"It works a lot better than we ever thought it would," says William Braymen who, along with his son Glen, rebuilt an Oliver 77 tractor to run at super slow speeds of 2 to 12 ft. per minute to pull a tractor-powered field tiler.
The two Iowa farmers needed a tractor to power their pto-driven Vermeer tiler. The tiler is designed to be operated by a 35 to 40 hp tractor. But unless the tractor is hydrostatically driven, the tractor can't be geared down slow enough to pull the tiler so the tiler and tractor are winched along by a steel cable reeled in by a "deadhead" tractor parked down field from the tractor and tiler. The Braymens wanted a slow-speed tractor that would eliminate the need for the second winch tractor.
To convert to hydrostatic drive, they first cut off the belt-drive pulley on the side of the tractor and replaced it with a 1-ft. dia., 60-tooth sprocket. The sprocket is chain-driven by a hydraulic motor mounted on the tractor frame just ahead of the sprocket. The hydraulic motor is driven by a 27 gpm 3-pt. mounted pto hydraulic pump. To power the tractor, they simply put the belt drive in gear, lock the clutch down and turn on the pto. With the engine running wide open, the tractor has six gears that range in speed from 2 to 12 ft. per minute.
The Oliver 77 was ideal for the hydrostatic conversion because it has a belt drive and a live pto. According to William, another feature of the Oliver that makes the conversion work is that it has a greasable throwout bearing so they can keep it well-lubed even though the clutch is locked down all the time.
"It provides a very even, steady pull that lets us do a better job of tiling. When you use a winch and cable to pull the tractor, it continually speeds up as cable winds up on the spool. We can set this tractor at a constant speed and keep it there," says William.
"The conversion should work on any tractor with a belt-drive pulley and a live pto. A 300 or 350 Farmall would have worked fine, for instance," says William, noting that with the belt pulley disengaged, the tractor operates normally. They also use the tractor to rake hay.