Preventing Pushing

It was!? lol I honestly don’t remember, I discovered it by mistake when I was building my chassis, but it sounds like something you’d say and I’d forget.

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Is it easy to be pushed with an x-drive? Haven’t had the chance to build and test yet.

I haven’t built one competitively to test, but I think you could out-maneuver defense with an X drive better than directly fight it.

You’d be easier to push than a locked Omni drive, but harder than an H-drive. You can also fight pushing with all 4 motors if need be.

Tbh i dont really mind using bling wheels, since they are somewhat descriptive of the appearance of the wheel, so i wouldn’t consider it a senseless name like Danny lift or goliath intake.

if you told a team who knew nothing about terminology that you have a bling drive they’d just be confused, but if you told them you were using locked omnis, they could infer that you have omni wheels that are locked.


True that, but then again, they wouldn’t even know what omnis where much less locked omnis.
Locked omnis is preferred over bling wheels since they are even more descriptive, but in my opinion, bling wheels is fine too, just use them around more experienced teams.
Plus it sounds cool :slightly_smiling_face:

Why not just have a traction wheel in the center of your robot rather than a sideways omniwheel? It would probably resist pushing better. Also for the wheel to significantly resist pushing, you would probably need to drop it a little below the rest of your drive, and that might negatively impact drive performance. Not to mention any robot with a wedge would lift that wheel off the ground, whereas with center-traction drive you’d still have a traction wheel on the ground to resist pushing.

They would still have pretty much the same effect. Ad a matter of fact, the omni would work better because the rollers make the wheel slightly larger than just 4 inches.
A traction wheel would work however. It would just be slightly harder to build (by a microscopic amount since it it spins unlike the omni)

If you’re using 4" omni wheels on your drive and you put a 4" omni wheel in the center, it won’t push into the mat any more than your other wheels. I certainly wouldn’t recommend a normal 4" traction, but you could easily use the rubber band-ziptie wheels that some teams used last year.

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what some teams did last year is they had plastic plates on hinges on the sides of their robot that made like a ramp so that robots pushing would have a harder time actually pushing and not just riding up on the ramp.

About 15 posts up I mentioned this as well

A sideways traction wheel wouldn’t have the rollers that omnis have, thus impending movement.
Plus, tests (I can’t remember the source) have shown that (with a heavier robot) omnis have more traction due to compressing rubber than the traditional traction wheels.

2.75" omni wheels have the grippiest rubber, followed by 4" omnis, then by 3.25" traction wheels (the square ones, not the round ones), and then I’m not sure. 3.25" omnis have a very slippery surface compared to 4" omnis.

Don’t 4" omnis have more grip than 2.75" wheels? They have treads therefore more things to grip onto.

The physical shape of the wheel is only one factor determining its coefficient of friction with the field surface. The material used in the wheel will also play a big role. The only way to know for sure how the wheels compare with each other is to conduct tests, which someone has probably done but I can’t remember seeing.

(maybe @ranOOm has seen such test results and that’s what they were referencing in their post above - if so, and they can dig them out easily, it’d be really cool to see them.)


sorry omnis** are grippiest from 2.75->4->3.25

Stack in the protected zone.

For those curious, one of the simplest ways of measuring the static friction of two surfaces is to put one on the other then very gently tilt them until the top one starts sliding:


i have built an x drive , and i can confirm that its very easy to be pushed around, even with using 100rpm cartriges

It also depends on the state of the rubber on the rollers. On older omnis they could dry out and get dirty. It is a good idea to wash them a couple of times a year with warm soapy water to remove the stuff they pick up from the field.

Then you would expect 2.75" and 4" omnis to have almost identical traction because they use identical rollers. More details could be found in the linked post: