Self-Propelled Grain Cart Built From Mack Truck
"It gets grain out of the field fast and frees up a tractor," says Gerald Bruner, Conrad, Mont. He and his son, Brad, built a self-propelled grain cart using the frame of a 25-ton Mack "rock truck" used to haul rocks out of mines. It?s equipped with a home-built 900-bu. hopper on back that measures 20 ft. long by 13 ft. wide. It travels at speeds up to 28 mph.
The cab came off an Elgin street sweeper, complete with dash, steering column, seat, heater and air conditioner. The 450 hp Cummins diesel engine, with Allison automatic transmission, was pulled from an old semi truck. The hood is off an old Versatile 950 4-WD tractor. The machine rides on 5 1/2-ft. tall wheels on back and 5-ft. tall wheels on front.
"We used it on our wheat and barley crops for the first time last fall. It worked great with no problems," says Bruner. "It'll unload the 900 bu. load in only about 5 min. with its 16-in. dia. auger.
"My son drives the combine and I haul the grain. In the past, every time I took off for the grain bin I knew that when I returned to the field the combine would be waiting for me. I didn't think adding another pull-type grain cart would be the answer because it?s too slow and would need another person to operate it."
The two men lengthened the Mack truck frame 6 ft. on front and 4 ft. on back, using 3 by 2 and 2 by 2-in. sq. tubing to build a frame for the hopper. The sides were fashioned out of sheet steel from old fuel tanks. A pair of side by side, 12-in. dia. drag augers bring grain to the back.
One auger discharges grain out a chute on one side of the hopper to load grain bins, and the other feeds grain into a 16-in. dia. fold-up auger that's used to load trucks. Both drag augers are covered by a series of trap doors that are connected together by a metal rod, allowing a hydraulic cylinder to open and close all the doors at the same time to adjust grain flow. Each door sets inside a separate compartment, making grain cleanout an easy job.
The grain cart has four hydraulic systems, which were designed by Big Sky Hydraulics of Great Falls, Mont. One system drives the twin augers at the bottom of the hopper; one drives the 16-in. dia. unloading auger; one opens and closes the trap doors; and one operates the machine's steering system.
"It's an awesome machine and works amazingly well. We spent about $40,000 to build it," says Bruner. "We scrounged most of the materials and worked on it for 3 winters. The Mack truck came with an awesome set of brakes, which is really important when hauling this much grain. We even made our own fire extinguisher system, mounting a 30-gal. water tank and 75-ft. hose reel on one side of the hopper. The water tank is pressurized off the Mack truck's air brakes.
"We also fitted the machine with 3 remote-controlled cameras" one on each side of the hopper and one on back" and they really come in handy," notes Bruner.