Rubber bands

How would I know when to use them, how much to use, and where? Still learning, thanks for your patience, especially with these past few threads of mine!

For a lift, you are supposed to add enough rubber bands so that the lift can hold its position at any height. You would need to take out the shaft connecting the motor to the arm in order to do this.
If you have a scissor lift, you might want to mount the rubber bands near the “x” part of the scissor lift, since stretching rubber bands 17.5 inches is difficult.

Overall it will be pretty clear when you have too many rubber bands. You’ll start to notice that your lift doesn’t want to go down very easily and it won’t want to stay down. At that point you have too many rubber bands, but up until that point, use as many as you can!

The idea of using rubber bands on a lift is they help the lift go up, and take strain off the motors powering the lift. So to achieve this in any type of lift they need to connect two points that get closer together as the lift goes up, otherwise they will resist the motors and cause problems. The actual placement of rubber bands on a lift really depends on the lift type and your design, however as long as the two connection points only get closer together as the lift goes up they will help.

As mentioned above the rubber bands should allow the lift to stay up without any motor power, but make sure they do not make it too hard to lower the arm.

Rubber bands are also very useful for making many kinds of spring-loaded intakes.

Could you use any rubber bands? Like the ones at the dollar store or something.

Legal rubber bands include the #32 and #64 which are sold by vex. Because of rule <R7)b> you can use any rubber bands so long as they are identical to the ones sold by vex.

#32 and #64 Rubber bands are available in bulk at most stationary shops or online, and they are much cheaper to buy there than from VEX.

My team used to make jokes saying that rubber bands are the infinite power source of vex robots… makes sense, but my practical experience tells me that they cannot replace motors on the lift. They do help a lot, but they mainly cancle out gravity when a lift is not loaded. When a lift is loaded, motors still need to provide enough torque.

I talked about no-motor elastic assist tuning with some people on the forum earlier. We talked about how we wanted to take off all motors and make the lift stay at any position with only rubber bands. This I was able to achieve decently in toss up, with the small eight bar being something easier to deal with. This year, it was impossible for me to achieve perfect elastic assist on my scissor. It was an extremely tedious process to tune the lift with only black tubings, because we only had them back then. I never had the tenacity to perfect the tuning on the 3 stage scissor. Usually, the scissor is stuck at bottom, springs up after being lifted a little bit, then remains at a high position. But my lift worked decently with a stronger ratio. So yeah, rubber bands are amazing. But maybe not as controllable as motors and pneumatics.


https://www.youtube.com/watch?v=35jwrwdaOS0
:wink:

https://www.youtube.com/watch?v=35jwrwdaOS0
:wink:

Yes it is possible but it’s not effective to use it on a lift for this year because your lifts have to go up to 60 inches.

Completely identical (color, thickness)? or only identical in size?

This is cover by the applicable rule, R7b: