texts:
Do you need to take the bearing size tolerance into account when creating the tolerances for the mating hole/shaft when using ISO 286 tolerances?
For example, a 125 mm OD bearing with a desired H7 housing fit clearance should be +.04mm/-0. The bearing OD tolerance from the manufacturer is 125 mm +0/-.018 mm.
Should the hole size and tolerance be: 125 mm +.04/-0
or 125 mm +.022/-0 [.04 nominal clearance -.018 bearing tolerance]?


texts:
I want to build a small device (beacon) that can send its location (inside of a building) and can receive signals in order to output information on an LED screen. The beacon should communicate with a central unit.
So the device would be pretty similar to a Tile in many ways.

Here's a picture to illustrate the problem:

The beacon is currently located in area 1. When pinged, it should either send back its exact coordinates (so that the central unit can calculate that the beacon is positioned in area 1) or the current area id.
Once the beacon is moved, it should of course update its position.
The areas are inside of a building, always rectangular and I can install hardware on site (e.g. on the four emitters in the corners of the rectangles). The side length of the areas is between 1 and 20 meters.

Right now, I am evaluating different possible technologies. The biggest challenge is that I need 2-way communication.

Other requirements:

The beacon should have a battery life of several months
The beacon should update its location on a regular basis (e.g. once a minute) and on demand (when triggered from the central unit)
There can be up to 5,000 beacons in one area at a time. They all have to work simultaneously

RFID
+ Passive (no need for batteries)
+ Cheap
+ Location detection should be fairly easy with "gates"
- Range probably too short for my scenario
- No 2-way communication possible (would need additional module)

Bluetooth
+ Battery life with low energy BT
+ Range should suffice
+ 2-way communication possible
- Not sure how many BT beacons can be connected to the central unit at once (probably not 5,000)
- Not sure how locating the beacon would work (signal strength?)

Wifi
+ Range
+ 2-way communication
+ Connection to thousands of beacons at the same time possible
- Not wure how locating the beacon would work (signal strength?)
- Battery life?

I highly appreciate any recommendations, tips and improvements. Right now, I don't really know which way to take and it would end in a lot of trial and error :)

Thanks so much.


texts: Design behind typical keyed construction joints in concrete walls

texts:
Construction Joints

Construction joints in concrete footings or walls are places where the concrete pour can be stopped so that everything doesn't have to be poured at once. Later, once the concrete has hardened, the next part of the concrete can be placed against the previous pour. These locations are sometimes planned for in the design, and special details are added to the plans to show how the construction joint is to be formed.

A typical detail of one of these joints from MODOT is shown below:

These joints have a "key" formed in them so that when the next batch of concrete is placed, there isn't a flat shear plane across the entire wall thickness. The "key" is supposed to help to transfer shear across the joint. In the US, the blockout is typically formed by placing a 2x4 (2 in x 4 in nominally) board in the fresh concrete.

Sometimes a rubber or plastic waterstop is cast into the concrete at these locations to help keep water from flowing through the joint.

Shear key design

While I have seen this detail used many times, I have never seen a calculation done to design it. This exact same detail is used no matter what the thickness of the wall is or the shear force that may be acting on the wall.

How do you design (or check) a shear key like this?

Do you only consider shear-friction across the joint, ignoring the key?
Do you only consider shearing of the concrete in the key?
Is it some combination of the two?


texts: What is the typical rpm variance-tolerance of a roller bearing?

texts:
I have a high speed roller bearing rated at 3000rpm.

I know in the electrical industry that tolerances of around 10-15% are built into components so that they continue working in fluctuating electrical environments.

Is there a similar tolerance in the bearing industry ?


texts:
Could a Stirling Engine replace the cooling system of an engine?

Instead of having a clutch and fan attached to the main drive shaft to cool an engine, could a Stirling Engine and clutch share that drive shaft to cool and add torque? What problems may arise?


texts: Setup Invention Process in Engineering CAD Software

texts:
I need to develop a collapsible metal construction. I have a few specific prerequisites. Generally speaking, it will be something like a big construction toy, but not be a toy. It has the specific purpose - the basis of the obstacles for a cycling trial.

Many riders over the world make their own huge welded constructions. Usually they are heavy, unstable and cannot be completely disassembled.
The construction shall be based on standard square tubes and be

fully collapsible, up to individual pipes and connection points
based on triangles to provide rigidity, but the triangle must be able to disassemble into individual tubes
has maximum possible rigidity assembled
based on common tubes, bolts, connection points
easy to assemble and disassemble
has only a few universal types of elements
take up as little disassembled space as possible
has the opportunity to assemble in several ways
has the opportunity to easy assemble several concrete obstacles variants

The list above is just to show what kind of task I'm dealing with.
The rough sketchy set of the required obstacles ideas

Of course I cannot easily resolve the issue.
I'm not a design engineer. I searched for engineering CAD systems. I like the Autodesk Inventor functionality and ideas. The problem is that I don't have completely idea of the elements in my mind, and therefore I cannot just model the components. Furthermore, I have no experience in engineering systems, only a little experience in 3ds Max. But I hope a modern engineering systems could have the functionality to help the engineer invent the construction, not just create a model.
I need advice on how to build a workflow in Autodesk Inventor (or in some another software may be) for such the invention process. Automatic element updates, checks, suggestions in the software, some way to invent via top down design. What would your first step in the Inventor for such a task?


texts: When freezing rain brings down power lines, is it usually because the power lines have too little slack?

texts:
I did the math and figured out that according to the laws of physics, for any specific type of wire between poles a given distance apart, the more slack the wire has, the less its weight between those two poles gets magnified into tension force. When there's a buildup of ice on the wire and the wire has very little slack, the weight of the ice is already a lot heavier than the wire but the weight of the ice also gets greatly magnified into a force of tension that's much bigger than the weight of the ice on the part between those two poles. My question is

Did most of the places where part of a power line that fell down during a freezing rain storm fell down only from the weight of the ice on the power lines and not from a tree branch that fell down from a buildup of ice on it bringing down a power line with it? If so, did most of the spots where part of a power line fell down only from the weight of the ice on it have very little slack?

If so, this fact might be so useful for research. Maybe in the future, power lines could be built with more slack to account for the possibility that so much ice might build up on them during a freezing rain storm.


texts: How to turn a photo receptive sensor into an emitter of light?

texts:
I try to understand how is possible to turn a photo receptive sensor into an emitter of light.

Settings, tools, modulation..


texts: How to reduce tilting in self-made gimbal

texts:
I made a gimbal at home with PVC. Used some cement filled PVC pieces as hanging weight to make the phone steady. But when I shoot with it, I feel some tilting movements in the video due to the momentum of these weights. How can I reduce this?

Is it really possible to make a gimbal at home which can produce some decently stabilised videos? image of gimbal


texts:
I was reading about characteristic of a comparator.
It states
Comparator indicator device should be such that the readings are obtained in least possible time and for this magnification system should be such that the readings are dead beat.And there should be no backlash

Can someone kindly explain what is dead beat reading and an example about blacklash in comparator

Thank you


texts:
I want to fit a Hub motor ($15kW$ BLDC motor) to my car to convert it into a hybrid vehicle.
Would it be possible for me to use the same motor (as a generator) to charge my battery pack, while the vehicle runs on it's normal Internal Combustion engine?


texts: Determining the threshold condition of an ABS brake system

texts:
In an ABS system there are sensors on each of the wheels which determine the angular velocity in order to pulse the brake of an individual wheel which registers a diverging reading indicating brake lock-up.

My understanding is that when one of the angular velocities is significantly lower than the others, indicating that the wheel is sliding or about to slide, the system kicks in on that wheel.

My question is, what would the best way of determining quantitatively:

1) which of the wheels is in danger (some multiple of std dev from the mean of all wheels?)

2) how much deviation would be permissible, because there is always going to be a variation when the car is turning and we would not want to activate the ABS for such a situation.


texts: Switching a Circuit on-and-off In-step with the Rotation of a Drive-shaft (Mechanically)

texts:
I'm working on a project. The Salient part here is a drive-shaft connected to a bearing, onto which a simple circuit is mounted. I want to switch the circuit on every $π$ and off for the other $π$ of a full $2π$. In other words, I want it on for every half rotation. I want to do this mechanically because non-mechanical solution seem like they might be hard to sync. Also, the solution needs to interfere with the machine's operation as little as possible. It is a complex machine that will be subjected to high moisture and so forth, so ideally, the switching system would entirely co-rotate with the shaft.
I don't know if there are any 'ready made solutions,' or not, but i'd be thankful to be pointed in the right direction (towards something plausible), or told I should wing it and create something from scratch (presumably because there isn't any solution that can simply be bought at a hardware shop).
thanks.


texts: I have a very long beam which is subjected to a torque (I have the moments and shear forces with respect to X along the beam). I can calculate the critical load when the beam would bend if it was loaded axially, however I don't know how to calculate the critical torque on the beam before it "buckles" by twisting. How would I go about calculating this critical load/torque?


texts:
Section 3.12.6 of CSA-S6-06 mentions that

  "Ice accretion load shall be taken on all exposed surface of superstructure members, structural supports, traffic signals, luminairies and
  railings. In case of sign panels, bridge girders, and solid barriers,
  ice accretion shall be considered to occur on one side only".

Why in the latter part of the above statement, ice accretion is considered to occur only on one side?


texts: What is the most lightweight geometry for a vacuum holding vessel?

texts:
Referring to von Guiricke's early experiment to hold vacuum using Magdeburg hemispheres, what is the best known shape to hold say 10 atmosphere vacuum (external pressure) using any material or material combination without buckling its walls? I.e., using the least amount of material so that the vacuumed vessel is as lightweight as possible.

EDIT1:

Material choice relaxed in question as better materials are now available compared to Magdeburg test time.


texts: Would a cross correlation between vibrations in the X and Y directions help determine vibrations in the Z direction?

texts:
I have a 2D vibration sensor that can only measure in the X and Y directions, and it is mounted on top of a motor that is fixed into place, as shown in a rough sketch below.

Would I be able to work out the vibrations in the Z direction based on a cross-correlation of just the vibration in the X and Y directions?


texts: Why does rebar in reinforced pre-stressed conrete reduce in deflection if compressive stress is applied to member?

texts:
According to What is Prestressed Concrete? - Practical Engineering, one way to reduce deflection in the steel rebar is to pre-stress the rebar by applying compressive stress in the member before service which is done by tensioning the steel rebar.

