# Questions tagged [mechanical-engineering]

Questions within the problem domain of mechanical engineering. Mechanical Engineering can be a broad field; consider choosing more specific tags if they apply.

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### How to secure a rotating disc so that it has no wobble

For a 3D printing application, I need to have a spinning disc(that I will rotate via geared stepper motors) that will wobble as little as possible. By wobble, I mean that it will only rotate around it'...
851 views

### Velocity of flue gases through a pipe

I was wondering if there is any equation that helps to calculate flue gas velocity through a pipe? Can I use the Poiseuille Equation to solve this problem by assuming the flue gas is acting as a ...
27k views

### Physical meaning of shear lag [closed]

What is the physical meaning behind the concept of shear lag in fibre reinforced composite structures or the concept in general for any structure?
7k views

### What is Saint Venant Principle?

I am having problem with the application of Saint Venant principle.I have heard that quite often we use that knowingly or unknowingly.I would be very greatful to anyone who would explain this very ...
2k views

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

How would I find the second moment of area of a parallelogram, as shown?
5k views

### Reading stepper motor datasheets to get torque and speed

I don't understand how to use the information in a stepper motor datasheet to understand how much torque it can generate. I was going to do a simple board and try to lift a small weight as an example ...
2k views

### Large deflection of a cantilever beam with distributed normal load

I have a strip of stainless steel encastree'd at one end to which is applied a constant pressure on one side, and I need to know what the deflection equation y = f(x) is at equilibrium. If the ...
671 views

### Are smaller heat-pumps more efficient?

I was a doing a placement at a company, and they were designing a new heat pump. I was told the more compact you can make a heat-pump, the better it is for efficiency, and they mentioned something ...
2k views

### Modeling Transient Heat Transfer between two 1-D materials

I have been working on creating a 1-D model of a material with a layer of heat resistant material stuck to it. For this I have been trying to use the implicit finite-differential method. The equations ...
107 views

### Equating $\frac{dp}{dt}$ and $F$ at a hydraulic jump?

A journal I am reading about circular hydraulic jumps provides the equation and I quote: $H$ Depth after hydraulic jump, $h$ depth before hydraulic jump, $V$ velocity after hydraulic jump, $v$ ...
3k views

### How to simulate car acceleration

I am a high school physics student and I've been trying to simulate the acceleration of a car as it fully accelerates from rest, but I'm finding it's much harder than I thought. Here was my first ...
4k views

### How is the long-term creep of a spring determined?

Spring Design In spring design, there a a variety of parameters to consider. Some of the parameters are solely physical (wire diameter, coil diameter, length, etc.) and some are determined from the ...
3k views

### Losses through holes drilled in a pipe

I asked a previous question about pipe t-junctions with pipes of varying diameters, and it got me wondering... How are losses handled and calculated in pipes with holes drilled directly into them? ...
464 views

### Fluid mechanics - how to calculate flow distribution in piping network?

I am trying to build flexible, visual tool to calculate flow distribution through the piping network (mobile hydraulics). I have root node of the network which has defined flow and pressure inputs. ...
190 views

### How small can you get a stream of molten steel to be at low pressure?

I'm designing a crucible / extruder, and right now it has a .6mm hole to extrude from. Will this work? A chart with various metals listed would be nice. Pictures: Click to expand
290 views

Suppose we have a horizontal rigid bar hinged at one end to the wall. An inclined straight link hinged at one end to the same wall, is pinned to the rigid bar at its center. A load P is acting at the ...
2k views

### 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 ...
685 views

### How to find angle of timing gears

I am trying to figure out how to calculate either the distance or angle of 2 Idler Gears in a Timing Gear Configuration like so: I have been able to eyeball things, so they are approximate. I would ...
531 views

### How to calculate the steering ratios on multiple axle vehicles?

I'm building a model of a long vehicle with 6 axles and I want to be able to steer it. How do I calculate the amount each axle should steer to minimise dragging of some wheels round sideways as it ...
869 views

### How can I attach a rotary encoder to a retractable dog lead?

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 ...
2k views

### How does Hysteresis in tires helps create friction?

I am currently reading “Fundamentals Of Vehicle Dynamics” by Thomas D. Gillespie. The author states how tires generate the required frictional forces for movement by 2 methods : 1)Hysteresis 2)...
96 views

### Sizing a motor for a floor jack-like mechanism

I've been trying, as a thought exercise, to run some calculations on a floor jack-like mechanism that is expected to lift 130kg (287 lbs). Dimensions and setup are as per the image below. The 130kg ...
563 views

### Flow in a T-Junction with pipes of different diameters

I have been trying to model a complex pipe network recently and have come across something I can't find any information on. In my model, I have been assigning equivalent lengths of pipe to various ...
66 views

### Does the Hyperloop One suspension require constant current through copper windings?

As a follow-up to How does the pressurized suspension of the Hyperloop not affect the tube pressure?, I believe (though I can't find where I read it now) that the Virgin Hyperloop One implementation ...
2k views

