Questions tagged [applied-mechanics]

Questions about using applied mechanics to model engineering problems.

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5
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1answer
148 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
590 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
437 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 ...
0
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3answers
101 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
651 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
108 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
341 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 ...
1
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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
418 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
97 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
508 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
148 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
665 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
121 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
333 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
122k 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
13k 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 ...
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2answers
294 views

Find the load applied to each wheel by the anti-roll bar

Wikipedia says that an anti-roll bar is a device that balances the weight of car between the wheels, preventing it from rolling. I want to simulate this in a game, but I don't know the equations ...
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1answer
957 views

Bearing Alignment Moment Reactions

I'm trying to analyze a simple shaft supported by two bearings and subject to a single point load. But I keep coming across assumptions that only consider the vertical reactions and neglect the moment ...
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2answers
78 views

What mechanisms can be used to move a drum at constant speed without an electrical system?

How could I design a paper spool or drum that is moving at constant speed without electrical system? What mechanisms are available? I know that some paper tracing system was being used in 19th ...
0
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2answers
6k views

What is the relationship between drive shaft diameter and torque output?

I have a DC motor with a shaft with a diameter of x. It would produce some torque T because torque is proportional to radius. If I stuck a pulley on the shaft of radius 2x, then I would produce twice ...
5
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2answers
9k views

Calculating torque needed to climb a graded hill

I've been designing an electric skateboard which is driven by only one of the rear wheels (for the moment). As I was picking out motors for the board, I soon realized I would need to find a balance ...
0
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1answer
580 views

Converting accelerating linear motion into constant rotational motion [closed]

Suppose there is an accelerating mass along a straight line, and you would want to convert that linear motion into rotary motion. Is it possible to convert that accelerating linear motion into ...
1
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3answers
649 views

Cantilever with three parallel rods

This is slightly similar to a question I previously asked but now I decided to simplify the question and model it similar to a design I have in mind. I sketched out a slightly simplified model. It is ...
0
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2answers
512 views

Deflection of parallel rods with force at an angle

As in the picture below, there is a static force $A$ being applied at 45 degrees to a rigid rod attached to a rigid plate. The plate is supported by two rods of length $B$ and diameter $D$, each of ...
10
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2answers
4k views

Why do we neglect the radial stress in case of a thin pressure vessel?

A cylindrical or a spherical pressure vessel, having inner diameter $d$ & thickness of wall $t$, is called thin if $\large \frac{t}{d}<\frac{1}{20}$. $\bullet$ Thin cylindrical pressure ...
3
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2answers
2k views

Pneumatic cylinder force output and impact energy

I'm designing a little tester for a project which uses a pneumatic cylinder. The pneumatic cylinder's purpose is to apply an impact on a hard surface to test for deflection of the surface. When I ...
2
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2answers
5k views

How do you find the kinematic degrees of freedom of a mechanism?

In the above mechanism it is required to find the generalized coordinates to write equation of motion of the MDOF system. I just want to ask how do we actually approach such a problem? How to identify ...
7
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3answers
1k views

Compound gear system ratio

This might be a stupid question, but I'm new to mechanics, so please bear with me. Suppose I have a compound gearing system defined in the image below (not to scale). The green gear is the driving ...
13
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1answer
3k views

From an engineering standpoint, what is the purpose of the indent in a coffee lid?

I've see the same lids every day but I never really thought about their construction. There is an indent in a "Solo Travel Lid" for coffee cups that is just above the hole that you drink the ...
7
votes
1answer
2k views

Calculate effort to raise hinged lever with distributed load

My father-in-law would like to install a hinged stair system in his garage that allows him comfortable access to his attic space. He wants the stairs to swing up flush with the ceiling when not in ...
5
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1answer
543 views

How to transfer rotational energy into lateral energy only when rotating one way?

Is there a general way to convert rotational energy from a gear or something into lateral motion toward or away from the gear? I could use a piston type construction, but I only want the lateral ...
1
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2answers
696 views

What is micro-electromechanical systems (MEMS)?

I know definition but how would you explain to complete layik ( as me ) what is MEMS and how it is used. Examples: Silicon nanopore membranes (SNM) have been prototyped from silicon substrates by ...
2
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0answers
378 views

Impact force with unknown deformations or time duration?

I expected to find more documentation on analytical solutions to determine the contact force between bodies, where deformations ($\delta = \delta_{1} + \delta_{2}$) and impact time ($t = t_{f} - t_{i}$...
2
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1answer
4k views

Finding Neutral Axis of a simple shape undergoing axial load

I know that the neutral axis occurs where the sum of stresses (bending + axial) is equal to 0. I have found the stresses and drawn a diagram to represent forces. How do I determine the neutral axis?
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2answers
68 views

Optimizing support board placement on work table wing

I'm currently building a work table that will have "wings" on each side that are fixed to the mid section of the table via a hinge. These wings, in turn, have hinges that fix a support board to them ...