Strange problems with hood
Our hood is controlled by a 775 pro motor with a TalonSRX motorcontroller. And it has a 100:1 gear reduction ratio. However, when l use Tuner to test the hood, l set the 0.1 percent output to the motor controller and the hood just doesn’t rotate. That’s strange. Is the gear ratio too large? If so, what’s your gear ratio in your hood and how do you get it?
Strange problems with shooter:
Our shooter is controlled by two Falcon500 and it has 4 backrollers. When l use Tuner to test the shooter, l set 0.3 to the Falcon and it rotates at a normal speed/ However, when l set 1.0 percent output to the shooter, the motor just seems to be stuck. That’s strange l think. Can anybody who are expert at mechanisms give some solutions?
Secondly, when l try to use velocity to control the falcon in the shooter (also in the tuner), l set 1000 at first and the shooter runs at a fast speed. When l use the Tuner to get its value, the velocity is 5000. That’s also very strange since l only set 1000 to it.
Besides, the 1000 units per 100ms seems to be close to the shooter’s max speed (the nearly same speed when l set 0.8 percent output to the shooter by tuner). That’s also very strange. l think 1000 units per 100ms is to slow to falcon.
l am not very familiar with FRC mechanisms, so l am not sure l have provided enough mechanism information.
Thanks, but when l set 20% output to the motor, it still can’t move (it seems that the motor is stuck). When l set 50% output to it, l hear that the 3D printed gear is broken and it still can’t move and the motor seems to be stuck. What if l use Falcon500 to control it? l guess that the force that 775 provides isn’t big enough, so can Falcon do it? But falcon’s max rpm is a lot lower the 775’s max rpm, so l am worried that falcon with such a big gear ratio will be easily burned up.
Falcon does have lower max RPM but it has significantly (around 6x) more torque, meaning it can apply more force to stuff. 100:1 is probably too large even for a 775 pro. I would definitely lower that first. Our lead screw-based hood was a NEO 550 (~1.5x more torque than 775pro) on a 7:1. Unless your hood is extremely heavy you really do not need that much.
On the former: that’s what ours does as well. Your shooter is (hopefully) pretty light, so you’d be surprised how little force you need. Don’t quote me on this but a 20:1 or so should be plenty for your case.
On the latter: No idea, haven’t got that far in physics just yet. My initial thought was that a 2:1 has 2x more force than a 1:1, but that’s probably wrong. Perhaps Google or a mechanical-oriented person here can help
Edit: Actually everything I see agrees with my “hypothesis”, so there you go I guess.
All right, thanks. l am curious about what’s the max rpm of the Falcon’s integrated sensor? l am worried about whether a falcon with a large gear ratio will burn up the integrated sensor.
You won’t need a large gear ratio for Falcons. A mechanism that worked on a 12:1 on a 775 would need something like a 3:1 or even a 2:1 for a Falcon. Additionally, Falcons have built in thermal protection (alongside a pretty high thermal mass), so it’s not very easy to burn them up.
Additional note: 100:1 is a gear ratio that’s used for lifting 120lb robots off the floor with 775s. A 5-10lb hood needs WAY less.
But with a 100:1 gear ratio, my 775 pro still can’t lift my shooter( l think it is around 5lb). l don’t know why, l want to make sure that how do you test a motor to see whether it can lift a mechanism?
It most certainly can, however you would need to run it at a much higher speed. With a 100:1 gear ratio there’s gonna be a LOT of static friction going on, and in general, the mechanism will be moving really slow (given the 775’s max RPM is about 17000, I think* a 100:1 would run at 170 max RPM), meaning you need to input even more power to overcome gravity.
*Take everything here with a grain of salt. This is entirely hearsay and best guess stuff. I’m a programmer.
Thanks, l am also a programmer.
However, when l set 50% output to the 775, it seems that the 3D printed gears on the hood is broken. However, when l try to use a ratchet wrench to move the hood and it can be lifted up. Is that the normal case? (l think it’s strange😂
Try removing the gear installed on the output shaft of the VersaPlanetary with the 775 motor.
Test if you can move the hood mechanism by hand.
Then test if the tuner software can make the output shaft of the VersaPlanetary spin.
Make sure the shaft is spinning in the proper direction. If the hood mechanism is already at one end of the travel and the motor is being commanded to make it go past the mechanical limit, it may start breaking things like you have described.
l have tested it and the hood mechanism can be moved.
Besides, it seems that our shooter mechanism can’t shoot out the ball, but l think there is no problem with the shooter mechanism. Can you help me with it?
Thanks!
l don’t know why, l want to make sure that how do you test a motor to see whether it can lift a mechanism?
