Scissor Lift Help

I have a two-stage scissor lift, with rubber bands going…you know…where they always go. My problem is that it works, but lifts up relatively slowly, and crashes down at the bottom. The scissor lift is powered by a 1:7 gear ratio, with the metal gear on the motor, the 84-tooth gear attached to the other lifting arm thing, and a 60-tooth idler in between. It uses the linear slides to…uh…slide. The only reason I can see a problem with my setup is because of a twisting axle or slop in the gears. Is there a better way to position the rubber bands? (So that they provide even force as the lift lifts.)

I’m pretty inexperienced when it comes to scissor lifts but the people who can help you will probably want pictures to understand what you’re saying

As @Vyx Said, it would really help to post pictures if you can.

I’m not too experienced with building scissor lifts, but I have a relatively good understanding of how they can be built.

That being said, judging from what you wrote, I would say that you’re speed control isn’t good. A way to improve that is to use rubber band better to increase the uniform tension and/or to use a PID speed control algorithm.

Here’s a good post: Click Me.

If it’s crashing down, and going up slowly, you may need more rubber bands. Also you may want to use more motors on the lift so you can use a faster ratio

+1 to what @Easton said. I have built a few, and the general rule for any lift applies just the same, but is a little harder to get right here. If you can take the motor(s) off, and the lift stays anywhere you put it, it is rubber banded correctly. If it falls, add more… if it goes up automagically take some off(unless you need it to do this, for your specific case). For a scissor, (assuming the bands are horizontal across the x’s, like you implied) they are most stretched when down, but they are pulling almost inline with the beams. This negates the massive amount of stretched force, because of the lever action the bands are now fighting. So you most likely will need a separate set of bands that push up, but only are stretched at the very bottom and are unused when the scissor is more that 6-8in up.