Wheels..

[ksafin]

Hi all,

I was hoping to have a discussion about.. well.. wheels.

Barring Mecanums and other specialty wheels, it seems like most wheels come down to just varying weights and tread patterns.

I'm eager to find out - why one wheel over another? What makes or breaks a wheel for your team?

Versawheels, AndyMark performance wheels, kitbot Grip wheels, Colsons - why one or the other? A lot have similar CoF's. Which tread? Why?

I guess it's because we're looking into a WCD this year and I'm trying to figure out what wheels to use and why - when choosing wheels we've never really thought deep into it because we've never seen much depth to it - "well these are grippy, so they'll do" - is how we've been.

Of course, different situations call for different wheels, but in general I'd like to hear some feedback and guidance.

[sanddrag]

I like Colsons because you install them once and then it's done for the rest of the robot's life, through parades, demos, and everything. But, they don't come in every size I need, they can be heavy depending on size, you need to make hubs for them, and arguably they're ugly.

If I'm going to go through the trouble of machining a hub for a Colson, it's not a big step for me to just machine a whole custom wheel.

I like wheels that are light, strong, look cool, and most importantly, can be made to have a 7/16" hex bore. Many do not meet my last requirement, and for that reason we're likely to make wheels.

[ksafin]

Originally Posted by sanddrag

I like Colsons because you install them once and then it's done for the rest of the robot's life, through parades, demos, and everything. But, they don't come in every size I need, they can be heavy depending on size, you need to make hubs for them, and arguably they're ugly.

If I'm going to go through the trouble of machining a hub for a Colson, it's not a big step for me to just machine a whole custom wheel.

I like wheels that are light, strong, look cool, and most importantly, can be made to have a 7/16" hex bore. Many do not meet my last requirement, and for that reason we're likely to make wheels.

There are absolutely no COTS hubs for Colsons?

What's the reason for 7/16" hex bore? What's wrong with 1/2" ?

[DampRobot]

Originally Posted by ksafin

There are absolutely no COTS hubs for Colsons?

What's the reason for 7/16" hex bore? What's wrong with 1/2" ?

WCP sells a very nice one.

I won't try to speak for Sanddrag, but some teams (like 254) like to have round bearings in their DT. They have a 7/16" hex in the wheel (which can go through 1/2" round bearings) and a 1/2" hex for the DT sprockets. On the other hand, I've never had a problem with hex bearings, so I wouldn't say there's a problem with using 1/2" hex in wheels.

[ksafin]

Originally Posted by DampRobot

WCP sells a very nice one.

I won't try to speak for Sanddrag, but some teams (like 254) like to have round bearings in their DT. They have a 7/16" hex in the wheel (which can go through 1/2" round bearings) and a 1/2" hex for the DT sprockets. On the other hand, I've never had a problem with hex bearings, so I wouldn't say there's a problem with using 1/2" hex in wheels.

So is it just semantics?
Or is there a minute performance difference?

[ttldomination]

So, choosing a wheel is a very vague and open field, and like anything in FRC, you need to weigh the pros and cons that apply for your robot and your team.

You've mentioned quite a few variables, and I'll attempt to touch on each of them below. I could go into more detail, but I want this post to be semi-digestable in one read.

For wheel tread, the major players are wedgetop, roughtop, colson, and VEX Tire.

Wedgetop and roughtop are really just conveyor belting material that has crazy friction with carpet. This makes this a good material with a fully carpeted field, but throw in a slick surface or two (bridge and key in 2012), and you'll find yourself sliding around a bit.

Colson and VEX Tire are your basic rubbery tire material. They have relatively less friction than roughtop/wedgetop, but this tends to give some transient benefits that some teams really dig. Therefore, some teams default to colsons/vex tire when they have a choice.

For wheel size, you really want to cater to the needs of your machine. Now, the popularity of smaller wheels stems from the fact that smaller wheels generally yield a lighter DT and lower ground clearance. However, at the end of the day, you really need to choose what works best for your robot.

For wheel brand, you need to thing about factors such as; price, flexibility, quality, strength, availability, ease of machining, etc. The major players in this field are really the AndyMark performance wheels, AndyMark plaction wheels, VEXPro VersaWheels, VEXPro traction wheels, and colson wheels. With all of this choice, you need to do a fair amount of research to see which one has the blend of the aforementioned qualities that best suits your team/robot.

