Hello, this is my teams first year doing vex for a class, I was wondering if anyone could give tips, point out flaws, or help us with a problem. It’s just a minor problem and I have code that I have yet to implement to try to fix it, but when we go up, it goes up tilted wherever the claw is. Here are some pictures showing our robot:
Tilting is a common issue with scissor lifts, especially with that kind of Skyrise builder. I would highly suggest syncing the lower tier, meaning to add a shaft between the two sides to keep the gears in sync with each other. This will reduce a lot of the tilt because the sides will be forcibly kept together. I would also suggest maybe adding a few more supports on each stage (probably just one would do) and adding a lot more rubber bands.
Although this isn’t related to stability as much, add enough rubber bands to counteract the weight of your lift and manipulators and it will move much faster and work better.
Additionally, you might try reducing the size of the spacers connecting your scissor bars to reduce flex in the joints. The white spacers have a larger surface area and tend to offer a bit more support. We’ve found the 1/4" white spacers to be great for this.
This next part is harder. To reduce the slop in your lift (and therefore the degree to which it tilts), you might try adding the black delrin bearing flats like usually used for shafts to all of the joints on your scissor lift. The hard part is shaving all of them down to fit inside the edge of the C-channel.
The skyrise building design your team has chosen to use is not an easy one, so don’t be discouraged if it has issues at first (Although it looks pretty good so far). Some teams with this design have two motors on the first tier of their scissor and two on the third (both synced as mentioned earlier), although that is a much larger change than the others listed.
Try the things I mentioned and if they aren’t enough, the community can keep trying.
You don’t have to necessarily add an axle, you can just extend the ones you’re already using in your gear train. Essentially, just make it so a few of the gears are sharing an axle with the other gears on the other side of the lift, and it should force the bottom tier to stay together and reduce the tendency for one side to go faster or for it to tilt. That won’t entirely solve the problem because there is still enough slop between the top tier and the bottom for it to tilt without turning the gears, but it should reduce it significantly and keep the bottom tier from tilting nearly at all. The you’ll have to work with the upper tiers to reduce the slop to reduce their tilting. That can be tricky because its so far from the point where the lift is powered.
Something else that might help is to make your pivoting arm stick out past the other end of the gear that’s rotating it and add a weight to it so that it counteracts the offset weight of the claw and skyrise piece when it rotates.
Kind of like in this video
Also, add more cross supports. I found with my scissor lift that having a cross support on each side of the center pivot in the X is good enough.
I would try to add another support between the two motors in the second photo. Having gears on the ends of axles, and them not being supported on both sides could result in bent axles and/or teeth skipping. Just a C-Channel with bearings on it to keep the gears meshed would work.