# All Questions

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### What happens in a cone-shaped nozzle?

So I am learning for thermodynamics now and there is one thing that is bugging me. In the book it shows a laval nozzle (very simplified) and a diffuser. with the formulas: (a is the speed of sound) ...
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### Push button design for small gadget

I'm looking at designing a small gadget (think something like a Fitbit in size) where the case has a couple of buttons on it. For various reasons the buttons have to be around the narrow side (edge) ...
90 views

### Is it OK for a 2 story house not have a column or pillar

sorry for my english. I was looking to buy a house. I saw some in my hometown, which is very affordable. but on a picture of the house they are selling I found on the net troubled me. no pillar/column,...
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### Whats the correct name for the filament driving mechanism used in 3d printer extruders and MIG wire feeders?

Looking for the correct terminology to for the cable/filament feeding mechanism used in 3d printer filament feeder where the filament is gripped between a bearing and a gnarled gear tooth driven by ...
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### What are the materials most transparent to microwaves?

I need to build special equipment for a microwave oven ( 2.45 (GHz)). But even glass and plastics do heat up in microwave ovens. Where can I find a list of the materials that are the most transparent ...
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### Identifying Compression and Tension as well as Hogging

Im looking for clarification on how the solution identified the moment to be hogging, as well as the axial stress to be in compression? Also I'm confused as to how the solution came to a conclusion ...
41 views

### How is the stress concentration factor calculated in FEM?

I have written my own finite element code for a linear elastic (plane stress) problem consisting of a plate with a circular hole in the middle, fixed on one side, having a tensile force acting on the ...
33 views

### Max compression & Tension

I'm seeking an explanation in reference to the photo below. I'm unsure how the solution within the red box calculates the max tension of the Aluminium beam and the max compression off the Aluminium ...
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### Ideal gas law, theory vs reality

I am trying to get an idea of the amount of hydrogen that I can store in some pressurized steel tanks underground. Based on the ideal gas law PV=nRT I did a simple calculation pressure = 200bar ...
102 views

### Max Tensile & Compressive Stress Question - Identify the equation

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!
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### heat transfer from flowing water in a tube to air

Currently I am doing a project on heat transfer .I have considered a system in which , there is a chamber with desired volume (1 m3 ).Air is filled inside the chamber at 5 bar and 35 degree Celsius ....
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### Tempered glass physics

I have two related questions Why is a thicker tempered glass stronger than thinner? For example, I have to hit much harder at 3/4” tempered glass panel surface than I hit 1/4” panel in order for ...
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### How to analyze a bent beam: Stress concentration?

I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam. When I was learning about ...
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### Shouldn't brittle materials be the ones failing under shear deformations?

It is known that brittle materials tend to fail under normal stresses, that is, tensile or compressive stresses. Brittle materials often are bound together into crystals by ionic bonds between atoms, ...
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### Info concerning an old AC unit [migrated]

I have a Panasonic cu-g125ke ac unit which trips the curcuit breaker 30 seconds after its's powered on. I have searched the manuals for what to do but it says: contact a dealer in your area. The ...
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### Why is deviatoric stress the one causing distortions?

I'm reading this text on stress. It is mentioned that the Cauchy stress tensor can be split into a sum of two other tensors: hydrostatic pressure $\pi$ and deviatoric stress. Hydrostatic pressure is ...
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### Equation for the spring constant of an orthotropic, rectangular wire spring

I hope I can get some help with this problem as I've been struggling with it for a long time. I have a helical tension spring with radius $R$ and a square wire cross section and made of orthotropic ...
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### How to find a dimension that isn't explicit if there are tolerances

For a part like the one shown, let's say I wanted to find the dimension labeled 3", if it wasn't already labeled. Since there are tolerances already on the part, how would I determine the 3" value ...
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### How does polygonal effect affect the effect of angular synchronization in car engines' timing train drive?

Is a regular roller train drive used in most car engine's timing chain drive? If so, wouldn't the polygonal effect affect the accuracy of strict angular synchronization between the camshafts and the ...
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### fluid mechanics

in question A2 part (ii) why P2 is considered to be zero
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### Efficiency of TurboJet engines with nozzles

As per Bryton Cycles, most of TurboJet engines' Thermodynamic efficiency should be around 40%. Rest of energy gets rejected as waste heat in exit gases of after the turbine. But if these hot gases ...
58 views

### Machine Frame Design

How do I select the cross section for a machine frame? Do I need to refer to the AISC steel construction manual to find the capacity of beams, columns, etc?
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### Spring Industry Naming Convention

I am currently prototyping a part for a personal project. My CAD design was contracted out and there are some off the shelf parts that I need to order per the design (springs, screws, etc.). My ...
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### Why do some guyed towers come to a point at the bottom?

