Patent ID: 8819966

Claim:
A machine comprising: a chassis; a ground drive propulsion system connected to the chassis; a trencher attachment connected to the chassis, the trencher attachment including a boom that supports a material reduction tool; a control linkage and a lift control valve configured to adjust the orientation of the boom relative to the chassis and hold it in a fixed position relative to the chassis, the control linkage including a hydraulic cylinder in fluid communication with the lift control valve, the lift control valve being movable to a lock-out position wherein fluid is substantially prevented from flowing into and out of the hydraulic cylinder thereby holding the boom in the fixed position relative to the chassis; a boom load measuring system configured to measure the load on the boom when the lift control valve is in the lock-out position, wherein the boom load measuring system is independent of the pressure of the hydraulic fluid that drives the material reduction tool; and a drive control unit that receives information from the boom load measuring device and is configured to automatically slow the ground speed of the trencher based at least in part on the load on the boom.