Scissor Lift Help

Ok so my team is brand new to doing scissor lift designs( this is also only our third year as a team) and we needed a tad bit of help. What are some of the best ways to have the sliding part at the base of the scissor lift? Also what are some of the best was to power it, and how can we stop it from wobbling side to side? And further information: we have 16 of the long c-channels for the lift.
Thanks people, and also pictures will be very helpful!
Thanks

I’ve seen some great designed scissor lifts this year! The biggest problem is scissors that are unstable from side to side, so I would recommend mounting both motors in the middle and gearing them in unison so they power both sides of the lift equally. Also, I saw a great design recently that used two small traction wheels rolling in small c-channel instead of the linear slides - much less friction. I believe that was from team 2437 (not sure if I’m right about which team it was). I don’t have any pictures myself, but they do have pics and videos on their Instagram.

I would use the linear slide kit with inner sliders for that, as they are light, small, and easy to use.

There are many different ways to power it, you will have to figure out which works best and fits into your design.

To prevent wobbling and other issues, make the lift as solid as possible. Make sure the joint are stiff but have low friction, and try to connect the two sides in multiple places.

Yeah we have the long linear slide right now with the small inner slide with the rack gearbox bolted to them so they can be the thing that the c-channels are attached to. But the problem is that the small inner slide wobbles so that causes the entire lift to wobble. Any idea how to fix that? Besides that the actual scissor part is very stable.

Also attached is a picture that can kinda show what we have so far.
IMG_3516.jpg

You might have a look at this. I can’t vouch for anything specifically but it might help you somewhat:

https://vexforum.com/t/scissor-lifts-best-type-and-parts/26632/1

I think it looks very good. At this stage it will wobble a decent bit, no matter how good it is built.

I would keep going and build the second side, and then attach the two together at multiple stages. If it still wobbles too much you can then see how you can possibly improve the joint and other parts.

One idea that may help to counter a side to side wobble would be to connect the two individual scissors with a few crossbars. By attaching a bar that connects the two scissors together, you can limit the amount of flex that either one has when it sways to the side. I would suggest something similar to how the bars are mounted on the robot in the attached.

(DISCLAIMER – All credit for the picture and the robot go to team 1492 WASABI and yaokailing1492)

This is not my photo or my robot, I am just using it as a reference. If you want to read more about their robot visit this thread: https://vexforum.com/t/1492-wasabi-pre-season-prototype-reveal/27013/1

https://vexforum.com/attachment.php?attachmentid=8557&d=1409351475

Yeah, scissor lifts can be very tricky.
Use lots and lots of elastics, but distribute them evenly up and down the lift.
Cross bracers between the two sides is key. think about including a 3 sided lift to completely eliminate side to side movement.
put grease in all of your moving parts. Lithium grease used in car bearings works perfectly.
BEARINGS EVERYWHERE!!!
the hardest part of lifting up a scissor lift is the very beginning push, so plan accordingly. use leverage to your advantage.
Good Luck!

-team 4270 N Sprocketry

Ok thank you people, YALL have really helped a LOT! Now we found another small problem [ATTACH]8566[/ATTACH]
If you look at the picture you will notice that we had to stagger the c-channels because there is not a hole in the definite center. We thought that would solve the problem, it did, but that also caused it to be longer than 18 inches. How have yall positioned the c channels so that that are all even, it’s under 18 inches, and all the different sections lift equally?
ImageUploadedByTapatalk1409938979.137909.jpg

Or will I have to just cut off like 1/2 inch on each bar to make it work correctly?

There are 34 holes on the central line of holes and 35 on the other two lines of holes.

Usually the longest bar we use in VRC middle/high school is 35 hole, 17.5 inch bar, because it fits into the size limit pretty decently.

If not getting the central hole is annoying you really much, try switching to outer lines of holes, which is what most of us would do.

We tried doing that but when we extend the scissor lift, all the sections aren’t even. As in one fully extended and another still has a slight gap in it. Or if we have it so all the sections are equal it will not collapse correctly. We may be doing it wrong, but we aren’t quite sure! Any hints?

It’s a very easy fix. Simple don’t use one of the holes at the end, making the section you are using 33 holes long instead of the full 34 that are in the middle. You can then cut the end off, but I would keep it so you can use it when the robot is taken apart.

What I mean by that is that you can just use the following holes:
-Far Left
-The hole that is slightly to the left of true middle
-The second last hole, one in from the right.

And mirror/flip this accordingly for other pieces.

Alrighty thank you everyone for all the hints and tips and ideas! We will put them into action at our meetings next week and if we need anymore help we will let yall know!
But thank you a lot for the help