My question is: Why does applying compressive stress to member decrease deflection?

especially with relation to the formula:
$y=\frac{FL^3}{48EI}$

where

$y$ is deflection
$F$ is force applied to member at $L/2$
$L$ is length of beam
$E$ is elastic modulus
$I$ is second moment of area


texts: Do PVC concrete joint water stops degrade over time? Or were they never installed correctly?

texts:
A UK subterranean reinforced concrete structure built in the late 1960s has experienced sustained water ingress over time as shown by the deposition of minerals of the walls:

According to the original drawings the construction joints were detailed with 190 mm PVC eyeleted watafoil waterbar.

My question: Has the PVC water bar degraded over the 50+ years since installation? Or was it never installed correctly and ground water has been leaking in ever since?


texts: How strict is the direction of air flow in a single direction pneumatic solenoid valve?

texts:
I am currently designing a small pneumatic system that pumps air into an airbag, holds the air in, then releases it to the atmosphere. Each pump in the system actually feeds two sets of airbags and solenoids.

I have decided to use normally closed (NC) solenoids as the air has to be held in the airbag for a long time (and I don't want to deplete my battery by energising a normally open solenoid for all of that time).

The set up is as follows: I have a dc pump, connected to a 2/2 NC solenoid valve, which feeds into the air bag. The second solenoid is connected to this line (using some kind of T connector) in order to release the pressure from the airbag when necessary. As mentioned before, the dc pump actually feeds two sets of airbags and solenoids.

My question: The first solenoid in the set up only needs to let air pass in one direction, however when it is closed it will likely experience a pressure differential in different directions at different times. Can a NC, single direction solenoid valve stay closed when the pressure differential is in either direction?

Here is a link to one of the solenoids that I am considering (warning - its a chinese site, so may run a little slowly)


texts: Why don't cellphones use unidirectional antennas?

texts:
Why don't cellphones use unidirectional antennas instead of omnidirectional (single dipole) antennas?

This could be accomplished by using a unidirectional array of dipole antennas (specifically, a broadside array) placed at different locations in the phone, where each antenna's phase could be changed in such a way to minimize radiation directed into the user's head and maximize radiation sent in the direction of the cell tower, producing a radiation pattern as is shown in the picture below.

But, with digital electronics, arbitrary phase-delays could be introduced to change the orientation of the major lobe.

Cellphone batteries would last longer and there would be less adverse health effects due to EMF exposure.


texts: Is there a type of check valve that allows gas to flow in both direction but stops liquid from flowing back?

texts:
I have a pressure regulator to maintain a specified pressure in a vessel that also contains a liquid. The regulator can pressurize or relieve pressure of the vessel. I want to prevent the liquid from flowing back to the regulator while keeping the gas flowing both ways. I can imagine a device that would do that but can't find a readily available one on the market. Any ideas?

EDIT:

I thought simplifying my problem was gonna help but now I'm thinking that sharing the exact context of my situation might help you help me.
So, this situation is happening on a counter-pressure beer canning machine (cheers!) The pressure regulator maintains a set pressure of CO2 in the machine's can filling tank. The level of beer is this tank is regulated by an actuated globe valve and the beer transfers from the BBT to the machine's tank by a differential pressure between the two tanks. During operation, the regulator has to supply and relieve pressure from the machine's tank (two-way flow). My issue is that if for any reason the beer supply valve doesn't close completely, the beer level rises up to the CO2 supply port, eventually overflows right into the regulator and ruins it...so as a safety, I want to install a check valve that would only close in the presence of liquid (beer) while allowing gas (CO2) to flow both ways the rest of the time.


texts: Why not use just one electric motor in a car?

texts: Instead of using an alternator to charge the battery, and  a starter to start the engine, why not just put one electric motor which is always connected with the engine? When we want to start the motor, we supply electricity to it; and when the engine is started, it spins the motor to generate electricity and charge the battery.


texts: Can pressure drops in a heat exchanger shell side be super low?

texts:
i'm a chemical eng. student from Italy and i'm "sizing" ("setting"?) a heat exchanger to cool some octane with toluene.

Is it possible that pressure drops shell side in a 1,2 pull-through floating head heat exchanger are lower than 0.001 atmosphere? I used really wide buffles and buffle cuts opened at 45%. The heat exchange is in range and the pressure drops tube side are "normal" (0.2 atm). I just find it weird that shell side they are so low. Can someone help me?


texts: Which Gen IV reactor types use nuclear waste as fuel?

texts:
I have read the Wikipedia article on Generation IV nuclear reactors, but from that article it is not clear to me which of the main reactor types that use nuclear waste to fuel the process. As far as I have been able to understand, Molten Salt Reactors (MSR) and some Sodium-Cooled Fast Reactors (SFR) are capable of doing this. Are there any other other reactor types that also can be fueled by nuclear waste?

Furthermore, when using nuclear waste as fuel, how large a percentage of the waste is actually consumed?


texts: Which way to put two fans for a wood shop air cleaner - paralel or series?

texts:
I'm building a small wood shop air cleaner to suck dust floating in the air. I understand a radial blower (squirell cage) is usually used to get some static pressure to overcome the resistance cased by the filter (for instance: Record Power 400). But as a radial blower is more expensive and quite a bit louder, I'm hoping to get about the same suction using two 19 cm (actual blade size) computer case fans (Spectre Pro 23 cm / 156 CFM / 1.81 mm H2O air pressure).
I understand that that putting them parallel doubles the air flow and putting them in series doubles the static pressure - not affecting the air flow much compared to one fan, but I still have a couple of questions with this:

Does putting the fans in series give anything like the same static pressure like the Record Power 400 has? Just an educated guess...  (the Record 400 is just an example of the approximate filtering  capacity I'd like)

Also, putting the fans in series doubles the static pressure, but is it that simple in an air cleaner where there is a under pressured air chamber/cavity (the space between the filter and fans) in front of the fans? Obviously two fans in parallel would cause a bigger under pressure in this cavity.

So which would filter better, the two fans in series giving more static pressure or two fans parallel giving a greater under pressure in the cavity between the filters and the fans?


texts:
I don't really understand the explanation in the circled part of the image below (from here).

From the diagram, we can see that the shear stress that cause the element to turn clockwise is positive, but in the text there, the author stated that the shear stress that cause the element that to turn clockwise is negative. So, which is correct?

[


texts: finding the center of rotation between 2 rigid bodies

texts:
I feel a little lost. I think my problem is quite simple, but unfortunately, my knowledge of math is also simple.

I have two rigid bodies that move relative to each other. I know two points of each body (see picture).

How can I find the place or point where the lower body rotates against the upper body? My idea was to just connect the points of each body and the intersection is the point I am looking for.  but this doesnt seem right.

Thank you in advance for your help, I really apreciate it.


texts: Maximum transmissibility of sky hook damper

texts:
I have been studying the sky hook damping system.

On page 14 of paper linked above, I found that the maximum transmissibility of sky hook system can be calculated by:

$$T_{max} = \dfrac{1}{2\xi}$$
where $\xi$ is the damping ratio and $T_{max}$ is the maximum transmissibility.

The condition for maximum transmissibility was $\xi>0$, and $\dfrac{\omega_d}{\omega_n}=1$ in the following transmissibility equation.

$$ T = \sqrt{\dfrac{1+\left(2\xi\dfrac{\omega_d}{\omega_n}\right)^2}{\left(1-\left(\dfrac{\omega_d}{\omega_n}\right)^2\right)^2+\left(2\xi\dfrac{\omega_d}{\omega_n}\right)^2}}$$

But, when I simply substitute $\dfrac{\omega_d}{\omega_n}=1$, I get the following.

$$T_{max} = \dfrac{\sqrt{1+\left(2\xi\right)^2}}{2\xi}$$

What is wrong with this equation? Could anyone explain how to correctly induce the maximum transmissibility of skyhook system?


texts: Why would a specfication for a motor require that overtemperature protection be realized by modeling heat generation and not with an embedded sensor?

texts:
I'm reading the procurement documents for the R211 railcar contract, which is for electric multiple unit subway cars designed for rapid transit applications in New York City. The railcar's propulsion is specified to use AC induction motors powered from PWM inverters with IGBTs.
The specification related to propulsion motor overcurrent is given as follows:

10.3.20.2 Over-temperature protection shall be provided as follows:
a) If the winding temperature rises 27°F above (15°C above) the operating class temperature limit, the control unit shall decrease the motor duty cycle by removing the dynamic braking and converting to frictional braking, until the temperature falls below the operating class temperature.
b) If the winding temperature rises above its design class operating temperature limit, the control unit shall remove power to the affected truck, until the temperature falls below the operating class temperature.  The condition shall be reported and recorded by the MDS.
c) Motor temperature shall be calculated using a thermal model of the motor and the power that the motor is handling.
d) The measurement of winding temperatures using embedded sensors is not permitted.

Points c) and d) stand out to me as a little bit strange, since the motor is expected to be modeled with its loads, instead of directly measuring the temperature. The only reasoning I can determine for this is that it protects against the failure of the thermal sensor.
However, it's not clear to me why this failure more is harder to guard against, than (for example) the failure of current sensors needed to track the motor's power, or an obstruction of the normal cooling process by dust or debris. Is there a common technical reason why motor thermal protection is specified to use only modeled heating rather than measured heating or a combination of safeguards?


texts: Which material is suitable to be fiiled in a thin-walled workpiece to increase the rigidity during the machining process?

texts:
My client is aksing me if I can manufacture a small but long strip-shaped aluminum-alloy (7075 T651) part. The sectional dimension is about 15mm by 12 mm and the length is about 1000mm. Ideally, this part shall be made as extrusions. However, the client just needs one piece of the product, so he asks me if I can manufacture this product by milling.
The main problem is that there's a through slot in the lengthwise direction, and the wall is very thin, about 1mm. The process I come up with is that I mill the slot first when much stock is left around it and hence the wall is thick enough, and then fill something into the slot so as to maintain/increase the rigidity of the part for the next milling process.

So my question is: which material shall I use?

