texts: Why is there such a strong focus on 5G in context of remote surgery

texts:
Almost every time I see an article or advertisement on 5G, a reference is made to remote surgery.  The point that is being made is that 5G has lower latency and remote surgery would be more practical because of it (for example, mainstream media, ad publications, and research papers).
Question: Is this just a marketing angle, or is there a real latency benefit of 5G over an optical fibre (only) infrastructure in the context of remote surgery?
My expectation is that during a remote surgery separated by thousands of miles, the last mile(s) network would be 5G but in between it would still be fibre optic cables.  So why not just use optic cables between the surgeon and the robot?  And even if it was 5G all the way between these two devices, I understand radio waves and light travel at the same speed.  So I imagine whatever low latency tech used for 5G infrastructure could also be implemented on a fibre optic infrastructure to achieve the same benefits on fibre optic.


texts: How can we model viscoplastic softening using slider, dashpot & springs?

texts: I am working on a brittle material which shows elastic behaviour followed by viscoplastic softening & hardening in the end (in compression with accumulating damage). I am not able to think of an arrangement of Spring-Dashboard-Slider system to emulate the behaviour.


texts:
Hello I am reading a book about transformers and confused by the following paragraph about synchronization check.

When the transformer trips or is taken out of service, the primary and secondary voltages decay because the supply voltage has been disconnected. However, the voltage on the load side of the transformer decays more slowly because of the back EMF induced by induction motors located downstream. Thus, the two sets of windings become out of synch. This occurs at approximately 40% of rated voltage, causing the synchronization check relay to activate and the transformer breaker to trip if it is not already open. This protects the transformer from electrical system upsets or loss of supply that cause a loss of synchronization while the transformer breaker is still closed.

What is the point of relay opening if transformer breaker has already tripped? Also, what do they mean by "40% of Rated voltage". Primary side or secondary?
Please help me understand.
Thank you for your help.


texts: Modelling reactor jacket with or without insulation, how to proceed?

texts:
I am currently trying to derive a model to help estimate as precisely as possible how much time can be saved by insulating the jacket of a reactor used for eating and cooling.

EDIT: I edited my post so that it is clearer for everybody, I understand it could have be quite confusing. I also corrected a few typos.

Presentation of the system

Let's consider the following reactor:

where, $T_{iJ}$ denotes the temperature at the jacket's inlet, $T_{oJ}$ denotes the temperature at the jacket outlet, $T_{surf}$ is the temperature at the surface of the jacket in contact with the ambient air and $T_{film} is the temperature very close to the jacket.

The temperature of the air far away from the jacket (compare to the width of the film at the surface of the jacket) will be denoted by $T_{\infty}$.

Energy balance with insulation of the jacket

The reactor is supposed to be perfectly adiabatic and operating as batch, therefore:

$$\left(\sum_i m_i c_{p_{i}}\right)\frac{dT_r}{dt} = UA \Delta T_{ln} = UA \frac{T_{iJ}-T_{oJ}}{\ln \left(\frac{T_{iJ}-T_r}{T_{oJ}-T_r}\right)} \tag 1$$

The temperature in the jacket can be averaged knowing the temperature at both inlet and outlet. If the temperature at the outlet is not know on the process and if the jacket is insulated, thus:

$$F_j c_{p_j}\left(T_{iJ} - T_{oJ}\right) = UA \Delta T_{ln} \tag 2$$

where, $F$ is the mass flow rate of water into the jacket.

which leads to,

$$T_{oJ} = T_r + \left(T_{iJ}-T_r\right)\exp\left(-\frac{UA}{F_j c_{p_j}}\right) \tag 3$$

Then $(1)$ can be directly solved. It can also be solved as equation $(4)$ using $T_j = (T_{iJ} + T_{oJ})/2$.

$$\left(\sum_i m_i c_{p_{i}}\right)\frac{dT_r}{dt} = UA (T_j - T_r) \tag 4$$

Energy balance without insulation of the jacket

If the jacket is not insulated, therefore $(2)$ becomes the following:

$$F_j c_{p_j}\left(T_{iJ} - T_{oJ}\right) = \underbrace{UA \Delta T_{ln}}_{\text{exchange jacket/reactor}} + \underbrace{h_c A_c \left(T_{film}-T_{\infty}\right) + h_r A_r \left(T_{surf}-T_{\infty}\right)}_{\text{convective and radiative exchange between the jacket and the room}} \tag 5$$

Rearranging the terms it leads to equation $(6)$ as follow,

$$\ln \left(\frac{T_{iJ}-T_r}{T_{oJ}-T_r}\right) = \frac{UA}{F_j c_{p_j}} + \frac{h_c A_c}{F_j c_{p_j}}\cdot\frac{T_{film}-T_{\infty}}{T_e - T_s} + \frac{h_r A_r}{F_j c_{p_j}}\cdot\frac{T_{surf}-T_{\infty}}{T_e - T_s} \tag 6$$

where $T_{film} = (T_{surf} + T_{\infty})/2$ and $T_{surf} = f(T_j)$ but can be set for this problem as $T_j - 3$.

Here comes the tricky part as the temperature we need to solve, $T_{oJ}$, depends on partially itself, $T_j$, and must be used during the numerical solving to calculate so solve $(1)$.

I have no idea on how to proceed to solve the whole system of equations $(1)$ and $(6)$.

I would be glad if you could bring some hints on either how to proceed to solve this messy equations or another method much easier and sufficiently precise to forecast the savings on the process.


texts: What are the key technical challenges to development of traveling wave reactors?

texts:
I recently learned about traveling wave reactors (TWRs) on the Netflix Bill Gates special, as an example of a cutting-edge technology Gates is funding which has the potential solve several environmental problems.

The TWR is a nuclear fission reactor which sounds a bit too good to be true (via Wikipedia):

Uses spent fuel from other fission reactors, meaning it doesn't require mining of new uranium
Consumes the spent fuel from these reactors, meaning it could be used to dispose of this nuclear waste
Doesn't produce any of its own toxic byproducts
Can run in containment for decades, with no need to add/remove fuel, reducing operational costs and risk to operators

So, what gives? Why don't these exist yet? The Wikipedia article (and the Netflix special) mention some political challenges that have delayed construction of a demonstration reactor, but I wasn't able to find any additional detail on technical challenges.

Like fusion reactors (which have both political and financial support, and never seem to get any closer to existing), I assume there must be some specific, unsolved technical challenges.


texts: Best placing of fans for makeshift fume extractor

texts:
I recently had the need to quickly build a fume extractor for soldering, and since at the place there was a ton of 80mm CPU fans lying around, I used those to build something like this (not to scale):

Where the components were (all airtight "sealed" with duct tape)

Intake of an old clothes dryer hose (100mm diameter, a bit more than 1m long when extended, fixed to some big metal lump to have it stay in place). This is positioned dynamically to suck in soldering fumes
the hose itself
A cut off pyramid shaped cardboard construction
A 3x3 stack of 80mm CPU fans. Directly behind it, the air comes out (future enhancement might be some coal filter)

So the airflow is from 1 to 4.

This thing did its job, but not in any terrific way. So I was wondering if anyone with experience in fluid dynamics could tell me how to improve it, or more specifically which of my ideas to improve it might make sense.

For the sake of this question, lets say the resources are limited to about the items described, reasonable additions that most people have in their workshop included (so e.g. hot glue is fine, but I am not looking for "add a bigger fan" kind of enhancements).

The items are:

The hose (2m of it, 100mm diameter)
Enough cardboard
10 fans, 80mm diameter, all assumed to be equal in performance

My ideas now included:

instead of making 3x3 fan configuration, I take two 2x2 configurations and put them "in series" (that is, a box like 4 to its right, with reasonable space in between, whatever that space needs to be)
at point 3, add an additional 80mm fan or
at point 2, add an additional 80mm fan or
at point 1, add an additional 80mm fan (all assuming for that additional point I would only have one last fan left in case of a 3x3 configuration)

Which of these ideas (or combinations of one additional fan and the other fan configurations) would noticeably improve the performance of the device (that is, move more air)?


texts: signal-to-interference-plus-noise ratio (SINR) and others calculation

texts:
I am considering some empirical signal propagation models (like Hata, Ericsson models) to calculate 4 parameters:

Path loss
Received Signal Strength (RSS)
signal-to-interference-plus-noise ratio
Throughput

Path loss is okay as each propagation model has its own formula, but how can the other three parameters to be calculated?


texts: Mathematical representation of hinge and pin connection

texts:
Following on from this answer, I am reading about the difference between hinge and pin connections here, and I don't quite understand about it. I think I would need to see the mathematical representation ( the boundary condition) involving pin and hinge connection, in order to actually understand it.

How can I represent, in mathematical terms, the pin and hinge connection? And how can it be represented in the Stiffness matrix method, as boundary conditions (maybe)?


texts: What is the side way force on a flat membrane place perpendicular to the flow of current on one side, and stagnant water on the other

texts:
So basically imagine a plate being placed parallel to the direction of flow of water with water flowing with a certain velocity on one side of the plate and on the other side it is almost stagnant. What would be the force on this plate? Can I use the lift equation that is used for air-foils or there is any other method?
Water flowing ... |
with Velocity .....  | Almost stagnant water
..........................        |<--
`     ........................       |<-- Lift Force?
..........................      |<--
...........................     |
...........................     |


texts: What is the energy and capital cost of NH3 from Haber Bosch plant that takes in pure H2 and N2?

texts:
A question that becomes particularly relevant for "the hydrogen economy" or in the event that IGCC coal baseload electric generation seeks off-peak markets for hydrogen.
I can't seem to locate a breakdown of the costs of Haber Bosch plants adequate to tell me about just the Haber Bosch reaction stage of the plant*.
In particular, I'm interested in the energy consumed to and the capital cost per capacity.
*I did find an IGCC conceptual design paper that proposes a Haber Bosch stage consuming 375MW producing 8731kg/hr implying NH3 would cost 43,000kWh/tonne but that seems quite exorbitant.  By contrast, there is another proposal that says 6MW is adequate to produce 1000tonne/day implying a cost of 144kWh/tonne.  An additional dataum is capital cost of 3000€/kgh ammonia capacity I located from a slide presentation pdf but it isn't clear whether this includes the air separation unit capital.


texts: How is the energy production of solar and wind compared with the prospect of nuclear fusion?

texts:
I am trying to find reliable information and comparisons about the energy production of renewable energy technologies, specifically, how solar and wind alternatives compare to nuclear fusion.

