Elastic Tension

Hello. I am working on an 8 bar lift and I was wondering how you knew once you had the “perfect” tension. Usually I would add as many rubber bands until the lift could barely stay down without power, but I’m not sure that’s best.

Any suggestions?

Don’t put the motors on yet. Get the tension so the lift can stay at any level without motors. That way the motors are just lifting the weight of the game objects, and not the whole lift too, but the motors aren’t stressing to put the lift back down.

Ok, I actually did that earlier but figured it was wrong.

Couldn’t this also stress the motors since it has to restretch the rubber bands to lower the lift?

Stressing the motors would be placing enough load that the motors only spin at 40% or less rpms than the original rpm. Even at 40%, the motor can continue for a long time, however completely stalling out can only last for a couple of seconds

The issue with this is that you are lifting the game objects going up, but have much less strain going down. What I have done and would recommend is to do this, but get it to hold itself with elastics with half the load you normally intend to have on it.

Not necessarily. With the loads of 10 cubes that some people say they will have xD. lifting 5 cubes is still a bit of weight. My thinking was, if the motor is working to put the lift up and down the whole match, the motors will wear out quicker. I haven’t done any math on it, so I’m not sure if that’s right, but that was my thinking.

If I’m wrong, just tell me; I haven’t done tons of testing or math.

I think that balancing it is a lot better than having different strains in terms of how quickly the motors will quit. But the big advantage would be that you have more capacity that you can move with less motors. We did this for our Toss Up scissor lift and it was balanced so the motors would run at capacity both up and down, that way we could lift 3 Bucky and 2 Large Balls very quickly.

If the elastic is balanced JUST to cancel the weight of the lift on the way up, then the weight of the lift will cancel the pull of the rubber bands on the way down. That way the motors are never under very much strain at all.