has anyone else had any problems where when they tried to go over the PVC pipe with the mechanum wheels where if they came in at an angle occasionally the wheel rubber pieces would pinch the pipe and get stuck?
This what a lot of people predicted, so if you can I suggest switching to traction.
Don’t use mecanum, they suck.
it does make sense to use the traction wheels but from what we’ve been doing we found that it works really well with omni wheels.
In starstruck and toss up, we had a tank drive that uses two traction wheels in the back and two omni wheels in the front (helps with turning). This is my favorite chassis design since it is reliable and fast.
However, I think an x-drive will be the best bet for this year.
I don’t think a x drive would be optimal for getting up the pipe, going over the pipe with the lack of force on an x drive is questionable and might net you the 20 point zone because of it
I don’t think X drive is the way to go, because (0) you might get stuck on the bar, and (1) you will end up being significantly slower, which is incredibly important
Well, actually, x-drives are faster than tank drives (check out this video). Also, in regard to getting over the pipe, I guess we will see 
Maybe you can build a modified 6 motor x drive that looks like this. (Edit: called an Asterisk Drive.)
Asterisk Drives are something to consider because I’m fairly certain I want to devote 6 motors to my drive. IDK, seems like I can build a much smaller drive base that would end up being significantly lighter. I’m going for super minimalism this year, just a few aluminum parts, to be as fast as humanly possible
You could also try this:
Just run a modified dragon drive.
We had both an X-drive and mechanum drive in Toss up, they both could go over the bump pretty easily. The X-Drive did sometimes burn out, but that was with a heavy robot and a much bigger bump than 1". Though I definitely wouldn’t suggest using mechanums.
We tested out the x-drive with our starstruck robot, and it works pretty well for getting over the first pvc pipe. a normal forward facing drive could be better than it, but in reality you don’t need to cross the second pipe so there is no reason.
I’ll warn you to be really careful with such analyses. Even on that very page there is a note “faster… with less torque.” Any time you make such a comparison, you’re comparing apples to oranges. That’s why I really dislike seeing statements about x-drives and all being fasters with the same gear ratio. The question you really need to consider for which is fastest is, “Which is fastest when providing the same torque?” In other words, if you’re asking them to manage the same load, which is fastest? Otherwise I can just build a tank drive geared for a lot of speed and just as correctly say my tank drive is faster than an x-drive, but with less torque.
There are generally two types of problems with x-drives, mecanum wheels, swerve drives, etc. Either
- When you’re driving all the wheels, you have them somewhat fighting each other and so lose out on torque, or
- You have an excess of motors (or pneumatics) for what you’re doing at any given moment and so have fewer motors to use elsewhere, effectively losing out on torque.
There is nothing inherently wrong with any one of these drive systems because you’re gaining something for your loss. You gain mobility, which could be extremely valuable, depending on the task. Imagine parallel parking a car built with a system like these. It would be trivial. But your mileage would get shot driving around in an x-drive car instead of our normal cars which aren’t as great at parallel parking.
The main issue with mecanum and holonomic drives that I’ve seen, is that your drive motors are all “isolated”. You can’t chain together wheels like you can in a tank drive, which means that if one of your motors/wheels encounters an issue (gets stuck, slips, stalls, etc) you’re pretty much dead in the water.
discovery, I’m a little confused. I know losing a motor isn’t good, but is it really that bad comparatively?
Let’s look at mecanum wheels and let’s say your front-left motor stalls. You should still be able to drive on two of your four diagonals at full normal speed because the front-left and rear-right would be at 0 power on those two diagonals. You should also still be able to rotate. You’ would tend to drift along a diagonal, but you could drive slightly on the opposing diagonal to offset this.
Meanwhile, let’s look at chained-together tank drive. Again, your front-left motor stalls. This will cause the left side to be under-powered compared to the right side, so you’ll have to steer as you drive to go straight forward or backward. You should also be able to turn, though not as quickly. These would seem to be comparable issues to those above.
Now, I have seen particular problems in each case. Mecanum wheels don’t deal with bumps as easily and are more prone to getting stuck that way (the issue mentioned in the OP). I’ve also seen a seized up motor on chained-together wheels in tank drive stop the other motor from being able to turn, so one motor took out both motors on the same side, leaving the robot pretty much dead in the water.
Chained motors almost never stall individually, but it is more difficult to stall the whole drive than just one motor. Even one stalled motor causes drifting, and it pretty much ruins any X drive.
Can also confirm… Rip starstruck X Drive… Feels bad
not necessarily, i used my x-drive to get over a 1-inch pvc
it might not be irrelevant like we all think
i thought it wouldn’t work but then my friends forced me to test it
Maybe this isn’t as bad with mecanum wheels, but as others have mentioned even a slightly slower motor makes an x-drive drift like crazy, making it hard to drive. There are also problems if your weight isn’t balanced properly, in starstruck our x-drive was often running on only two wheels when the lift was up, which is why we abandoned it early on.