This is our pre-season drivebase project. It uses the standard AndyMark gears and gear ratios but the gearbox with motors can be removed quickly from the drive train with 6 bolts for a quick replacement if necesary. The 2 gearboxes and 2 drive train modules can be built independently and then put together at the end which allows groups of students to work in parallel. It has an optional 3rd motor (775Pro) which has a lower gear ratio to give more power and speed to the drivebase. The frame components weigh about 1 pound more than the Andymark chassis. It has omni wheels on the front and back to allow for easy turning so that will add a little more weight. Also if the 3rd motors are used that will be about 3 lbs more weight.
STEP files and solidworks files are all posted on GrabCad.
I like it. I’m always concerned about having to access drive gearboxes buried deep inside the chassis, so making them removable makes life a lot easier.
I would pay attention to that fact that the whole gearbox is only attached to the frame at the bottom, and there is significant weight from the motors hanging a decent distance from the single attaching plate. You may run into some gear meshing problems if that plate bends even a few thou. Perhaps there is a way to move some of the attachment point up higher to shorten the cantilever, extend the motor mounting plate down and connect to the frame with standoffs, or something else to keep that single plate from bending.
Agreed with everyone else, you might consider mounting the gearboxes in a second way, potentially to a base plate or use a churro/other cross member between the gearboxes to increase rigidity.
Thanks for the feedback everyone. That is really useful. I like the idea of making some kind of reinforcement that goes across the chassis as long as it can be done in such a way that it doesn’t make the removal of the gearboxes more difficult. I may also consider a brute-force solution and make the mounting plate 3/8" thick instead of 1/4" and not be quite as aggressive with weight removal.