Why is it generally consider, as I have read, that nuclear fusion is the ultimate renewable energy? Is it really that clean? Would a fusion reactor be safe? Is the infrastructure required cheaper than solar and wind (considering long-term returns)?

If the answer to all or some of the above questions is affirmative, then why countries around the world invest anything at all in solar and wind? Why aren't the efforts directed to obtaining nuclear fusion?

I'm guessing a reasonable answer to these questions could be the inmediate mitigation of ongoing climate change and shortage of non-renewable resources. But then we should say that solar and wind alternatives are a 'transition' towards nuclear fusion. In this case, the main objective for countries worldwide should be obtaining nuclear fusion. But, in the future, when we harness nuclear fusion, wouldn't solar and wind become obsolete?

P.S. I just asked this question in Physics and it wasn't well received by some user because it is about 'politics'. Please, note that I am not interested in a political opinion, but a scientific assessment. The political and economic issues that may be involved are inevitable given the nature of the question. I posted here because now I think it is more appropriate for this site.


texts: Is it Possible to Generate Power From Sewage Sludge?

texts:
I have read about the application of sewage sludge incinerators1 but they do not have a net-positive power-generation.

Is there a way to generate net-power from sewage sludge?
What are the processes to do so?

1: German: www.berlin-klimaschutz.de/...


texts: How can I make a rotating hinge airtight?

texts:
I am designing a product that requires internal mixing of a sealed container. If you need to visualize the container, imagine some quasi-oil drum that holds about 20 L of fluid.

I am looking to use as little electrical input as necessary so I will be using a manual hand turner with some sort of paddles attached to mix the liquid appropriately. However, the seal on the joint or input valve connecting the manual crank to the tank must be as airtight as possible.

How do I make the hinge connecting the crank to the tank as airtight as possible?


texts: Is it possible to solely use a P-controller for velocity control?

texts:
Let's say I want a robot to run at a certain speed. I have one motor attached to each robot rear wheel. The feedback value to the controller comes from an encoder, which outputs pulses per time unit, i.e. the measured variable is speed of the robot.
Something has been bugging me, so please correct me if I am wrong: I don't think it is possible to solely use a P-controller for velocity control. I seems to me that it is impossible to reach the desired target speed if your output signal from the controller (i.e. a velocity value) is proportional to the error value. Then when the error goes towards zero (which is what the P-controller strives for) the output signal (velocity) would go towards zero. But then how can you maintain a non-zero speed? Instead you will probably reach an equilibrium point were the robot velocity control is in a steady-state error. Is this reasoning correct or wrong?


texts: Why is the All-In-Sustaining cost for mining gold so high relative to silver?

texts:
The All In Sustaining Cost for mining an ounce of gold at the moment is around \$1,000 ; i.e. if gold mines sold gold at around \$1,000 an ounce they would make neither a profit or a loss. The equivalent cost for mining silver is \$10 an ounce. Silver is about 20 times more common than gold in the Earth's crust and from what I can tell the physical mining and refining process for the two metals is basically very similar so naively I would expect it would cost about 20 times as much to mine the same weight of gold as of silver. However the true figure is 100 times as much.
Does anyone who has experience in this area know why? Thanks in advance!


texts: Why don't car manufacturer's use a combination of disc brakes and electeomagnetic brakes to reduce braking distances?

texts: It many be due to costs or that the brake discs would have to be made out of aluminium/copper for the electromagnetic braking to be effective or there may not be a significant reduction in braking distance. I'm just not sure if these are valid reasons or not.


texts: Difference between phase and grain in a material

texts: I couldnt get a good explanation differentiating phase and grain.From what I understood, a collection of unit cells arranged in the same orientation is called grain.A collection of grains with similar structure is called phase.Is this interpretation right?


texts: Calculating the gas constant of saturated moist air

texts:
How to calculate the gas constant of saturated moist air at 16 degree Celsius and 1.013 bar?

I'm not sure where to go with this. I just know that the saturated vapor pressure from steam tables, at 16 degree Celsius is 0.018173 bar. Is this data even useful for calculating the gas constant?


texts:
Is there a way to fix a pull up bar when the tip screwed right off and won't screw on again?
The thread hole hits the screw (detail) and just clunks there, spinning round and round without latching.


texts: How do I read this engineering drawing for this screw?

texts:
I am trying to recreate this screw hole in 3D modeling software Siemens NX.

This drawing is from page 4-14 in MagneMover LITE User’s Manual document.


texts: Quantifying inertia on the electricity grid

texts:
A lot of discussion about the modernisation of electricity systems is about "inertia". This is usually a qualitative discussion about how turbines (in hydro, coal & gas plants) with lots of kinetic energy in the form of angular momentum and fast responsiveness provide voltage and frequency stabilisation at the scale of quarter-cycle (5ms in 50Hz grids) to a small number of seconds.

However, discussions often stall because it's quite rare to see this "inertial response" quantified, and its source identified. As I understand it, the system itself has very low electrical capacitance, so I guess most of the inertial response comes from the rotation of turbines.

How is inertial response quantified for national electricity systems and what are some typical values of system inertia?


texts: Drained and undrained shear strength of clay correlated?

texts: When we measure the undrained strength of clay via CPT or triaxial test for instance, is there a way to correlate this to drained strength? How? I ask because measuring drained strength takes very long time but undrained strength can be measured quickly


texts: Is there any plastic film material stronger than Mylar?

texts: I am looking for plastic film in the 10-50 micron range. The property I value most is high strength to weight ratio. Is there some material that is superior to BoPET/Mylar?


texts: What is a 'swept path' in a valve system?

texts:
I have been doing some research on valve systems for sample analyzers. In many of the valve systems' product documentation they refer to a flow path as 'fully swept'. From the context I can conclude that it increases the rate of purging a previous gas or liquid from the system. My best guess is that it's a path that minimizes 'dead zones' in the flow, where gas or liquid may get caught. Is it simply marketing jargon, or is there a fluid mechanics definition?

An example usage of the term (page 7)


texts: Why is reverse osmosis permate corrosive?

texts:
I encountered a corrosion problem with a reverse osmosis (RO) unit years ago. A cooling water system in a remote gas compression plant used RO-processed river water to supply makeup water. The cooling tower blowdown (outlet from the cooling water system) was sent to a WAG injection system. The problem was high levels of corrosion throughout carbon-steel portions of the cooling water piping system. Tests showed low pH and low amounts of dissolved solids.
I had heard of this problem in university courses. My mental bookmark was:

RO permeate water could be corrosive because Le Chatelier's principle
says the lack of dissolved solids causes the equilibrium of 'solids
dissolving versus solids depositing' to shift towards the 'solids
dissolving' end of the balance.

In the cooling water piping system, I guessed the solids that could be dissolved might be the passive layer protecting the parent metal of the carbon steel pipe.
The solution ended up being: open up a bypass valve to permitting some of the RO's inlet water to bypass the RO elements and mix with the permeate in order to bring the conductivity of the water up to a satisfactory level.
However, I would like to know more about the RO permeate corrosion phenomenon. What is the exact chemical mechanism at work when the inner surface of carbon steel pipe corrodes?


texts:
I'm working through the derivation for the Kalman filter using orthogonal projections. It's pretty intuitive that if we want to generate the best linear estimate for an $n$-vector $x$ using some $m$-vectors $y_0, \dots, y_t$, we would take the orthogonal projection of $x$ onto the subspace $\mathbb{R}^m$ spanned by the vectors $y_i$.

In the Kalman filter case, it seems that we assume $n>m>t$. That is, a lower dimensional observations $(y)$ than states $(x)$ we are trying to estimate. Similarly, we are trying to build a recursive estimator that uses additional observations $y_i$ such that at timestep $t$ we have $t$ observation vectors and our subspace is of dimension $t$.

My question is this: what happens when $t=m=n$? This would mean, I think, that the orthogonal projection is meaningless and it wouldn't help your filter to gain new estimates... is this correct?


texts: Why downlink frequency is greater than uplink frequency in mobile communications?

texts:
Generally, downlink freq. > uplink freq. in mobile communications. I was able to gather some answers as to why is so. But my seniors (in my company) seem not to be satisfied with the below answers.

High frequency means higher attenuation. So lets suppose that BTS (as in case of GSM) transmits using low frequency on the downlink. So, that means lower attenuation. Hence, data is received as it should be (without attenuation). So, MS (mobile) has to transmit on uplink using higher freq. in order to avoid interference. But high freq. means higher attenuation. So, in order to overcome the attenuation, MS has to transmit on high power. But due to the constraint on the amount of energy available on the MS battery, this approach is not feasible. Hence, downlink frequency should be greater than uplink frequency.
This point is from user perspective. Generally, people download more than upload (however, its converging now). So, we require more bandwidth in DL than in UL and it can be attained only if DL freq. > UL freq. Hence DL freq. > UL freq.

I have searched almost everything (however, that's not possible). If you could help me regarding the same, it would be very kind.


texts: Where is the contact point between screw spindle teeth and nut teeth?

texts:
So this is a screw press used to hmm disconnect the clamp connection (sorry if these are not the correct terms I really don't know how to translate it properly). Anyway, I think it's obvious what this is used for to anyone familiar with the matter.

I need to draw the detail A

There's a big discussion among my friends on how it's supposed to be drawn. There are two options shown on the picture below, which one is correct?

Obviously, I used green color for the screw and red color for the nut.

Those who think case no 1 is correct, think that that screw teeth press upwards because of the reactive force that the clamp connection is giving.

