Basic R/C Rubber Tread Tank

thingiverse

My current solution for a rc vehicle I can drive in grass up to around 6" tall while still doing ok on smoother surfaces. Overall design objective was a simple setup with a modest overall cost (especially if you have a few makeblock parts already). Tank uses two brushed high turn 555 motors running on 3S. Unit is about 250mm (10") long with an overall weight around 1.3kg (3 lbs) and top speed of 18 kph (11 mph). Practical speeds in grass are limited by the lack of suspension, tread slip on the grass, and retention of the rubber track - but it is at least 10 kph (5-6 mph). Post-Printing Bill of Materials Frame and wheels 2 144mm 0824 Makeblock Beam (9 sets of holes) 1 112mm 0824 Makeblock Beam (7 sets of holes) 2 64mm 0824 Makeblock Beam (4 sets of holes) 2 8x8x24mm makeblock shim (printed) 2 12v motor mounts (printed) 1 plastic skid plate / makeblock mounting plate (printed) 2 56T spur gear (32 Diametrical Pitch (per inch)) - printed 2 90T makeblock wheel 2 Large makeblock wheel (printed) 2 large makeblock wheel mounted (printed) 6 threaded shafts with 4x8x3mm bearings and shaft collar 48 pieces of rubber makeblock tread with pins M4 hardware Electronics 2 High turn 555 motors or similar - I had WB555-12 (6000rpm no load at 12VDC) with a 11T gear on hand 2 Brushed ESC with brake (10A is enough) - Unit drives fine without reverse and easily pivots around the stationary tread, 1 3s battery or similar - Used a 2200mah 25C and run time is 30+ minutes Transmitter and receiver with programmable mixing and limits Assembly Tips Make sure the center wheel is mounted so that it pushes the tread down slightly between the front and back wheels. This reduces power when turning and dramatically improves tread retention while turning on harder surfaces. Observations Tank travels thru the grass at about a 15 deg angle. The angle increases for taller grass. The vehicle performs best on grass that is reasonably even and free of sticks where it will ride suspended on the grass an inch or two off the ground. This grass suspension allows for higher speeds. A quick application of full throttle can cause a wheelie and usually a flip onto its back. After an extended run, the vehicle usually smells like freshly cut grass due to ingestion of grass between wheels and tread and into the open gearing. I'd like to improve tread retention in future revisions.