Ideally, this material should adhere/stick to the metal part, and more importantly, it is easy to be removed from the part after I finish all processes. Maybe paraffin wax is a candidcate, but I suspect if it's strong enough. Someone suggested I use PVC soldering rod, but I tried and failed. It didn't stick to the part. I also considered expoxy resin, but it's not easy to be removed and cleared from the part.In thi case, I may need to polish the slot remove the resin. That would be annoying. Can someone here shed light on the material selection? Thank you very much.


texts: What treatment is necessary after welding carbon steel pipes?

texts: When welding stainless steel pipes, the welds need some treatment (e.g. ball blasting and pickling). Is there anything equivalent for carbon steel (not stainless)? I'm looking at a tender document where someone specified pickling etc. for C-steel and I'm wondering wether someone copy-pasted from the specifications for stainless steels.


texts: Using the bitrate value on a calculation is causing contradiction, why?

texts:
Do you have any idea on why the Calculation 1 below doesn't match?

Reference:

Audio buffers: frames, samples and channels

VLC - Media Information:
   num channels: 2 (stereo)
    sample rate: 44100 Hz
bits per sample: 32 => bytes per sample: 4
        bitrate: 192 kb/s
       duration: 7 mins, 23 secs => 443 secs

Windows - File Properties:
           size: 10,642,422 bytes => 10393 KB

Calculation 1 (without using bitrate) (using rounded values for simplicity)

1 second: 44100 samples => 44100 * 4 = 176400 bytes => 172 KB (looks a lot for just 1 sec)
This way: 443 secs => 443 * 172 KB = 76196 = 74 MB, but the file just 10 MB (!!! Contradiction !!!)

Calculation 2 (using bitrate)

 bitrate: 192 kb/s => 24 KB/s
1 second: 24KB => 443 seconds: 443 * 24 KB = 10632 KB = 10393 KB (like above) + [some metadata] (!!! Match !!!)

Thanks!


texts: Can I reduce the column moment due to beam, by setting the beam end to pin?

texts:
I have a structure, which contains only frame elements ( beam and column).

From what I know, if I apply point load at the columns on both left and right hand side,and if the beam-column joint is rigid, then the column at the center will experience extra moment, because the beam moment will be transmitted to the center column.

In other words, the center column will take moment because of the beam's existence, am I right?

In order to eliminate this extra moment taken by the center column, can I then set the beam-column join connection as pin? How would the structural behavior changes?


texts: What engineering topic builds upon the concepts of basic statics?

texts:
I'm interested in learning what I might call "advanced statics" but am not sure what concepts this would include in engineering parlance.

Would it actually be called "matrix structural analysis"?


texts: Is a pyramid considered axisymmetric? Why so?

texts:
I read a source, I will not reference the source on this platform.
They stated a pyramid is axisymmetric. Can you explain why if yes?


texts: Flanged connection studbolt length calculation

texts:
I am struggling with the ASME B16.5 code and the specified stud-bolt length that is taken into account in the tables (7, 10, 13, 15, 17, 19 and 21).

If you calculate the stud-bolt length according the "guidelines for stud-bolt calculation" for a NPS 24 Class 150 welding neck flange, the stud-bolt length should be 7.45in.

When I look in the ASME B16.5 Table7 the length is 6.75in this is 0.7in difference with the ASME B16.5.

What are the required number of free threads? As far as I am aware from bolt size 1in and up the number of threads per inch is the same and size S is fixed. If you keep calculating with S = 1/3 bolt diameter the number of free threads will only increase with no use?


texts: How to calculate the relative contribution of each mode in seismic dynamic mode analysis?

texts:
In structural dynamic mode analysis, one would have to carry out modal analysis in order to get different modes that contribute to the response of the seismic ( or wind) force. Here is a nice summary.

In a large structural model, there are so many modes, and we can't take them all. So we can only take the first few prominent modes ( with low frequencies), assuming that the modes will grow less and less important as the frequency becomes higher and higher.

Then the issue arises: how to judge the relative importance of different modes ( whatever the term 'importance' may mean?) I find that the often-cited mode participation factor

$\Gamma=\frac{\sum M \phi}{\sum\phi^T M \phi}$

doesn't work, because it depends on how we normalize the eigenvector, as one can readily see from the above formula.

Is there any other factor that allows us to judge whether a mode is more important or not?


texts: How can I calculate the evaporation rate for a hazmat spill?

texts:
I was given formulas for general evaporation, for a spill calculator I am building.

These are formulas, that are supposed to approximate evaporation, are for a number of different chemicals. Molecular weight is pulled from the chemical itself, same with vapor pressure.

We have a number of different spills at this location. Some spills will go directly onto asphalt/gravel or soil. We do have a number of different areas that have secondary containment, which is referred to as a "Berm", so that is the reason we have two formulas below.

Here are some of them:

General Evaporation Rate Formula From Asphalt

$$E =\frac {0.284 v^{0.78} M^{0.667}AP}{82.05T}$$
Where:

$E$ is Evaporation in pounds per minute
$v$ is the average windspeed
$M$ is the molecular weight in g/mol
$A$ is the surface area in feet squared
$P$ is the vapor pressure in mmHg
$T$ is the temperature in Kelvin

Evaporation Rate from Berm

$$E =\frac {0.284 \cdot \text{MW}^{0.667}(\text{Average windspeed})^{0.78}(\text{Surface Area})(\text{vapor pressure})}{82.05 \cdot \text{temperature in K}}$$

Surface Area Equations:
Scenario 1:
$l$ = Length of the liquid spilled
$w$ = Width of liquid spilled
$l \cdot w = A$
$A - (\pi \cdot (\frac {\text{Diameter of tank in berm}}{2})^2 \cdot (\text{How many tanks in berm}))$

Scenario 2: If we have 3 tanks in the berm
$l$ = Length of the liquid spilled
$w$ = Width of liquid spilled
$l \cdot w = A$
$A - (\pi \cdot ((\frac {\text{Diameter of tank in berm}}{2})^2)) \cdot (\text{Number of tanks of that diameter in berm}))-\pi (\frac{(\text{Diameter of tank in berm})}{2})^2 \cdot (\text{Number of tanks of that diameter in berm}))- \pi(\frac{(\text{Diameter of tank in berm})}{2})^2 \cdot (\text{Number of tanks of that diameter in berm}))$

I don't trust the formulas given, because they were given by another student assigned to this task. These formulas are not found in any workbook, website, etc. I am always skeptical about using other people's work without documentation making sure they have proof to backup their claims that this stuff will work.

I am asking precisely this: are these formulas suitable to use as an approximation for evaporation? If not, what would be a better formula?

I am not an engineer, I am a computer science/mathematics major. This project has nothing to do with school though. It is a work project.

Research
The closest thing I can find to an equation I can use is from here, but I am unable to decipher the characteristics it is asking since it is extremely technical in that field. I'm willing to do some research but I still have yet to find an acceptable formula/equation I can implement in this program. Another example is here where equation #7 is the formula it says to use for spills but I have no idea how it works.


texts: Technical term for loose drawers jamming more readily than those with tighter clearance?

texts:
A loose drawer or loose sliding parts in general jam more easily than ones with tighter clearance. There is a name for this problem but I can not remember what it is, and searching for "loose drawer jamming effect" is not helping.

There are simple recommendations that mechanical engineers learn involving the ratio of the depth of the motion and the looseness, perhaps 10:1 or 20:1 is a recommended minimum from what I recall, but now I lack the words to even search for this.

Can someone remind me what this principle is called?


texts: Measuring EM radiation power over surface area

texts:
I didn't make it obvious enough below that I was interested mostly in infrared, as the current use case is measuring power radiated from warm objects and from the ground. As pointed out in comment by @gerrit (thank you):

  You may want to clarify that you're interested in the Earth surface, so about 0.3 – 100 µm will cover everything you need.

In my naivety I first asked a related question over at Earth Science here. Ultimately, I would like to know how much electromagnetic energy power I could detect from an object or a surface.

For a home project, is there a way to measure how much EM power is being radiated from a nearby object? It's fine, preferable even, to ignore energy that radiates away from the detector and only measure what is captured by a nearby detector.

At work we have things like spectrum analyzers and power meters and such that measure power at different frequencies in wired communications, and that's similar to what I'm after, but I'm looking for a way to measure EM radiation, mostly infrared power.

If I could wave my hand and magically have exactly what I want pop into my hand, it would be a 1 meter square flat device with 1 side measuring EM power so I could hold it just above the ground and get a result of "1 watt" (1 watt per meter squared, since the device is 1 meter), or hold it next to a tree or a person and measure power coming off of them.

This is both for my own use (both curiosity and possible future personal projects), and also as a science project for my kids since my oldest one is experimenting with measuring power with a multimeter and solar panel.

If there is a type of device that does this, then that's great and the name of the device would be helpful.

If this kind of measurement requires a process (eg: "use device such-and-such to measure power at lots of points and then use method so-and-so to integrate across a square meter") then that is acceptable as long as it can be done by a hobbyist and doesn't require expensive tools worth thousands of dollars.

How do you measure electromagnetic power over a surface area to find the watts per square meter?


texts: What does the word "pararail" mean? I would like to know the meaning. Search over web does not help much.


texts: Estimating Maximum Speed for a Pneumatic Cylinder

texts:
I am designing an machine that is going to use a pneumatic cylinder to accelerate a projectile. I have a tentative cylinder specified, and am working on the control and supply side. I have verified that I can generate enough force, have enough air pressure and volume, etc. The next thing I need to figure out is roughly how fast I can expect the cylinder to be moving by the end of its stroke. Is there a way to estimate this that takes into account fluid dynamics?

Here's what I know:
the cylinder has a 4" bore and a 6" stroke.
The air pressure available is approximately 100psi (I expect I'll probably need to regulate it down to moderate the speed.)
The inlet port on the cylinder is 3/8 NPT, fed from a large tank via a short piece of 3/8" schedule 40 piping for a true ID of approx .493".
The outlet port is also 3/8" NPT venting directly to the atmosphere. (I will probably add a muffler, but we can ignore it for the purposes of this estimate.)

Simplistically, I know that once the full inlet air pressure is acting on the piston, the force on the cylinder is the effective area (12.6 square inches) times the air pressure (100 psi) for a force of 1,260 pounds-force. The mass of my projectile + the piston is around .3 slugs, so my acceleration should be roughly 4,200 feet per second squared. From that, I get a final velocity of roughly .875 feet per second.

