is cN.m. I wonder what unit this is, and how to convert N.m (Newton meter) to cN.m.


texts: Formula for finding the optimal weight for a given torque and vice versa

texts:
Whenever i see videos of two trucks pitting with each other to see who has a stronger, i always see comments that sounds like:

If you load the other truck more it would beat the other one

That truck is an all wheel drive and the other is 4 wheel drive

It got me thinking how to you calculate the optimum weight for a given torque of a four wheeled vehicle.

To make everything simple lets assume that out truck is a Tesla truck where each motor can generate torque equally on all the wheels and the wheels are evenly spaced. If the the motor on each wheel can lets say generate a 1000kg-cm of torque how would i find the optimal weight so that the truck can push to its maximum potential.

My follow up question would then be. What happens if the other truck has double the torque at half the weight which one will be able to push better? What would then be the formula for the pushing power?


texts: Is a bridge more stable on concrete or soil?

texts: I understand that foundations are used in structures to support and spread the weight of the bridge over a large area. However I am struggling to understand why certain materials such as concrete are used in foundations over others. My first thoughts were based on how uplift may be effected.


texts:
I'm not entirely sure if this is the right place to ask this, so apologies in advance if it doesn't belong.

I have a curved surface with many small, irregular holes in it that I would like to measure. The surface is in a location that makes it awkward to work with, and is effectively immobile. Are there any technologies or techniques that could let me take a 1:1 imprint or copy that is more portable? Being able to 'flatten' the copy would be convenient but not required.

The surface is thin and the reverse is accessible (though again with some difficulty) if at all applicable.

Edit: Specifically, i'm trying to gauge the accuracy of another measuring process, so computer vision techniques are undesirable.


texts: What would you call this mining vehicle? (Ural-20R, used in mining)

texts:
On the image below is a mining machine produced by the Kopeysk Machine-Building Plant. I'm not sure how to call it in English. The Russian name is "prokhodchesko-ochistnoy kombain".

Multitran offers the translation "heading and winning machine", but I'm not sure: when I enter this term in Google, it finds predominantly Russian-based websites.

The machine is used for underground mining. This particular model is mentioned in a text I'm translating about an overpricing row between the Russian potash producer Uralkali and the machine-building plant.

I found the company's description of the machine:

  The «Ural-20R-00» heading-and-winning machine is designed for longwall operation in сhambers and driving of oval-arch shaped workings in potash ore seams with thickness of 3.0-3.7 m at dip angles of ± 12° and rock resistance to cutting of up to Аp=450 H/mm.


texts: Does a closed loop biomass-fired cogeneration/CHP make sense?

texts:
I'm working on a project concerning electricity production using biomass, and we have seen that making use of cogeneration is very attractive in order to increase the efficiency of the installation. This would be a smallish power plant, of around $1 \ \mathrm{MW}_e$.

In particular, we are exploring an installation that is next to an industrial plant that needs both hot water and steam. Most of the designs I've seen for a steam turbine cogeneration power plants use an open loop, where part of the turbine exit steam is feed to the installation, and feedwater has to be added in order to replenish the system.

However, it seems to me that using a closed loop system would be very beneficial. In this case, we were thinking of having a steam-steam condenser that heats up the steam for the industrial plant (and condenses the process fluid) followed by a water-water heat exchanger that heats up the water for the industrial system. However, I'm not very well verse in heat exchangers. Does a design like this make sense?

We read about Organic Rankine Cycles, and it seems like a good solution in order to implement closed systems; however, if it is plausible, we prefer to use water/steam as the working fluid.


texts: What engineering research field is concerned with the mechanics of adhesion; more specifically, how objects behave in soil media such as sand?