Those who support the case no 2 think that since you are 'pushing' the inside of the clamp connection downward, then the teeth of the screw also push down on the nut teeth.


texts: Are there offsets in these accelerometers signals?

texts: How you can see in the picture below, there are 3 signals from 3 piezo accelerometers placed on a oscillating 3D structure. The structure should vibrate only along the z axis (blue track), but there are also some other parasitic vibrations on x and y axis (green and red). The 3 axis are perpendicular to each other. You see that the green track is almost everywhere positive and this makes me think; indeed a vibration signal should be a zero-mean signal. So I'm thinking that this is due to a offset, but if so, the three signals seem to have three different offsets (the blue one will have the smallest one I guess). Is it right or I'm wrong?


texts: Is 0.0 the appropriate external static pressure to use when sizing a high flow exhaust fan that is not ducted on either the inlet or outlet?  I can't find any specific guidance on this practice, yet I'm reluctant to assume 0.0 due to friction losses. On the other hand, I can't think what values to use to even begin trying to quantify the pressure.


texts: Composite beam- increase in bending moment due to reinforced steel

texts: While trying to solve this question and using the flexure formulas of bending for composite beams  I obtained a lower value of moment for steel than for aluminum.How is that possible?


texts: Boundary layer thickness decreases as fluid velocity increases, so why is the boundary layer thicker in the turbulent region for higher velocities?

texts:
I am modelling transitional fluid flow over a flat plate, and investigating the effects of free stream velocity on boundary layer thickness. From what we have been told, increasing free stream velocity should decrease boundary layer thickness. The critical distance should also move towards the front of the plate with increasing free stream velocity, which holds true for all free stream velocities tested.
In my Excel model, the assumption for boundary layer thickness holds true for the laminar region. However, past the critical distance, when flow is turbulent this does not hold true.
I have modelled a flat plate 2m long by 0.2m wide. Free stream velocities used are 0.7 m/s, 1.05 m/s, and 1.4 m/s. Using water, with density = 1000 kg/m^3 and Dynamic Viscosity = 0.001 kg m^-1 s^-1.
Using the Blausius equation and the 1/7th Power Law the same boundary layer thickness is found at the critical distance, indicating the modelling is done correctly.
I just cannot understand why the boundary layer thickness is not lower in the turbulent region for greater free stream velocities. Any help in understanding would be very much appreicated!
Below I have included an image of the graph obtained.
Thanks!


texts:
We have some metal parts in our machines, which are anodised aluminium. Those machines are due to be shipped to the customer in the near future, but I have noticed some pitting or slight rust developing on some of the anodised aluminium surfaces. I have tried cleaning it with 70% IMS, but to no avail (the surface is clean, there is no dirt). This doesn't really affect the proper function of the machine, but for something that is supposed to be brand new and relatively expensive, I would like it to look better.

Here are a couple of photos to illustrate what I mean:

Click for larger images

Can anybody suggest a cleaning method for removing slight surface pitting/corrosion on anodized aluminum parts?


texts: LabView or another software for experiments

texts:
I used LabView for a lot of my BME undergrad, but the labs focused mainly on things dealing electrical signals.

In the real world I'm working mostly on ME projects, but we lack a good deal of experimentation equipment.

What are the limitations of LabVIEW as it relates to ME experiments?


texts: Permission Denied copying to (User Data) dir -Haas Next Gen Control

texts:
We recently purchased a new Lathe - Haas with Netshare, Next Gen Control. We are copying a file to the Haas Drive's (User Data) folder from a network PC. The problem we're seeing is random and intermittent.

When things are working smoothly we can repeatedly overwrite existing program files on the Haas drive's (User Data) folder without problem. However, occasionally when we try to delete or copy-over the file a Visual Basic (70 Permission Denied) error is displayed on the PC we're copying (from).

To me, it seems that something on the Haas device if holding onto this file, the file in it's (User Data) folder that we're trying to delete or copy over.

Does anyone know what might be causing this?

This (URL below) is the error message we're seeing if of any interest
https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/error-messages/permission-denied


texts: Could pre-stressed graphene be used to reinforce granite block construction?

texts:
I am curious whether this will become an option, especially for longer lasting structures. Could pre-stressed graphene or another high tensile strength material by used to reinforce granite block construction?

Potentially relevant values:

Thermal Expansion Coeffiecients:
granite  7.9−8.4⋅10−6 m/mK,
graphene: it has a negative thermal expansion value

Compressive Strengths:
concrete: ~40 MPa
granite: ~200 MPa

Tensile Strengths:
Rebar: 420 MPa
Graphene: 130.5 GPa

Please note I am not certain of these values.


texts:
I’m a electrical engineer but an amateur in mechanics. I’ve been checking some tools and machines in the market for small works which would allow me to manufacture small but precise pieces, such as a 5mm H6 tolerance shaft to fit a bearing bore under interference. The thing is this shaft should have a tolerance of +-4um, maximum. Ok, so usual lathe setups allow you to position the cutting tool in a scale of 50um marks, with god knows which accuracy. I’d guess no less than +- 50um. But even if it was perfectly match, 50um is rather large near H6 tolerances for my shaft.
Ok, let’s assume I could iteratively remove material using a lathe and use a top precision micrometer to check if my shaft is within required dimension. Still it seems to be a very non-professional way to do it, basically a try-and-error approach, moreover I could accidentally remove more material than I should and end up losing all the work and also money.
Could anyone tell me if there’s a more efficient method to produce such precise pieces?


texts:
When trying to change the mesh sizing of an element by selecting it and then choosing the apply option in Geometry, when I try to change the default element size and click enter or click elsewhere the size changes back to the default size.
I have read that this may be because you need to select the appropriate options under Adaptive sizing in sizing but I do not know where those options are located. Has anyone experienced a similar issue?


texts: How to write a literature review for a DIY-style electronics project?

texts:
I am working on my BSc Electrical Engineering final-year project, and have been asked to do a literature review to include in the project report.

My project is an Arduino-based power strip which can be controlled wirelessly using an Android application, and has power consumption reporting capabilities (among other things). It doesn't involve reading scientific papers, journal articles and the like - rather it is simple, hands-on electronics. It can be constructed easily by following tutorials and Instructables.

I chose it because it is in line with the whole 'home automation' theme, and will give me practical experience, not because I was looking to solve a scientific problem of some kind.

From what I've read about literature reviews, it seems as if they only apply to research-based projects that do solve a scientific problem. The student compares the previous work in that field, and expands on it in his project from a 'scientific' point of view. In my case, I just have a cool product that fits a particular market, but there is nothing scientifically new about it.

In this case, what should I do differently compared to a 'normal' literature review?


texts:
I'm not exactly sure if this is where I'm supposed to ask, but engineering stack exchange is the closest because my question is about robotics. I'm sorry if this doesn't fit.

  Question: Are there any intake mechanisms that are efficient and quick, but are designed to accommodate obstacles that are in the way?

Let me explain my question. Essentially, let's say you have a robot with an intake that's supposed to take in different sized objects like cubes and spheres. However, to get to the cubes and spheres, there's a three inch tall wall in the way.

The standard way of retrieving the objects is to go over the wall, which might be possible, but I'm asking if there's another way without going over the wall. I've thought about some sort of extension that goes over the wall, but it's risky if your actual intake is heavy.

Any thoughts? I've spent some time thinking about this and I'm still haven't come up with an idea.


texts: How do I convert cubic metres/feet per minute to a pounds per hour flow rate?

texts:
I am checking the leak rate of a carbon seal installed on an aircraft engine bearing. The test cart has a reading of pounds per hour but my manual says the leakage should not be more than 0.08 cubic metres (2.5 cubic feet) per minute of free air.

Since pounds are a weight measure and cubic metres/feet are volume measures, I can't compare them directly. How do I convert the volumetric flow rate to a mass flow rate?


texts: Why is the heat addition process in otto cycle assumed constant volume while in diesel cycle it is considered constant pressure?


texts: How can I change a turning lathe's spindle o-ring?

texts:
I bought an old turning lathe ( Żebrak TOS S32) but there is problem with the o-ring of it's spindle.

I have opened the lathe and don't know how to take out the spindle shaft and replace the damaged o-ring with a new o-ring.

The following pictures show the part in question:

So as you can see from the pictures, how could I separate the spindle shaft from it's gear wheel to remove the  spindle shaft and change it's o-ring?

The manual for the lathe can be found here:

Żebrak TOS S32 manual

Żebrak TOS S32 manual in 4shared

And, I also found this:


texts: Autodesk Inventor Constraints for Clockwise / Counterclockwise / Dead Points

texts:
In the YouTube video Spherical 4-Bar Infinity Mechanism by Thang010146, Dead Points are not compensated for by mechanical means. How can Autodesk Inventor Constraints be applied to such a mechanism to ensure that it does not change "modes" into a Spherical 4-Bar Paralellogram Mechanism? I'm not looking for a mechanical solution. I'm trying to learn the constraint logic.

Here is my own, similar assembly. One of the bars keeps switching direction on me.


texts: Measuring beats/bounce in a closed cubed glass

texts:
Suppose that we have a $2$ by $2$ by 2 $cm^3$ closed box, made up of glass, with thickness $0.1 cm$. Yes, it is a very small box. Let's say in that box there is a ball (also made with glass) with diameter $0.5 cm$. If we shake the box as fast as we can for one minute, making the ball bouncing like crazy inside the box, how do we measure (exactly or approximately) how many times the ball bounces/makes contact with one out of the six sides of the cube?

I never heard of any device that can do this. The closest ones are vibration meter and drumometer, I believe? However, it looks like vibrameter does not measure the number of bounces and drumometer is, well, too huge? Perhaps we need a mini drumometer? I mean, whatever that device is, does that mean a very small sensor that is connected to the device must be put into that side of the cube?

Also, since the stuffs are made with glass, meaning they produce sound, can we measure the bounce by measuring (from the outside) the sound made from the shaking? My guess is that a device called sound level meter is what we need but it still won't count the bounce?

Note: Please correct my tags/title if needed as I have very little engineering background.

Additional question: What if (instead of one particular face) we measure the number of impacts coming from any face of the cube? Well, in this case, we don't need cube, but it can be a ball-shaped glass large enough to contain the small one.


texts: Cutting mechanism for a robot in confined spaces

texts:
I'd like to build an exploratory robot that can fit within confined spaces1.

As the robot moves along the inside of a 4" pipe, it's likely to encounter some obstacles that need to be removed.  Typically, that will be tree roots up to 1/2" thick.  There could also be globs of tissue paper caught by the roots.

The majority of the pipe is made from clay, but a small portion of the pipe is cast iron.  The portion that has the obstacles is clay and was laid in the early 1960's.

The pipe to be traversed will likely have fluid (assume water) within it to varying degrees from partially full to completely full.  I'm initially planning on tethering the robot with coaxial cable and possibly an additional line like a steel cable.  The propulsion mechanism is still being defined, but I expect that the robot will have some ability to fix itself in place while clearing out an obstacle.

The typical way of removing roots and other obstacles is through using a drain cleaning system.  The cutting head is usually a pronged piece of metal that can burrow through the obstacle.  The problem with this approach is that the pipe is damaged as part of the cleaning process and some amount of roots are left behind.

Another commercial approach that completely clears the line utilizes a spinning wire brush.  The downside of this approach is that pipe wall is severely damaged as part of the cleaning.

I would like to devise a cutting mechanism that doesn't significantly damage the pipe but also removes the majority of the obstacles encountered.