Is this an appropriate way to make the estimate, or am I right in assuming that the cylinder will take an appreciable amount of time to reach full force and my actual final velocity will be lower than this? Is there a conventional way to estimate this behavior of the cylinder? If not, is there a way I can calculate what the pressure acting on the cylinder will be as a function of time to plug in to my model above?


texts: Why is it more reliable to use the land/pit transition in a CD-ROM?

texts:
I was reading about how CD-ROMs work and I came to this:

  Although it might seem simplest to use a pit to record a 0 and a land
  to record a 1, it is more reliable to use a pit/land or land/pit
  transition for a 1 and its absence as a 0,so this scheme is used.

Now, I'd like to know why?


texts: Changing (alternating non linear) screw motion

texts: I'm looking to put gradual pressure on a syringe.


texts: How do you find "this" Vx in the given circuit?

texts:
So I was told that $V_x$ is equal to 10V.
I tried reasoning out why $V_x$ was 10V and this is what I got:

-You can treat the Vx as an open circuit which means current does not flow through the resistor (meaning it's a short circuit) and thus from KVL we get $V_x$ = 10V

However, I am still not convinced that $V_x$= 10V.
A better explanation would be greatly appreciated.


texts: Why is oil used as the lubricant in power generators, while water is the most available, cheapest and accessible lubricant?

texts:
The lower viscosity of water reduces friction.  Besides, the water can transfer heat way better than oils.  So why not use water as a lubricant in wind or hydro turbines, especially on equipment which is operating in the ocean ...

It seems to be a perfect material.  It's the most abundant liquid on Earth, and it causes no ecological damage.


texts: Pulley question: Which 10N block will accelerate faster?

texts:
Background:
My professor for system dynamics at my university gave us an engineering dynamics concept quiz. A particular question I am interested in presented two figures I have re-drawn below. The pulleys are stated to have no mass or friction. No gravitational accelerations, or mass was given for the left figure.

My professor said (without proof) that the figure with the idealized force (right figure) will accelerate faster. I would like to know why.

I am posting here because my professor could not understand where my confusion was and thus could not answer my question to my satisfaction.

I thought that regardless of the source of force, the accelerations should be the same. How is this possible?


texts: How much ballast is required in 110 mph winds to stabilize: a 60 lb., 20’ pole; 3' below ground/17’ above ground, with a 24lb. wind turbine atop it?

texts: I can’t seem to find an answer that doesn’t involve more than a ton and a half of concrete. The manual for the wind turbine reports that the load on the turbine in a 110 mph wind is only 155 lbs. When I add the weight of the pole above ground that’s just over 200 lbs. Shouldn’t 3x or 4x that amount of weight in ballast be sufficient? The county won’t let me set up my alternative power system until I get a solid answer to this question.


texts: How to best mix a viscous fluid, multiple mixers or a single mixer?

texts:
I am designing a mixer for some 3D printer resin vats and am stuck on the best way to approach the problem. At the beginning I thought I should use three mixers in a line, all spinning in opposite directions so as to compliment each other (like an egg beater but with an extra mixer). But the more I research the less sure I am that this would be better than one, large mixer. Without doing a complex CFD I have no way of knowing which would be better.

I am hoping that someone with a bit more knowledge on fluid mechanics can inform me on the pro's and con's of each, and which approach would be better to mix fluid?

EDIT: I appreciate all the answers but they seem to avoid the question. I would just like to know the advantages of using a single mixer vs multiple mixers with a slightly viscous fluid.


texts: Sinking speed of particle in shear thinning fluid?

texts: For Newtonian fluids, the sinking (or rising) speed of a particle is (reasonably) well known. What is a relationship for shear thinning fluids?


texts:
I am wondering if there is a spring strong enough and light enough to inflate an airtight membrane so that it floats at Standard Temp & Pressure.

As an example, a 10cm cylinder would displace just under 1 gram of air, but a cylindrical spring would have to oppose 162kg of atmospheric force in that configuration.  Is there such a thing as a 162kg 10cm cylindric spring that weighs less than 1 gram?

But that's just one spring design.  More generally, what spring designs provide the highest rate/weight ratio?  What are the current practical limits on spring rate vs spring mass, and using what materials?


texts: Find average electron velocity on copper bus bar(um/s)

texts:
I was given this problem:

A current of 1,400 Amps flows in a copper bus bar.  The bus bar is 0.6 cm wide by 9 cm long.  You can assume the current flows only on the surface of the bus bar (so you can ignore the “depth” of the copper bar).  Find the average electron velocity in the copper bus bar.

Copper has a free electron density of 1029 electrons/cubic meter.

Charge C = 1.6022e-19 Coulombs

Current = i = charge times velocity

n = amounts of charge per volume

However because Im asked to ignore the third dimension of the copper bar
 Im not sure if Im solving this problem correctly

$$\begin{align}
i &= \frac{dq}{dt} \ldots \frac{n(volume)q}{dt}=\frac{n{A(V_dt)q}}{dt} \\
i &= \frac{n*A*V_dq}{dt} \\
V_d&=1.618E^{-8}um/s
\end{align}$$


texts:
When the box is upside down and filled with water, is it possible to rotate the white wheel freely without water being leakage by any method or any existing technology?

White is wheel and green is axle.


texts:
When I was in school, photosynthesis was taught as this amazing biological process that took light and water and turned carbon dioxide into oxygen and carbon. It was implied that this was limited to the domain of plants.

Have we industrialised photosynthesis so that we can shine light on a test tube and have it brake cardbon dioxide into oxygen?

My question is: Is there an industrial process that makes use of photosynthesis?


texts: I need help figuring out the most efficient way (NOT electronically) to manually compress plastic in a small confined space. I was thinking there were small compression shocks that would help to triple my human body force but have been unsuccessful in finding something that works.


texts: Why are rear wheels not placed at the extreme rear of a bus?

texts: In some cars, I have noticed the rear wheels are located at the extreme rear of the vehicle. However, I have noticed that the rear wheels of buses are always located about 1/4th of the way forward from the rear. What is the reason for this?


texts: Direction of the resultant force in hinge supports

texts:
In my lecture material on different types of structural supports, there is the above picture of a hinge. It is explained that a hinge is a type of support that exerts no moment on the rod, but prevents the end of the rod from moving. On the right, the supporting force is shown not to be necessarily parallel to the rod.

However, often in solving problems we assume that the force in this type of rod is parallel to the rod itself, such as here:

Why is it assumed that the force exerted by the hinge against the rod is parallel to the rod, if the resultant force in a hinge is not always parallel to the rod it supports?


texts:
How does water sink works?

I tried to do the same thing but the water just stayed:


texts: Imagine a source of oscillating magnetic field, say 10 Ghz.  Now change in a  magnetic field propagates at the speed of light,  assuming a vacuum. Consider point B to be 30 cm from the source. The change in magnetic field will take 1 ns to reach B.   Does this mean that B will experience changes at 10 Ghz but delayed by 1 ns? Is my inference correct or am I wrong?


texts: Is it possible to avoid the emission of CO2 and other greenhouse gases from thermoelectric plants?

texts: Since the deleterious effects of greenhouse gases are well known, I was wondering if it is possible, for example, for thermoelectric plants to avoid this kind of emissions. More exact, I think it should be possible to compress the residual gases at the plant's outlet into tanks. Of course this would imply a more expensive plant and also an higher fuel consumption due to the compression stages, but it would avoid emissions at all. Moreover there also would be the problem to store the tanks once they are full, however I'd like to know if this kind of strategy could be used in a real plant.


texts: Use of iron oxide as surface cleaning agent

texts:
Metal oxides are hard in nature, that's what my professor says. Technically  Iron oxide is a metal oxide and must be hard.

Then is it used in industries for surface finishing operations like buffing? If not, why so?


texts: Equal illumination of an actioncam's field of view

texts:
My goal is to have an array of LEDs arranged in such a way that I can light the view of my action cam. My action cam has a horizontal field of view of 175°.

My first idea was to determine the angle of light emission of a given LED and stack them next to each other, each time being rotated by their angle of light emission around each LEDs vertical axis. So if I have an angle of light emission of 15°, I need equally spaced 175 / 15 = 12 LEDs. To make mounting easier, I could create an element that is shaped in a circular way, so I don't have to calculate each rotation but only watch out for the same distances between the LEDs.

Then I would do the same for the vertical axis.

Is this the best approach or is there a better approach?


texts:
I am trying to get an idea of the amount of hydrogen that I can store in some pressurized steel tanks underground.

Based on the ideal gas law PV=nRT

I did a simple calculation
pressure = 200bar
volume   = 2000Liters
temp     = 25C

My results were about
16136.7 moles of hydrogen

1 mole of any gas is about 22.4 liters but that's at standard temperature and pressure.

At these elevated pressure it should be about 361,671 liters?


texts: Covariance of an uncertain vector going through an uncertain rotation

texts:
I have a vector $\omega$ and it associated covariance, a rotation $\mathbf R$ and its associated covariance. What is the covariance of $\mathbf R \cdot \omega$ ?
More rigorously:
I have an estimation of a vector expressed in the $A$ frame: $^A \mathbf \omega \in \mathbb R^3$, and its associated covariance $\Sigma_{^A\omega} \in \mathbb R^{3\times3}$. I also have an estimate of the rotation between $A$ and $N$ expressed by the vector $\mathbf \theta \in \mathfrak{so}(3)$ such that the rotation matrix from $A$ to $N$ is: $^N \mathbf R _{A} = \text{expm}(\theta) \in SO(3)$. This estimate of the rotation vector $\mathbf \theta$ has the associated covariance $\Sigma_{\theta} \in \mathbb R^{3\times3}$.
Given that $^{N}\omega= \;^{N} \mathbf{R}_{A} \cdot \,^{A} \mathbf \omega \;$, what is $\Sigma_{^N\omega}$ ?
Thank you.
[EDIT]: If the rotation is without covariance (fully known), then $\Sigma_{^N\omega} = \, ^N \mathbf R _{A} \cdot \Sigma_{^A\omega} \cdot ^N \mathbf R _{A}^\intercal  $


texts: Solar Thermal heat gain formula converted to CO2e and trees saved

texts:
We have invented a solar thermal heating system with interseasonal storage, recently patented. I want to display the trees saved and carbon offset on the control display based on temperatures coming down from the solar panels and that flow rate.

