The BDU Hydrostatic Transmission is designed for the transfer and control of power. It provides an infinitely variable speed range between zero and maximum in both forward and reverse modes of operation. The BDU transmission can be mounted to a variety of transaxles including most HYDRO-GEAR models.
The BDU transmission is a “U” style transmission with a variable displacement pump and a fixed displacement motor. The variable displacement pump features a cradle swashplate with a direct-proportional displacement control. Reversing the direction of tilt of the swashplate reverses the flow of oil from the pump and thus reverses the direction of the motor output rotation. The fixed displacement motor uses a fixed swashplate. The pump and motor are of the axial- piston design and utilize spherical- nosed pistons which are held against a thrust race by internal compression springs.
The fluid supply for the BDU-10L/21L transmission is contained in an external reservoir and passes through an external filter prior to entering the transmission and feeding the fixed displacement gerotor charge pump. Excess fluid in the charge circuit is discharged over the charge relief valve back to the charge pump inlet. Constant flow across a small fixed orifice connecting the charge circuit to the transmission housing supplements the cooling flow.