What are the pros and cons of treaded wheels and solid rubber wheels? What wheel do you use? Why?
Treaded wheels usually get you a better COF on carpet, where you can actually dig into the material*. Solid rubber/urethane wheels are great for flat, hard surfaces and usually great for intaking/manipulating game pieces, from my experience. So I guess it’s ok to say we use both wheels, just for different purposes.
*in the case of a game like 2012, where half of the field is plastic, going with wheels with a good COF on carpet and hard surfaces (Colsons cut to mimic a tread) is a safe bet.
I think this needs some clarification.
There are molded rubber wheels of various types, most of which are molded onto plastic hubs to keep them light. Some have a molded tread pattern (AndyMark HiGrip). Some are molded flat (Colson Performa, AndyMark Stealth). Some are pneumatic (AndyMark).
There are also solid metal rims that accept tread (wedge top, pebble top, blue nitrile)
Others are molded flat rubber, but not great for driving (Banebots, Battle Treads (heavy), Various Other Urethane Wheels (for shooters) )
-matto-
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Speaking specifically about Colsons versus roughtop tread here. Other materials may vary.
Colsons wear very slowly, and basically do not need to be changed through an FRC season. Colsons have pretty good grip on carpet and are basically maintenance free wheels.
Roughtop treaded wheels require more maintenance (the tread may need to be changed once or twice per event depending on material), and they have an additional failure mode in tread loss. Depending on the wheel geometry, roughtop tread can give more traction than any Colson wheel can, though the difference is somewhat small.
If you want an easy, robust drivetrain with no maintenance without a huge traction compromise, go Colsons. If you want the best traction and pushing performance and you’re willing to put in a little work in maintenance, go with roughtop.
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How would you cut a colson to mimic tread?
We have used treaded wheels mostly, but for this year opted for colsons and omnis for their good universal grip. I like the higher CoF of tread wheels, but the universality of colsons is great.
I know about this. I am just wondering how they did that.
They index the wheel in a jig that holds it at an angle to a table saw blade.
EDIT: Found a picture. Like in the second step of the process that 25 used here: http://www.chiefdelphi.com/media/photos/14625
Just imagine rotating that 45 degrees and doing two sets of grooves per wheel.
We did that in 2014; we used a jig and a Japanese pull saw. Worked fine, though not sure it was worth the effort.
I’ve heard of some teams treading their colsons by being very careful with a bandsaw. (IIRC I think 11 did that in 2013).
I’ve cut treads on Colsons a few times using a dividing head with a three jaw chuck on a horizontal mill. Bolt the dividing head on an angle across a couple of t slots, put a piece of hex shaft in the chuck, use a hex shaft collar to hold the wheel on. The angles aren’t critical. I cut every 15 or 20 degrees, use a 1/8 slit saw, high speed and feed and cut both directions. Do all your wheels at one angle and then move the head to get the other angle for a diamond pattern.
Cutting treads for more traction should probably warrant testing similar to how AM did their traction testing this year for the new treads. I bet the extra stress would decrease the life of the plastic hex bore in VEX’s Colson wheels, similar to the original 4" knobby VEX wheels with the plastic square broach (or the large green VEX gears before there was a metal hub option)
Remember, VEX’s Colson wheels have yet to be tested in live, repeated defensive pushing matches. IMO spares are a good idea for this year.
I honestly think there’s no reason for concern whatsoever - the hub is solid and thick plastic, the hex is a very tight fit, and teams have run hex bore plastic hubs in drivetrains before. I’m quite confident the guys at Vex wouldn’t design an entire product line of drive wheels that couldn’t stand up to basic defense.