The pump station/controller has many sensors and we have added a flow meter. I can read the temperature rise (in from solar vs out to solar), & judge the flow rate (2-25L/Min) accurately. Typically the DeltaT is 15c but can vary wildly based on actual insolation. Flow rate is typically 15L/Min

I am trying to  build an algorithm to show CO2e offset. I need to calculate in energy terms (kWt or Mj) the energy injected into the heating system based on temps and flow rate. From that I can calculate the CO2e and trees saved.


texts:
WiFi at 60 GHz provides a theoretical data-rate of 7 Gbit/s. The trade-off is limited range and penetration. The main reason for this awesome data-rate is a 9 GHz bandwidth, from 66 GHz to 57 GHz. I think this is country/regulation dependent, so 7 Gbit/s doesn't depend on the full 9 GHz bandwidth. Instead of focusing on increased frequency, why not scrap all the obsolete bands and reassign the 1 GHz - 6 GHz range to WiFi?

The range and penetration of the 1 GHz - 6 GHz bands limit suitability to home usage. Therefore, does it need to be regulated as part of a global spectrum? Regulations should ensure availability of some bandwidth for other home uses only:
Punch out some small bands for bluetooth, cordless phone, TV remote, etc. (below the 1 GHz cutoff: cellular phone, NFC, etc.)
Adaptive frequency hopping to avoid local interference (other routers, microwave, etc.)
Backport latest technology from previous standards: QAM, MIMO, etc.
Make the standard versioned so newer features can be tacked on without requiring a whole new range.

Right? Now tell me why this is a pipe dream.


texts: Is a distributed load in two parts equal to a full distributed load?

texts:
I have a structure like such:

Due to my lack of knowledge of ANSYS, I have made the singular distributed loading (GI) represented as two distributed loadings (GH and HI).
Would this be an accurate model?

I feel like there should be some bending in the middle (HE to EB).

When I model it is a singular 240kN force on the center points I get:

Which of these would be more accurate?


texts: Are ABS/PLA too volatile to be used in cryo vacuum?

texts:
I need to use a custom part inside high vacuum (cryo vacuum), for example as a shadow mask. If PLA/ABS are not volatile, I could just print the part I need.

The question is, are ABS or PLA too volatile to be used in cryo vacuum chambers?


texts: Placement of a refractory wall excess temperature sensor?

texts:
I am working on a burner management system for a gas/coal fired pulp dryer. We are providing a thermocouple temperature switch on the roof of the firebox for an Excess Temperature Limit Interlock (per NFPA86 8.18.2). The code is ambiguous and the manufacturer of this old dryer has long been out of business. Some sources are recommending the temperature be measured in the refractory, while others are recommending direct measurement. Below the surface increases the reliability of the sensor while exposed gives you quicker response and slightly more accurate data.
Is it industry best practice (and/or code compliant) to install the thermocouple just below the fire side of the refractory surface, and calibrate for the small temperature reduction or should the sensor extend into the firebox?

NFPA86 excerpts:
"8.18.2.6* The temperature-sensing components of the excess temperature limit interlock shall be rated for the temperature and atmosphere to which they are exposed.
8.18.2.7* The temperature-sensing element of the excess temperature limit interlock shall be located where recommended by the oven manufacturer or designer."
"A.8.19.8 The sensing element should be positioned where
the difference between the temperature control sensor and
the excess temperature limit sensor is minimized. The
temperature-sensing element of the excess temperature limit
interlock should be located where it will sense the excess temperature
condition that will cause the first damage to the furnace
or work as temperatures within the furnace rise above the
maximum operating set point most critical to safe operation."


texts: Does anybody know where this calculation for the mass moment of inertia for an eighth of a circle comes from?

texts:
These attached photos describe flaps which are a portion of a circle and equations are attached as the mass moment of inertia, but there are no descriptions. I am using this for part of my research, but I do not know if this was something calculated through an integral or not, but I am very unaware of this being anything related to what the mass moment of inertia would be. The equations I am given are:
$$
l=2R \frac{\sin{\alpha}}{\alpha} \\
\alpha=\pi/8 \\
I_3 = m_3 k_{y'}^2 \\
k_{y'}^2 = \frac{1}{72 \alpha} [18 \alpha^2 + 9\alpha \sin{2\alpha} - 32 (1-\cos^2{\alpha})]
$$


texts:
Why is it not recommend to have pump shut off head lower than its operating head?
Is the answer related to dropping curve by any chance?
Also why is the discharge valve closed when starting the pump operation?
Any help on this appreciated


texts: I am working on a DIY project, I am trying to replicate a bar compressor which for some reason is only sold in Europe so I thought it would be fun to make my own without having to waste so much material. I simply want to make sure the force going down with the plate somewhat replaces a person to jump in the trashcan. Somewhere above 80+ lbs, since I am no engineer I was wondering how would one go about finding the force applied going down to the trash if about 50lbs is pulling down the lever. I understand that materials are key to this but as an amateur I just wanted to know how to get started. Sorry for posting here but I thought it would suit this page the most for this question. Thank you.


texts:
So lean times are upon us, and I started paying more attention to my car's onboard computer saying what the MPG is. I have a couple of questions...
Does engine braking really save fuel? The car states that the MPG while going downhill, foot off the gas and using a low gear is 0. If I put the clutch in (i.e. neutral), the MPG rises to a small but finite value (engine idling value).
In an ideal world the car should detect that work to compress the air in the cylinders is being supplied by the car going downhill, therefore it should shut off the fuel injectors. However, in my experience, going downhill in 6th gear actually speeds up the car compared to going downhill in neutral. Which means that fuel is being injected and the engine is generating power.
To summarise the above observations, when the car is going downhill:

Low gear - slows down car, onboard computer reports fuel consumption = 0.
High gear - speeds up the car (faster than neutral), onboard computer still reports fuel consumption = 0.
Neutral - the basis of comparison for both above, onboard computer reports idle fuel consumption.

As a rule of thumb, is driving in as high a gear as possible the most fuel economical way to drive? If I wanted to accelerate from a low speed, say 30 km/h, but don't mind the acceleration time (say I am in a clear road and in no rush), from a fuel economy perspective, is it better to floor the accelerator in 5th gear, or to apply moderate gas in 2nd gear?


texts: Kalman filter for sensor fusion — what is the advantage?

texts:
Is there any meaning of using Kalman Filter for cases when you do not have good statistical model of the system?

For example, if you have a drone and it has IMU sensor and GPS sensor. You do not have any statistical information, like variance, covariance, etc. If you want to estimate your current position, is there any advantage of using Kalman filter over just averaging the two sensors?

For the above problem, if in practice the Kalman filter has some advantage, what are the reasons behind it that I did not consider in my above example?

Thanks in advance


texts: Is there a name for a structure/building technique comprising three arches that share a central column?

texts: I saw a few minutes of a documentary that mentioned the domed roof of the largest mosque in Istanbul is supported by the strength of sets of three arches assembled so they share a common pillar. I'd like to learn more about that building technique but I'm not sure what the name is for that kind of structure. Also, can four stone arches share a central column or would the shared column likely collapse?


texts: AT Commands for FTP Server Connection on SIM Modem

texts:
I am trying to connect to a FTP server on a raspberry pi and transfer a file onto the server. I am using the SIM5320A chip on a breakout module and I am having trouble getting the module to connect to the server. I have forwarded the proper FTP port (21) on the router that the pi is connected to and I also have the vsftpd set up on the pi (which is a FTP linux program). I have tested the ftp server by transferring something from an ftp client on my computer to the ftp server on the pi and it works. I will post the commands I used as well as some of my thoughts. Please help me out and give me feedback.

AT+CGSOCKCONT=1,"IP","fast.t-mobile.com" (something I am not sure about is the apn, does anyone know if this one for tmobile is correct? I can't find that much information online)

AT+CFTPSERVER="xxx.xxx.xxx.xxx"

AT+CFTPPORT=21

AT+CFTPUN="*******"

AT+CFTPPW="*******"

AT+CFTPPUT="/files/fromcell.txt" - At this point i should be prompted to enter the text that is going to be in this txt file after I save, but instead of prompting me, the module waits while the red light on it flashes 200 ms on and 200 ms off which is supposed to mean that the data connection I requested is active. It then gives me an error that says "+CFTPPUT: 215" and this error code means "failed to connect socket".

Does anyone have any insight on what the APN is and how it should be set? I can't seem to find much else information on how to set it online.


texts: Does a washer really increase static friction force?

texts: Suppose I have a bolt that goes through a hole in a plate and is under tension. If I place a washer between the bolt head and the plate, does static frictional force (torque actually) really double? I'm assuming the bolt, washer, and plate are all of the same material for simplicity.


texts: Actuator recommendation for oscillating motion of a 6 kg object

texts:
I have a general question without many specific parameters, but I hope someone will be able to point me in the right direction - at least what actuator best serves my purpose.

I am working on a project where I will be moving a 6 kg object in an oscillating manner up and down, from ideally about 0.1 Hz to 20 Hz at different times. The max vertical motion I would hope to be 30 cm or so. I will be controlling the speed with a microcontroller via serial. It would be ideal to have some control of vertical range of motion, though this is not necessary if it proves to be too difficult. Ideally it would also be able to brake quickly.

I'm not quite sure how to go about this - my first thought was a servo, but I assumed that it would be difficult to get it to move up and down as quickly as I would like, and perhaps the startup torque would be a problem on the up stroke. It would otherwise be ideal as I could control the angle, and therefore the vertical range. Perhaps there is a very fast and high torque servo that can handle this?

I then thought of using an industrial sewing machine motor with a clutch to vary the speed, but all of these seem to use a mechanical clutch which would be burdensome to control (would have to use a separate motor to change the speed via a lever). Also, I would have to convert the rotation to linear motion, and I'd rather avoid making more complex parts if possible.

I also thought of a linear actuator, but these seem to be rather slow, and pneumatics are too imprecise.

