Gear pair to drive AndyMark Placation wheels from Pitsco Tetrix hubs by benmcl

Last crawled date: 3 years ago

My FIRST FTC Team #4357 wanted to use 8" wheels for this year's competition to get up the 'mountain' and over the bars, but the Tetrix build kits only include wheels up to 4". We found the wheels we wanted at AndyMark (http://www.andymark.com/Plaction-s/103.htm), but their hub pattern is different than Tetrix. We tried to recreate a hub+gear with the same tooth dimensions used in Tetrix, but the teeth were way too small to 3d print and make strong. Our solution was to make a gear that fits the Tetrix MAX hubs (http://www.tetrixrobotics.com/Search/hubs?st=0) using a much beefier tooth, then designed a matching gear+hub for the wheels.
The Gear+PlactionHub places the gears very close to the tread which keeps things strong (less unwanted torque). We had to create the Gear+PlactionHub+Spacer when we needed extra space to wrap traction tape around the tread.
The current gear ratio is 30:60 (or 1:2). We included the design files so you can adjust the gear ratio to your liking. We created the designs in FreeCAD, but also exported as STEP so you can import into your favorite CAD program.
We printed in ABS, 0.3mm layers, 4 perimeters, 25% infill and the gears lasted the entire FTC competition season. All the extra holes act as hollow rivets binding the top to the bottom shells.