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Mechanical Engineering

Dusty Devil Dale

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The other thread on spring length reminded me of a couple final exam questions in one of my long-past Mechanical Engineering classes.  just as brain teasers.


Q1.  You've flown out to Hawaii on a fishing vacation.  On the second day out, you hook up a huge yellowfin tuna that is streaming away from the boat at 1,000 m/minute.  Your reel is a 10/0, strung with 120 lb line with a diameter = 0.04 ".  The reel spool is 170 mm wide and has a beginning depth of 58mm.   


1.  Develop a formula to calculate the changing reel RPM as more and more line is stripped from the reel by the tuna running at constant speed.    


2.  Develop the formula to calculate line strain applied by the tuna against the reducing line spool diameter.   Show all steps and derivatives.  


Q2.  A 1-1/2" vertical shaft with a 5 rev / inch normal Acme thread is to be rotated to lift a 220kg weight.  The thread tolerance/fit is Class B.  There is no gearing or other diametral speed reduction.


1.  Calculate the torque in foot-pounds required to rotate the shaft clockwise to raise the weight. 


2.  What size (in HP) motor would be needed?  


I could work these 60 years ago, but today?

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