Gearbox for FRC Denso Throttle Motor

thingiverse

This gearbox was designed specifically for use with the Denso Throttle Motor supplied with the Frist Robotics KOP over several years. The entire gearbox housing and gears are 3D printed in PLA plastic, which appears strong enough for the motor's limited power. After several minutes of running and loading the output shaft of the gear box, I noticed no degradation in the printed gears. Two sets of gears provide a total gear reduction of around 10:1 and 18:1. The combined weight of the motor and gearbox is less than one pound. The gearbox and gear files are available to all FRC teams courtesy of "Andromeda One - TEAM #4905." Our only request is that if you print or use the gearbox, you post a picture on our Facebook page: https://www.facebook.com/frc4905. If you have any suggestions for improving the design, please post them here on Thingiverse. I intend to find and use a plastic safe lubricant if we decide to use the gearbox on our robot. Starting with the gearbox back, look inside and you will see a hex opening that fits a #8 nut. Place a #8 nut in the hole. Using the motor terminals as a guide, insert the Denso motor on the outside of the gearbox back. Place a lock washer over the #8-32 x 3/4" bolt and lightly screw it into the hole containing the nut. Don't tighten the screw until all screws are in place. Now place the 1/4" shaft into the 1/4" hole inside the gearbox back and place one of the brass washers over the shaft. Now press fit the brass bushing into the gear with the 5/16" hole. It should fit snugly. If not, add some tape to the bushing and insert it. Now place the gear over the 1/4" shaft so the plastic gear mates with the motor gear. Place the second brass washer over the 1/4" shaft onto the gear. Press one of the HEX flange bearings into inside opening of the gearbox back. Place the ThunderHex shaft into the bearing. Place the second gear over the ThunderHex shaft starting with the non-gear side. The first and second gears should mesh well. Place the second HEX flange bearings onto the ThunderHex shaft starting from the flanged side. Crimp the 0.187" Female Terminals to the ends of 16 - 18 AWG stranded wire. These will be your connection to the motor. The motor draws 7A at stall, so 18 AWG wire or larger is all that is needed. Once the wires are attached, press the terminals onto the motor terminals. Now take the gearbox front and mate it with the gearbox back. Place two of the #8-32 x 2" Flat Phillips Countersunk Machine bolt into the holes attaching the motor. Place a lock washer and nut over the end of both screws and tighten down the motor evenly. Place the last Flat Phillips Countersunk Machine bolt in the hole with the counter sink and attach using a #8 washer, lock washer, and bolt - in that order. Tighten to about the same tension at the motor bolts. The last three #8-32 Round Head Machine bolt act as both the gearbox mounting bolts as well as bolts that hold the gear box together. The length of the bolts will depend on how you are going to mount the gearbox. You will also need to determine how you will keep the ThunderHex captive to the gearbox. This could be done with a bolt and washer on the motor side, and a hex collar or gear on the other. Note that I have not used any lubricant on the gears yet and it seems to work just fine.