# All Questions

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### Multiple Electric Motors on single shaft to improve efficiency

I am trying to build a super-efficient electric boat. The dilemma I am coming across is this: In normal long range running mode the boat will go at a slow 2.5 knots and only require 400 W power. This ...
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### 2PL / 3PL annotation on arc in technical drawing

I found a technical drawing of a popular guitar shape online and I'm having trouble to understand a certain annotation on some arcs in the drawing. It basically says stuff like "0.43R 2PL" or "3PL" (...
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### Punching of soft materials

The process of punching a soft material uses a hallow punch with beveled and sharpened edges that is driven into the material. The backing material is usually a soft metal or wood. I am working on ...
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### Why is the saturation pressure of the refrigerant desired to be slightly greater than atmospheric pressure in an evaporator?

I read that it "is a positive pressure against the environment". But I am not too sure what that means.
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### What are the advantages of different types of groove in welding?

In welding, we have different types of grooves like V-shaped groove, U-shaped groove, Double V, Double U, J and Double J. What is the advantage of each kind over the other?
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### How does placement of a pressure gauge in a tank of fluid affect the pressure readings?

This is not a real system but rather something I made up to understand how the placement of pressure gauge in a tank takes its readings. Here’s a diagram of it- The pressure gauge placed in the ...
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### Why increasing the coefficient of friction results in evenly distributed load in rolling machines?

I'm designing a rolling machine for reduction of steel ingots of $5 mm$ to $1.96 mm$ thick. I can convince myself using equations why increasing the coefficient of friction (in case of lubrication ...
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### Rf energy after reflection

If rf energy travels d distance, its intensity can be calculated using inverse square law. But what if it travels d1 and bounces off a perfect reflector and travels d2, what will be the intensity? ...
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### Series connection of household AC

Household supplies are 110v AC. Is it possible to series connect two plug points and get 220v AC?
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### how to choose a good motor based on application

I'm new in motor industries. I have a project which is to spin a platform disc which is the weight is 1kg and the maximum speed I need is 10000 rpm. Could you suggest what kinds of a motor is good for ...
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### What does modern sonar sound like?

Many people are used to hearing the stereotypical sonar noise in films, especially when those films are set in the Cold War. The enemy nearby, scouring for the protagonist's vessel. But my ...
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### Why does the water pressure initially drop then stabilize when pressure testing a valve?

Sometimes the dropping goes on so long(10-15 minutes) that the test is thrown out and the valve is opened and filled with water for a longer period of time. Pressure testers claim that it is because ...
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### What are some advantages of masonry over prefab for homebuilding, or, why are prefab homes so rare in the United Kingdom?

The United Kingdom has a housing crisis (see Financial Times, Shelter, The Independent, The Telegraph) and a housing quality crisis (killing 3000–15000 per year), due to poor insulation. Cash-strapped ...
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### Calculate the torque needed to turn a rod it's own axis

If a rod is turned around it's own axis, force/torque is needed. Let's assume the rod it self has a diameter $d$, a length $l$, the mass $m$ and should be turned by a motor on one side. The other ...
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In addition to the machine parts we manufacture in our foundry we also produce high quality steel abrasive including low carbon round corn, cut wire, steel grit amongst others. We will be happy to ...
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### Gate thickness of transistors

Gate materials and thickness is not mentioned in transistor data sheet. Where to get these values, say for BC547?
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### Why the internal forces in section exist in its plane and equal to load applied

I am new to mechanics of materials.I am learning shearing stress from beer and Johnston mechanics of materials.In this book,when they have applied two opposite and equal transverse loads P and P' in a ...
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### Transistor and diode on induction cookware

Will a 1 kW induction cook top damage a transistor which is kept on its surface? If yes, what is the mechanism? Is it electromagnetic induction?
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### 3D printed houses and energy efficiency in Germany

I have just learned that in Germany you wouldn't be able to print a house because of existing rules, especially regarding energy efficiency. Isn't it possible to print an insulating inlayer to fulfil ...
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### Drilling holes in ground and fillin with gravel - to what ends?

Near where I live there's a construction site for a new supermarket. The last week or so they did things I don't quite understand. Some background: The ground in our area (Ruhrgebiet) is rather ...
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### What are the challenges in building a 'sports car' frame and body?

Clearly if it were easy to produce attractive looking cars for cheap, there would be a lot more 'modern' and good looking cars on the road. While beauty certainly is in the eye of the beholder in ...
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### Converting grams of fuel per kWh of energy

Is there a database showing how many grams of a particular fuel generates how many Kilowatt hours of electricity?
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### What determines the breakdown voltage of diodes?

Some diodes have reverse breakdown voltage of 50v and some 1000v. What determines this difference?
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### Breakdown voltage of electronic devices

Diode and transistor have reverse breakdown voltage. Are these devices permanently destroyed under such voltage? Also, do these devices have breakdown voltage when AC voltage is applied? How much AC ...
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### Modeling Rotation and Translation of surface B.C. in Abaqus

I am trying to model a test which has grips that can translate in X and Y directions, as well as rotate. I have been trying to model this using constraints and a reference point but have not been able ...
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### Induced voltage in an arc of wire

We know that time varying magnetic field produces voltage in a coil. But what if the wire forms a semicircle or an arc instead of a complete loop, will such magnetic field produce voltage between the ...
10 views

### classify ECG signal using neural network

I am looking to classify ECG signal using with neural network. I have never done signal analysis before. From the samples of data I have, I have noramlised, transformed using the FFT , get the pics, ...
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### Can AC carrying coil be used to destroy electronics?