texts: I am interested in conducting a research project involving the design of a tool to aid astronauts to perform experiments on lunar surfaces, but I am having difficulties coming up with appropriate key words or questions to ask to begin my research. The specific scenario of focus is to design a tool that can act as an anchor in a sand-like medium on the surface of the moon; the goal is to design a tool with a method to dig/lodge/bury itself underneath the soil surface in a way such that removing the tool requires a maximal load. The research I will conduct is for the purpose of selecting an optimal geometry for the tool (i.e. my initial concept is a helical drill). As this phase of my project, I will assume the design will be rely on geometry alone, however, I may also incorporate applied forces within the tool in some way (i.e. pneumatics) to aid anchoring. I am interested in this topic in order to submit a proposal to the NASA Micro-g NeXT challenge (you can see their webpage for more details). Is this design problem related to fluid mechanics, and if so, what sub-discipline of fluid mechanics is concerned with modelling the behavior of dry, granular media such as sand?


texts: Looking for sources of information regarding story of resilient design in Japanese nuclear power plants

texts:
I recently listened to podcast (not sure what podcast, it came up in my feed while driving).  There was in interview with an author of a book.  The author told a story about the design of nuclear power plants in Japan.

Specifically she told a story about a power plant the survived the tsunami that affected the Fukashima plant because it was built much higher.  Supposedly, one designer of this power plant pushed to have the plant situated higher because he grew up in a Japanese village that had a high hill with a sign on it that read something like "In the event of tsunami, don't go to this hill, go somewhere higher".  This sign was placed because of a tsunami that engulfed the hill some very long time in the past (maybe 500-1000+ years ago).  The author interpreted this story as that the designer had the "imagination" to envision a large disaster.

As someone who works in designing for flood "resilience" this story is interesting to me and I would like to know more about it.  I cannot find the podcast, the book, or the author, or any details of the story.  I have found the 1965 essay by Susan Sontag "The Imagination of Disaster", which I presume was an inspiration to the author I heard interviewed.

My questions are:

Is this story true?
Are there any scholarly references describing this story?
Does anyone know the book and author I heard about?


texts:
I am trying to bore out a red brass pipe from 3/8" to 10mm using my drill press and a standard twist HSS bit.  Running the drill at 600rpm I can't get more than half an inch in before the drill starts binding.  I tried running first with cutting oil, and then, thinking maybe the oil wasn't sticky/viscous enough, tried with Permatex silver, which only got me a few mm further before binding.

My guess is that I need some sort of metal-cutting bit that has a narrower shank so that there isn't friction except where it's actively cutting.  If so, what are such bits known as?

Is there any other practice I might be missing to make this work?


texts: MIPS Assembly stalls and forwarding when a register's value isn't modified in previous step

texts:
I'm going over pipelining and stalls and forwards with MIPS architecture, and there's a couple things I'm uncertain about.

If two adjacent instructions, such as the first two of each set bellow, both use the same register, but the first isn't actually modifying that register, is there still a stall? Like if the add and first addi of the second set each modified $t0, then yea, you'd want a stall because you'd want the updated $t0 value to be used in the next instruction. But here the result of the next instruction wouldn't actually be affected since $t0 doesn't change. So is there no stall in this case? Or is there a stall just because the register is in use despite whether or not it's being written to or only read?

And in the first set is the first addi between the add and second addi enough of a gap not to need a stall over $t1's use? Or would you stall need forwarding to help there?

add $t1, $t0, $t0
addi $t2, $t0, 1
addi $t3, $t1, 1

addi $t1, $t0, 1
addi $t2, $t0, 2
addi $t3, $t0, 3


texts: How to calculate the maximum size of a torus constructed in a given material

texts:
Consider a solid torus, which is a circular disk with diameter d with the disk's centre swept around a circle of diameter d, such that there is an open centre also of diameter d.  This torus is standing on its side so as to achieve its maximum height.  How it is supported so that it does not fall to either side is not an issue for this question.

For a given, arbitrary material, how can I calculate the maximum size that this solid torus could be before collapsing under its own weight in 1g?

For purposes of this question, consider the ground to be of infinite strength.


texts: How to choose a best sampling rate, according to time constant or bandwidth?

texts:
This is a follow up question of Rule of thumb for choosing a best sampling rate

I have a discrete control system with a reference input. The goal is to keep the output close to the reference input (like a room temperature control system). The difference between the output and the reference input is the error fed back to the controller, forming a closed loop.