### Oldham coupling vs Universal joint

I've heard that both of these coupling types introduce a degree of kinematic error in the driven shaft. What does it actually mean in practice? Is it that the driven shaft doesn't turn uniformly even ...
105 views

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

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 ...
151 views

### Fast and quitet linear actuator for lifting less than a kilo

I'm looking for a linear actuator that can lift a microphone of about 700 grams. It's for a goose-neck microphone (together with shock-mount) that will pop out of a small pulpit. Only the top part is ...
3k views

### How much force can a pole in ground take before falling?

Consider I have a pole stuck in the ground as illustrated below: When a force F1 is exerted on the pole, its bottom end will push against the ground it's stuck in; the ground then exerts a resistance ...
64 views

### how to avoid a clash of magnetic charge and electric charge

now I'm working on a project which involves a dc motor and high voltage. I'm developing a machine consists of a motor to rotate a platform disc and high voltage will be applied during the rotation. ...
1k views

### Can anyone verify this wall thickness of a pressure cooker?

I am working on designing a pressure cooker. I've have tried to find, using two different models, the wall thickness based on the following assumptions: Cylindrically shaped container Made of ...
140 views

### Does a change in specimen dimension affect the measured yield strength and tensile strength?

I am having a hard time trying to understand the effect of geometry on a specimen's yield and tensile strength or if there even is one. If there is an effect or not, why is it so? Thanks in advanced!
6k views

### How to prevent deposition of dust on ceiling fan blades

It is well known that dust gets deposited on a rotating ceiling fan because formation of a boundary layer over fan blades. The air layer next to blade surface is stagnant due to no-slip condition and ...
3k views

### How do I calculate the strength of a weld joining two crossed rods?

While considering this recent question, I started wondering how to determine the strength of the welds in the steel mesh. As AndyT points out in his comment: The welds at the connections are only ...
12k views

### Distance sensors with accuracy of 1 mm?

I am making a device for measurements. I would like to measure the distance within accuracy of 1 mm. Range could be 2 cm to 15 cm . I looked at Proximity Sensors but the readings displayed by these ...
3k views

### How are high gear ratios achieved in a small space?

I have a very basic understanding of how gears work, and while trying to learn more, I've run into a small point of confusion. If a 2:1 gear ratio is achieved by having twice as many teeth on one ...
612 views

I am having trouble to calculate the differential equations of a simplified loading bridge. The system is build as shown in the picture below (just a sketch): If I use the Newton approach, I am ...
2k views

### Contours of radial-flow impeller vane

I've been studying the design of turbopumps and their impellers, all the design equations and what-not; this question concerns the contours of the impeller vanes. I'm going to attempt to enter ...
7k views

### How do you attach something temporary to a smooth metal shaft?

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at ...
212 views

### Cutting mechanism for a robot in confined spaces

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. ...
773 views

### How efficient are jet engine thrust reversers?

Most reasonably sized commercial aircraft rely on jet engines for propulsion. Upon landing these aircraft use a number of means to come to a stop with the two most important being (I believe) ...
5k views

### Why ductile materials fail in shear when subjected to torsion?

I was reading the book Mechanics of Materials by Beer and Johnston.The author points out in torsion chapter that ductile materials generally fail in shear.And brittle materials materials are weaker in ...
115 views

### Traction mechanisms for a robot in confined spaces

I'd like to build an exploratory robot that can fit within confined spaces1. What traction mechanisms should I consider to propel a robot along the inside of a 4" pipe? The pipe to be traversed will ...
7k views

### How can I improve traction on a wheeled vehicle yet reduce friction?

This is inspired by a project I undertook for my Physics class last year; I'd like to apply it in the future. Background: For the project, I and a few classmates were required to build a small car ...
3k views

### Why are turbo compound engines not more widely used?

Turbo compound engines extract some exhaust energy by using it to power a turbine connected to the driveshaft. Why are these engines not more widely used?
4k views

### Snap-fit design

I'm designing 2 objects that should be attached to each other and removed when it's necessary. So I though about snap-fit as a solution. There is a lot of types of snap-fit but I'm planing to use a ...
341 views

### Why does the standard $k-\epsilon$ model use zero equation models?

According to Hoffman, the standard $k-\epsilon$ turbulence model incorporates a two-layer approach (inner region and outer region formulations to reperesent mixing length) when it comes to regions ...
5k views

### Does having 2 engines together increase anything?

If I have a vehicle (V1) with one 100 kW engine and an identical vehicle (V2) with 2 of these 100 kW engines, will this mean that V2 will have double the torque of V1 and double the top speed of V1? ...
1k views

### What level of vibration testing should I perform on my product?

I'm trying to determine a level of vibration testing I should perform on my product. I understand electrical stress/life testing and I'm looking for a mechanical equivalent. I have a DC motor running ...