Acceleration load

[ag89]

I need an approach to come up with the longitudinal load induced by acceleration/deceleration of a car body mover in an automobile plant. The capacity of the mover is 3000 lbs and runs about 450 ft/min. I would the time to reach this velocity is about 1 sec.

 

[trainguy]

Here's an attempt at some long lost dynamics skills:

v = v (init) + a * t

450 = 0 + a * 1sec

so, accel = 450 ft/min^2

Then, F = ma

My English units skills are limited (lb force vs lb mass), so I'll pass the torch to the next contributor...

 

[austim]

Try this (working in ft, second units only) -

The final velocity is 450/60 = 7.5 ft/sec.

That gives a = 7.5/1 = 7.5 ft/sec^2, which is approximately 23% of gravity. (7.5 ft/sec^2 = 27000 ft/min^2 - the time in trainguy's post should have been 1/60 in minutes).

I don't know the total mass of your mover (including its 3000 lb load), so I will assume that it weighs 4000 lb. in all. Then the mass = 4000/g, where g is approx 32.2 ft/sec^2.

Thus the average force over the 1 second duration = 4000/32.2*7.5 = 932 pounds force.

Were this my project, I would add a healthy 'ignorance allowance' so that the mechanism had sufficient capacity for the peak acceleration.

 

[trainguy]

OOPS...[purple]

I KNEW the math seemed way too easy...

Maybe I should stick to Sum(F) = ma where a=0 (statics).