Questions tagged [applied-mechanics]

Questions about using applied mechanics to model engineering problems.

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4
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1answer
1k views

How to Calculate the Minimum Radius a Rod Can Can Be Bent Staying in the Elastic Range?

I am wondering if there is a formula (or how to derive one) for calculating the minimum radius a rod (with a given radius/diameter) can be bent around while staying in the elastic range. Obviously, ...
0
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1answer
482 views

I need to determine the RPM of a rotating cylinder over which a silk thread is wound and is moving along in the fashion of a screw.

Recently I visited a sericulture facility in India and I saw that people there 'degummed' (https://www.youtube.com/watch?v=h13fctiTylI) silk in a batch process. As a Chemical Engineer, I thought of ...
2
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1answer
299 views

How to calculate bending of shell

I'm an electrical engineer, so please bear with me :). I came across this situation and I tried to find some equations to solve it, but all I could find was some Finite Element Theory, and I was ...
2
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0answers
181 views

Worm Drive Calculation

I have this setup: -Pully with a mass attached. -Worm gear drive to lower the mass with a constant speed. (Section A-A) Now if we look at the cross-section A-A, we can see the worm gear drive: ...
1
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1answer
232 views

How does friction help a car to turn?

I know that friction helps car to move forward. The engine of the car turns the wheels, and the tyres have to grip the road in order for the car to start moving forward. If there is no friction, tyres ...
1
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2answers
3k views

Help with a simple calculation of the required mass for a counter-weight for a horizontal hatch

Hello fellow engineers, A friend is part-way building an outside storage chest. For whatever reason, the materials and size of storage that he is going for means that the door is heavy to lift and ...
5
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2answers
150 views

Longitudinal impact of steel rod on a steel plate to verify the contact duration

So I'm doing an experiment to verify the contact duration when a steel rod (Material: Mild Steel) is allowed to free fall longitudinally on a steel plate. The arrangement is real simple: The rod is ...
0
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1answer
294 views

Two-way pulley system considering inertia of pulleys

This is the following question. [![This is how i tried, but I know it is wrong.][2]][2] This is our attempt but We can't seem to solve it with inertia.
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2answers
138 views

Can buckling failure at the first critical load be avoided by “instantaneous” loading?

Previously, I was told by someone I trust well that a column can avoid buckling at the first critical load by applying the load "instantaneously" with a magnitude between the first and second critical ...
1
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2answers
1k views

Design a trolley with four casters

I need design a trolley with four casters, the four casters are installed on the four corners of a 460mmX405mm metal plane. And the load will be a cubic 380mmX225mmX350mm (Height is 350mm), weight ...
0
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1answer
59 views

How I can compute cutting processes with continuum mechanics?

In YouTube I have seen various videos where someone cut with a sword into hard objects and has cut that into pieces. For example: https://www.youtube.com/watch?v=EVCWGwvctt4 Given the mass, the ...
1
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1answer
560 views

Reaction forces in a structure

I have the following structure, in which I am failing to calculate the two reactions: Cz (apparently vertical) and Dz, in the roller support of the beam. The beam length is 7.5 m, the reactions Az, Cx,...
2
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1answer
456 views

Reaction force on a beam

I have the following problem most of which I have calculated but have a difficulty with the beam under angle. The angle is 56,30 degress. I just cannot figure out how the forces there are acting - the ...
7
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1answer
3k views

Principle of Virtual Work vs Castigliano's (Second) Theorem

I had a look online and into some literature however I did not seem to find a good comparison for the two different methods. They are both used for determining displacements and slopes (rotation by ...
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3answers
155 views

Compound gear system: Finding velocity

In the figure below we have that the gear $A$ is has an fixed axis and has the radius of $R_a = 0,1m$ and, in the instant represented in the figure spins clock-wise with angular velocity $\omega_a = 4\...
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2answers
58 views

How to pump same amount of paste every time?

