Tank Track, Worm Gear Drive Cases

thingiverse

These gear cases have been updated to a new design and are listed in Thingiverse #2694014. Gear cases go with Tank Track 2in and other items in my things. This is a left and right side Worm Gear Drive Cases and Covers for a Kyosho RFW002/RF006 High Speed Worm Gear Set, out of a Rock Force Kyosho Crawler. The Kyosho gear has a shaft Diameter of 6mm (.235"). 6mm shafting is available from ServoCity. You can use 5/8" or 16mm OD bearings in the cases This is a small light rugged little gear box and works very well in a tank or robot. This is the second design with bigger back bearing on worm. The velineon brushless motors totally melted the small bearing I ran with the Mabuchi RS 540 motors. There is a lot of backwards thrust on the back worm gear bearing depending on tank weight or load on the gearbox, so the larger bearing will take more thrust and hold up. This gear case is made to work with a National 3/4"x1 1/2" metal angle brackets in the corner of the frame. Will require some drilling of the angle brackets. To complete this gear case you will need (1) 6x15x5 MR696-2RS bearing, (1) 6x13x5 686-2RS bearing for the worm and (2) 6x16 bearings for the axles. (bunch) 4x3/8" and 4x1/2" sheet metal screws. You will also need a special 6mm hub for the spur gear to fit on the input shaft of the worm. The only place I could find one was a company called Photoshipone. Works with Kimbrough type spur gears. This hub takes odd 5-40 screws to hold spur gear to hub and do not come with them. Recommend 60-66 tooth 48P spur gear. Sure there are many ways to hook a motor up to it, but spur and motor gear give you lots of gearing options for your tank. The Kyosho worm gear set is a 30T spur, the worm is a two stop or two turn worm (two teeth per rotation) so the ratio is 15 to 1. I ran 24-66 gears on the Mabuchi motors and 33-66 gears on the Velineon brushless motors. You will need to line the gear up straight in the case, use 1/4" nylon washers to shim the gear side to side so the worm hits the gear right in the center. Really helps to run a little grease on the gears. For the Sabertooth 2x12 to be able to fit in between the gear cases you have to trim one of the fins to clear the spur gear. Added updated gear cases that will be less drilling for the angle brackets. Okay think we have the final PDF drill guides, but keep checking back for updates. This is a work in progress. Update, I see that Servo City has both 6mm shaft and 6mm .770 hubs that can be used with their gears. Update Dec 2017: I downloaded some different gear cases that are a big improvement over these cases. Please see the Tank2 gear cases in my things. Also I have CNC machined Aluminum motor rails for sale on eBay, that will make it easier to make a tank. Instructions Gear cases left and right will print without raft or support. Drill out the screw holes to right size for #4 screws (.089"-.093") cases will crack if too small screw holes. Clean out the inside with a drill mounted sanding drum. Carefully clean out the bearing holes going a little at a time and fitting the bearings in the cases tight. Gear case cover A left and right are the covers for the output shaft through the side rail to drive track. They will need raft and support to build. It has a cutout to use a 1/4"x3/8" flanged bushing through the frame rail if you need more support for shaft. Gear case cover B is for the other side of the output shaft and will fit either case. Build with no raft or support. Gear case cover C left and right are for the big back bearing on the worm. Build with no raft or support.