pic: Off-Season Custom Wheel

[Henrique Schmit]

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[Ari423]

No experience with custom wheels whatsoever, but that looks like a lot of machine time when you can buy a similar product COTS. What about that wheel makes it different than a COTS wheel that takes no machine time and doesn't cut into the withholding allowance?

[R.C.]

It looks like a bulk of your weight is in that hub, I would look at machining it down or something.

[cadandcookies]

Very cool wheel! Do you have the resources to fabricate these or are they just a thought exercise?

I'm also curious about what features you've designed into it to make it more optimal for a chain drive?

With regards to custom wheels, here are my opinions on them:
Custom wheels aren't something you do because they'll save you time. They're something you do for the journey along the way-- the experience of designing and manufacturing them. They're a mountain that you climb because it is there. With modern COTS wheels, there just aren't very many situations where custom is a competitive advantage when it comes to wheels. This makes them perfect for an offseason project.

With regards to your questions, I'd ask how these compare to your targets-- are they cheaper than comparable COTS products? How much better are they for chain? Did you achieve your goals? If not, how can you reach them?

Best of luck with your project.

[JVN]

Looks good!

What material are you looking at making these out of?
If you're thinking aluminum -- I suspect the hub in the center is over-designed.
If you're thinking plastic -- I suspect the "spokes" are under-designed.

You can also probably get away with only (3) sprocket attachment holes.

You should consider some form of piloting feature to keep the sprocket concentric with the wheel (or cheat, and use the bearing to pilot the sprocket).

Why did you decide to go 4"+tread? I think you should consider making the wheel 4" at the OD of the tread. This way if you have robot turning issues, or need to swap in some COTS omni-wheels or other traction wheels in a few places you'll have options. (This has 100% happened to me in the past... being able to swap wheels around has saved my butt several times).

Keep going. You've got plenty of time for more iterations before you need to make these for realsies.

[Andrew Schreiber]

Originally Posted by Ari423

No experience with custom wheels whatsoever, but that looks like a lot of machine time when you can buy a similar product COTS. What about that wheel makes it different than a COTS wheel that takes no machine time and doesn't cut into the withholding allowance?

In the states (and probably Canada now) this is true. International teams can't overnight parts like we can here, as a result these teams tend to have a lot more custom built parts.

[Henrique Schmit]

We are planning on producing this wheel cutting it out from an 1" thick aluminium plate using a sponsor's water jet and using a lathe to take material from the inside. The hub is a separate part so we can choose whether we'll use it or not on both sides. These are supposed to be used in place of the versa W wheels we've been using, we believe we can get the materials and machining from sponsors while also having a better thread. We calculated the size of the hub based on where the sprocket will be so we can be a bit more effective with our space and the bearing will be held in the wheel by the plate sprocket. Like that we'll be able to make the wheel be assembled in only one piece and make it a bit easier and faster to assemble.

What would make the wheel more practical, having the sprocket hold the bearing on place or the bearing keep the sprocket concentrical? Thanks for all the advices, we'll add the suggested changes to our project to make it better

[Knufire]

Originally Posted by Henrique Schmit

What would make the wheel more practical, having the sprocket hold the bearing on place or the bearing keep the sprocket concentrical? Thanks for all the advices, we'll add the suggested changes to our project to make it better

IMO, I'd use the bearing to keep the sprocket concentric. Just making sure the right spacers are on the shaft when you install the wheel should keep the bearing in place just fine.

[cbale2000]

Our team built custom wheels on our 2007 robot (which used 14 of them in the drive system). Personally, I don't recommend it due to the time it takes to manufacture and the weight of the resulting wheels in many cases.
These days it's easier to just buy some VexPro Traction wheels, they're more than durable enough and they weigh less too.

Now granted, this is based on what I know about my team. We've always had terrific manufacturing capabilities (a full machine shop at our disposal, with CNCs, Lathes, and more) but limited manufacturing manpower (we have more machines than we have people to run them). As a result, we try to prioritize making only the parts we absolutely have to, and use off the shelf products for everything else. If your team has the resources and manpower to build something like this and not have it slow down other parts of your build, go for it.

[Seth Mallory]

Most years we make wheels. We have a large team and all of the students have machine shop training provide by team members in the fall. The students take pride in what the team makes and it provides project management training in scheduling shop time. I just wish the Middle school still had the foundry that they had when I went there in 1970. We could pour aluminium wheels that could be machined in less time. As a seventh grader I would love doing it and it would help to inspire at a younger age.

[jpetito]

Why not cast them in aluminum and drill/ream the holes? Ditch the bearings as they make the thing over-engineered and heavy.

Requires a bit of machine shop work, but with so much gear on ebay and craigslist, maybe a sponsor would donate cash or equipment. Go to them with a workable plan and lots of shops, because they need these skills, will help you teach and learn the skills.

It's truly the journey and the learning, not the cost.

[Sam_Mills]

Originally Posted by jpetito

Ditch the bearings as they make the thing over-engineered and heavy...

Uhhh, bearings are important, don't ditch your bearings.

[lbarger]

What keeps the tread on the wheel? Commercial wheels have a lip that captures the tread when two halves are brought together. (No bad feature for molded wheels, but requires lot more machining otherwise.) I assume you are thinking rivets at several places around the perimeter?

[Henrique Schmit]

Originally Posted by lbarger

What keeps the tread on the wheel? Commercial wheels have a lip that captures the tread when two halves are brought together. (No bad feature for molded wheels, but requires lot more machining otherwise.) I assume you are thinking rivets at several places around the perimeter?

Exactly that, multiple rivets