I am not sure if I am on the right site for this, but here it goes. I have a friend who makes a hot sauce for a company he runs. It is very pasty (made of pepper flakes in an oil). The problem is, ...
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1answer
69 views

Improvised weighing machine from broomstick and 1kg counterweight [closed]

Let's say I want to measure the weight of a bag of clothes (or some other object), in a situation where I don't have a weighing machine ("scales"?) available. Objects that are available: A broom. ...
1
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2answers
5k views

Force required to rotate an object on a plane - moment of inertia?

I have a rectangular shape with uniform mass, approx 6m x 1m. It rotates around an axis in the centre of its width but 1m from one end. The axis has some friction but this is not known. What I need ...
4
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3answers
127 views

Finding downward force of lever bar

I am working on a DIY project, I am trying to replicate a bar compressor which for some reason is only sold in Europe so I thought it would be fun to make my own without having to waste so much ...
5
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1answer
154 views

Poisson ratio boundary condition

Let's say I have a large isotropic body in uniaxial tension, onto which a small rectangular piece of film is applied. Think of a strain gage on a big body, but the 'strain gage' is one single ...
1
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1answer
356 views

Gear ratio and motor power

I have a small drum that will be immersed half way in a water bath (drag). The drum will contain some 500ml of photo chemicals (weight). The questions: is there an easy way to calculate the gear ...
2
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0answers
603 views

IV drip/flow rate controller design

I have a question about intravenous flow rate controllers, which are controlled using microprocessors. For example: I want to control the IV flow rate, the flow is in range from 0 to 300. So, I just ...
2
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1answer
70 views

Glass panel engineering at work

We are designing a button panel at work, made out of glass and are running into some issues. Glass, of course, can shatter. But we noticed that when dropping a steel ball in the center of the glass it ...
0
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1answer
40 views

Efficiency of off road vehicles [closed]

Im working on efficienxy of heavy vehicle. Since i never had any experience with this kimd of things ( cars ) i dont have so much insight in what kind of efficiencys are important in vehicle. I have ...
0
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1answer
466 views

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

This question is going to have an application in aviation (to avoid doubts and relocation to other forum) but let's concentrate on theoretical mechanics here. If I want to allow a shaft to rotate in ...
2
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1answer
6k views

Derivation if the formula for the surface moment of inertia of an isosceles triangle

For a isosceles triangle with base b and height h the surface moment of inertia around tbe z axis is $\frac{bh^3}{36}$ (considering that our coordinate system has z in the horizontal and y in the ...
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3answers
102 views

Formula (or heuristic) for calculating force required for incremental change in angle of attack of an airfoil

Assume I have a system comprising of an airfoil A immersed in a fluid. Further assume, that the airfoil is affixed via two bolts at one end, and is untethered at the other end. The system can be ...
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3answers
1k views

Applications with combination of high friction and low wear?

What would be some common applications involving high friction and low wear rates? for example, gear-driven mechanisms which require high friction between the gear teeth but ideally low wear between ...
3
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1answer
667 views

How to simulate the simply supported boundary condition in experiments?

I want to do some experiments on the dynamic behavior of the beam, plate and so on. Four boundary conditions I want to simulate: Free Clamped Simply supported For free boundary condition, I can use ...
2
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0answers
109 views

Mathematic modeling of an overshot water wheel [closed]

We're working on a project that require some mechanical engineering and electronics engineering. In this project we've to model this overshot water wheel (so the water comes from the left top side and ...
3
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1answer
5k views

What is the difference between tolerance and uncertainty in measurement?

Please explain with theoretical concepts and a brief example.
5
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1answer
349 views

Contradictory units for moments of inertia

I'm looking at a motor datasheet where the moment of inertia is specified in units of "oz in sec^2". I would think that inertia should have dimensions of mass * length^2. I did some further Googling ...
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1answer
1k views

How to design a gear escapement like in an old pendulum clock?

I've already got a gear that has its teets as in the picture: I want to create the mechanism from the picture, but it's harder than I expected. I think my gear is not the problem. But I'm not able to ...
0
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1answer
6k views

Counterweight of Crankshaft

I want to know the function of counterweights on crankshaft. I heard it is to able the piston to go back up, to repeat the explosion stroke. But doesnt the piston on one cylinder goes back up because ...
5
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5answers
8k views

Why are spur gear ratios not always whole numbers in practice?

