Too many rubber bands?

I am using 4 (torque) motors on my lift on a 1:5 (driving:driven) gear ratio. The raw lift capacity without any elastics was 4 stars, but we added rubber bands to increase it to 5 stars. What I want to know is if we can get away with adding many more rubber bands, such that the lift automatically goes up and needs to be held down by constant motor power after deployment.

I think the limiting factor in your case would be how hard the motors can torque satisfactorily against the rubber bands without overheating and tripping the PTCs inside. If you get up to max motor power and the lift still won’t go down, well, you found your absolute limit.

I would say that if your motors need to run at 30 or more out of 127 you will probably be tripping PTCs.

Let’s say, for example, that at 80 your PTCs do not trip in a 2 minute match. The problem will be that in a tournament, there will not be sufficient time for complete cool down between matches. You will end up tripping near the end of the day or during elimination rounds. The plastic casings for the motors do not dissipate the heat well at all. You might get things cool on the outside, but the heat is still there on the inside.

When the PTC eventually trips, it will reset in about 5 seconds. The problem is that there is still heat. With constant pressure, you will trip them again, only faster. Every time you trip them, the times between will get shorter.

Constant pressure with your motors in not necessarily bad, so long as the number is pretty low. Our teams try to not go about 15 for constant pressure settings.

Sounds like there’s still some extra friction in there. We ran a 1:5 on an older iteration and could lift 7 stars with about 4 rubber bands. Make sure spacing is done well, all your motors are running, and everything else that goes with reducing friction.

Too many rubber bands? No such thing.

At our last competition, we thought it would be a good idea to put diagonal rubber bands to increase our 6 bar lift speed and strength but at our match, our size was supposedly larger than 18 inches since the lift wouldn’t go down all the way due to so much tension on the rubber bands. Just something to consider

The ideal amount of rubber bands would be to have enough to where it requires almost no force at all to lift the lift by itself from the ground, otherwise you’ll trip the PTCs if you hold the lift down long enough. Also a minor nitpick, if 1:5 is driving to driven, it means your lift goes five times faster and has five times less torque than the motors.

If the twelve tooth pinion is driving and the 60 tooth gear is driven, that’s 1:5 and definitely increases torque, not 5:1 which increases speed.

We have a team with a 1:5 gear ratio with 6 high speed motors and it was easily lifting and throwing 4 stars mostly in the high zone and that was with one of the motors unplugged. So they actually had 5 motors and working against 1 motor. All that is with no rubber bands.

I think your biggest problem is friction. How are your gears set up? I think the robot that our team has is using two towers. they have two motors across from each other powering a 12 tooth gear on each tower and one motor by itself on each tower powering a 12 tooth gear. All the 12 tooth gears are directly on the 60 tooth gear (planetary gear box) with one 12 tooth under the gear on each side and one behind it.

We have two towers: that each have a 60t HS gear near the top with a pinion underneath, the pinion is powered by two motors on the same axle. How would I go about reducing friction besides checking spacing and motors?