I work for a small fab shop and we are making a trailer for a foundation contractor. On this trailer will be two reels that are 20inches in diameter when empty and 60 inches when full. These two reels will be used to roll up plastic matting that will be used to drive equipment over to protect the customers lawns. The plastic matting weighs 400lbs and 300feet long. The contractor plans to unroll the matting by hand, engage the gearbox and then roll up both mats at the same time with one gearbox, so the gearbox will be mounted between the two reels.
I am at a loss to calculate the torque, maybe I am overthinking it or greatly underthinking it. Typically thinking torque I think weight * radius, which would be 400lbs * 30in=12000in-lbs. But wouldn't I have to calculate the torque needed to lift the mat from the ground up to the roll? Lets say from the ground to center of the reel is 48" * 1.33lbs(400lbs/300feet gives me 1.33lbs per foot)= 64in-lbs needed.
Then what about the torque needed to pull the mat off of the ground? I am thinking that figure would be rather high after having a vehicle driving over it, further pressing it into the ground increasing the friction.
I contacted two gear companies a few weeks ago for help but so far no replies.
Any type of guidance would be greatly appreciated. Thanks to all who reply.