C Channel On Outside Of Wheels

I have noticed that almost all robots have a c channel on the outside of their wheels. What is the point of this? Is it too protect the wheels and make sure they do not get stuck in any of the outside environment, or is it structurally more sound with a railing? Right now I have no railing on my wheels and I am wondering if I should change that.

That is a possibility, but it’s mostly for it being straight and more consistent driving/auton

Yes change it. I had a horrible experience w no support last year

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The c channel is so the axil is not canterleverd, meaning that the axil can wobble around, go up and down, and side to side.

You NEED to put metal on both sides of any axil you have, and make sure there are barring flats on both sides too.



Under high loads, cantilevered axles can bend, ruining them.
Unless of course you’re going for that stance look, then go ahead :wink:


They can still bend when sandwiched, it’s just much harder.

You dont need to, but you should. Especially with shaft joints, you generally want all axles supported by two points of contact to minimize wobble and the risk of bending. If you use a gear ratio, sandwiching them will also help ensure that the gears stay meshed.


It’s always recommended to have two support points any time wheels are involved. Without that c-channel there, your axles will most likely bend, ruining them, and just causing a lot of inconvenience for everyone involved. Take it from someone who’s messed up more than one, and save yourself the trouble later.


So, you need them for wheels

Out of curiosity, where did you learn to build like this. In my experience, having the outside channel is a 100% necessity. Heck, I wouldn’t even consider it a chassis if it didn’t have outside bars (not to be rude). I’ve seen some people do it before and I was wondering why it might’ve happened.

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Because until you learn about having shafts supported at both ends, it seems like the logical way. After all, almost all vehicles have the wheels outside the chassis.
And so does the Clawbot which is what most people learn to build with.

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Okay, I see now. Considering the clawbot is most people’s first robot in vex, it seems like a bad thing to be teaching tho.

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Yes, absolutely change that ASAP. Having Cantilevered wheels can ruin your axles as well as your ability to drive completely straight, making coding autonomous not so nice. Add a C channel IMMIDEATLEY before you begin other things because it will be harder to do once more stuff is on. (And put bearing flats on both C channels as well , thats also VERY important)


Thanks for all the helpful information, this makes much more sense now because already my wheels are so wobbly and I was wondering how we were going to fix that

Originally we planned to have an outside c channel but we built it incorrectly and didn’t have enough space to put a c channel on both ends. So we weren’t sure if it was worth the hassle to take it apart and put the c channel on it.


One exception to the general rule around having wheels supported on both sides is if you use high strength axles. I have had a team do this (for very specific size reasons) but it takes very strong focus on build quality or friction will kill you.


Still, not canterlevering the axil or scrub joint is better

You can get away with canterlevering score joints

It is very hard to get away with canterlevering high strength axis.

In my opinion it is definitely worth the effort to put the c-channel on the outside. This gets rid of wheel wobble and increases the stability of your base.


RoboKnight is right.

You should look at the instructions for the Super Clawbot, that has the style frame you want to start with.

In the middle of the responses is to use bearing blocks as a suggestion. It’s not a suggestion it’s a must. If you are passing an axle through metal, it needs to have a bearing block. Depending on what the load is / location, having a bearing block on BOTH sides of the metal plate may help.

The biggest issue with the basic clawbot isn’t the cantilever wheels, it’s the “push pin connectors”. They are junk, actually they aspire to be junk. If you are mentoring a team that is trying to use them, do them a huge favor and replace them with real bolts and nuts.


I thought vex called them barring flats? Or am I wrong? (Like most of the time :stuck_out_tongue: )

Once I saw them i. Our park box, and googled their use, and tried to use them. After 2 minutes of trying to get them through thy metal and flat, I came to the conclusion they are JUNK

Edit: emoji

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@RoboKnight I’ll meet you half way, the official title is “Flat Bearing”

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Barring flats is closer than barring blocks…

Meet me 1/4 way… :stuck_out_tongue: