Tagged Questions

0
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1answer
40 views

What lifting mechanism is likely to have the best energy recovery ratio?

Suppose I was designing an apparatus which needed to lift 250kg 5cm high, hold it there for a few seconds, and then lower the object back to the original height. Such a process would need to be ...
0
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0answers
125 views

How to calculate mechanical advantage of a worm gear?

How to calculate mechanical advantage of a worm gear? My textbook simply use the turn ratio as the mechanical advantage, but I'm not sure how that works. My thinking: If the worm has a radius of ...
-2
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1answer
61 views

Measuring vibration and converting to force (N) [closed]

The test is: To have a rotating machine, bolted into a factory floor. To measure the vibration on 3 axis (output of accelerometers can be acceleration or velocity in $\mathrm{m/s}$ or ...
0
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1answer
107 views

Shear Flow corresponding to Eccentric Shear Force of a Closed-section Beam (Structural Analysis - Mechanics)

Been stumped with this question for way too long... its a beam with a thin-walled rectangular cross-section, and a shear force is acting at a distance from the shear center. I know my decomposition of ...
2
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0answers
95 views

Internal moment in the hull of a pressure vessel

This question is related to the course structural analysis. As part of our exam grade every student has been given different multiple homework assignments which we have to solve. One of the problems ...
1
vote
2answers
160 views

Total Mechanical Advantage

How do you find the net Mechanical Advantage (MA) of two joint machines. Do you add or multiply the individual MA? Suppose I have two sets of wheel and axle connected by a fixed pulley. Each of the ...
0
votes
0answers
215 views

How to decide velocity profile for two stepper motor in robot driving

A robot has 2 parallel driving wheel. I don't know the friction of the ground surface. However, I can set the acceleration, starting velocity, ending velocity. The velocity profile has to be ...
0
votes
2answers
141 views

Why aren't stratospheric balloons compressing their helium to descent?

I can't find a reference of a working stratospheric balloon mounted with a compressor to control its altitude. Is there a big physical difficulty (such as compressor weight/power ratio, or power ...
1
vote
1answer
212 views

How to find the value of the parameter a in this transfer function? [duplicate]

Possible Duplicate: How to find the value of the parameter $a$ in this transfer function? I am given a transfer function of a second-order system as: $$G(s)=\frac{a}{s^{2}+4s+a}$$ and I ...
1
vote
1answer
84 views

How to find the value of the parameter $a$ in this transfer function?

I am given a transfer function of a second-order system as: $$G(s)=\frac{a}{s^{2}+4s+a}$$ and I need to find the value of the parameter $a$ that will make the damping coefficient $\zeta=.7$. I am not ...
0
votes
1answer
242 views

Why is the optimum wheel size of a bicycle about the same as that of a car?

The optimum wheel diameter of cars and bikes appear to be roughly the same, certainly well within an order of magnitude. This is despite very different average speeds and propulsion mechanisms. Can ...
0
votes
2answers
813 views

Calculation of the maximum load to the bar

Looking for a way of calculating the maximum weight (W) to the rod with the given length (L) where the rod did not break and that only bend for (b) mm. Need only approximative solution (read: ...
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3answers
3k views

Yield Strength versus Ultimate Strength

What is the qualitative difference between these two: As seen on the table Typical yield and ultimate strengths. I am trying to resolve the meaning of the phrase "contact yield stress" from C. ...
4
votes
2answers
1k views

Shape of Fan Blades

How is the shape of the blades of an air fan determined? Trial and error, or is there a theory behind it? What are they trying to maximize, volume of air dislocated per rotation?
1
vote
3answers
5k views

What is the difference between a moment and a couple?

In mechanical engineering, the torque due to a couple is given by $\tau = P\times d$, where $\tau$ is the resulting couple, $P~$ is one of the force vectors in the couple and $d$ is the arm of the ...
0
votes
3answers
314 views

How does solar activity affect the ISS?

Currently the sun is launching some intense solar flares. http://www.guardian.co.uk/science/2011/feb/17/solar-flares-northern-lights-uk Th article I've linked also mentions how a "coronal mass ...