We need a little help checking gearbox rations if someone has a moment. We have tried klib and recalc and are a little confused about how to interpret the results. All numbers below are from ReCalc
For our intake, we have a mass of 15 lbs, offset 12". We are thinking 1 Neo with 60:1 reduction to give us a rotation time of 0.482 s. We do need some fine control on the stop angles because we need to be able to adjust the angle. We want the intake to retract and extend pretty fast. We have a through bore encoder on this axis.
For our adjustable shooter, we have a mass of 20 lbs, offset at 12" we are thinking 1 Neo with 35:1 reduction which would give us 0.613 seconds to traverse 20 degrees. We are very concerned about controllability on this. Speed is not so much of an issue. We have a through bore encoder on this axis.
For climb - we are using two climber in a box units from Andymark. AM recommends 16:1 gear ratio on these but we are worried about drifting down during the 5 seconds after the end of the match. It seems like 36:1 or higher might be better since the drop distance is so small this year. No other braking mechanism used. We dont want things to be too slow though.
Bonus side question - this is the first time we have used a climber like this - do you start the robot with the arms up and when you start the robot do you just push the arms down? I’m wondering if we need to machine in a pin or something to pin the arms in the lowered position for safety but I think that would kill the springs.
my team used climbers in a box in 2022, we started matches with the climbers down and lifted them up when we needed to climb, it doesn’t affect the springs
i’m not exactly sure what motor you are using for climbing but you can set your climber motors to brake mode and that should keep you from drifting down unless your robot is too heavy
Have you looked into counterbalancing with gas springs so the mechanisms is “weightless” (same idea as CF springs on elevators). If you had a ~ 40lb gas spring at 6" on your shooter (or even 3 inches) things become a bit easier to deal with. With some careful placement it can also help with the different loads of being mass @ 90° vs mass that is vertical.
Second: it looks like you are using the NEO freespeed^ (which is fine for some things, but not realistic for constrained axes like this) the motor will never get up to freespeed and back down, for a more realistic guess I would halve these numbers at least as they would require some very aggressive control loops. The NEO produces max power (with 1.5 Nm of torque) at ~2000 rpm. There is a pretty wide range of solutions reasonable solutions for gear ratios in here without bogging down the motor.
^Recalc does account for the motor getting up to speed (or at least does its best).
Ok, so a few questions to ponder:
Does your shooter only need to adjust 20°? If so and you are worried about control you could increase the reduction. Traveling the full range of the axis in less than as second may not be necessary in your application.
How are you achieving these reductions? If it is via planetary gearboxes from Rev or Vex then things are pretty easy to change and give software a little bit to adjust code and control constants.
The pin for safety is probably a good idea for transport. I don’t think it hurts the springs to be uncoiled any more than to be coiled, but I have no idea. You can leave the climber deployed when not being transported if you’re worried.
Thank you everyone for your input - very much appreciated! We will be implementing the advice that was given here and I very much appreciate you taking the time to respond.
We are using max gearboxes - we are switching over this year from vex so our options to adjust on the fly are a bit limited right now.