Wheel and Drivebase Choices for Platforming

Hi, so I want to revamp my drivebase with 4 inch wheels. I plan to add 4 inch omni wheels on each corner and a traction wheel of some sort in the centers. I’m thinking of using a 3:7 gear ratio to get 257 rpm with 4 motors. My question is that which type of wheel should I use for the center traction wheel to make it so that the robot can platform?

Should I use the 4 inch high traction tires? I’ve heard that these would be slightly smaller than the omnis so I would have to put rubber bands ziptied around the tire to get it up to size. I also don’t know if these would give me the most traction or the flex wheels.

Should I use 4 inch flex wheels? These are also smaller than the 4 inch omnis, and I don’t know what kind of hub I should use to get the most out of the wheel or how I can get the wheel up to the size of the omni. Some have suggested I cut the flex wheel and put it around an 84T gear, or use a sprocket and wrap the flex around it, or just use the 4 inch flex wheel with a regular Vex VersaHub.

While on the subject of the drivebase, I would like to ask if anyone has even had any success platforming on a 4 motor drive (while also being decently fast) with two or more mobile goals. It seems like many people use a 6 motor drive to platform, so I don’t know if I should even try to get my robot to platform with a 4 motor drivebase.

As always, thank you so much for your help, it’s much appreciated.

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if you want a super grippy wheel you might look into 4inch Omnis with locked rollers. We use a 6motor 257 rpm to climb the ramp. we can climb OK but not great because we don’t have locked Omnis and are missing a little traction.

Would you suggest 4 unlocked omnis on each corner, and the two locked omnis in the center? Do locked omnis have more traction than high traction tires and flex wheels?

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The reason teams use locked omnis in the middle instead of high traction wheels is that the omnis are slightly larger. In order to defend against being pushed sideways in a match the center wheel needs to be the same size or slightly larger than the corner omni wheels, otherwise there is not enough downward force on the foam tiles to gain traction.

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For my robot, I need traction forwards to climb the platform more than I need it for traction sideways. Would locked omnis, flex wheels, or high traction tires be better for this? For the flex wheels and high traction tires, I would have to find a way to make them bigger, but I would do so if it meant I can get the most traction forwards as possible.

imo either locked omnis or custom made flex wheels like @Xenon27 has . you could maybe do tractions wheels with rubber bands around them sort of like some of the fly wheels.

A 6 wheel drive is really only important if you care about not getting pushed from the side- if you want the ability to drift, you should probably just do a 4 wheel drive with all omnis. If you are using 4" omnis, you should really be fine with those, and won’t need to do anything with flex wheels- 4" omni wheels are very grippy, more than enough to use to climb the platform with.
If you want to have some traction wheels in the middle, then you have a few options. You can use locked omnis, which are made by putting screws in all the rollers so that they do not spin. This gives you lots of traction, and is pretty easy to do.
Another option is generally called the “169 traction wheel”. It consists of a 30t sprocket with a layer of chain wrapped around it and a 4" high traction tire stretched around it all. This will have a less traction than a normal 4" omni. It will also, due to being a little larger than the 4" omnis, give a slight drop center to your wheel, which will improve turning.

The other option, if you really want to be able to platform well (or just want to look really badass) is to use a cut 4" flex wheel stretched around hs gears, like here:

You can also do something like this, if you don’t want to cut your flex wheels:

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