Harbor Freight Gearbox Conversion to Ball Bearing Support on a Diet

thingiverse

This project resulted from adapting the previous BB printed gearbox housing to fit within the designated chassis. The original project can be found at https://www.thingiverse.com/thing:2761685. I initially utilized a Harbor Freight cordless drill for drives on both sides of my 12 lb bot, as well as the weapon lift. You can use the stock gearbox housing, but it is only supported by bushings and would require regular greasing to remain lubricated and cool. The bottom line is that the HF gearbox is not designed to handle side loads imposed by the driveline. Here's a redesigned gearbox mountable from three different sides using M5 fasteners. The gearbox is held together with three M4 x 35mm long button socket head screws. The motor attaches to the gearbox cover using the same fasteners as it was attached in the original design. The original snap ring and one of the thrust washers complete the assembly with minimal endplay. The bearings are 28mm OD x 12mm ID x 8mm high shielded, available from Fastenal for $1.49 each. Two bearings are required per gearbox. Bearings can be sourced through Fastenal at https://www.fastenal.com/products/details/0474374?term=bearing&r=~%7Ccategoryl1:%22603582%20Power%20Transmission%209and%20Motors%22%7C~%20~%7Ccategoryl2:%22610631%20Unmounted%20Bearings%22%7C~%20~%7Ccategoryl3:%22612457%20Ball%20Bearings%22%7C~%20~%7Ccategoryl4:%22610637%20Radial%209and%20Deep%20Groove%20Ball%20Bearings%22%7C~%20~%7Csattr01:%5E12mm$%7C~%20~%7Csattr02:%5E28mm$%7C~ Fasteners can be found at http://www.mrmetric.com/M11836. The output shaft can be modified as desired. My design is being converted to a .375" Hex. All this work was done for my 12 lb bot, which can be seen at https://www.thingiverse.com/thing:2602044