An air core coil carrying AC current of frequency f will produce an oscillating magnetic field of max amplitude say b inside it. If an electronic devices or component say transistor is placed inside ...
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### Limit for poles&zeros in System Identification

When doing system identification it is not possible to identify dynamics (i..e poles) related to frequencies higher than the excited signal. Let's say my excitation signal has a highest frequency ...
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### Shear forces along a beam using singularity functions

$\newcommand{\a}[1]{\langle#1\rangle}$ As you can see, the left end of the beam is fixed, and a distributed load is applied to the beam. I calculated the shear forces by conventional means, but when I ...
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### How widely used are ethylene receptor inhibitors in fruit packaging & shipping?

Ethylene works as a gaseous "aging" hormone for many fruits. There are lots of papers on ethylene receptor inhibitors (e.g. 1-MCP) to delay this process. I also found out that 1-MCP has been EPA-...
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### How to create tapered beam in Patran

A hollow cylindrical beam with inner radius is constant and have a varying outer diameter. How can i create this structure using 1-D or 2-D in Patran
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### Is there any entrance losses in this particular Pipe design?

Let’s say this odd design, the arrow is the direction of water flow (don’t ask why because I’m just curious about it)... I drew this out and just wanted to ask if water were to flow into the pipe ...
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### structural radius for strain evaluation - Propeller Design

What is 'structural radius for strain evaluation' in aircraft propeller design?
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### Controlling 4 24v DC motors with a Raspberry Pi using L293D circuit. What do I do to make sure I don't damage my components?

I have a RaspberryPi that will control 4 DC motors. I will be using 2 L293d ICs. The 2 ICs will be powered by a 24v 5A Power Adapter. Question: What other components do I need? I imagine I would ...
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### Dimensions on a STL model

I have an STL file, all I want is to be able to measure dimension from point A to point B on the model in the file. How can I do this? I do have access to Solidworks but don't know if that the best ...
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### Minimum thicknesses of an elliptical cylinder pressure vessel

For pressure vessels in the shape of circular cylinders, we can use $\sigma_{hoop}=\frac{pr}{t}$ to find the minimum skin thickness by setting the hoop stress the maximum allowed value, and then ...
29 views

### Microspeaker enclosure design for headphones

I want to embark on an acoustic project of designing an enclosure for some 40mm microspeakers, identical to ones found in a typical on-ear headphone solution. Are microspeaker enclosures treated in ...
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### Maximum Gain For Chopper Stabilized Instrumentation Amp (MCP6N11) [migrated]

I am using a Microchip MCP6N11 chopper stabilized instrumentation amplifier to amplify the signal from a MPX2300DT1 Wheatstone bridge pressure sensor. My schematic is attached. As shown the gain is ...
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### How do I figure out how much force a screw is applying to a wedge?

I am looking at Mitee-bite Uniforce clamps, model no.60750. How would i calculate the force applied by the wedge. So if the center bolt was tightened to 50 inch lbs. What would be the amount of ...
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### Science of Lock Picking: bump hammer - gimmick or scientifically superior? [on hold]

Premise In the lockpicking community, there are mixed opinions about bump hammers. Some say it is merely a gimmick, while others boast of its superior performance. Where there are product reviews, ...
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### Equation for water rower

I have this water rower (Sunny Health & Fitness Water Rowing Machine w/LCD Monitor) : I am going to make a monitor for it (to calculate time/500m and watts). I am going to attach a magnet to the ...
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### How do you interpret a pneumatic regulator symbol?

I'm an EE trying to interpret a pneumatic schematic and have a few questions regarding the symbols being used. I've come across two different regulator symbols (or so I believe them to be regulator ...
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### Detect valleys of a signal [migrated]

I have raw values that are coming directly from a sensor (on the fly). I do a quick calculation on these values and I end up with a graph like the bellow image. I would like to be able to detect ...
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### Go-to resource for open hardware engineering resources? [on hold]

If you would search for open source software projects, you'd probably run into GitHub and BitBucket. Is there a similar site/community around open hardware to share and version CAD files, curcuits, ...
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### air ventilation/filtering [on hold]

i have asthma i very soon hope (august 20-28) to be temporarily moving to las vegas, as i have the last two years, to gamble throughout the football season i just went there preliminarily from ...
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### Utilize multiple vehicle power outlets to increase wattage capacity of inverter

I'm trying to determine whether it would be possible to use multiple power outlets in vehicle to increase the wattage that can be obtained. This question is driven from a desire to install an DC to ...
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### Vibe Table: Increase Peak Force Capability?

I'm driving a small, benchtop vibe table (shaker) with two Crown DSI-1000 PA's, and also cleaning my signal with a DBX 231s EQ. Currently running the system at 6.8 GRMS, but I'm looking to increase my ...