Why do some guyed broadcast towers come to a point at the base. It seems that it would be more stable if each vertical bar was anchored separately rather than being balanced at one point.
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### Water in basement plug install

I have a basement which floods, the water comes through a drain in the floor. I am therefore looking to use an HFT Pipestoppers to stop the water coming in I think the water comes from an old tank (B)...
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### Correct sizing of fastener for console

Following situation: I need to mount a console holding a load to the edge of a 25cm concrete plate. I want you to check my reasoning. This is the situation: My thinking is: The load is 170kg, which ...
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### What chemical can be used to restore synthetic rubber?

When rubber (I don't know the specifics, but I assume it's butyl rubber) gets old, it turns into one of two states usually: It becomes sticky and gummy. It becomes hard and brittle. I'd like to know ...
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### How were horizontal and vertical structures ensured in old times?

In modern times bubble levels and water levels are used to check if a surface if strictly horizontal/vertical. How did people ensure vertical/horizontal surfaces in older times?
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### Effect of Pressure on Combustion efficiency (of hydrogen) in excess air

Can somebody explain relation between combustion efficiency and pressure in lean mixtures using any kind of chart or mathematical equations? At first glance I thought, combustion efficiency increases ...
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### Can someone please give me a hint on how to draw velocity triangles for this specific inward flow reaction turbine problem?

I'm trying to calculate the hydraulic efficiency for this turbine by using the formula: E(hyd) = (VwU)/gH where Vw= Velocity of whirl at inlet, U=velocity of runner at inlet, H=Given Head, and g=...
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### Cheap electrical motor that can spin freely in both directions when unpowered

I am looking for a cheap (preferably under 2000 USD) electrical motor that can spin freely in either direction when the motor is unpowered. The motor will be used as an alternative source of power to ...
29 views

### Factors for Rope Elasticity

What factors, given the same material, change the elasticity of a rope? For instance, nylon rope can be configured to stretch elastically anywhere between 5% and 30% under a specific load. This is ...
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### Pin support, why is there no horizontal reaction force?

I am trying to understand this problem: If we break down the 10T, they behave like this: The right end of the beam can move as much as it wants, but the left end is pinned. Why is there no ...
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### What is a common polarizing 50/50 beam splitter cube coating

I am having problems locating references of the typical thickness and material of the coating along the hypotenuse side of 50/50 polarizing beam splitter cube. Does anyone know what these coatings ...
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### Pushing fluid through microfluidics

my team is working on a project where fluid (mostly water) need to be pushed through small channels (like small pipes) in order to reach larger reservoir. We were considering using air to push the ...
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### Torque required to move the skid steer robot

I have a 4 wheel skid steer robot. My motor can deliver up to 6 Nm with a gearbox efficiency of 70% up to 170 rpm. I want to find out whether I will be able to make a pivot turn and move. So I ...
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### Solenoid stroke limits

Im new to rotary solenoids and I had like to understand the definition of stroke. For example, some rotary solenoid has in its technical information a parameter called stroke options and it says 25-...
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### Design of Gating & Runner system in Gravity Die Casting

How to design gating and runner system in permanent dies so that material flows smoothly throughout the design without spilling back from the gating channel. What should be the shape of gating system ...
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### Describing values as being 'assumptions' or 'assumed' - what is the correct approach in academic papers for civil engineering?

I am a language editor of academic papers in civil engineering (typically written in English by Poles). I frequently encounter the term 'assumption' being used to describe a value that is adopted ...
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### Adhesion of Super Glue (containing ethyl cyanoacrylate) and PVDF (polyvinylidene fluoride) film

Would it be considered safe to use super glue, which contains ethyl cyanoacrylate, to attach a PVDF film to a metal alloy? It says super glue is not recommended for polyethylene or polypropylene. ...
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### Locations of max stresses in a circular beam?

If a torque and axial force is applied to a beam with a circular cross section, where along the cross section of the circular beam is the location of the max shear stress, max bending moment, max ...
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### Interpreting Nyquist plot

When implementing the control for my application I got this Nyquist plot which made me flabbergasted. If I zoom on the point $-1 + 0j$ I get the following image How do I interpret this contour going ...
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### Moments of Fixed-Fixed Beam

I have a quick question related to the topic of mechanics of materials. If I were to have a beam that is fixed at both ends and has a central point force, do moments develop at the fixed supports? e....