The system has a dead time, as well as a time constant, both at the scale of 1 to 10μs. I have found the open-loop transfer function $G(s)$, and derived that the bandwidth is at the scale of $10^4$ rad/s. The fastest sampling interval of the output is at the sacle of 0.1μs.
The noisy of the input can be neglected, and the control accuracy is not very strict.

I want to find out an optimal, or at least good, sampling interval. Till now I find two rules to choose the sampling interval:

Sample time should be at least 10 times smaller than the time constant, as I decribed in the previous question Rule of thumb for choosing a best sampling rate
The sampling frequency should be between 20 to 40 of the bandwidth, which can be found in many papers and books.

As these two rules lead to different sampling interval (0.1μs to 1μs by rule 1 and ~10μs by rule 2), which rule should I take?


texts: What's the slowest airflow speed a ramjet could work?

texts: Thinking experiment about a flying device having the fewest moving parts, whats the slowest cruise speed achievable using a ramjet, no matter the scale of this device. Working altitude is troposphere. What would section cut view of this engine look like?


texts: shear force calculation with velocity and mass

texts:
I have made Image which is self explanatory. It has the question

Suppose I have a metal plate that is travelling at V m/s.
A stationary body acts as a shearing body. When the metal plate contacts the still body, it starts to shear off. The plane in which it will be sheared is shown in diagram (red line). So I want to ask how much force will get applied for the shearing.
This is just an idea that I'm working through. I haven't seen this in any book that I have read (I haven't yet seen various books yet). This problem came in my mind yesterday while I was dreaming.
Also I am assuming that the acceleration of the moving plate will be equal to change in velocity (after shearing the plate stops), so a = (0 - V) / 1 (unit time)
So question is

how much mass should be considered for the equation F = ma ?
basically I want to calculate force required.

If am wrong in some calculation then correct me.


texts: Is there such a thing as a modern-manufactured, flat, fake CRT TV?

texts:
CRT TVs were great, and an absolute must for all classic video games. However, it cannot be denied that it's impossible to buy a new CRT TV today, at least in any kind of normal store, and you rarely even see any old ones being thrown away anymore. At least not here. A few years ago, I would still spot them regularly just for picking up for free. Such is no longer the case, probably because all "normal" people have switched to flat screens at this point.
It's possible that somebody might find a "new old stock" CRT TV in a warehouse somewhere, but that's insanely lucky and I don't have any such connections (or luck). Besides, they are large, heavy and clunky. They will likely be impossible to repair or find spare parts for if and when they break. Opening one up myself and poking around can literally be lethal.
Hooking up a classic console to a modern TV never gives you the right look, not even if you buy a special "upscaler" device to put in between. (No matter how expensive the upscaler is, it just isn't logically possible because a completely different technology was used to display the picture with the old TVs. Maybe it can one day be accurately simulated with future, ultra-hi-res and superior to today's TV tech, but we aren't even close to there yet.)
This made me think of this theoretical "fake CRT", built new and physically flat, but not using the standard flatscreen technology of today, but rather some sort of "simulated CRT" technology. Is there such a thing? Imagine being able to order a flat, convenient 14" or 21" CRT "panel" that you simply place in your home which produces an image just like the old CRTs, but without all the problems that come from obtaining and keeping a CRT TV around.
I'm not looking for a general TV which also "doubles as" a retro gaming display, but a dedicated one which is only for retro gaming and has no requirements of displaying normal modern TV/whatever signals. All I want is an accurate simulation of what the CRTs produced, so that an expert eye could not tell the difference if you placed this thing on a wall next to an actual CRT which is built into the wall.
Is there such a thing, or is anyone working on one? If not, what's stopping this from existing? Too small market? Physical limitations that prevent this from ever existing?


texts: What is the straightest, longest and strongest pole that could be launched into space?

texts:
Which of these poles would be straighter and stronger then the others?

These are some poles that are compacted making them possible to send to space. Sending a single solid pole .5km long will not be possible.

STEM ( Storable Tubular Extendible Member), a pre-stressed piece of thin metal that could be rolled up like a carpenters tape measure. On Alouette electric motors would roll out the thin pieces, which would form tubular semi-rigid antenna once they were deployed.