What type of cutting, shearing, grinding, etc... mechanism should I consider in order to clear out the path in front of the robot as it explores the line?

1 It's a rather boring application, actually.  I want to see how badly the roots are creeping into the sewer line from my house.  Ideally, I'd like to clear out the roots too without damaging the clay pipe.


texts: Speed and Feed values for log slitting of paper

texts:
Context:
I have a paper roll of about 8 in (20 cm) diameter mounted in a 3 inches core (7.62cm). Its length is about 1.2 m. The paper is bond of 95 g/m2. I have to cut slices of it of about 10-18 cm in length, down to the paper core.

As this is a very eventual task, I can't afford a log slitter, which is the right tool for the task, so I'm trying to do it in either a lathe or a cutoff machine.

What I've tried:
In the lathe I've tested with two different options: a fixed blade (a knife and a machete) and a rotating one (a lightweight circular saw with wich I've used ceramic and wood cutting discs). The machete produces the best cut, but as it's fixed, it dulls very quickly. The circular saw produces a lot of small paper chips that cause problems in the process that follows after the cutting.

I've experimented with different RPMs in the lathe, specially in the trials with the fixed blade, but haven't quite controlled for the feed of the blade into the roll. With the circular saw the RPMs of it are so high (5800), that I'm afraid the relative speeds (even if I have rotation of both pieces in the same direction) are too high (diameter of the cutting disc is about 19cm or 7.5 inches).
In the lathe I've mounted the roll both between points (as standard steel would be) and on a central bar (a core inside the core) to avoid tightening of the cutting area.

In the cutoff machine I've tried with discs of different tooth sizes, but all of them end up burning the paper in the cutting face (I don't have the RPM of the cutoff machine, but I can provide it in a few hours).

I have searched for available information on speeds and feeds for paper in log-slitting operations, but have found nothing so far, and the available tables of speeds and feeds are just for metals and some plastics.

What my expected result is:
I'll appreciate if someone can provide an adequate speed and feed value for cutting paper, or if can point me in the right direction.

Regarding the cut of the paper roll: I need a cut that is as clean as possible, without significant burning, that requires as less sharpening of the tool as possible, and that can be considered safe for the operator.


texts: Difference between Serial-to-RJ45 adapter and Serial-to-Ethernet server

texts: I'm wondering what causes the price difference between a Serial-to-RJ45 adapter and a Serial-to-Ethernet server. Given a serial-interfaced instrument, can one use either to connect the instrument to a computer? (Of course, the first must be wire correctly first).


texts: What's the Difference Between LT and T Directions?

texts:
What is the difference between LT and T directions in MMPDS (formerly MIL-Handbook 5)?

I hand understood that forming metal orients its grains, destroying the isotropic nature of 'pure metal' and that the "Long" direction is the length of the sheet/extrusion/etc, and that there were two transverse directions. There is the "Short Traverse" which would be the thickness (or "depth") of the sheet/extrusion/etc. There is also the "Long Traverse" direction which would be the width of the sheet/extrusion/etc.

But then MMPDS throws in a "T". Is this just for the times when you cannot distinguish between LT and ST (such as in a rod)? I also see datasets where specimen orientations are T and ST, which furthers my confusion. MMPDS itself doesn't seem to offer much further guidance.

Any explanations?


texts: What is the accepted way to write units when specifying multiple dimensions?

texts:
When writing out dimensions in the form height x width x depth, what should you write for the units? For example, I can think of a few ways to approach this (assuming each dimension is measured in millimetres):

$1\times2\times3\,\mathsf{mm}$
$1\times2\times3\,\mathsf{mm}^3$
$1\,\mathsf{mm}\times 2\,\mathsf{mm}\times 3\,\mathsf{mm}$

Is one of these more generally accepted in engineering than others?


texts:
I am a novice welder (D.I.Y).
I need to weld in a very sensitive area. It will be surrounded by PVC and other plastics withing about 30-50cm of where I have to weld.
I have an inverter arc welder, and I am worried about spatter etc when welding in this sensitive area. I can have absolutely no welding spatter touch the PVC and other plastic areas as they will undoubtedly destroy whatever they land on.
I am thinking about using a welding blanket(s) to pad the area. I have no experience with using welding blankets, and I am a bit nervous. If something does get through, it will be quite an issue.
My other idea is to build a metal "funnel" if you will, to enclose the area, and then weld inside the "funnel". The weld should be a quick weld, but I may have to do it in multiple locations for the foreseeable future every time something breaks.
If you are really curious about the scenario... I have a trampoline park, and from time to time I have to remove some of the starts where the trampolines are strung from, to make repairs. The struts (locked with big grub screws), work their way loose and fatigues the metal to the point of breaking the head of the strut where it slots into the main pillar.
This normally happens at an awkward time, and I have to fix it early before opening the next day. I have to completely remove the strut, rebuild the head (L-shape), and reinstall and re-hook all the springs.
This is a re-occurring problem, and I want to create a permanent fix. I want to weld the strut beams to the center pillars. This will not carry any weight, but just stop it from moving side to side and fatiguing the metal. I will be a quick weld. I am not worried about heat transfer, just spatter.
I cant unhook all the trampolines and padding every time this happens, as it takes quite a while to re-hook and reassembles (4) trampolines encompassing where the break is.
My idea is to unhook just a few springs in order to be able to work, and then cover that surrounding area, padding, and trampoline mats, with welding blankets... Do the weld, and get on with my day.
Ideally I would have unhooked ALL the trampolines and padding, make all the welds, and re-assemble. To do this I would have to probably close the business for a few days, which I really cant afford.
Am I barking up the wrong tree?


texts: Would an afterburner on a turbine drastically improve acceleration lag?

texts:
A little bit of context. My friends and I were watching the "Dark Knight Rises" and a discussion about the Batmobiles ensued. I, being a former ME student, said it was stupid that batman has a turbine in his car at all because they aren't responsive enough for the very Fast and Furious way Batman tends to drive. Batman seems to need a car with an engine that can produce a lot of power and adjust its power output very quickly; Batman needs a car without much acceleration lag. Turbines can produce a lot of power, but they simply can't be responsive. I suggested Batman use a rocket instead, though he should probably just be using some turbo and super chargers or be driving an electric vehicle at this point.

At this point my friend, with an English degree, said that Batman did in fact have a rocket on the back of his car, and pointed out that the jet engine in the Batmobile has flames coming out of the back of it, which means it has an afterburner. He then argued that would make the Batmobile responsive enough for the driving style to be fine.

I disagree, but I can't find any sources on how an afterburner actually effects the responsiveness of a turbine. After looking I learned that an afterburner produces extra thrust. My thought is that the turbine would already need to be working in order for an afterburner to do anything. In a car that would still lead to a responsiveness problem right?

Can an afterburner make the turbine in Batman's Batmobile responsive enough satisfy his insane driving requirements?


texts: How to combine ODE parameters values from several estimations?

texts:
I would like to perform parameters estimation for a differential equation from experiment. If the value of these parameters are obtained from several experiments (repetitions) where for each experiment different final cost function is obtained, how can I calculated the final parameters values from these experiments?
Thank you.


texts: Maximum bending stress at particular section of beam

texts:
For this question, I am having problem for part b. We know that the bending stress $$ \sigma = My / I $$
For part (b), the author only stated he wanted the bending stress at a section 2 m from A, but he didnt specify at which point of the beam (cross-sectional view)?
So, how to do this question?


texts: How to model leaning columns in opensees?

texts: I want to modelling three buildings next to each other in opensees software . Duo to modelling leaning columns , buildings overlap with each other . Now my question is that for 3 adjacent buildings how can i consider leaning columns ?


texts: Does the stress on exhaust hanger amplify sound transmission into the vehicle chassis?

texts:
I have an exhaust that drones with the vehicle. However, outside, it's not a loud exhaust. So my assumption is the vibrations are transmitted into vehicle interior via the points of contact - in this case the rubber exhaust hangers.

The exhaust hangers are used fit very tight and are somewhat stretched, so is my theory correct - does the pre-stretch on the hangers allows more vibration transmission into the vehicle?


texts: Estimating joint angles using accelerometer data

texts:
the question I'm working on is the following: three IMU sensors have been placed on the lower limb, one of the hip, one on the thigh and one on the shank.
The IMU sensors collect acceleration data in x/y/z directions, and gyroscope data for the three axes.
I want to use this data to estimate joint angles: hip angle and knee angle.
Starting point will be to align the sensor coordinate systems. Assume two separate systems: to estimate the hip angle, work with sensor on the hip (1) and on the thigh (2). To estimate knee angle, work with data from sensor on the thigh (2) and the shank (3).
So, need to align (1) and (2), and (2) and (3).
However, struggling to work the rotation matrix. How to do this?
Once rotation matrix calculated, then what are the next steps?
Thank you.


texts: How can I tune the parameters of a lqr controller?

texts:
From my internet research, it seems there's no systematic way of tuning the design parameters for the LQR controller. I have found Bryson’s rule as an initialization. However I don't know how to proceed from this point besides trial and error or grid search.
Ideally I want to tune the parameters such that the settling time for specific state variables are below a threshold. Additionally I want to make constraints on the sensitivity function, such that disturbances up to a specific frequency are attenuated.
Is there a recommended way to tune my parameters such that requirements can be fulfilled ?


texts: I am wondering how the screw top of a container made of either aluminium or brass is manufactured at scale. A picture of the sort of thing I am talking about is below. Currently the only method I can think of is hydroforming. Can anyone enlighten me?


texts: Why is buckling caused by nonlinear geometry?

texts:
I've been reading the Comsol post on geometric nonlinearity. The article introduces situations where the small angle approximation and linear analysis of structures gives inaccurate results. For example, the case of a beam attached from both ends is discussed, specifically when the deformation is so large that the horizontal supporting force must be taken into account and the stiffness of the beam is no longer constant. Buckling also comes up. Here is a quote:

  Buckling, or the loss of stability when the load reaches a certain critical value, is caused by geometrically nonlinear effects.

Why is buckling caused by geometrically nonlinear effects? What is meant by this statement?


texts: Bills of Quantities for Highway Works (UK)

texts:
Does anyone know a software/tool, which allows creating Bill of Quantities in accordance with Manual of Contract Documents for Highway Works (UK)? In particular, I am interested in working with the Library of Standard Items and also using a tool, which would allow to choose standard items and relevant option to avoid the need of scrolling the PDF.
I would be grateful if you could share some information if you are aware of anything.

