Climber Gear Boxes

So as we know, a spool with velcro seems to be a popular strategy for now as we get all the legalities sorted. For those that are using this design or something similar, I was wondering what gearing ratio and motor you all are using and what would be best for a full weight robot?

For what your team specifically needs as far as ratios and motors, I would suggest you use JVN’s Mechanical Design Calculator (most updated here: If you download the most recent file, it will give you an excel spreadsheet with many different tabs. I would suggest using the “linear mechanism” tab to find out exactly what the best solution is for your specific team.

As posted above!

Start with the motor (or a small slate of candidates), then figure out a gear ratio required.

To figure out the motor, calculate the power you want from it. In the case of a steady climb, power = weight * height / time. If you do weight in pounds, height in feet, and time in seconds, know that a ft-lb/s is about 1.35 watts (or for mental math, 3 ft-lb/s is about 4 watts).

Look at the power output of various motors. Try to find a motor where the power at maximum efficiency is close to the desired power. If none work, try two of these motors. Then, go back to the JVN calculator and try out those motors and look for the best gear ratio. Remember that the key things are that you do not trip your breakers (draw way more than their rating for any length of time) or burn up your motors (run them at inefficient slow speeds or stall). Gear ratios will have to be calculated separately for different motors, even if they have similar power because they run at different speeds.

We’re using a Mini CIM on a VersaPlanetary at somewhere between 30:1 and 50:1 (haven’t decided yet; both are fine). The VersaPlanetary is rated for this kind of torque output, and it will lift our robot in about 5 seconds.

Shameless plug here. If you aren’t sure what motor(s) and reduction to use for your climber (or any mechanism), check out the spreadsheet calculator I just posted here. It lets you vary motor type & number, force, and moment arm and calculates the reduction that will put the motor at peak power output. Then you can check the top speed and see if the chosen motor is strong enough or you need a stronger motor.