Seamless gutter maker modified to make a round symmetrical pole.

http://zippermast.com/

Each pole produced would have the same weight per measure.

What advantages and disadvantages does each pole made from these methods have?

Are there any other types of extendable poles I am missing that could be added to this list?

How would a long pole be transported to space?


texts: Why do modern consoles require active cooling when old consoles did not?

texts:
I grew up with the Pong, NES, SNES, Mega Drive, Saturn, Nintendo 64, PlayStation, Game Boys, etc. None of these made any kind of noise when powered on. They were 100% silent. You just flicked them on, and they electrically were powering the game cartridge/disc with their chips and processors to full power.

Once the Dreamcast was released, that console and every other console after it has had these obnoxious, loud fans. So called "active cooling".

Why is it that the old consoles apparently had superior technology to the new ones? Why are the old ones not noisy whereas the modern ones (such as Xbox 360) sound like a jet engine when you turn them on?

Even if we exclude the major issue of the noise pollution, they just generally feel way more "fragile" than the old ones, since you know there's some fans in there spinning away at super speed to cool down this (apparently) badly designed system.

The Nintendo 64 was anything but "weak". It featured insanely advanced 3D graphics and effects, unthinkable for previous generations, yet still had no fan whatsoever.

There are "Raspberry Pi" computers today which also have no cooling, so clearly they are still able to technically make ones that don't require a fan.

Why, 23-24 years after the Nintendo 64 was released, is the only option to buy these loud, inferior (IMO) consoles? Why is there not a console like Nintendo 64 now, which makes zero noise and has no "active cooling" inside? With several decades of technological progress, what could they do today fanless?


texts:
What is the solar altitude at Bangalore at solar noon during summer solstice, March equinox, Winter solstice and September equinox? In other words, What is the solar window (solar altitude angle range) of Bangalore?

PS: Consider latitude of Bangalore to be 11 deg, North.


texts: Typical dirt bike clutches - is there a norm?

texts: I have several of the typical 49cc 2 stroke engines used for dirt bikes. They all have the same type of centrifugal clutch. Recently I have ordered a Honda GX-35 (4 stroke) engine and - what a surprise - it uses the same type of clutch. I am wondering, is there a standard for those clutches or why are they all compatible? Also are there clutches of the same format that engage quicker? For my Honda GX-35 I need to put like 25% throttle to engage the clutch at 4200 RPM, however I would like to have the clutch engage at like 2-3% throttle already. What do I have to look for to get something like this?


texts: How to prove Bossert inequality for the symbol error probability?

texts:
In the book : Coding theory-Algorithms, Architectures and Applications p.20, the authors have introduced the following inequality ( and precised that it was taken from Bossert's Channel Coding for telecommunications ):
$$\frac {P_{err}}{k} \leq P_{Sym} \leq P_{err}$$
Where $P_{err}$ is the word error probability and $P_{Sym}$ is the average symbol error probability.
While the rightmost inequality is intuitive, I cannot fathom the left side.


texts: Controlling temperature using PIDs on two separate controllers

texts:
I have a pellet smoker, and I am customizing it for tighter temperature control. Currently, I am controlling how much material is burning to control temperature using a PID loop. I want to achieve tighter control by also slowing down or speeding up the fan in response to temperature changes. I'm looking to find an algorithm that would allow these two to work together.

A pellet smoker works by using an augur to feed wood pellets into a burn chamber. Temperature is controlled by turning the augur on or off to control the amount of material that is burning in the burn chamber, and varying the speed of a fan to control how much air is flowing to the burn chamber.

Currently, I am controlling temperature with a PID loop controlling only the augur motor. The fan is running at a fixed speed of 90% of its maximum.

This leads to an acceptable temperature range, but I would like to achieve tighter temperature control by also using a PID loop on the fan speed rather than running it at a fixed speed.

I can control the fan with a completely independent PID loop. But I was hoping someone can point me towards and algorithm that would get them working together since they are pretty tightly coupled, and the fan influences temperature faster, but also doesn't work at all if the augur isn't feeding enough material.


texts: Deflection of Rectangular Plate with 2 Simply Supported Edges

texts:
As shown in the figure provided, a Uniform load acts upon a rectangular plate with edges at Y = 0 and Y = b which are simply supported.

