The human power tractor allow a man or several to move very large weights. A solid back axle with two 64" tractor tires and a 16" gear. A gear the size of the tractor tire drives it -- this is driven by a 12" gear on thee same axle with a 121" gear. This gear spokes have handhold that multiply by ten times. Two more 12" by 121" axles add one hundred fold increase in power. A human inputs force on to the face of any of the three 121" gears allowing the human to act as one to a thousand transmission any of the gears above become a flywheel and allow steady flow of power to the wheels.
Yes it would be very slow at heavy loads slugs would blow by you. However with this a hundred pound man can pull 100,000 pounds and ten men a million pounds.