Vex Linear Slide Lift Tutorial and Explanation

This was something that my team struggled immensely with last year, eventually settling on this design for the lift, and I figured I would share the love (and knowledge) by making a video. Any comments or suggestions would be appreciated.


Here is the new and improved video utilizing the techniques presented in this thread for anyone who is interested.

I’m confused about two things:

  1. Why did you go through all that effort with the screws instead of putting shorter ones in from the other side (as intended), meaning the screw heads are outside of the bracket and the tips point toward the slider?
  2. Toward the end you keep saying “pillow bearing,” but I don’t see any. Nor do I see any bearing flats. I do see what appear to be two nylon spacers. But these won’t stop the axle from rattling around in the square slots. Or did you do something like cutting the nylon spacers to create small square parts to fit inside the square openings to act as bearings?
  1. How were the screws supposed to screw in? At least from everything I have seen, I haven’t seen any examples of this in the wild.

  2. I see I have misheard. You are correct, I had heard that those nylon spacers were called pillow bearings and had called them that. They essentially just space the gear out. With a slide in place, bearings are not necessary, as the gear is not moving too much from my experience.

I didn’t describe it well. You screw them in from the opposite direction. So their heads will be where you placed your nuts. The screws screw into the plastic and don’t need nuts. You just have to make sure the screws aren’t too long.

You should really put two bearings in there, one on each side. Sure, there isn’t a ton of slop, but there is some. The bigger problem isn’t with the rack, though. It’s with the motor. It’s really bad to force the motor to support a relatively loose shaft end. If you put a bearing on each side, the two of them will remove most of the slop so the motor won’t get abused.

Wow. Thats interesting. That was not apparent at all.

Good suggestion. Thanks for the update.

I should add a note for you. If you put a bearing flat on the motor side of the bracket, between the bracket and the motor, the long gold screws will fit perfectly into the motor instead of the short motor screws. That may not be where you want it, but knowing you can do that and have the right screws available can be handy.

Another note to add: Always put at least two bearings on an axle to make it work better by getting rid of slop and thus protecting the motor. I’ve seen a lot of robots built with a single bearing between a motor and a wheel, and it’s really, really bad for performance and for the motor. In the case of something like wheels, you just need some space between the bearings, preferably with one fairly close to the wheels if they’re on the same side. If you’re dealing with gears meshing, you really want a bearing on either side of a gear, two on the same side commonly not preventing the gear teeth from slipping.

Thanks again. I’ll be redoing the video shortly. I’ve already refilmed the assembly and am going to go back in and rewrite the script. Do you want credit for the heads-up?

No, no need. I appreciate the thought. I’m not providing anything original here, just helping out to better the community.

Thanks again, I’m so surprised that my entire team failed to notice the screwing in from the bottom. Its quite crazy.