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A Champion For Two-Wheel Drive
While tractor makers around the world have turned to 4-wheel drive to utilize the engine power available in today's large agricultural tractors, a young enthusiastic engineer and tractor maker in Australia crusades strongly for the 2-wheel drive configuration.
He's Carl Upton, of Uptons Engineering, a country manufacturing firm in Southern NSW. He believes, up to a point, that 2-wheel drive tractors will do everything and more than 4-wheel drive. That point is up to 350 hp!
What's the secret? Carl says there is none: "It's just a matter of weight - plenty of it in the right place - and tires big enough to accept the load at reasonable wheel slip performance."
Well, if it's weight you want, the 2-wheel drive tractors built by Carl Upton are not lacking. How does an operating weight in excess of 51,000 lbs. for a 2-wheel drive sound? Admittedly, we are talking about a 350 hp. tractor (gross engine) but that's considerably more weight than is found in many of the big 4-wheel drives.
Upton has been custom building big tractors for some years and is adamant that four drive wheels are not needed for tractors under 350 hp. Many tractor men would argue about that and are skeptical about Carl's philosophy and his claims that he can build tractors up to 350 engine hp that have lower wheel slip than 4wheel drives and higher drawbar efficiency.
The rear half of Upton's 350 hp. 2-wheel drive tractor is constructed from 4 in. thick plate steel and the bare chassis weight is 6 tons, with main front chassis members constructed from 15 by 6 by 1' in. channel.
Another example of the massive weight and strength built into the Upton machine is the 350 gal. fuel tank which has a floor made from 2/8-in. plate with the balance of the construction utilizing 1 in. plate. Weight of the fuel tank empty is 3 tons.
The drawbar itself weighs 1,500 lbs. and is made from 6 by 4 in. plate and is contained within a 4 in. plate frame. The pull is taken on a 3 in. dia. hardened steel pin.
For tires, Upton used earth mover tires, measuring 33.5 by 33 by 20 ply which have a circumference 20%
greater than the 30.5 by 32 agricultural tires commonly used on big 4-wheeled drives.
Upton believes that any 2-wheel drive tractor should carry most of its weight on the rear drive wheels. The Upton tractor puts this into effect with static weight of 20% on the front and 80% on the rear, and the long (3.9 meters) wheelbase helps stabilize weight transfer and provide a smooth ride. When the tractor is under load, dynamic weight on the drive wheels can be as high as 88% of the total vehicle weight.
The tractor's drive axle has a capacity of 65,000 lbs. and the planetary gearing incorporates guided needle rollers and nitrided gearing. Reduction ratio is 4.32:1.
The driving head assembly is an Eaton 23121 series with a 6.17:1 ratio. Overall ratio is 26.65:1. The axle is wholly of Australian design and manufacture, excepting the Eaton driving head.
An exclusive feature of the cab control layout is the method of mounting the throttle pneumatic gear shift valve and parking brake valve on the side of the swiveling seat. This permits the operator to control tractor speed and gear changes regardless of the direction he is facing inside the cab.
The tractor is powered by a turbo charged and after-cooled Cummins 6 cylinder diesel engine which produces 350 hp. at 2100 rpm. Driveling components include a Spicer 2-plate 15'/2 in. clutch, a Spicer SST 14 transmission and Spicer 1710 series universal joints.
Field tests have indicated the tractor can produce a sustained pull in excess of 20,000 lbs. without ballast in the rear tires.
Despite its high engine power for a 2-wheel drive configuration. the engine can be fully loaded in the field at speeds as low as 6.4 km/h. The low speed lugging ability can be attributed to the high weight to horsepower ratio of 147 lb.Ihp. The adjustable height drawbar (through 24 in.) fully utilizes weight transfer and provides increased traction under load.
For more details, contact: FARM SHOW. Followup, Carl Upton, Uptons Engineering, PO. Box 55, Corwa

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1980 - Volume #4, Issue #1