Experimental study on the steady-state performance of closed-circuit hydrostatic transmission drives for the rotary head of blast hole drill machine using different capacities bent axis hydro-motor

Blast hole drill machines are used for drilling in rocks, which are of soft and medium-hard nature. In such machines, the drilling is accomplished via a hydrostatic transmission (HST) drive. This article presents the steady-state behaviours of two different HST drives for the rotary head of drill machine. In the first drive two high-speed low-torque (HSLT) hydro-motors, having an individual capacity of 10 cc/rev with the gear reducer having 15:1 gear ratio; whereas in the second drive identical numbers of hydro-motors, having an individual capacity of 16 cc/rev with the gear reducer having 10:1 gear ratio is employed. Bond graph technique has been used for modelling the drives. Based on the model, the analytical relations associating the torque loss, slip, and the overall efficiency linked with the drives are derived. By utilizing them, the performance corresponding to the HST drives is obtained in terms of the normal operating speed range linked with the drill machine utilized in mining applications. From the study it is observed that, for the constant load torque and the drill speed, the second drive (combination of two identical higher size hydro-motors along with a lower size gear reducer unit) shows better performance than the first drive (combination of two identical lower size hydro-motors along with a higher size gear reducer unit).