Personally, VEX has won me (and my team) with their prices, their flexibility, and the amount of engineering they've put into their wheels. The VEXPro traction wheels have the flexibility to use roughtop, wedgetop, or tire, with 1/2" keyed, 1/2" hex, or 1/2" bearing bore, with a variety of configurations to whatever wheel modules you need. Furthermore, their VersaPattern makes it super easy to make sure sprockets, bearings, and the wheel are concentric. My team was extremely happy with the wheels last year, and we'll be using then again this year (barring any Lunacy-esque rules).

- Sunny G.

[DampRobot]

Originally Posted by ksafin

So is it just semantics?
Or is there a minute performance difference?

The major difference is that you don't rely on 1/2" hex bearings, which have had defects and gone out of stock in the past. Of course, it depends on you being able to broach 7/16" hex and have access to a active tooling lathe to make your wheel shafts.

Like I said before, the benefits of plain ol' 1/2" hex outweigh the advantages of 7/16 hex in the wheels (at least for me).

[sanddrag]

Originally Posted by DampRobot

The major difference is that you don't rely on 1/2" hex bearings, which have had defects and gone out of stock in the past. Of course, it depends on you being able to broach 7/16" hex and have access to a active tooling lathe to make your wheel shafts.

This is exactly it: the desire to use standard R8-2RS bearings in our bearing blocks. Also, I should note that we use 7/16" hex on the sprocket side as well. While a live-tooled lathe would be nice, we get by with doing our hexes (and snap ring grooves) on a 3 axis CNC mill, with the axle standing vertical in a 5C collet holder. It works great. You could even mill hexes with a hexagonal 5C collet holder on a manual mill.

[AlecMataloni]

Well, it's Christmas Eve and I'm really bored, so here goes.

W-treaded Versawheels-
Light, cheap, and very high traction, but the W tread wears faster and needs to be replaced more often than most other COTS wheels on the market. (source: 341)

Colsons-
Slightly less traction than Nitrile, but friends who use them say that their wear properties are quite nice. I remember 11's driver telling me that their 4" Colsons were worn way down after the offseason ended, but they did 1 regional, 2 districts, state championship, Worlds, IRI, and 30 hours of driver practice with the same set of wheels. So, I'd say that's pretty reliable. Sanddrag's correct to say they're heavy, and the press fit hubs that WCP/VEX sell don't help with that.

One of the Colson wheel's biggest boons is the fact that they have REALLY nice traction on the plastic surfaces that FRC loves to implement (HDPE/lexan on the Bridges in 2012).
I've seen 11 and 228 cut diamond tread patterns (using a table saw) in their Colson wheels in order to boost their CoF on carpet. Not sure how much it helps, but I'll leave that topic to someone who has more experience with that practice.

Freakishly Huge Skyway Wheels-
Unless you're 25, I wouldn't bother. Using massive wheels like this is a lifestyle choice that I can't personally agree with; however, since this is America, they can make their own choices. Not for WCD use for sure.

Higrip-
Haven't used the new ones at all, but they're rated to a higher CoF than the old ones. 111 has been using the old kit wheels in our swerve drives since 2007, and we also had them on our Logomotion robot. Benefits are cost and ease of use, for sure. CoF on carpet has improved from the old design. Team 20 broke at least two of those 6" wheels at 2013 IRI, not sure if they decided that the ones they had were defective or not. Regardless, not a bad choice for simplicity's sake. Solid all-around wheel choice, and easy to fall back upon if you decide to change wheel types.

Vexpro Traction-
Drilling rivet holes is annoying. That said, this ain't a bad choice if you want a cheaper wheel that can take a removable tread. Very nice wheels when it comes to versa(haha)tility. The new tires (no rivets required) they sell supposedly have a CoF close to Colson tread, but last I checked, they haven't released the specs yet. I also like how you can make wheel width larger by adding more slices of plastic (included) to the center. Definitely worth looking into. Plus, it interfaces with all of the VP lineup, so that's another positive.

Performance wheels-
I've heard negative things about the current implementation of the AM Performance wheel's tread attachment method. IIRC, teams like 2338 said they had issues with throwing tread very quickly. If you buy these, you're gonna want to to drill into the wheels and rivet the tread on =/. Otherwise, great wheel. Very nice, very robust, never heard of one of these guys failing. Has a hex bore/key bore (hint: use hex =D) cut into it, so no hubs required for purchase.

