Scissor Lift Not Working

Here is the specs of my scissor lift:
4 393 Motors
Elastics on Both Sides
7:1 gear ratio
4-Staged Scissor Lift
Powered Horizontally

I have checked each motor individually, all are turning the right direction. All my joints are loose with washers in them. Using power expander. It can’t even lift one cube!!! WTF!!!

How far down does each section compress? Ours is 4 section that is expanded at rest to just shy of 18" with 6 motors at 11.67:1. We can lift 4 cubes and a skyrise but it struggles. 2 is much more efficient.

Remember that the initial movement of the scissor is the most extreme so 4 motors at 7:1 might not be enough.

It would help if you could provide some photos and/or at least a more detailed description of what’s happening when it fails. Are the motors tripping out? Gears grinding? or what? Photos are most helpful.

It’s like yours, just shy of 18".

I have no idea why… Don’t really have a camera right now.

Wait it’s horizontal 7:1? Can you provide a picture of how you are powering it.

Don’t have a camera right now. It’s where you have two motors with small gears rotating around a larger gear.

Do you power at the joint? Because that wouldn’t be considered horizontal hence my confusion.

As others have said, pictures will help us understand your setup much better.

Have tried to tune your elastics and check for friction without the motors? Just pull out the axle slightly so the gears spin freely, and you should be able to easily move it up and down. Then, add elastics so you get to the point where they can hold up the weight of the lift, and possible one cube.

Here’s a picture

That isn’t powered horizontally.

hmmm my bad, this is only my second year doing vex so i dont really have the jargon down :frowning:

It’s ok, you’ll get it. For reference, you are powering the scissor at the bottom most rotational joint.

One fix you might be able to try is powering the scissor from the second scissor rotational point. By powering it closer to the center of the lift, it puts less strain on the motors, causing the lift to go up with more ease.

This is a very interesting idea. I’ve never thought about moving the powered stage from the first. I wonder if this would reduce the amount of slack that scissor lifts often have.

You don’t have enough rubber bands, or at least thats what it looks like.
Be sure to add lots of tension, but the least at higher stages, most at the bottom and be sure to put the same number of them on each side.

Wait, you’re trying to power a four stage scissor lift with four motors ang a 1:7 gear ratio? That didn’t turn out well for us, and clearly isn’t for you either. Four motors just isn’t enough torque to get four stages moving. If you want four stages, go for a six motor lift. Otherwise, remove a stage and run it with three stages.

Or increase the gear ratio, which should be more than sufficient.

Also, make sure you have bearings on each joint.

One of the reasons I recommended this idea is because our team has had a lot of success with it so far. The slack is definitely at a minimal, however for additional power we did opt for 6 motors on the lift, which has given us the power to lift the equivalent weight of up to 4 cubes. However, this has limited what we can do for a scoring mechanism because we want too use a 4 motor base, thus maxing out our motor count. Stanley is definitely right in saying you need more rubber bands, they help tremendously in reducing the stress on your motors as the lift runs.

+1 (or +30-60 #32 rubber bands really) Add more rubber bands at multiple levels. Take off the motors and ensure you can lift the scissor with essentially just the rubber bands. This will let you know when you have enough.

Having trouble keeping the scissor in the down position is a good place to stop as well.

I would almost disagree with you. This many rubber bands would be counterproductive when coming down with the scissor lift. Seeing as how it’s pretty much pointless to come down with a cube or other weighted objects, a ton of rubber bands can really stress your lift out on the way down. Not to mention that with too many rubber bands your lift would go up faster then come down.