New Deere Mower Targets Increased Productivity

Diesel Progress North American Edition, July, 2001 by Mike Mercer

The Worldwide Commercial & Consumer Equipment Division of John Deere has introduced a new line of lawn tractors for consumer applications. The new SST tractors feature a drivetrain incorporating Deere's Spin-Steer technology (SST), which is designed to give the lawn tractors zero turning radius capability in a conventional engine-up-front design that mirrors current lawn tractor styling. The SST tractors also exceed ANSI safety standards for weight distribution from front to rear, according to Deere.

The two tractors, the SST16 and SST18, are powered by Briggs & Stratton Vanguard V-twin gasoline engines rated 16 and 18 hp respectively. The cast iron engines feature an overhead valve design and include fill pressure lubrication with filter and dry replaceable air filters with precleaners. The engines have displacements of 480 cc and 494 cc, respectively Both lawn tractors feature an electric PTO, and a 2.5 gal. fuel tank.

The heart of the SST technology is a Tuff Torq Corp. transaxle designed and built in cooperation with John Deere. The new differential steering type transaxle allows use of a steering wheel and Twin-Touch foot controls to control vehicle movement rather than traditional lever type controls used commonly on zero-turn radius riding mowers already on the market.

The new transaxle uses a pump and motor for steering and a pump and motor for drive, along with a double planetary differential module to control speed and direction of rotation of each rear wheel. This design allows the wheels to counter-rotate for tight spin turns, and at low speeds the turning radius is the footprint of the tractor. The slower the tractor is going, the tighter the turn it will make, according to the company.

For maximum control and safety at high speeds, the differential steering continuously matches steering response to ground speed. The system provides a self-centering steering wheel that allows straight tracking. The system is also designed to be inactive while the tractor's foot-controlled transmission pedals are in neutral.

The SST16 mower is available standard with either the 42 in. all-purpose or the Freedom 42 in. mower deck. This deck features two blades, a cut height range of 1 to 4 in. and a 42 in. cut width. The SSTl8 mower is available with the 48C Convertible deck which features three blades, a 48 in. cut width and a 1 to 4 in. cutting height.

The SST's foot lift raises and lowers the mower deck by pressing a pedal. This system is easier to operate and more convenient than conventional hand lever systems, according to Deere. Hydraulic flow for the deck raise and lower functions is provided by the transaxle.