AndyMark Evo Shifter Stages

What are the ideal gear ratios for a two stage AndyMark Evo Shifter gearbox powered by two NEO motors and driving four 4" Colson wheels in a tank drive chassis?

I highly suggest you take a look at my design spreadsheet and ILITE’s drivetrain simulator. Have a go at answering the question for yourself, then you can come back here if you have questions.


Totally with @AriMB here. The answer to your question will depend greatly on the answers to these three:

  • What is your robot’s expected total weight? Include battery and bumpers. Other things equal, heavier robots will benefit from slower gearing, and lighter robots from faster.
  • How long you expect your sprints to be? A PowerUp vault filler had a sprint distance of less than ten feet. D. Deep Space and many PowerUp cases were about 15 feet. Gear-running in STEAMWORKS was 40-50 ft. Boulders in STRONGHOLD were usually 20 foot sprints separated by a slower defense crossing. In general, the shorter the sprint, the slower the gearing to optimize the sprint, because acceleration is more important than top speed.
  • Why you are shifting in the first place? - is it to get a blazingly fast top speed for long sprints with a good startup, or so that you can switch to low gear for pushing matches or powering through obstacles? The first case calls for faster, the second for slower gearing.

You should figure out the answers to these three questions before you start trying to use Ari’s calculator.

Added: and OBTW, if you’re not planning a shifting gearbox, the first two questions are still the key questions to answer on the way to figuring out your optimal gear ratio for a given set of motors and wheels.


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