Using this form of the Plate Equation:

$\frac{\partial^4 \omega}{\partial x^4} + 2\frac{\partial^4 \omega}{\partial x^2\partial y^2}+\frac{\partial^4\omega }{\partial y^4} = \frac{P}{D}$

Where P is the Uniform Load and,

$ D = \frac{Et^3}{12(1-v^2)}$

How do you determine an equation that describes the Deflection of the plate?

Also, how is load  'P' put into the equation?


texts: Can one move the zeros of a transfer function?

texts:
This may be a very simple question and I think I know the answer but I would like it to be confirmed by somebody else.

My questions regard the zeros of a systems (the roots of the numerator of a Transfer Function).

Question 1) Is it possible to move zeros around (kind of how one can do with poles)?

My current answer to this (correct me if I'm wrong) is no. The reason is because the zeros of the closed loop transfer function are at least the same with those of the plant (of course more zeros may be presented by a controller). As a results, regardless of the controller method, the zeros of the plant/system will not move. If this is correct, this leads me to my second questions.

Question 2) If the Plant/system has an unstable zeros, doesn't this automatically mean that, as far as loop gain is concerned, Robust Stability is never achieved?

The reason I think this is because if one plots the Root Locus, a pole will always move to that zero (assuming at least proper closed loop transfer function). So from a control engineering point of view, the only thing one can do, as far as stability is concerned, is to move the poles as far away from the imaginary axis as possible. The further away the poles, the more gain can be presented in the system that would not lead to instability.

Am I correct to think the above?

P.S. as far as Robust Stability, this is what I currently understand it to be. That being said, I am not very sure if it is correct.


texts: How does excess water makes soil compaction more difficult?

texts: I understand how water content helps compaction, by being kind of a lubricant between the soil particles, that helps them slide into position. But I don´t really understand how it starts affecting negatively after surpassing the optimum water content, but not surpassing the zero void line.


texts: How do I calculate the delay of two signals from different sensors?

texts:
Suppose:

I have two sensors attached to a vehicle
I have recorded the output of these two sensors (for example GPS) during a test ride
each sensor has a different frequency
one sensor is way more accurate than the other sensor

How do I compute the latency of the 'bad' sensor with respect to the 'good' sensor using the output data?
Example output data:
GPS 1
t (s) = 0, 1, ...
position (latitude, longitude) = (x_0, y_0), ...
GPS 2
t (s) = 0, 0.5, 1, ...
position (latitude, longitude) = (x_0, y_0), ...
I have considered cross-correlation, but I am not sure if it is applicable here.


texts: Effect of multiple shear pins used in combination in a coupling

texts: Does using multiple shear pins under a limiting torque case reduce the minimum required shear pin diameter for the coupling or is the complete load distributed over the shear pins regardless of the number of shear pins that are used?


texts: Determine elevation from the difference in air pressure

texts:
Given:

A problem in my thermodynamics text reads as follows...

The barometer of a mountain hiker reads $13.8$ $psia$ at the beginning of a hiking trip and $12.6$ $psia$ at the end. Neglecting the effect of altitude on local gravitational acceleration, determine the vertical distance climbed. Assume an average air density of $.074\cdot\frac{lbm}{ft^3}$ and take $g = 31.8\cdot\frac{ft}{s^2}$.

My Solution:

Our solution begins by solving for the change in air pressure and using this to determine elevation climbed...

$$\Delta P=P_1-P_2$$

$$=(13.8-12.6)\frac{lbf}{in^2}=1.2\frac{lbf}{in^2}$$

and...

$$\Delta P=\rho g h$$

rewrite as...

$$h=\frac{\Delta P}{\rho g}$$

But first we needed to convert $ft$ units to $in$ since that is how we traditionally define pressures in the English system...

$$\rho=.074\frac{lbm}{ft^3}\times\frac{ft^3}{(12in^3)}\times.03108\frac{slugs}{lbm}=1.33\times10^{-6}\frac{slugs}{in^3}$$

$$g=31.8\frac{ft}{s^2}\times\frac{12in}{ft}=381.6\frac{in}{s^2}$$

We can now solve for $h$...