I'm not sure if Andymark still sells the performance wheels with the old style of tread attachment. If yes, get 'em. You'll be doing yourself a favor.

There's really no point in cutting your own wheels, unless you have crazy awesome resources and a very specific design goal in mind (cough cough 971). COTS wheels will get you where you need to go (design-wise) 99.99% of the time.

There's two main types of conveyor belt material that FRC teams like using on their treaded wheels: Roughtop and Wedgetop

The roughtop tread VEX sells is REALLY soft. Soft to the point that we were wearing that stuff out really quickly.

Blue nitrile roughtop is what you want if you're looking for the best conveyor belt tread:

http://www.mcmaster.com/#catalog/119/1248/=pyezdo

Stuff's VERY grippy on FRC carpet. If you use it with thicker wheels (~2"), you might experience more wheel scrub, so be aware of that and compensate by increasing your wheel drop to ~3/16 if that's the case.


Wedgetop isn't as aggressive of a tread on carpet like the roughtop product I mentioned; however, like Colsons, they stick better to non-carpeted surfaces like HDPE or Lexan (IE 2012 Bridges).

When/if you're cutting tread to size, I recommend using I trick I saw on here a while back: put the tread rubber-side down on a piece of butcher paper and stick it on a bandsaw. the paper will benefit you twofold: the rubber won't make a mess everywhere, and you won't have to worry about the rubber tread getting hung up on the work surface of your bandsaw while you're cutting.

If anyone's got issues with any of this, be sure to let me know.
Hope this helps!

[Chris is me]

Originally Posted by sanddrag

This is exactly it: the desire to use standard R8-2RS bearings in our bearing blocks. Also, I should note that we use 7/16" hex on the sprocket side as well. While a live-tooled lathe would be nice, we get by with doing our hexes (and snap ring grooves) on a 3 axis CNC mill, with the axle standing vertical in a 5C collet holder. It works great. You could even mill hexes with a hexagonal 5C collet holder on a manual mill.

Pardon the off topic question: If you're not going to step hex, why not step up to 5/8" round bearings? The bigger bearing is annoying but doesn't seem like it would utterly ruin a west coast drive, plus then you don't have to custom make every single drivetrain part.

[AdamHeard]

Originally Posted by Chris is me

Pardon the off topic question: If you're not going to step hex, why not step up to 5/8" round bearings? The bigger bearing is annoying but doesn't seem like it would utterly ruin a west coast drive, plus then you don't have to custom make every single drivetrain part.

Teams locked into 7/16" hex before cots wheels with 1/2 were big. also, show me a 5/8 bearing that isnt crazy expensive that fits in a bearing block in 2" tube without removing too much tube material.

[Cory]

Originally Posted by Chris is me

Pardon the off topic question: If you're not going to step hex, why not step up to 5/8" round bearings? The bigger bearing is annoying but doesn't seem like it would utterly ruin a west coast drive, plus then you don't have to custom make every single drivetrain part.

Even if you used 5/8 on the wheels it wouldn't work on the center, since you step 5/8 to 1/2 to 7/16 on the gearbox output shaft hexes.

A big part of why we don't switch is backwards compatibility. Everything we've done since 2007 is interchangeable with any subsequent robot. This was a big help in 2010 when we were able to make an 8wd drive base (identical to our normal one except riveted instead of welded) in approximately 24 hours in the first two days of kickoff in order to test bump climbing ability.

[avanboekel]

What options are there for COTS 2" wide wheels? I'm aware of the vex ones, but are there any others out there?

[R.C.]

Originally Posted by avanboekel

What options are there for COTS 2" wide wheels? I'm aware of the vex ones, but are there any others out there?

http://www.robotmarketplace.com/products/BPDWC10.html

We don't advertise it, but you can use 2" wide Colsons with the same WCP Live Hub. There is more than enough hub for the wheel width.

[DampRobot]

Originally Posted by avanboekel

What options are there for COTS 2" wide wheels? I'm aware of the vex ones, but are there any others out there?

I believe you can get 2" wide colsons, but I'm not sure.

EDIT: RC beat me.