Thanks!


texts: Does a single-wheel brake intervention from ESC cause one wheel to be not brakeable by the driver?

texts:
Source: https://www.kfz-tech.de/Engl/Buchprojekte/HBremse/ESP3.htm
Firstly, I don't know if this is the right StackExchange, but I will try nevertheless.
Above I posted a picture of the hydraulic circuit of an ESC (Electronic stability control) system (with ABS (anti-lock braking system). Now the upper 4 valves (2 per circuit) are used to autonomously build up pressure (ESC intervention or autonomous emergency brake). Normally the inner valve is open, which leads thought the ABS valves directly into the wheel.
When ESC wants to brake on its own, it closes the inner valve and opens the outer valve ("suction valve"). This way, the path leads through the hydraulic pump and backflow is blocked by additional directional valves (I guess this is how the autohold function is working). By operating the pump, the system can now build up pressure. But since this option is only available circuit-wise, it would put pressure on two wheel at a time. As commonly known, ESC stabilizes a vehicle by braking a single wheel to induce a rotating force countering the instability.
The only possibility I see braking just one wheel is by blocking it with the ABS valve. Does that mean that, even when the driver steps onto the brake pedal, the wheel which is not intended to be braked is completely not brakeable? I dont think this would lead to a good dynamic, since it would have much less pressure than the whhels in the other circuit which are unaffected. Or does the ESC react to this and works like an electronic brake force distribution by temporarily letting fluid flow into the unbraked wheel, so that the pressure in this wheel is regulated to be the same as in the other circuit?


texts: Connection for beam very close to concrete wall

texts: The following picture is pretty self-explanatory. I need a connection for a beam that is coming in very close to a concrete wall edge (north/south beam in picture). The embedded plate with nelson studs in already in place. I was thinking a T type welded plate with bolts already fixed to plate (as drawn in purple), but they wont be able to weld both sides of the plate. Maybe with a full penetration backed weld? Any better ideas on how to fix this beam? Required shear for full beam capacity is about 175 kN and factored load is about 50 kN to give a quick idea.


texts: Are there any instructions on how to install and run Natran-95?

texts:
there is a source code for Natran-95 on Github. I need to install it on Window 10
but searching on the web there is no clear tutorial on installation. while I click on the nastran.exe on this package in the hyperlink to GitHub, I get windows error the file not found in directory.
the specific reason to use nastran is to generate a superelement from a PSHELL model. it seems that MYSTRAN 12.0 has added sparse solver that some of its subroutines do the reduction of sparse matrix, but I am not sure if it also saves it or only uses for solving, but uses the same craig bampton method
could anyone tell me if there is a compiling step missing ? just if you know how to install it, and also use it, please write an answer? it will be a great source for internet


texts: Should I use shaft or hole basis on a constant diameter shaft with both clearance and interference fits?

texts:
I'm looking to manufacture some steel pins and plates, with a view to large scale production in the future. One of the pins of the design has a constant diameter. This pin passes through holes in two different plates. One of the plates has an interference fit with the pin and the other has a clearance fit with it.

To me, this sounds like it should use a shaft-based system, where the shaft diameter is constant and the hole sizes vary. Given, however, that the difference between hole diameters is only a matter of tens of microns and I've heard that it is typically harder to make non-standard holes than non-standard shafts, I am wondering whether I should use a hole base system, where the hole sizes in both plates are the same and the pin has a small step (tens of microns) to accommodate the different fits.

I think the hole-base system could work but the question really comes down to whether it is easier to accommodate the tiny difference in fit through the manufacture of the shaft or the hole.


texts:
I am looking to test the FlexiForce sensor in measure force, however for accurate readings the load needs to be disturbed evenly over the sensing area. As such I am having "discs" made to cover the sensing area. For my application the thinner the material of the disc the better (1 mm or less in thickness). Which of the following materials will be most suitable to manufacture the disc for the stiffest/strongest possible part?

Brass & Copper
Aluminium
Stainless Steel
Mild/Carbon Steel

The disc will be 25.4 mm in diameter with a thickness of 1 mm.

Here's an illustration of what I mean:


texts: Could tic-mark labels on a graph have individual decimal digits with different signs?

texts:
I'm currently looking at a graph (figure 5 of Ede (1967), "Advances in Free Convection", in Hartnett and Irvine (eds.), Advances in Heat Transfer vol. 4, New York: Academic Press), in which the tic-mark labels on the vertical axis are of the form $\overline{1}.4$, $\overline{1}.5$, $\overline{1}.6$, etc..  It's fairly clear that the overline is intended to mean a negative sign.  However, comparing the curve on the graph with the equation for that curve given in the text, it looks to me like the negative sign might apply only to the digit on which the overline appears, so that the digit after the decimal point represents positive tenths, i.e $\overline{1}.4$ means $-0.6$, $\overline{1}.8$ means $-0.2$, etc..  Does that sound remotely plausible to anyone?
ETA: I found this Wikipedia article which confirms ('Most of the other early sources used a bar over a digit to indicate a negative sign for a it') that such a notation exists.  However, my question still stands, in the form "Does it sound remotely plausible to anyone that someone might have used that notation to label a graph in a book on heat transfer in 1967?"


texts: What's the methodology for adequate tetrahedralisation?

texts:
I'm running a linear elastic solver generating the tetrahedron's using tetGen. It's not clear to me though how one defines what's an acceptable tetra density that provides sufficient accuracy.

You can see that in the picture below the maximum displacement drastically decreases alongside an increase in tetra count.

This is a much as my machine is able to process but I assume it would converge around 90k tetrahedron. Is it at that point that we can consider the results to be accurate?

Can someone provide a guideline that can be translated programmatically?


texts: What do the short parallel lines mean in a symmetrical value?

texts: I was wondering if the short parallel lines at the ends mean anything?


texts: How can I remove Ozone from a sealed enclosure

texts:
One of the processes in a current product design catalyzes the conversion of atmospheric oxygen into ozone:
$$
3\text{O}_2+\text{energy}\rightarrow 2\text{O}_3
$$
Ozone is highly reactive and, over time, will degrade the components in the sealed enclosure.  One technique which I have read about for removing the ozone is to actively cycle the air in the enclosure through a catalyst such as silver oxide ($\text{Ag}_2\text{O}$) or manganese oxide ($\text{MnO}$).

Given that the enclosed volume is 1-2 liters, is it necessary to actively cycle the air, or can the catalyst simply be placed in the enclosure? Are there any other techniques for ozone removal which I should consider?


texts:
I am a physics teacher, but have found myself teaching engineering.  I have come across the following pulley question, and am starting to doubt my own understanding of pulleys !
Until now the rule that mechanical advantage equals 2*no. of moveable pulleys seems to have hold fast, but I am not sure that it works in this case.  I am wondering if instead a better rule is that mechanical advantage equals no. of supporting ropes ?
For this particular question, would the no. of ropes supporting the load be three or four ?
I am not sure whether or not to count the far left section where the effort is applied.
Any thoughts on which is the most reliable rule, and how to apply it to this question, would be most gratefully received please.  Thank you.


texts: Can I convert multiple point loads into a single uniform distributed load?

texts: I have a beam that has a given limit of 1690 lbs uniform load for a 24" span. I will be subjecting this beam to multiple point loads at different locations on the beam. In order to determine if the loads will exceed the beam allowable limit (1690 lbs) I was wondering if I could add up all these point loads into a single uniform load to compare to the load allowable. Is this possible?


texts: VTOL Aircraft Take-Off Mechanics Question

texts:
These question(s) could be potentially trivial, but its difficult to find visuals on CFD of VTOL aircraft. While watching a video of the f-35 performing its vertical take-off/hovering, I noticed the horizontal stabilizers, as well as the flaps being deployed down. Does this happen as a means to "scoop" as much air as possible, to help further push/lif the aircraft up?
I'm also curious what the overall affect of airfoils on VTOL aircraft such as the harrier/f-35. Do airfoils affect hovering performance or only horizontal transition/flight?

Thanks in advance!!


texts:
I am designing a roof rack for my car that attaches to my canopy and extends over the roof of the cab. I am deciding what size of aluminum.

It would need to support me walking on it ideally (80kg).

It would be a 1800x3600mm rectangle that is welded onto the canopy for 2400mm from one end, leaving the 1200mm overhanging the cabin. There will be 8 cross supports including the ends. Options are all in box section:

32 x 32 in 2 and 3mm
40 x 40 in 2 and 3mm
50 x 50 in 2,3 and 5mm.

if needed, I can add a central support.


texts: How can high carbon steel and stainless steel be connected firmly without using nuts and bolts?

texts: I am an engineering student who is working on a project. One of the things that will make the project a success is I need to know how to join a very thin type 304 stainless steel wire loop onto a slightly bigger high carbon steel pole in a very efficient way and can do it in an industrial scale. I know high carbon steel has low weldability and it is the interest of this project that the strength of the carbon steel and the ductility of the stainless steel(its softness) are not undermined.The mechanical shop in my school doesn't know anyone that is involved with these processes. So could you guys help me out here?


texts: Fluidic muscle in reverse, as a pump. Does this exist?

texts:
A fluidic muscle is a pneumatic or hydraulic actuator, consisting of a flexible tube. When the tube is filled with a working fluid (pressurized air or hydraulic oil), it balloons out and shortens. In some applications, fluidic muscles are superior to pistons.

In theory, you could imagine the same principle in reverse as a pump: Water flows into the tube under gravity, ballooning it out. The tube is then pulled apart, reducing its volume and ejecting the water. Check valves ensure proper water flow. Tbh, I don't see any advantage over other diaphragm pumps, but I could be wrong of course.


texts:
I need a 1 to 1 planetary gear box that torque increases
I was told torque in planetary gear sets are because of the number of teeth moving over the sun gear.

I was told the more spur gears with teeth means the more torque regardless of the increase .

Any ideas?


texts: root locus question - root locus 'begins' at finite open loop pole locations

texts:
This is a general question about root locus plots. I notice that there is a source that says:

"The root locus begins at the finite and infinite poles of G(s)H(s)".

Note the part that says 'finite and INFINITE poles'.

Should the part that says 'infinite' be omitted? The root locus only begins at the FINITE open loop pole locations, right?

If the statement is indeed correct - about cases where a root locus may start at 'infinite' pole locations, then are there any examples of such cases?