$$h=\frac{\Delta P}{\rho g}=\frac{1.2\cdot lbf}{1.33\times10^{-6}\frac{slugs}{in^3}\cdot381.6\frac{in}{s^2}}=2364\frac{lbf\cdot in^2\cdot s^2}{slugs}$$

Answer in text:

$$h=2363\cdot ft$$

Question:

The scalar values are almost identical but the units just don't fit. Where did I go wrong?


texts:
I am affixing a servo motor with a machined enclosure to a base plate with drilled holes. The current design uses eight M-2.5 bolts in a figure U pattern (3-2-3) around the enclosure.

Tightening that many bolts/screws takes time, and the small gauge makes them finickier than larger-gauge bolts (missed nut thread starts, etc.)

If I were to change this design to use fewer, bigger, bolts, what would be the pros/cons of this? Is the amount of position slop significantly different between, say, three M-6 bolts, and eight M-2.5 bolts? Is there a formula for the affixing force that N bolts of size S will provide?


texts: Why is longitudinal slip necessary for car to be able to move?

texts:
Suppose, the wheels of a car were to be replaced with solid concrete wheels, which do not deform,flex, etc. Would the car not be able to accelerate, take corners, etc ?

I do not understand why is it necessary for tires to develop slip for them to be able to move the car.


texts: How does an air-bearing "pre-load" work?

texts:
I've been reading into air bearing recently and keep coming across the term "pre-load". References online and wikipedia both state that a pre-load helps stiffen the bearing such that their is less variation.

I'm guessing the pre-load ensures the air-gap is maintained/little variation.

However, I'm having a difficult understanding how adding some force (pre-load) would actually help with this.


texts: Momentum of a free-floating body being hit by a projectile

texts:
The Problem
I'm proposing a 2D problem in the x-y plane. Say there is a free-floating disk of radius R and mass Md (no velocity), at which a projectile is shot. The projectile (velocity Vp, mass Mp) has a velocity which is parallel to the x axis. If taking the disk's center for the origin, the projectile contacts the disk at a distance Y above the x axis, and it sticks (no energy lost).
The Question
I'd like to know what the ending velocity and angular velocity of the disk/projectile system is. Using conservation of energy, I end up with two variables, and I can't figure out what else to use to create a system (I'm very rusty on conservation of momentum, but I figure that's where the solution lies?).
Disclaimer
I'm not a student, if you're worried about doing my homework. Back in those days, I wouldn't have blinked at this, but now... software engineering has done me wrong XD


texts: Standards for safety car seatbelts locking condition

texts:
Is there an (international) standard which determines the condition when a car seat belt locks? Which standard is it? Does the standard determines a speed in m/s of the belt, such that it locks if this speed is exceeded or does it determine an acceleration in m/s^2? How are the values?

Is there also a standardized testing procedure to ensure that the values are satisfied?


texts: I need to conduct nano-indentation within a glovebox of a split-test cell for battery testing. I know that vibration may be a potential issue, and I should probably buy an isolation table. However, I do not know how to select the proper isolation table for this application. Does anyone have any advice? Thanks!


texts:
I'm trying to create a mechanical setup to transfer motion from a motor to two shafts. I need a method to do it that fits the following criteria to the greatest extent possible:

Does not slip
Does not introduce vibration

It's not a strenuous job with a lot of torque behind it. None the less I did quite like the idea of the chain or timing belt.

My question is twofold

A) Would a chain or timing belt introduce extra vibration to the system compared with a v belt?

B) Is there a way to get V belts slip free?


texts: How difficult would it be to build an entire engine (block and all) in 16th century conditions?

texts:
I was ruminating over A Connecticut Yankee in King Arthur's Court. In the book, a trained American engineer goes back in time and creates guns. The book itself predates tanks, but one could imagine shoddy homemade technicals rolling around in medieval England.

