Wheelift builds two types of wheeled transporter systems — fluid power and electric power. 

Fluid Power:  In the fluid power configuration, and depending on the weight and operating conditions, there will typically be two or four power driver modules and the rest will be unpowered idler units. Steering torque is delivered from hydraulic motors through a slew gear connecting to the upper portion of the wheel module and anchored to the underside of the transporter frame. Rotational torque is transmitted from the frame to the lower axle assembly via a square shaft and square nut assembly in the center column.  In a two driver configuration, the drivers will be located on diagonally opposing corners of the transporter.  This layout assures that tractive effort is applied to the center mass of the transporter uniformly in both linear and lateral travel directions.

Elelctric Power:  In the all-electric configuration, every wheel is driven.  Steering occurs by precisely varying the travel speed and direction of each wheel — “differential steering.”  Interestingly, this is the only instance in mechanical design that steering does not rely on applying torsional anchor on the frame to force the axles to turn. There is no torsional force reacting on the transporter.  Torsion only occurs between the tires and the floor. 

For infinite precision control, AC servo motors provide the tractive and steering effort.  Without the need for slew gear rotation, several inches of reduced deck height are acquired.