ATR5-b0 - Front

ATR5 build 0 (initial state) is a Snapper Hydro manufactured around 1993.  Briggs & Stratton 14hp OHV gasoline engine, model 287707, type 0228 01.  Purchased used for $135 (with hood missing), ATR5 is somewhat weaker than ATR3 but has three key advantages:

• Continuously variable hydrostatic transmission, obviating the need to actuate the clutch to change speed and even direction of motion. In fact, experiment indicates that the clutch can be left engaged at all times, even during engine startup.
• Integrated choke/throttle lever, eliminating the separate choke actuation point.
• Lower weight and volume for ease of prototyping.

Dimensions:

• 

  ATR5-b0 - Rear

  The metal chassis is 29″ wide at rear, plus 2.5″ protruding tire edges on each side.  Mowing deck extends an 9″ beyond the left chassis edge, 2″ on right.  Front wheels are 33″ wide including tires.  The engine is 16″ wide.

• 64″ long, plus a support bar extending 4″ from the stern.
• The gas tank is 6×12.5×7″, but is not a regular cube. Capacity is approximately 2 gallons.

Control actuation points:

• Steering: 270 degree (3/4″ turn) in each direction results in a 40 degree rotation of the front wheels.  Approximately 20lb torque at 5in (110 lb-in) on a smooth concrete surface.
• Hydrostatic shift: Lever travels 7″ through a 70 degree curve.  7lb actuating force required.
• Lower deck engage: Lever travels 3″ through a 45 degree curve.  40lb actuating force required. Normally-On relay blocks power to starter motor when deck is engaged.
• Throttle/choke: Lever travels 2.5-3″ linearly. 25lb actuation force.  Choke detent is above highest throttle position.
• Ignition key: 90 degree turn.  Actuation torque difficult to measure.
• Clutch: Pedal travels 6-7″ through a 90 degree curve.  Torque is difficult to measure as the pedal seems to be somewhat damaged at the swivel point. Normally-Off relay blocks power to starter motor when clutch is engaged.
• Hydrostatic release valve: Lever located between the rear wheels.  Only necessary for freewheeling motion when engine is disengaged.
• Deck height adjustment: Requires 2D motion due to height detents. Torque not measured.

R5-b0 - throttle/choke