Question is: is that possible? Let's imagine we have the full support of an entire kingdom, and we're working purely from memory. We still have bad quality steel, primitive tools, and no CAD. Can we make an engine at all, even a terribly leaky one?


texts: Below what Froude number can I neglect wave-making resistance on a vessel?

texts:
I want to do some very simplified drag calculations on a vessel. My hope was that calculating the skin-friction resistance would be enough to get a good estimate of the surge resistance.

Because wave-making resistance is very speed dependent, I assume you can neglect it when the vessel is below a certain speed. I also assume that I have to work with Froude numbers instead of velocities, to take vessel size into account.

I have seen Froude numbers below Fn = 0.1 and Fn = 0.2 mentioned in books and on the Internet, but if you calculate the velocity for a vessel with a 100 m long waterline you get:

$$V = 0.1 \cdot \sqrt{9.81\ \text{m/s}^2 \cdot 100\ \text{m}} \approx 3.13\ \text{m/s} \approx 6.08\ \text{knots}$$

$$V = 0.2 \cdot \sqrt{9.81\ \text{m/s}^2 \cdot 100\ \text{m}} \approx 6.26\ \text{m/s} \approx 12.16\ \text{knots}$$

This values seem way too high in my opinion. 12.16 knots is almost service speed for some vessels and 6 knots is also quite high.

Are Fn = 0.1 and Fn = 0.2 reasonable numbers, and if not, below what Froude numbers should I stay to be able to neglect wave-making resistance?


texts: Analysis method for two-way slab floor with central column

texts:
What method would be appropriate to analyze this concrete structure?
A two-way rectangular concrete slab with walls and central column.

I would like to understand how to model it with either yield line method or equivalent frame method. Or both to be honest.

I'm studying those methods at introductory level, but haven't found any example of a similar case, so unsure how to draw out the analytical models.


texts: How the connection is between a Hollow core slab and an embedded beam?

texts:
If I have a rectangular embedded beam in a slab supporting hollow core slab how is the connection and detailing between these two elements ? (any sketch would help)

If the beam parallel to the hollow core how is the connection between these two ?

I need to know how the connection between the hollow core and the beam how is the bars between these two are connected ?


texts: Which way of solving from nonlinear control to choose?

texts:
I have a nonlinear system:
\begin{cases} x'=f(x)+u \\ y=f(x) \end{cases}
where $f(x)$ - gradient of some one-extremal function (for example $f=e^{-(x)^2}$), i.e. $\frac{df}{dx}$.
Task:
I want construct a continuous control $u$ that ensures the following condition:
$y(t)=y(0) e^{-\beta t}, \beta>0$
Which method to use for the solution: MRAC, asymptotic output tracking, feedback linearization, or something else?
I am not an expert, please do not pass by and give advice.


texts: Structural mechanics - computing bending moment

texts: I am having difficulties trying to work out one problem. I've attached a picture explaining the situation - the task is to determine internal forces in C but the bending moment M(x) doesn't seem to get me the correct results (I used equivalance and went from LHS). I would greatly appreciate if somebody helped me construct a correct equation or find the mistake, thank you.


texts:
I'm building a shelf out of an Oriented Strand Board (OSB-3), reinforced with steel strip attached to it's bottom side. Please check my calculations for deflection.

The OSB thickness is $h_{OSB}=18 \text{ mm}$, it's width $b_{OSB}=500 \text{ mm}$, I googled OSB's modulus of elasticity to be $E_{OSB}=3.5 \text{ GPa}$.
For steel strip it's $h_{st}=4 \text{ mm}$, $b_{st}=60 \text{ mm}$, $E_{st}=200 \text{ GPa}$. The shelf span $L=2000 \text{ mm}$. Load is uniformly distributed $q=500 \text{ N/m}$.

