Abstract: A method of activating a drive system with a portable power source includes performing at least two actions between the power source and the drive system to effect activation. Performing any one of the two actions without the other of the two actions will not activate the drive system. The power source is preferably a hand-held power drill or a power pack.

Abstract: A slip clutch acts between a shaft and a housing. The slip clutch includes an oil reservoir within the housing and one or more slipping surfaces disposed in the oil reservoir that are keyed to the shaft and possibly alternately to the housing. The slipping surfaces may include stacked plates or washers. Each of the washers includes an oil groove or other structure on one surface thereof that maintains a consistent film of oil on the washer surfaces. The stacked washers slip relative to one another such that the shaft rotates relative to the housing upon an application of torque that exceeds a predetermined torque.

Abstract: A retractable wheel assembly includes a wheel frame supporting a wheel, and a pivot bracket assembly secured to the wheel frame. The pivot bracket assembly is displaceable between an extended position and a retracted position. A biasing mechanism is coupled with the pivot bracket assembly.