Thanks all!


texts:
I did a Civil Engineering course some years ago and from my textbook I had a question on a pipe with a bend.
Now I think I have the part of the question on force correct, but I am not sure how the torque will be calculated in this situation.
Can someone please help and give me an idea as to how to work this out?

I have the question as an image with my calculations below.


texts: How do I read the component dimension labels given in a schematic?

texts: How to read the dimension labels of this IC?


texts: Conversion of Piezoelectric coefficients

texts:
I am interested on simulating the converse Piezoelectric effect of materials and I have given the mechanical (Young's modulus and Poisson's ratio) and electric material properties (Electric Permittivity, Piezoelectric coupling matrix etc). However from the literature I got double index notation, I am struggling to convert double index notation to triple index notation.

The double index notation from literature is as follows:

Double index notation

$$\begin{bmatrix}
d_{11} & d_{12} & d_{13} & d_{14} & d_{15} & d_{16} \\
d_{21} & d_{22} & d_{23} & d_{24} & d_{25} & d_{26} \\
d_{31} & d_{32} & d_{33} & d_{34} & d_{35} & d_{36}
\end{bmatrix} =
\begin{bmatrix}
0 & 0 & 0 & 0 & 21.3 & 0 \\
0 & 0 & 0 & 21.3 & 0 & 0 \\
-2.6 & -2.69 & 3.65 & 0 & 0 & 0
\end{bmatrix}$$

I would like to convert them to Triple index notation used by some commercial software providers like Abaqus and MSC Marc etc and is written as follows:

$$\begin{bmatrix}
d_{11-1} & d_{11-2} & d_{11-3} \\
d_{22-1} & d_{22-2} & d_{22-3} \\
d_{33-2} & d_{33-2} & d_{33-3} \\
d_{12-2} & d_{12-2} & d_{12-3} \\
d_{23-2} & d_{23-2} & d_{23-3} \\
d_{31-2} & d_{31-2} & d_{31-3}
\end{bmatrix} =
\begin{bmatrix}
0 & 0 & -2.6 \\
0 & 0 & -2.6 \\
0 & 0 & 3.65 \\
0 & 21.3 & 0 \\
21.3 & 0 & 0 \\
0 & 0 & 0
\end{bmatrix}$$

Am I doing the conversion correctly? Are the values placed in correct positions?
Double Index = Triple Index = Coupling Matrix Value

$$\begin{alignat}{2}
d_{11} &= d_{11-1} &&= 0 \\
d_{21} &= d_{11-2} &&= 0 \\
d_{31} &= d_{11-3} &&= -2.6 \\
d_{12} &= d_{12-1} &&= 0 \\
d_{22} &= d_{22-2} &&= 0 \\
d_{32} &= d_{22-3} &&= -2.6 \\
\vdots \\
d_{16} &= d_{31-1} &&= 0 \\
d_{26} &= d_{31-2} &&= 0 \\
d_{36} &= d_{31-3} &&= 0 \\
\end{alignat}$$


texts:
I got the Ikea SKARSTA desk http://www.ikea.com/us/en/catalog/products/S49084965/, it's a sit stand desk that uses a manual shaft to rise and lower the desk.

So I plan to make the desk motorized using a satellite dish motor and a satellite positionner to control the motor (I removed the linear actuator part and kept only the motor).

The problem I'm facing is that the space between shaft and tabletop is about 1cm, so I'm not sure how can I transmit the rotation from the motor to the shaft (which is simply a long Allen key).

I looked into pulley systems and cogs but couldn't find suitable pieces, please advise.

Many thanks.

Update Jul 9:

The problem is how to transmit the rotation from the motor (green) to shaft (orange), motor can be placed at any position relative to table top but shaft isn't.


texts: Mechanical advantage of the 3-ring release system

texts:
I'm quite curious about the 3-ring release system used in parachutes, as described in this Wikipedia article:

https://en.wikipedia.org/wiki/3-ring_release_system

I wonder why is this system so popular? I've been told it's nearly ubiquitous in the industry, but even after Googling and asking some skydivers I haven't been able to find out what makes it better.

More specifically, the Wikipedia article mentions that each of the loops multiply the mechanical advantage of the small cord loop that is secured by the yellow wire. Could somebody describe in detail how this multiplication of mechanical advantage takes place, and why is the number of ring chosen to be 3 instead of say, 5?


texts: Skew-Symmetric Gain Matrix to Encourage Exploration

texts:
I am reading a paper on controls and it has the following snippet:

We propose to use the control law
$$u_i = K(CV_i − p_i)$$
, where K is a (potentially time-varying) uniformly positive definite control gain matrix, which may have a skew-symmetric component to encourage other tasks, for example exploration.

Question: How does skew symmetric gain matrix encourage exploration, and also exploration of what exactly?


texts: maintenance of steady flow through pressure or mass flow

texts: let's say I have two points in a line, A and B. Between them there is a valve that can regulate the amount of the stream from A to B. Considering that there is a steady flow of the stream between A and B, and is to be always maintained. Is it better to regulate the valve in accordance to the pressure or with the mass flow? what is the difference of using pressure regulator instead of the mass flow meter if the aim is only to maintain the pre-set steady flow?


texts:
Good day! We (undergraduates w/o prior foundry experience) inspected a foundry for its health hazards, our problem is we are not permitted to be accompanied by a laboratory assistant, so we don't have any idea what the following parts are for, kindly help us, thank you for your help! :)

(a)

(b)


texts: How to adjust power requirements for a propeller working against a pressure head

texts:
I'm in the process of building a hovercraft. In order to lift it, I'll need a motor directing the flow of air into a skirt. The specs for the motor I'm looking at say that it can turn a 15x5 dual-blade propeller at 6,000 RPM with 262W of power.

However, the motor is designed to be used by a large drone. In that case, the motor only has to work against atmospheric pressure. My hovercraft will have about .17 psi of pressure within the skirt. How do I adjust the required power for a given RPM based on the pressure below the propeller?

Mass is 87kg

1.6m x .45m

Airgrap: 12.7mm

Cushion Pressure: 1.185 kPa

Inward flow during static flight is 3,000 CFM (I believe that means flow out is also 3,000 CFM?)

These are the motors I'm looking at:
https://www.getfpv.com/tiger-motor-mn4014-330kv-antigravity-2-motors.html


texts:
I have a $100\ \text{psi}, 300\ \text{cfm}$ air compressor that we use for running power tools, I need a way to inject mortar deep into a small opening and was wondering if anyone had experience with setups like this.  From doing some research on the topic it sounds like historically it's pretty much what they did before the specialized concrete pumps we have now were around.  I'm not worried about air mixing with the mortar but it would be interesting to know how much force this would have on the person at the operating end of the hose.  I can't see it being more than a fire hose as long as we stick to a relatively small hose (the air input is $1"$ and I was planning on $1/2"$ for the output hose)  All fittings and hoses are rated for $150\ \text{psi}$ and I was planning on buying a $200\ \text{psi}$ rated pressure tank.  Am I missing anything here?

edit Just in case someone wanted to see my math here, I used the the following numbers
density of (flowable grout) $= 128.7 \ \text{lbs/ft}^3 = 2061.6 \ \text{kg/m}^3$
Operating pressure $= 100\ \text{psi} = 689.476\ \text{kN/m}^2$

using $P =\rho*g*h$, we get $689476 = 2.0616*9.85*h$, where $h=\frac{689476}{2061.6*9.85} = 34\ \text{m}$ of pressure $= 111\ \text{ft}$ of available head (minus what's lost from friction with the hose/pipe/fittings)
Should still be plenty enough pressure for what I need though also pressure at the nozzle would be $\frac{100}{0.7853} = 127.3\ \text{lbs}$, probably gonna bump that hose up to $3/4"$

edit - Drawing explanation
As addressed in the comments I was just going to use ball valves at the grout intake air inlet and grout outlet, the pressure tanks I was looking at were 200 PSI 5 gallon water tanks that have like 8 ports already built into them.  The mortar works out to about 4.7 gallons of flowable mortar/40# bag so it should work out for the smaller jobs we'd be using it for.


texts:
I've been working on simulating drone flight in Gazebo (an open source robotics simulator).

Currently, I'm trying to control the drone's pitch / roll rotation using PIDs. It's important to remember that a drone moves linearly only by angular rotation (forward / backward requires pitch rotation, left / right requires roll).

Right now, I'm testing PID pitch control.  The goal is to get the drone to rotate to a specified angle and hold that position - perfect job for a PID.

But the physics implementation complicates that.  Essentially, the PID takes the setpoint - the desired pitch rotation angle (in radians), and the current pitch rotation angle (which I get directly form the simulation state).

The PID output is then used to calculate the resultant torque.  The torque equation is t = I * a (torque = Intertia * angular acceleration).  So, essentially, I'm using a PID to control the angular acceleration of the drone given the current and desired angles of rotation.

The problem, of course, is that a PID output scales linearly with time, so although it decreases to zero as the drone approaches the setpoint, it has been applying positive accelerations through the entire time.  The result is that the drone has a lot of angular momentum, and so it naturally overshoots.  Then, of course, the PID responds by reversing the rotation, but with the same problem.

In the end, what happens is that the drone starts with a horizontal attitude, rotates to the setpoint, then rotates back to horizontal, then back to the setpoint.  If I add any I or D gain it becomes unstable.

The problem is really simple.  It's like controlling a vehicle in space.  Thrust is applied in pulses in order to give fine control over position / rotation.  The PID however, provides a continuous output.  Which means I need some sort of physical system that behaves as depicted here:

http://vignette4.wikia.nocookie.net...imation.gif/revision/latest?cb=20141124024926

or I need to rewrite the physics so that the PID output scales appropriately to bring angular velocity to zero by the time it reaches the desired angle of rotation.

Solving this is proving more difficult than I thought - probably because I'm not a strong physics or controls guy.

I've posted this problem already in another forum.  You can read the thread here:

PID control for drone rotations

where I get really specific.  I'm afraid I wasn't able to articulate the problem well enough, partly because the guy who tried to help wasn't really familiar with PIDs (or C++).

