Quote:
Originally Posted by Tristan Lall
Also, the load of 300 lbf in an arbitrary direction is a critical assumption. How was that arrived at? I can't help but think there needs to be some consideration of the other forces transmitted through the wheel and the frame in a collision—even in a static case, isn't the loading significantly more complicated in real life? Even neglecting other components of the loading, and focusing on this principal one, what was the reasoning behind this particular magnitude?
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If you assume the load case of driving into a wall with KOP grippies in the back. Assume full weight transfer to the rear or 150 lbs by both axles. Assume 0.9 COFriction and you would have a tractive force of about 70 lbs. Now for the important part. With an 8" wheel, and an approximately 3" dia sprocket, the break-free torque would require a chain tension of 8/3*Tractive Force or about 190lbs. Since the chain is reasonable flat, let's just add those and you get 260 lbs. Now a proper calc would have you draw in vectors and add in "dynamic factors" or "Safety Factors" or other "fudge factors", but these are all additional educated guesses. If you calculate the loads are hitting 250-ish, then a 300 lbs load is reasonable in order to study behaviours of the system.
Now if I was building a sattelite or a racecar, I would want better detail, but this is an excellent swag for this sort of analysis.