Defined the Gear Ratio ($i$) as the ratio between the number of teeth on the pinion (driving gear) ($N_{1}$) and the number of teeth on the gear (driven gear) ($N_{2}$). Why is this better, if ...
4
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1answer
427 views

Biaxial Bending Sign convention

I did a couple of quick calcs to better understand the phenomenon of biaxial bending. One thing that is currently tripping me up is the sign convention. For example, if we have a rectangular beam as ...
3
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1answer
98 views

Calculating the Motion of a Particle on a Moving Surface Due to the Friction Between Them

The Basics: I am trying to come up with an equation describing the motion of a particle resting on a non-stationary surface, given the motion of the surface. Imagine setting a coin on a board and then ...
7
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2answers
1k views

Writing a filtered derivative term of the PID controller into the C++ code

Everywhere I look, be it a PID, lead, lag control or anything else, there are Simulink schematics with transfer functions. This is all nice for system response simulation, however currently I have to ...
4
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1answer
512 views

Optimising driving speed of stepper motor for maximum acceleration by trial and error

I'm writing code for a microcontroller that will ramp up the speed of a stepper motor as quickly as possible, for a jig that I'm building, that moves a workpiece from one position to another along a ...
0
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1answer
236 views

Calculate force that can be exerted by a bending actuator

I have a model of a cantilever (fixed on one end, and free on all other boundaries) that bends in response to an internal stress field. How can I calculate the amount of force this cantilever can ...
-3
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1answer
153 views

diy drone w/ carrying capacity of 7lbs? [closed]

I want to build a drone that can carry around 7lbs. Is it possible to make a drone that can carry that much weight using electric motors without it being over /$500?
2
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2answers
702 views

Solid mechanics: Deflection of a rectangular elastic membrane

I am trying to solve for the deflection $w$ of a rectangular membrane with tension $T$ acting on two opposite edges. These two edges are fixed i.e. $w = 0$. The other two opposite edges are free. The ...
1
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1answer
1k views

Is there a way rotate a wheel in a single direction but have opposing motions every 180 degrees?

In order to give you a good idea of what I want to accomplish suppose you have a telescope mounted on a single rod extruding from the ground. The telescope is free to move such that you can tilt it to ...
9
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1answer
1k views

“u” vs “n” orientation of channel profiles: why difference in strength?

For example, metal tape measures can be extended and stay straight when in a "u" orientation, but collapse the other way round. I presume the same phenomenon is why metal shelving has sheet metal on ...
2
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1answer
303 views

Isotropic materials and levels of stress

I was wondering if I was to have two objects both made of isotropic materials such as steel and aluminum and the two objects were the same geometry and I was to apply the same load and boundary ...
7
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2answers
122 views

Adding a lubricant to an already lubricious material, how is CoF affected?

I have a dry film moly-graphite lubricant (CoF=.075) and a lubricious CVD coating (CoF=.05). The CoF of each of these lubricious materials was determined using the same ASME standardized test. The ...
6
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2answers
170 views

Force Balance Question

Hello, I've been asked to show that: $$d\Gamma=\tau 2\pi r^2 dr$$ Where $\Gamma$ is the torque applied to the shaft and $\tau$ is the shear stress of the sample fluid at radius $dr$. So, I know that $...
0
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2answers
345 views

Mechanical Linkage Question - Velocity Diagram

Can someone confirm the velocity of B, given point C has velocity of 3 units/s down and point A has a velocity of 5 units/s upwards? My approach has been to resolve for the tangent velocity component ...
14
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3answers
125k views

Calculation of Clamping force from bolt torque

I'm trying to calculate the clamping force resulting from torquing a nut and bolt to a particular level. I have found this formula in various forms in a lot of places. $$T = KDP$$ $T$ = Torque (in-...
10
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3answers
14k views

What is the difference between the Polar Moment of Inertia, $ I_P $ and the torsional constant, $ J_T $ of a cross section?

This question is so fundamentally basic that I am almost embarrassed to ask but it came up at work the other day and and nearly no one in the office could give me a good answer. I was calculating the ...