Anyway, Any thoughts from someone who has dealt with this sort of thing (or thinks they know more about it than I do...) would be really welcome. :)

Edit:  You can see the behavior in the following animated gif:

http://gph.is/2lKf9aT


texts: how can I control 2 stepper motors with RS-232?

texts: Hello everyone this is my first post to the forum. I want to control 2 stepper motors using RS-232 as a way of directly communicating with step drivers from my desktop. I am new to communication standards such as RS-232, 422, 485. I have two questions. One, is RS-232 like an I2C network where Devices such as sensors, servo drivers(PCA9685) are given an address and then you can program what happens to that device via its address? If not how does RS-232 work in a use case such as robotics where you have to control step motors? Thank you for any and or all help. My goal is to be able to control 2 nema17 or 23 motors and write python code to control them. I want to use a solution other than usb/arduino for the connection that gets made between motor controllers and the computer.


texts:
$ P_m=P_n*{G\frac1{G_{STC}}}*[1-\gamma*(T_c-25)]$

This equation is applied on sollar cells. $ P_m$ is the mean power produced in 15 minutes, $P_n$ is the nominal power [W], G is the insolation [W/m2], $G_{STC}$ (the subscript still in the wrong place, I don't know why) is the radiation [W/m2] in standard testing conditions reference here. Last, but nost least, $T_c$ is the cell temperature.

What is the parameter gamma ($\gamma$)? I have a value for gamma, 0.005 [adimensional], but I don't know what it means or its definition.


texts: How to calculate rock permeability in m^2 from gas flux in m/s?

texts:
I am studying rock caverns lined with concrete for compressed air storage. I would like to know if it's possible to convert the permeability coefficient from m/s to m^2 or Darcy.
Thank you.


texts: Heat rate through composite wall with non-constant thermal conductivity

texts:
I just started a job working with cryogenics and I am trying to solve an interesting heat conduction problem that I was hoping someone could help me along with.
I have a structure that spans from room temp (call it 300K) to 4K, and I want to calculate the heat rate at the 4K surface. The geometry of the structure is simple, just rods, plates, and tubes. Everything is under vacuum and there are heat shields and multi-layer super insulation so convection and radiation can be ignored, I am only looking at conduction.
Typically for these types of problems I just use the NIST material database (https://trc.nist.gov/cryogenics/materials/materialproperties.htm) to integrate the thermal conductivity over the temperature range, then multiply by the cross sectional area and divide by the length to get the heat rate (aka heat leak) in Watts.
This time I would like to treat the structure as a composite wall with each component contributing its own thermal resistance like the classic heat transfer problems we have seen where one sums up the resistance contributed by each element and uses the total to find the heat rate. https://www.sfu.ca/~mbahrami/ENSC%20388/Notes/Staedy%20Conduction%20Heat%20Transfer.pdf
The complication is that the thermal conductivity of the materials used varies greatly over this temperature range so I must use k(T) and integrate somehow but I am stuck on how to implement it. To start I can ignore the thermal conductance of the mating interfaces, I can bake that in later. Any thoughts?
p.s. Yes I am aware this can be solved with software but I want a clean solution that is more analytical to understand the problem better and inform the design.


texts: Max Tensile & Compressive Stress Question - Identify the equation

texts:
I'm struggling to identify which equation is used within the first red square.

Could someone please help identify which equation was used as well as why?

Thankyou!


texts: 2 SPDT relays as motor driver, flyback diodes

texts:
I'm trying to use relay as high current motor driver.  I'm not sure how to connect flyback diodes. This is my current sketch I've read a lot of on DC motors, but I couldn't find anywhere a schematic for 2 SPDT relay motor driver with flyback diodes protection. Because of SPDT relays I can't short circuit the PSU (S1 + S2)

I'd be glad with any advice/guidance.


texts:
Consider a spring like this (this one CoC hand gripper):

They claim on their web site, that the spring will not degrade during time:

  Do your grippers get weaker with time?
  No, so don’t worry if your Captains of Crush No. 1 gripper is feeling easier to you now—it’s because you’re getting stronger! What is mistakenly called “seasoning” by some people is actually a weakening with use, and it’s a reflection of an under-designed gripper with a spring that is bending, which is why it’s not uncommon for low-quality grippers to get narrower and easier as they are used. On the other hand, Captains of Crush grippers hold their line for a lifetime of steady training.

There is also a lot of discussion on this topic, referencing some re-measurements, but none of that seems really trustable.

My questions, from engineering point of view:

Is that possible/probable? I mean, can the degradation be small enough (for the given brand) so the user should not care? How likely it is true?
Is possible what they say about the "low-quality grippers" that they degrade over time significantly. How probable is that?

I can imagine that both options (degradable and also stable springs) are possible. But how probable it is. Note that such a product cost usally $10-25.

I know this is kind of opinion based question, however the experiment would take few years, so any theory and/or experience based answer can help.


texts: LS DYNA Material Model 163, Modified Crushable Foam

texts:
Question is on the meaning of input variable TID within material model 163 of LS-Dyna 971.

Definition of TID variable.

TID: Table ID defining yield stress versus volumetric strain at different strain rates.

Remark of TID: Rate effects are accounted for by defining a table of curves using *DEFINE_TABLE. Each curve defines the yield stress versus volumetric strain for a different strain rate. The yield stress is obtained by interpolating between the two curves that bound the strain rate.

What I understand of the yield stress is a single point on a stress vs volumetric strain curve for each individual strain rate. So wouldn't that give me a yield stress vs volumetric strain point for each individual strain rate.

Is the yield stress referring to just the stress. Having trouble understanding the inputs, any clarification would be helpful.


texts: How does one go about building an underground structure without concrete?

texts:
I was reading an article that was linked on another site I frequent  on "India's forgotten stepwells", which are basically elaborate wells with stairs to go down to the water level, sometimes 10 m or so below surface (maybe more, looking at the pictures). Some of these are whole temples underground, very impressive.

So I was wondering how one would go about building such a thing, or rather how they would have gone about it 1000 years ago. Would you just dig a very big, deep hole, build a structure inside, then fill the sides (can't imagine this)? Is there a way to start at the surface, then work yourself down, basically building layers under existing ones?

Similarly, how does/did one go about a brick well? Dig a deep hole, hope it doesn't collapse on top of you, start with brick once you hit the bottom during dry season? Or is there a way to work yourself down there? And does it make a difference nowadays; I mean are there new methods now with modern materials that let you do things they couldn't do 1000, 500 or 100 years ago?


texts: Calculating maximum internal pressure from maximum rated external pressure?

texts:
Is there a calculation / rule of thumb that can determine a containers rough maximum negative pressure (vacuum) from it's rated internal pressure (assuming a single layer construction so there is no additional bracing preventing expansion).

As an example for a 50 litre stainless steel keg (cylindrical with convex end caps) with an integral 580 +/- 140 psi bursting disc.

Would it be valid to assume that the weakest point (excluding the bursting disc) is calculated to withstand 400 psi of internal pressure (minus approx 14 psi from external atmosphere), directed outward so placing the material under tension. By reversing pressure differential (My logic says the weakest point still remains the same) the weak spot would come under a compressive force and the maximum pressure under vacuum would be a function of the ratio of that particular stainless steal grades tensile:compressive strength.

EDIT
I just realized the bursting disc pressure is not relevant since that only indicates when a rupture would occur. In the reverse situation deformation into a flat can would occur well before then. However if instead of the bursting pressure you were to apply the 'Maximum working pressure' of 43.5 psi which presumably implies no deformation does the above apply?


texts: How to specify the quickest movement a human can do based on MTM standards?

texts:
I am looking for a benchmark as a reference regarding the human Kinesiology that specifies the quickest movement a human can do on basic everyday movements like computer mouse clicking.
As far as I know, there is an standard called MTM (Measurement Time Methods) in the field of industrial engineering and ergonomics which specifies the required time for each basic movement to be done by human. This MTM standard time is provided on the basis of not putting the human (worker) in an overload or underload working situation. So I assume MTM cannot provide me with the shortest possible duration (time) a basic movement can be performed. Do you have any suggestion in this regard?


texts:
I'm studying Root Locus method and I still confused. The question below exemplifiques my doubt.

Determine the $K$ gain so that the dominant roots have a damping factor equal to $0.5$, where

$$G(s) = \frac{K(s^2+5s+9)}{s^2(s+3)}$$

I have successfully draw the root locus from this $G(s)$, but I can't figure out how I could calculate the gain $K$.


texts: Deflection of a rectangular plate simply supported (transverse load)

texts:
I am looking for the formula allowing to calculate the deflection of a rectangular plate with a "transverse loading in its center" (maybe the kind of loading will be more clear with this picture :

I already found this formula for the case of a rectangular plate with a concentrated load at center (and I know the one I'm looking for is very close).
https://www.engineersedge.com/material_science/rectangular_plate_concentrated_load_13645.htm

But I can't find the coefficients for my precise case with the load uniformly distributed across the width (as in the first picture)

Thank you


texts: Protecting heat-sensitive media from fire: fire-safe + Thermos?

texts:
Protecting paper documents from fire is quite straightforward with, for example, a Sentry fire chest. This product has been tested hold the inside temperature under 177°C (350F) for 1 hour. This is fine for documents, since they will not combust or deform. However, I'm looking for an inexpensive solution for items that would take considerable damage at these temperatures.

Sure, I could house the fire chest inside another larger safe. Or build myself some kind of drywall, brick and mortar box to house the fire chest in... but I'm looking for something smaller.

My idea is, if I stored my valuables inside a stainless steel Thermos, could this offer sufficient additional insulation if put inside the fire chest? The plastics of the Thermos might deform at some point, but could I get enough insulation? A Thermos works both ways, but how well...?


texts: At what negative pressure do gases separate from water?

texts:
According to this video, when a valve is quickly shut, the water hammer effect can lead to a high negative pressure in a pipe downstream. This leads to dissolved gases coming out of solution with the water. At what pressures can this occur? The experimental setup in the video reaches 100kPa below atmospheric pressure.
Does this also lead to water splitting?


texts: How do you mount a polystyrene foam wheel to a motor?

texts: I have a wheel I CNC milled out of foam and I need to mount a motor to it. I designed and printed a part that would attach the motor to the foam, but I anticipated that the wheels would be wood back then. It connects to the wheel using screws, but it does not seem like screws would hold well in foam because the foam can't hold threads. Is there any other way to do this? I was thinking of using longer screws with nuts on them, but I am open to other ideas.


texts: Building laser interferometer from CD/DVD drives parts

texts:
Is it possible to build interferometer, for linear displacement measurements, using old CD/DVD drive parts?

I am talking about using parts such as beam-splitter, detector, laser and frame where it all mounted if possible…

I have the XY stage on a microscope with piezo-motors. Interferometer should be the best linear encoder to be used as a feedback loop for proper driving of piezos. There are commercial linear encoders based on Michelson interferometer, but they are too expensive. Old CD/DVD drives appeared to be extremely cheap source of: lasers, laser drivers, 50/50 mirrors, detectors, detector drivers, maybe anything else.


texts: Would a "lifting body" design be useful for a train car?

texts:
Lifting Body

The idea of a lifting body design is to shape a vehicle's body in such a way as to produce lift without wings. Research has shown that this can be an efficient method of reducing drag while still providing lift.