Any idea as to what kind of actuator to use? I'm aware I am slightly vague in my usage - this is an art project so there is some flexibility as to how it turns out, other than the general parameters I've mentioned. Any suggestions would be appreciated.


texts: Multiple Electric Motors on single shaft to improve efficiency

texts:
I am trying to build a super-efficient electric boat. The dilemma I am coming across is this:

In normal long range running mode the boat will go at a slow 2.5 knots and only require 400 W power. This is the optimally efficient setting through the water. However for safety and practicality reasons like getting around in high winds etc I still need about 5kw max power available on the shaft. From my understanding any electric motor with a 5 kW capacity will be very inefficient at 400 W.

So my proposed solution is to put 2 motors on one shaft, a small one optimized for 400 W and a big one, the small one will be rigidly connected to the shaft and the big one via a clutch. I will then manually manually engage and disengage the large motor with a switch.

Can you please advise if this is a normal approach of if there is a better way to handle my situation? Am I misunderstanding something or reinventing the wheel?


texts: why we consider average current for dc while rms for ac in finding efficiency of half wave rectifier?

texts:
Efficiency= DC power output/Ac power input.
DC power= I²(av.)*R.
why average current?
AC power= I²(RMS)*R.
Why RMS current and not average this time?


texts: Angle Iron Cleat at Slab-Slab connection

texts:
We regularly bolt an angle iron against an existing building element (flange down), and use the flange as support for a new concrete slab. Is there any design approach to assist with the sizing / spacing of the chemical anchors as well as confirming the suitability of the angled section?  Epoxy anchors are one form of chemical anchor we use. There are other types of (chemical) bonding agents available like polyesters, vinyl esters as well as hybrid systems.

We have tried various design software packages none of them is very helpful with this configuration. Therefore a manual approach is all that is left, it seems.


texts: Could you recommend books on deformable bodies and beams (soft robots fundamentals)?

texts:
I'm researching about soft robots but most of the papers I've found have a very complex theory, which is making my study quite complicated. I was wondering if any of you who have some background on deformable bodies or beam theory could guide me in to the fundamentals of soft robots theory with some books you could recommend.
Thanks in advance.


texts: Is there any efficient way of using a large volume but low pressure (<2 bar) stored compressed air, either to drive an engine or some other application?


texts: Is it possible to "add" suspension systems?

texts:
Suspension often requires different ranges of behavior. Small amplitude and high sensitivity for vibrations and small sharp bumps but also high amplitude and low sensitivity for larger smoother road deformation.
So my question is whether or not it's possible to use two suspension system on top of the other.
I was thinking of a small fast shock (strong spring with weak damper) for small amplitude/high frequency and then a long slow shock (weaker spring with a stronger damper) for high amplitude/low frequencies.

My main concern is of course interactions between them.

Do you have any example of this setup?

Thanks


texts:
I am just posting here to verify that I am properly using a tool that is new to me, a micrometer. Here is what the precision label specifies, basically that it can measure up to an inch and down to 1/1000" (a notch on the round scale).

I would like to describe how I was converting the reading on the linear and on the round gauges and you tell me if I did it right.

In the above picture, the linear scale is reading 2/10" and the round scale is reading 15/1000".  So the total gauge I am measuring is 0.2" + 0.015 = 0.215".  I am particularly curious to verify if the round gauge's each notch is indeed 1/1000" and whether I am using the correct numerator in the fraction.


texts: (Non)simultaneous prestressing anchorage slip losses

texts:
Post-tensioned prestressed concrete beams suffer from a multitude of losses. When jacked, they suffer friction losses and their tension diagram is, for example (to simplify the drawing, I'm using the linearized version of the friction loss equation here. It also goes without saying this is all horribly out of scale).

This diagram obviously represents a beam prestressed from both ends. Also, the cable's path is clearly non-symmetric, with the right side probably being excessively curved, while the left is probably far smoother. The dotted lines simply demostrate what the digram would be if the cable were prestressed from only one end.

When the cable is then anchored to the concrete, the anchorage slips into the concrete, causing losses. These losses, however, are limited by friction to an area around the anchorage since the cable has by this time already been grouted. We can define the point where anchorage slip losses end as $X$. An anchorage slip of $\delta$ is by definition equal to
$$
\delta = \int\limits_0^X\Delta\epsilon_p(x) dx = \dfrac{1}{E_p}\int\limits_0^X\Delta\sigma_p(x) dx\\
\therefore A_pE_p\delta = \int\limits_0^X\Delta F(x) dx
$$
where $x=X$ is defined as the point where the anchorage slippage losses end.

We therefore have a relation between the constant $A_pE_p\delta$ and the area between the force diagram before and after these losses. All we need to do now therefore is find $X$ such that the equality is satisfied. For simple cable paths there are some analytical methods, but they aren't relevant to this question.

If the slippage losses are small enough, we just need to calculate the losses for each side, such that $A = B = A_pE_p\delta$:

That case, however, is quite simple. From now on, I am less sure of whether what I'm saying is correct, so please correct me if I'm mistaken.

If, however, the losses are such that one side interferes with the other, it is easier to find an area $A+B+C = 2A_pE_p\delta$, where $A=B$, point $D$ is defined as the point where the losses first encountered each other and $C$ is simply a uniform loss along the entire cable that occurs once point $D$ is reached:

My first question is: is this a correct calculation of the anchorage slip losses in case the anchorages are released simultaneously? Is there a simpler (but generic) method?

The other question is what if the anchorage slippage losses are not simultaneous?

For the left side we may find $X$ and reach the following result, where the area $A = A_pE_p\delta$:

For the right side I'd consider calculating the losses on the friction diagram considering that the cable was only pulled from the right side, so we get the area $B = A_pE_p\delta$:

We can then throw that on top of the results for the left side and get the following, where $C$ is the area overlapping with $A$ and $D$ is the part of $B$ after the end of $A$ ($C$ is contained within $D$ which is a part of $B$):

So, what now?

Should the area $D$ be transposed to accompany the force profile after the left anchor settled?

Is this correct? Is there an easier (but generic) method to solve this case as well? Throughout this, I've made use of the assumption that the friction (and therefore anchorage slip) losses are linear, which they are not. Other than the mathematical headache of dealing with exponential equations, is there anything here that simply won't work using the losses' true exponential form?


texts:
We shared Mechanics of materials with structural engineers back in college. I learned some basic concept about structural engineering, but besides the basic knowledge i don't know anything about structural engineering.

If i recall correctly, an engineer found a way to distribute the weight of buildings over a wide area to reduce the stress, i think he managed to solve the problem of sinking buildings for the first time in Chicago, and up to this moment, his solution has been popular.

If the area has a strong bedrock, manhattan for instance then, the buildings are much more stable, but my question targets the areas with very weak bedrock, The Hague for instance.

I can say, there is channel is every street, when i walk in streets i can actually hear the vibrations of water beneath my feet, if you dig the ground four or five meters, in city centre you'll reach water.

I wonder how engineers manage to build skyscrapers in this area?
The concentration of tall buildings is not as same as in manhattan, Chicago or ... . But still, how those few tall buildings are still on the ground?


texts: Proccess of a 4-wheeled vehicle taking turn

texts:
I have observed that when a 4-wheeled vehicle takes a turn, one of it rear tire moves with more speed as compared to the other. For example A car is taking right turn, its right rear tire will be slower as compared to left rear tire.

How is that done?
Without this system, the vehicle wont take a turn and collapse.


texts: How to use the moment-of-momentum equation for water flowing through a pipe?

texts:
I am having a lot trouble understanding this problem, I don't even know where to begin or how to articulate my difficulties, but I will try my best.

Is the question asking to find the torque developed at the part in the picture where it says "Pipe supported by wall"?
What is meant by the "Horizontal section" of the pipe? In the solution it says that it's going 24 in. into the paper. Okay, so what? Is water flowing through there? I thought it was flowing through the pipe supported by the wall. Or is it flowing through both the pipe support by the wall AND the pipe section that's going 24 in. into the paper?
In the solution, I don't understand how the moment arm for the inlet flow is zero and the moment arm for the outlet flow is 24 in. Where is this being measured from? I thought it was being measured from the "Pipe supported by wall"? Where is the force being applied?

I apologize for my extreme confusion. I will be extremely thankful for any help that I can get.


texts: How would I find the Second Moment of Area of a Parallelogram?

texts: How would I find the second moment of area of a parallelogram, as shown?


texts:
As an example of my question, imagine I have a small generator attached to a bicycle pedals. If this generator is connected to one light bulb, how would it compare with the generator being connected to multiple bulbs?

My assumption is that, as you add more bulbs, either;

The resistance on the pedals would remain the same, but you would now have to pedal faster in order to light the bulbs to the same brightness, or;
It would become harder to pedal when the extra bulbs are added, but the same rpm would be needed to produce the same brightness.

Which (if either) of my assumptions is the correct one?


texts: Motors for an omnidirectional RC toycar (with mecanum wheels)

texts:
First of all, apologies if this is an Arduino question. IMHO, I felt that the questions is more about motors and their comparison.
I'm trying to build an RC toycar using mecanum wheels.
The vehicle will have a standard 4 wheel configuration:

So far,  I'm planning to use an arduino mega for the communication and control
of the wheels.
In order to obtain the omnidirectional movement and rotation, I need 4 different motors (one for each wheel), to control the speed for each wheel.
I've sorted out communication with the remote control, and also figured out the relevant equations that determine the wheel speed based on the $v_x$, $v_y$ and $\omega$ (rotation).
Now the only thing that remains is selecting the type of motors to use.
The main option I'm considering right now is using a stepper motor driver like A4988 with a NEMA 11 or 14.
The main benefits I see with this design its the following:

I can control the speed for each motor.
only two pins are required on the Arduino mega
software control is well documented.

Possible disadvantages are:

not extremely efficient
possibly not the maximum speed, nor torque

However, I'd like to ask what other motor designs/configurations should I consider (e.g. BLDC's, DC, servo with speed control). I would be very interested in a possible configuration and to its the relative benefits/drawbacks with respect to my baseline option with regard to the following parameters:

pin requirements for control
requirements for external electronic devices (eg. ESC)
max speed
max torque
efficiency
control documentation for arduino
is it possible to control speed


texts: Can I replace terminal weight with an even stricter matrix yet ensuring stability?

texts:
Terminal Penalty is used to ensure stability of Model Predictive Control (MPC).

where the initial cost function is

$$J(u)=\Sigma_{i=1}^{\infty}[x(k+i)^TQx(k+i)+u(k+i−1)^TRu(k+i−1)]$$

it is modified to

$$J(u)=\Sigma_{i=1}^{p−1}[x(k+i)^TQx(k+i)+u(k+i−1)^TRu(k+i−1)]+x(k+p)^TQ_px(k+p)$$

The terminal penalty matrix $Q_p$ is calculated from solving a Riccati equation:

$$Q_p=A^TQ_pA−A^TQ_pB(B^TQ_pB+R)^{−1}B^TQ_pA+Q$$

I am wondering what if a matrix is used which has higher magnitude members? Does it still guarantee the stability?

