Our team is considering the Thrifty Bot elevator. We have obvious concerns about driving the elevator up and down, we’re likely going to use a chain&sprocket system to drive the elevator. However, we want the elevator to stay fixed at whatever position we set it to, so that we can have pre-configured buttons to set the height and ensure the elevator stays there.
What methods do you guys suggest using? How hard are worm-drive gears to back drive. We’re considering these worm gears from amazon, Would planetary gears work? We also don’t want too slow of a turn speed.
There’s also the Andymark RAW BOX, which is pricier, and I’ve heard it takes almost 100 lbs to back drive it with double CIMs on it.
Few questions have to be asked. What motors do you have access to? What are your manufacturing capabilities? Lastly, what are your programming capabilities?
While harder to back drive gear boxes are nice they aren’t entirely needed. A 9:1 or 10:1 gearbox with 2 motors should be enough to hold the elevator in place. A good PID will use the power of the motor to keep the elevator in place. In combination with an encoder, you can set certain distances your elevator can go. As far as gearboxes go, I recommend the MAXPlanetary System Kit from Rev. It works natively with thrifty’s elevator.
Oh Awesome! We already have x2 20:1 gearboxs and x2 neos, which could be effective to drive it.
I hadn’t considered using a PID system to keep the elevators in place. We were already planning to do this for auto-balancing in auto, so doing this shouldn’t be too much of a challenge comparatively.
jedgar6 is right, you don’t need a ton for force to keep an elevator in place when it’s only lifting a mechanism and not the whole robot. For the pre-programmed position, just make sure you have an encoder on the actual drive shaft of the elevator (the one your lower chain sprocket is on) and use PID and the encoder data to ensure that the elevator always returns to the same position.+
We use CTRE CANcoders exclusively these days, since they integrate with our other systems flawlessly. That would probably work well for you in this application, since you don’t necessarily need to plug it straight into your SparkMax controllers anyway. I’d suggest a CANcoder and the Hex Bore Mag Encoder Housing to fit on the end of the drive shaft. We used this very effectively in 2019 for our elevator, hitting three pre-programmed positions for the rocket hatches every time.