This has typically done for aircraft or spacecraft:

Could a similar approach help to make trains more efficient?

Passenger trains already look streamlined and aerodynamic:

Freight trains do not:

Air resistance is not the only form of resistance that trains must overcome. They must also overcome the resistance of their wheels on the track. This is where I would think that the energy savings from a lifting body design would come from. Any additional lift created by the lifting body design would reduce the friction between the wheels and rail, thus saving energy.

Train wheels have flanges on them, so they don't need traction to steer. The cars also don't need traction on the rails since the driving wheels are only on the engines.

Could a lifting body create enough lift at typical train speeds to make a noticeable difference?


texts: Temperature not changing in my code for 1-D heat equation: Explicit Scheme

texts:
I am trying to solve the following 1-D heat equation with provided boundary conditions using explicit scheme on Matlab. I have been trying to plot the results but I realized that my temperatures are not changing. How can I solve problem and include the boundary condition?

clc; clear all; close all;

a=0.45*10^-5;
U_Initial= 30+273.15; %converting to kelvin
U_Wall = 20+273.15; %converting to kelvin
U_BC = 100+273.15; %converting to kelvin
dt= 0.01;
dr= 1;
Lambda= (a*dt)/(dr)^2;
t=1:dt:3600;
r= 3:dr:100;
U = zeros(length(r),length(t));
U(:,1)= U_Initial;
U(1,:)=U_BC;
U(end,:)=U_Wall;
for j= 1:1:length(t)-1
   for i=2:1:length(r)-1
     U(i,j+1)= U(i,j)+Lambda*((dr/r(i))*(U(i+1,j)-U(i-1,j))+ (U(i+1,j)-2*U(i,j)+U(i-1,j)));
   end
end


texts: Stability with eigenvalues' real part equal to zero

texts:
I know, from Lyapunov criteria, that a system is stable (not asymptotically) if the system has eigenvalues with negative real part or it has eigenvalues with real part equals to zero, but in this case the algebraic multiplicity must be equal to the geometric multiplicity.
I don't understand why there's this condition when the real part is equal to zero.


texts: How to calculate reaction moments and forces in a fixed axle with multiple point loads?

texts:
I need to calculate the maximum moment and reaction forces in an axle with both sides fixed in bearings, the axle is 1010mm long and has downwards forces of:

236kN at 403mm
86kN at 499mm
32kN at 595mm
12kN at 691mm
4kN at 787mm

I need the results to determine what bearings to use and to calculate the minimum axle diameter, I have had lessons in how to calculate these problems but those only explained a single point load or a distributed load. How would I go about calculating this?
EDIT: The A drum will be mounted on the axle to make a winch, the forces are based on the cable windings pulling on this drum.


texts: How do you set up a PID-Control if the time constants of the controlled system are variable?

texts:
The common description for a continous PID-controller is written like this:
$$y(t)=K_p⋅e(t)+K_i\int_0^t e(τ)dτ+K_d\dfrac{de(t)}{dt}$$
The best value of the constants $K_p$, $K_i$ and $K_d$ for a given controlled system will depend on its time constant(s), be it a $\text{PT}_1$ system, or $\text{PT}_2$ system, etc. ...

What do you do if the time constant of such a system is variable. Lets say, it varies between $T_a$ and $T_b$ ($T_a < T_b$). How do you design the PID-constants?


texts: What is the gel used for covering the strain gauge in the load cell?

texts: We have one imported strain gauge load cell, which shown open circuit in the input impedance. I removed the protective gel and corrected the wiring. Now the load cell is working. But I want to cover the strain gauge with the gel for the protection against moisture and dust. I want to know the product/technical name of the gel. please see the image. the blue arrow pointing the material that I am talking about.


texts: How can I attach a rotary encoder to a retractable string/wire?

texts:
I need to know how I can attach a rotary encoder to something string/wire that I can pull and it retracts automatically

My idea was to take apart a retractable dog lead leash and affix it to it somehow, but I'm not seeing how I could make that work.

I've included a picture of the dog leash(right) and the rotary endoer(left).

Is there any other solutions that are not very expensive?

Edit:
The only goal here is to measure distance/velocity of a retractable string/wire. I'm not tied down to using a dog leash or rotary encoder, open to any suggestions.


texts:
I was studying this example but I didn't understand how the author arrived at (A₁ - A₂)G₁G
Please I need enlightenment


texts: Is stud bolts covered under ASME B18.2.1

texts: I want to know if stud bolt dimensions are covered under ASME B18.2.1. I could not specifically find them in the standard or they may be included under some other technical name within the same standard or covered in a different standard. I am a newbie. Hence the doubt.


texts: What is the purpose of those "dual parasols"?

texts:
Watching a live video stream from South Korea just now, I noticed these parasols in the background. They look like normal parasols but have two "layers". Like a hole in the top with another "smaller parasol" on top of the main one.
What is the purpose of this design? Could it really be just be for the visual look? Does it have some kind of practical purpose?


texts: Calculating the grip of a tyre for a given surface

texts:
Is there a formula to calculate the grip generated by a tyre on a vehicle for a given surface?

I have a 13,000 kg machine pulling nearly 200 N of weight. I need to figure out if we need to put any more weight onto the machine so that it has enough traction to start the initial pull. It's going to use pneumatic tyres and the surface is concrete.


texts: How could we possibly harness the energy from the Earth's negative charge?

texts:
I've been reading the Feynman lectures, and in this lecture about lightning, he describes how the Earth is negatively charged, and how there is thus an electric field of about $100\ \tfrac{\text{V}}{\text{m}}$ near the surface of the earth.
To me, it seems like $100\ \tfrac{\text{V}}{\text{m}}$ could provide a lot of energy, a lot of small appliances run on $9\ \text{V}$ batteries, and the power point provides $240\ \text{V}$, which would be the potential difference between $2.4\ \text{m}$ of air, not all that much. There are probably problems in attempting to harness the electric field around the earth, but if I were to design a simple machine to harness the energy, how would I do so?


texts:
Above picture is from Eurocode 3: design of steel connections. It gives geometrical requirements for a pin ended member. Looking at situation A, we have the minimum distance $c$ from the edge of the hole to the edge of the connection. I wonder where that term $\frac{d_0}{3}$ comes from?
Neglecting the safety factor $\gamma$ for simplicity, we should have the nominal stress on each side of the hole as:
$$\sigma = \frac{F_{Ed}}{A} = \frac{F_{Ed}}{2ct}$$
At the yield limit, the stress equals the yield stress $f_y$:
$$f_y = \frac{F_{Ed}}{2ct}$$
Solving for $c$:
$$c = \frac{F_{Ed}}{2t f_y}$$
Now, there is no extra term $\frac{d_0}{3}$ here. Where does it come from in the Eurocode formula? My guess is that it could have something to do with stress concentrations, which we know to be around 3 times the nominal stress around a hole, but I don't really see how we would incorporate that into the equation, besides maybe multiplying the nominal stress by 3 before solving for $c$:
$$f_y = 3\frac{F_{Ed}}{2ct}$$
$$c = \frac{3F_{Ed}}{2t f_y}$$
But that is not the same result.


texts: What type of fastener is this? How does it work?

texts: I'm trying to find more information on this type of fastener. It looks like a variation on a bayonet mount but I'm not exactly sure how it is locking in place.


texts: Software to find the common volume of intersecting cylinders?

texts:
I would like to find the common volume between cylinders for different radii and at different angles (3-D). Can I do this using ANSYS design modeller? Or what can I use (preferably a free download for a student please) and how long would it take to compute one solution?

I essentially would like to create a lookup table for the common volume between different cylinders that look like this for example.

Thank you for your help!


texts: How to determine whether plastic is ABS or Polypropylene?

texts:
I have a pump that I want to use to pump a solvent. It is hard black plastic so I'm pretty confident it is either ABS or polypropylene (it wasn't expensive enough to be some more exotic plastic).

My solvent will rapidly dissolve ABS but it will work great if its PP. Anyone have a strategy to tell which it is without destroying it if it happens to be ABS?


texts: How are electronics hardened against extreme accelerations?

texts:
How does one protect electronics against extreme accelerations/impacts? I mean accelerations of at least 2000g, possibly an order of magnitude more; essentially "payload" of an artillery shell.

The circuitry would consist of some radio receiver, a controller of an electric primer, and some kind of power source to keep both running for a couple minutes.

Size and weight aren't much of a problem (<1m, <1ton) but the acceleration would be sustained over about 1s of time, not just a momentary impact, also the initial jerk ($\dot{a}$) would be an extreme spike.


texts: Questions regarding Cornering Stiffness for RC Car

texts:
I am a bachelor's level student tasked with modeling the vehicle dynamics of an RC Car that will be made to drive autonomously. I lack prior experience or particularly specific education with vehicle dynamics so I have been studying the field a bit, particularly Vehicle Dynamics and Control by Rajesh Rajamani. By advice from a supervisor I will not be using the Pacejka Magic Formula. I think I have a good enough idea of the problem and how to approach it but I've hit a wall quite badly regarding the parameter 'Cornering stiffness'. As I understand this is a property of the tires, and something that I would find on data sheets on tires. However in my case the tires are considerably more simple, they're just solid rubber rings around the wheels. I have tried to read up on Cornering Stiffness to see if I can determine it myself somehow but I haven't really found anything I've understood.

So, how should I go about determining the cornering stiffness? Otherwise, considering the shape of these tires are there any assumptions I can make that would simplify the model?


texts: How do pumped flows combine in a Y connector?

texts:
I'm curious about pumping a fluid through two different tubes (coming from two different pumps) into a Y connector. The third side of the connector runs into a collector without any resistance (other than that of the length of tubing).

If each pump runs at a different rate, say one is twice as strong as the other, do I run any risk of any backing up into the weaker pump? What if one is three times stronger than the other, etc.?
Does the third side of my Y connector (the side the fluid leaves through) now pump with the equivalent of pump a + pump b total power? Are they averaged together? Is it diminished?
Does the type of fluid matter for parts 1 and 2 above?

This question assumes that all tubing is the same thickness, but answers regarding different thicknesses could also be interesting (and worth extra credit!)