For example if $\beta>1$, can I replace $Q_p$ with $\beta Q_p$ yet ensuring stability?

or if $(Q'_p-Q_p)$ is positive definite, can I replace $Q_p$ with $Q'_p$ yet ensuring stability?


texts: LTE coverage signal for different category

texts:
Been asking this earlier in Electronics,

Cellular provider said they mostly have LTE CAT 6 signal on my area,
will that means i am able to use them for other LTE's lower than that
category? Or they each have separate signal? Because from what i see,
either CAT 4, CAT 1, CAT M, or even NB cellular module i had have the
same frequency bands supported by that CAT 6 (specifically,
B1/B2/B3/B4/B5). I couldn't find answer elsewhere. Any input is really appreciated

To summarize,
Supported on my area: LTE cat6 - bands B1/B2/B3/B4/B5
Supported on cellular modules: LTE cat4, cat1, catM, NB - bands B1/B2/B3/B4/B5
Will it work?


texts: What is the reason for the intermittent motion and blocking of light during change of frame in Conventional projector?

texts:
Conventional Film projectors do not advance
from one frame to another by continuous movement of the reels. What is the reason for the intermittent motion and blocking of light
during change of frame in conventional film projector?what is the mechanism used in the projector to
achieve these two processes?


texts:
I have a drop of molten glass (but could be every solid with high plastic behaviour), and my goal is to calculate the max force during impact.
I think I could use the velocity at the impact point to calculate force like the drop will be a damper, but how can I correlate viscosity with dampening of an "ideal" damper?
Thanks


texts: Mecanum wheels begin to make robot spin around rather than move to the side

texts:
I am using mecanum wheels to steer my robot which I am programming using an arduino. The main problem that I am having is that whenever I attempt to make the robot move sideways like this:

Instead the robot is doing something along the lines of this:

Or this:

Either way, I was firstly thinking that this problem might have came from weight distribution, so I put the battery pack in the centre of the robot rather than having it at the back. This did nothing.
My next consideration that I am having could be to do with the power sources, I am using 6 1.2V AA batteries (all in series I think, I am not the best when it comes to electrical power, I am on more of the programming side).
What I have are 4 motors, the 2 front motors are connected to the the front motor driver and the 2 back motors are connected to the back motor driver. One incline I have is that the power the 2 motor drivers are getting is not correct in some way.  What I have are 2 wires each for the voltage for the motor driver, both of these wires are connected up to a piece of cabling which allows 2 pins to connect to 1 pin (like an adapter). These 2 pins for the voltage connect to the cable and the other 1 pin on the cable connects up to the 7.2V pin on the arduino pin.
The same type of cabling that I have mentioned above is used for the ground on the arduino as well.
One thing I have observed is that when the motors are moving the LED built into the motor drivers (this goes for both motor drivers) begins to get dimmer. The next idea I had after this was that perhaps one of the rollers present on one of the wheels is quite stiff. The final idea I had and I think might be causing the problem is that one or two wheels are having a large force acting down from the due to them not perhaps working properly.


texts: Difference between PI and PD controller?

texts: what is the difference between a PI and a PD controller? In which instance or for what kind of sensor(s)would you use one as opposed to the other?


texts: What is the contact area between threads and how does it change?

texts:
"https://www.youtube.com/watch?v=3l6EcBg9EPA" [@24:30 - 25:10] He says something about the load of a threaded interface being on only one small part of the spiral. To me this seems a bit odd right?

How much contact area is there really between a screw and a nut? "Where is the contact point between screw spindle teeth and nut teeth?" - Here one answer suggests that it's dependant on the thread type and tolerances which makes sense, but I couldn't find any reference values in my machining books, besides this link which briefly mentions a contact area of 30-35% without further explaining it "https://fastfixtechnology.com/rail/the-benefits-of-lockbolts/"

Can you even talk about "contact area" or is it like with the teeth of gears more like a contact line?

Isn't the contact area almost 100% along the whole thread because of the elongation of the screw when torqued down correctly?

Why doesn't this value apear when calculating screws, as I would imagine it to be important when considering surface pressure between the two threaded parts(e.g. what material to use)?

I guess it's important to mention that I was thinking about machined threads not self tapping screws or something like that.


texts: What is the value of Nusselt number in laminar flow?

texts: In a laminar flow along an Annular cross section with heating in one side and insulation in the other, what is the value of the Nusselt number in this flow? and is the diameter in the Nusselt expression Nu=h*D/k the hydraulic diameter?


texts: Will decreasing a pump's flow rate decrease the NPSHR?

texts:
I have a small open hydraulic system and I simply need to circulate hot (85C) water from the bottom of a reservoir back into the top at ~4GPM. At its lowest point the system has only 3ft of static head. The problem is that all the pumps I've found so far can't run without an inlet pressure (NPSHA) of 9ft because that would cause the water to flash inside the pump and the cavitation would damage the pump. I can't pressurize the system and I have no place to lower the pump to increase the NPSHA. Will closing the discharge valve after the pump lower the NPSHR and if so would it be enough to be able to safely run the pump?
Pump in question is Grundfos UPS15-58FC.


texts:
I was wondering how a minute repeater works - it is a complication in a watch that chimes the hours, quarter hours, and minutes.

For instance, if you engaged the repeater, and the time was 2:47, the watch would chime

dong, dong, ding-dong, ding-dong, ding-dong, ding, ding

What are the mechanisms needed in order to make this happen? There are probably many ways to build one. How would one describe the workings of the simplest minute repeater possible?


texts: Diffusers in turbomachinery are used to transfer some of the kinetic energy of the fluid to pressure energy and to direct the fluid to the ducting/second stage/... I understand this and the mechanism behind it (geometry of diffuser changes the mass flux which creates a pressure gradient which decelerates the fluid) but I just cannot find any information how diffusers create more suction at the inlet of the pump/compressor. In laymans terms, how does the diffuser make the pump better for the end user? Is it more efficient?


texts: Flash Corruption - Power Supply or X-ray Radiation?

texts:
I work with a system in which the microcontroller is exposed to X-ray radiation from time to time. Exactly how much radiation is hard to say... we've never measured it.

Anyway, we've seen a mysterious form of flash corruption on a small sample of our products in which random bits in code space are transitioning from 0 to 1.

We've previously attributed this to power supply issues and the controller not being reset quickly enough while data logging is going on.

But now we may be seeing it on a newer version of our product which has a higher end controller with better brown out protection.

Is it time to consider X-rays as a possible source?

The X-rays would be released due to breaking current high currents with a vacuum interrupter.

Has anyone ever heard of something like this before on nand-flash? Most of the articles I have seen have been with respect to Airport X-rays or X-ray inspection used in PCB FAB


texts: Designing a 1-button system allowing for a differentiated control of 2 different valves?

texts:
I'm in the processes of building something which requires I'll be able to control the independent opening/closure of two (small, ~10mm in diameter) different adjacent holes using one finger, and I'm trying to think of ways such a thing can be put together.

The movement required from the finger shouldn't be too convoluted, so my original vision involves having the two holes open when there's no pressure applied to the button, and then when the button is pressed half-way through it closes only one hole while when it's pressed all the way down it closes both holes.

The control in such a situation might be tough to perform with accuracy, so my other idea involves having the button's resting position rather at the middle of the available movement, allowing it to be moved up or down while the middle position leaves only one hole open, the upper position opens both and the lower position closes both (in this case the "button" won't be a button but rather a "cup" of sorts you can place your fingertip into).

The closed-open combination is unidirectional, so the possible closure patterns required are either both hole¹ and hole² open, hole¹ open and hole² closed, or both closed, but no requirement to have hole¹ closed while hole² is open.
They should be able to close the holes against the air pressure of exhalation (or less actually as there would be ventilation elsewhere).

I think the hole-closing structure itself would involve padded surfaces dropping onto each hole to cover it.

Any tips how could such a mechanism be built?

Thanks in advance!

EDIT (additional info):
I think some further clarification is required. The holes would be situated on a cylindrical surface. The controller should be placed at 90 degrees to the two holes (so it doesn't continue in the same line of direction), and the closing surfaces should open plenty so there's no obstruction in air flow, and possibly open to the side opposite the controller. Here's a rough sketch:

Obviously this is not an actual mechanical design, just guidance for the wanted form.


texts: Grinding Forces Problem - CNC on Zerodus

texts:
We, my colleague and me have follownig problem and now weIwanted to ask if you can provide us any help. It's the first time we are posting in this forum, so we are thankful for any ideas or input provided.
We are grinding Zerodur with a CNC milling-machine (5-axis) and want to calculate the occuring forces.
The glass is fixxed with beeswax on a glass plate. The glassplate is held with vacuum on an aluminium fixture. Between the glass plate and the aluminium is a rubber seal, for sealing the vaccum.
The grinding pencil consist of diamond coating on steel. Now we want to know which forces occur between CNC-grinding tool and the glass workpiece.
The simplest model we could bring up is calculating the static frictional force. In this case we say the zerodur work piece is a part of the glass plate.
And we want to calculate the maximum appliable force by the CNC-tool without moving the glass plate.
Thus we thought of calculating the static frictional force which is Fs = us * Fn.
us ... being the static friction coefficient between rubber and aluminium (have to look it up).
Fn ... normal force acting on the zerodur-glass workpiece.
Fn = Force(Weight of Glass plate) + Force(created by the suction of vacuum-pump)
Our idea was to calculate the normal force consisting of the weight of the glass plate and the force created by the vacuum suction below the glass plate.
The force created by the vaccum suction is Fv=A*p. With A being the area of the rubber and p being the pressure difference acting on the glass plate.
Now we wanted to ask if you think this approach is right. And what other forces during grinding should be consindered regarding rotation speed, feed rate and grain size of the diamond tool.
Pictures of the workpiece and the diamond tool are attached. The green fixture holding the glass plate will be replaced by an aluminium fixture.


texts: Attempting this kinematics question but not really understanding if what I'm doing is right or completely wrong. Should I be starting by finding Vp? Any help appreciated. Not an assignment, just practicing.


texts: Is the smaller gear (pinion) always mounted to the input shaft when meshed with a bigger gear that is mounted on the output shaft? Are there places where the bigger gear drives the smaller gear?


texts:
I've been working on implementing a new company standard for our file naming convention (super fun), and it has been mentioned to me that there is a "standard" that says that you shouldn't use spaces in file and folder names when saving documents.