I approach the task with utmost utilitarianism, using online tools and off-the shelf formulas:

I transform area of OSB into steel:
$$b_{eq}=\dfrac{E_{OSB}}{E_{st}} \cdot b_{OSB}=\dfrac{3.5}{200}\cdot 500=8.75 \text{ mm}$$
I find moment of inertia of uniform inverted T-beam from step 1, using an on-line calculator:
$$I=16079 \text{ mm}^4$$
I obtain max deflection at center
$$d=\dfrac{5qL^4}{384E_{st}I}=\dfrac{5\cdot500\text{ N/m}\cdot(2000\text{ mm})^4}{384\cdot200\text{ GPa}\cdot16079\text{ mm}^4}=32 \text{ mm}$$

My questions:

Does OSB modulus of elasticity look legit?
Did I miss something, are the calculators and formulas appropriate here?


texts: What happens to sewage if there is no river near by?

texts:
I know that in places where there are convenient rivers and streams the tendency is to dump the communities sewage into those waterways so that it is carried away.

But what about places where there is no river nearby? So, for example in Phoenix, or other midwestern cities where rivers are either very small or non-existent, what do they do?


texts: What is the name for a bolt hole with a slot that allows the bolt to be inserted or removed when the nut is loose?

texts:
I can't find the name for this kind of hole. It allows the release of the plate by just loosening the bolt a bit, without having to remove it completely.

Searches using "teardrop" or "hole with oblong" do not return the desired results.


texts:
I am looking for a method changing the coordinate system of RBE2 or RBE3 elements.

Below is the nastran description of RBE2 in Nastran user guide.

There is no field for coordinate configuration.

Now, I am wondering if coordinate change is possible or not.

Could anyone explain how to change coordinate of RBE2?


texts: How to attach a cylindrical load to a motor safetly

texts:
The project is to rotate a load using a motor with a varying speed between like 2000-10000 rpm.

I'm using a flange coupling to attach the cylindrical tube to the motor. Since I will rotate it to high speed, I think I need to tightly and safely attach the load to the motor.

Do you have any suggestion on what coupling or what is the best way to attach the cylindrical tube to the motor safely?

NOTE: the shaft and load are the same lines. this machine is about centrifugal electrospinning which is a machine to fabricate a nanofiber.


texts: Curious of drawing a hole for M3 countersunk screw, 5.5mm or 6.5mm?

texts:
Hello all I am drawing a hole for M3 countersunk screw(flathead) I have checked the specs online the diameter of the head is largest 5.5mm thick 1.65 90degree

But when I draw a 5.5 hole 90degree it's only 1.3 thick as I remember, so I measure the actual product that comes with M3 countersunk it's roughly 6.5mm diameter

So my question is which size should I draw for a M3 countersunk screw? they're on 3mm abs plastic and 2mm aluminum, thank you very much.


texts: Mechanical engineering, Please help me finding the torque and answering other doubts too

texts:
Below I attached two BLDC motor commonly used for skate boards, I am confused with the calculation of stall torque for these two motors,What i need to know,

What is the maximum weight lifting capacity in the condition fig 1 and 2(x and y in kg)?
Is maximum lifting capacity is just below stall torque?
In figure 1 and 2 they mention torque as 1-2N in yellow motor and 1-2N/N in red motor what they are?Is it a mistake?
In red motor speed is RPN is it a typing mistake?


texts: What kind of protection should I give structural steel in a natatorium (swiming pool) environment?

texts:
What would be the best type of steel to specify? Would a heavy galvanization suffice?

Are there specialty paints/coatings available for this particular application? If so, how long do they last?


texts: How can you spin a pipe connected to a rotary union?

texts:
If I have a 4 inch PVC pipe connected to a rotary union, that I want to spin at 200-300 RPM -how do I do it? It appears like the rotary unions themselves have some lateral give -- So, I would need bearings?

Are there rotary unions with built-in motors? Are there motors that can have hollow, 4 inch cores? Does it make sense to get a custom gear machined for this purpose?


texts: Heat treatment processes for ferrous metals

texts:
I am trying to find out information about the heat treatment processes of ferrous metals as part of a project which involves making a screwdriver. This includes:

Hardening, Annealing, Tempering, Carbonising and Quenching

What happens to the atomic structure of the metal at each stage of the heat treatment process?


texts: What is this linear movement mechanism called?

texts: Does anyone know what this mechanism for linear movement is called? I have a different model of something like this, and the black chain appears rigid, so I assume it is the mechanism moving the laser head. I could be wrong though.