R/C Tank Combat

Tank Destroyer #T010

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Two scooter wheels with ball bearings were used as tension idlers for each track. Tracking tabs on the inner surface of each track passed between the idlers and on the outside of each road wheel to prevent throwing track.
 

 
This closeup shows the track passing over the drive sprockets with the first road wheel between the tracking tabs.

This closeup shows the track installed over the inner tension idler with the fourth road wheel between the tracking tabs but the inner idler outside the tracking tabs.
 

 
Using two separate tension idler wheels per track allows much easier track installation and removal, as opposed to two idlers that are permanently connected.

The 5/16 inch DIA idler shaft passes through two horizontal slots in the side walls of the aft hull and through the eyes of two threaded rod ends. The rod ends are carried in horizontal holes through a 1 inch square aluminum tube mounted to the hull floor. The track is tensioned by adjusting nuts on the aft side of the square tube. The rod ends are locked in place with lock washers and nuts on the front side of the square tube.
 

 
This side view shows proper track tensioning that does not require a return roller. Note that the framework for the superstructure is almost invisible in this photo.

Motor/gearboxes from Makita 6216 cordless electric 12VDC drills carry nylon miter gears that turn the drive shafts. The miter gears fit over steel spacers with 0.75 inch OD that were tapped to mate with the 1/2-20 threaded output shafts of the gearboxes. Two 10-32 set screws were used in each miter gear. This photo also shows the 1/2 inch bore flange bearings used on each end of the drive shafts. Asymmetric mounting of the miter gears on the drive shafts allows CW rotation of each motor/gearbox to cause forward rotation of their respective drive sprockets. This prevents right/left track speed mismatch caused by motor CW/CCW speed bias.


Makita 6216 gearboxes have flange mounts with four holes. Four 8-32 by 2 inch long screws were used to attach each gearbox to the vertical flange of a 3 inch by 3 inch by 1/4 inch thick aluminum angle bracket. The angle brackets were bolted to the floor of the hull with a 1/8 inch thick aluminum backing plate. The motors were connected axially to the gearboxes using the same 8-32 screws and a plexiglass retaining ring. The gearbox speed selector wire was held in the low speed position by washers and extra nuts on the 8-32 screws.

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