I've done some looking and I haven't found a published standard that says one way or the other whether this is acceptable. Does anyone know of a standard relating to this?

example

"Released Drawings" as opposed to "ReleasedDrawings" as a folder name

or

"123 - Rev 0 - Important part" as opposed to "123-Rev0-Importantpart"

I'm hoping to find a a specific standard, not just a rule of thumb, or best practice.


texts: How can I couple two shafts along the same axis so that they rotate together, but only one shaft is allowed to drive the rotation?

texts:
This question is going to have an application in aviation (to avoid doubts and relocation to other forum) but let's concentrate on theoretical mechanics here.

If I want to allow a shaft to rotate in one direction and not the other, then a ratchet would be a solution.

But what I need is a base/platform with shaft M (master) and shaft S (slave) connected to each other the way that if I rotate shaft M (both clockwise or counter-clockwise) the shaft S will rotate with the same speed and direction. But if I try to rotate shaft S in any direction it should not be possible the same way as if I tried to rotate a ratchet in blocked direction.

What is the name of a device I described?

Shaft M --> ===[Device in]=== <-- Shaft S
_______________[question ]________ <-- platform


texts:
I have a building that is 7 story height (which 5 stories are basement floors which means they are underground) My water level is at 1.5 m from the surface. the stories have typical rectangular shape of 30 m x 36.2 m with a grid of columns as shown in the picture below.
When modeling the raft foundation that is subjected to gravity loads and water pressure (opposite to gravity loads) and since the raft is at a level of 19.5 m from the ground surface it is subjected to a lot of uplift the overall gravity load is of 108858 KN as for the uplift is (19.5-1.5)*10*30*36.2 = 195480 KN which is greater than the gravity loads so their will be an uplift of the building.

How to solve this problem ? I mean how many solutions that are available today for this problem and what is the most economical one ?


texts: Why do parallel fans/blowers show an oscillatory behavior?

texts:
I am analyzing an industrial ventilation system that at some point operates two industrial size blowers in parallel. They often show oscillating behaviour: one blower briefly draws more power / generates more flow, and the other performs less. Then the roles reverse. The only practical, known way to reduce the oscillation is to throttle down the vane valve in front of the fan and then open the valve again. The blowers are almost (but not completely) identical.

I seems that both blowers affect each other in some unstable way. Is this a known phenomena? I'm not finding anything when searching for fan/blower/pump oscillation/resonance/hysteresis.


texts: The torque I need to lift the device and correct gear ratio for the device to be as fast as possible

texts:
The device have to climb a pipe vertically. I have a DC motor with power rating 21.2 w, output speed 13360 rpm and maximum output torque 154.4 gcm.
My device is 1 kg and I have wheel with 0.012 m radius. I did calculations and I found that my gear box should be 1:72 but I am not sure about that. I need the device to go upwards as fast as possible. With gear ratio 1:72 is enough for the DC motor to lift the device? And what I have to do to make it go faster? Make the gear ratio smaller or bigger?


texts:
According to wikipedia there are 3 types of steel based on the crystal structure: austenitic, ferritic and martensitic. Austenitic steels are non-magnetic where 300 series stainless steels belong to. Ferritic steels have magnetic properties. But I didn't manage to find any information about martensitic steel magnetic properties.

In particular I am interested in stainless steel alloy 455. According to the data I have this steel is magnetic (though didn't manage to find the source of this data). But when I obtained a sample of this steel It appeared to be non-magnetic. This brings to possibilities: either my source is wrong or the sample I got is not steel 455.

Upd.
Turned out that the samples I got were “accidentally” made of austenitic steel 304 instead of requested 455.


texts: What material is used to hold molten iron in a furnace?

texts:
When iron is melted, I guess it has to be transported and contained. I think the container in which it is has to be able to withstand higher temperatures than what you want to melt.

According to this webiste, "Iron, Wrought" has a melting temperature of 1482 - 1593 °C. There are a couple of other metals which have higher melting points (e.g. Wolfram (tungsten) with over 3400 °C), but all I can think of are much more expensive. So what material is the oven / "bottle" / "basin" (or however you call it) made of?

(Side question: Iron has been melted for quite a while now. I guess this has changed over the years. Of which materials was it before?)


texts:
I am trying to build a simple DC motor for a project. I used a 9 V battery, 70 loops of copper wire, aluminum foil for the brushes of the commutator, and the commutator is wrapped by Aluminium foil and I used neodymium magnets with a pull of 16 Kg.

My motor worked for one minute and stopped and it is not working now anymore. What can be the potential problem that occurred?

(The copper wire has a thin layer of insulation, the brushes are touching the commutator, magnets are 6 cm close) Is it possible that a more powerful battery is required or can the brushes of the commutator be the problem? When the brushes are touching the commutator, I can feel that the motor vibrating but even if I try to give it a push it doesn't turn.


texts: What developments made diesel engines suitable for personal cars in the 1970s/1980s?

texts:
Both diesel and gasoline engines were developed in the late 19th to early 20th century. Diesel engines were for the most part of the 20th century used mostly for large applications in ships, trains, and for large vehicles such as trucks and busses, but gasoline engines remained the preferred option for personal cars during the 20th century. Only during the last decades of the 20th century did diesel engines begin to make a little bit of headroom in the personal car market. In the 80s more than 10 percent of new cars sold in Europe were diesels.

What developments in diesel engines started to make them more attractive for personal cars? What made diesel powered personal cars go from 0% in the 50s to more than 10% in the 1980s? I'm specifically interested in if there were any technical advances that made diesels more suitable for personal cars, but I'm not sure if there were any.

(NB: after the signing of the Kyoto treaty in 1997 many European countries started to promote diesel a lot, and the share of diesel personal cars increased a lot. I am not interested in this part, but in the period before governments started to promote diesel cars substantially.)


texts: What does it mean when actual member reaction is 100% of allowed?

texts:
I received construction documents for an extensive residential remodel and looking at the engineering there's a glulam drop beam with a calculated member reaction that is 100% of allowed (3965 lbs @ 5 1/2"). No other member comes close to 100%.
Does this have any practical implications? Is this common?


texts: Vibration characterization: how to convert acceleration noise density to displacement pk-pk value?

texts:
A spec characterizes the vibration stability by acceleration noise density

$$Na < \dfrac{1\text{ μg}}{\sqrt{Hz}}$$

for 1-100 Hz, where g=9.8 m/s2. But usually what I see is something like 3.5 nm pk-pk.

My question is, how to convert these two?

I tried this as below, but not sure if it's correct, any comment is appreciated.

Displacement noise density (is this correct?)

$$Nx = \frac{Na}{4\pi^2f^2}$$

Thus

$$\begin{align}
 x^2 &= \int (Nx)^2 df = \int \frac{(Na)^2}{16\pi^4f^4} df \\
 &= \frac{(1\mu g)^2}{16\pi^4} \int_{1}^{100} \frac{1}{f^4} df \\
 &\approx 2 \times 10^{-14} m^2
\end{align}$$


texts: Is there something called the stagnation volume?

texts: When discussing the stagnation flow properties we always discuss stagnation temperature, stagnation pressure, and stagnation enthalpy. Is there also a stagnation property called the stagnation volume i.e. the volume the fluid occupies when the fluid in the flow is brought to stagnation isentropically?


texts: Meaning of O-slash in data sheet about gear diameter?

texts:
I have this data sheet for a stepper motor:

The pitch diameter of the pinion attached to it is listed as "Ø6". What unit is this? Looking at the wikipedia page for Ø it seems like this is just a nonce symbol indicating that the measurement in question is a diameter, but then the question still remains, what unit is it? Does it mean 6 millimeters? Is there some convention about default units in data sheets I'm missing?


texts: Real life example of motor/piston involving an isoterm process?

texts:
So I am involved in an introductory course in mathematics for pilots. I have the following problem I would like to give them, as it can be a practical application of integration

However, does there exists -- however how rudimentary -- real life example where such a process naturally occur? I was thinking about Reciprocating engine / piston engine for example Wright R-3350 Duplex-Cyclone which was used during the second world war. However, I am not sure that the process that occurs in the piston is actually an isoterm process.

So my question is does there exists a real life example of an engine / piston / motor (preferably related to aviation) which can relate to the problem above?


texts: How much stronger than the bare minimum should a motor be?

texts:
A motor gives its strength in N-cm or oz-in, but how do you know how much  you require? I know you can just calculate the minimum torque you need to move the load, but is there a typical amount over that minimum that is standard? Like 20% or reaching a certain acceleration?

What I'm using a motor for is my electrical engineering capstone project.  I need to rotate a mirror about the z axis at between 30/60 Hz. The mirror is the only moving component, so there aren't any other mechanical considerations besides that. I don't know the mirror size yet, as I figured I'd buy as good a motor as I can afford and pick a mirror that's small enough to work with it, but I want to know how to figure out approximately what a given torque will get me. I don't want to spend $50 on a motor with something like "100 oz-in min holding torque" and then get it and find out thats only strong enough for a 2"x2" mirror or something.


texts: Servo drive gear placement relative to the body

texts:
Is there a universal rule for servo drive gear placement?

I'm planning to use this servo for a robotics project, but I need to know exactly where the drive gear is located relative to the body. The technical sketch provides the other dimensions very nicely, but they fail to provide that important measurement.

I assume that one dimension is easily found by taking half the width, but the other dimension can't be eyeballed; although it appears to be roughly 3/4 of the length.

If anyone knows why they didn't provide this dimension and/or how I could find it, that would be greatly appreciated.

Note:
If this isn't the right S.E. to ask this, would someone kindly point me in the direction of the correct one?