make vs. buy wheels

[kajeevan]

WOOD IS GOOD (use plywood)!!!!!!! light and strong substitute for aluminum. Backed by team 188 whose been using it for many many years with out fail. Also is relatively cheap i believe and easy to manufacture our team gets the new students to do them so they learn how to use a lath and drill press. MAX 2 days to make 8 wheels easy.

[artdutra04]

Time is the only thing that teams can never acquire more of during the build season. Everything else - money, materials, machining resources, mentors, Mountain Dew - all have the potential of acquiring more of them.

As such, during your six weeks, is it better for you to purchase COTS wheels with no or minimal modifications and move on to more important tasks - like the manipulator which actually does the scoring - or spend days machining wheels which more or less do the same function as COTS ones?

Now if you have sufficient resources at your disposal, and it is decided that machining/fabricating custom wheels will not detract from your ability to create an awesome robot, then by all means go for it. Otherwise, there's bigger fish to fry during the build season.

Remember: custom does not necessarily mean better. Engineering is just as much about optimizing time/ease of assembly and minimizing costs as it is about actually designing stuff.

[Dick Linn]

Our first year wheels were made out of wood. We couldn't afford anything else and didn't have much time. They worked OK, except for the really cheap "rubber" mat tread we got at Home Depot or somewhere. It was a dual-wheel setup, with the sprocket sandwiched in between the wheels, live axle with outboard bearings. They were made from glued 1 x 4 pine boards (the maximum size wood allowed that year) sawed out on a band saw.

That was back in the days when the drill motors and transmissions still came with the plastic drill housing/handle. We just sawed off the handle and used the cordless drill case as the motor mount

[jimbot]

The only real advantage to custom wheels is the coolness factor, and important factor yes, but can be overlooked if needed. I'd say try making them in the off season and if you like them, have time and the resourses then go for it. Me, I am a proud supporter of the KOP wheels, tough, great grip, just a little tricky to mount.

[AdamHeard]

Originally Posted by jimbot

The only real advantage to custom wheels is the coolness factor, and important factor yes, but can be overlooked if needed. I'd say try making them in the off season and if you like them, have time and the resourses then go for it. Me, I am a proud supporter of the KOP wheels, tough, great grip, just a little tricky to mount.

There are many advantages besides getting looking cool. You can usually save a good deal of weight, along with getting the exact diameter, width and mounting options you want.

I've preferred custom wheels for a while, but, depending on the weight, the new AndyMark wheels may sway me.

[RMS11]

Wood vs. Metal and also what is the best material to use for traction. Website please. Thanks

[EricH]

Originally Posted by RMS11

Wood vs. Metal and also what is the best material to use for traction. Website please. Thanks

Metal doesn't give you splinters if it's worn down too much or beaten up... but wood is cheaper. Anyone try plastic at all?

Lots of teams use blue nitrile tread (I think McMaster carries it), though others prefer roughtop or wedgetop tread (not sure on where to get those). A little suggestion: use CD's search feature, looking for "blue nitrile tread", and you should find some websites.

[AdamHeard]

Originally Posted by EricH

Metal doesn't give you splinters if it's worn down too much or beaten up... but wood is cheaper. Anyone try plastic at all?

Lots of teams use blue nitrile tread (I think McMaster carries it), though others prefer roughtop or wedgetop tread (not sure on where to get those). A little suggestion: use CD's search feature, looking for "blue nitrile tread", and you should find some websites.

The common tread people use on custom wheels (and on IFI and some andymark wheels) is sold as "incline conveyor belting" from mcmaster. There are two surface types, wedgetop and roughtop.

The wedgetop is just offered from mcmaster in gum rubber (but I've seen some teams, 188 in 2007, with black SBR rubber).

The roughtop is offered in many types, but is most commonly used in natural rubber (tan), SBR rubber (black) and Nitrile (blue). Nitrile seems to wear the best by far, although offering reduced friction. The natural rubber seems to be commonly used, but can wear very fast. I've seen very few teams use the black SBR roughtop, but it seems to be closer to the natural rubber in performance and wear.

[Jon Jack]

Originally Posted by AdamHeard

Nitrile seems to wear the best by far, although offering reduced friction. The natural rubber seems to be commonly used, but can wear very fast. I've seen very few teams use the black SBR roughtop, but it seems to be closer to the natural rubber in performance and wear.

We used the 'Wedge Top' belting in 2006 and it seemed to wear out pretty quick. I think in total we were forced to re-tread our wheels at least once a competition. Also, we've noticed that it dries out after 6-8 months which will end up reducing your traction.

We have used the black 'Rough Top' the past two years. It seems to hold up much better than the 'Wedge Top' does. Both years we were able to put about 15 hours of drive time, or roughly 415 matches, before the tread had to be changed on our practice robots. I don't recommend letting your tread get to this point in competition. We change ours about once every competition.

Also, the 'Rough Top' doesn't seem to dry out like the 'Wedge Top' does. Our 2007 competition robot has had the same tread on for the last 10+ months and it feels that same as when we cut it.

[Arefin Bari]

Originally Posted by EricH

MetalAnyone try plastic at all?

Team 1251 have used UHMW for their wheels for 2 years and have had success with them. UHMW stands for Ultra High Molecular Weight plastic. Perhaps, Dave from 1251 will probably come across this post and post their experience with those wheels.

[techtiger1]

UHMW or ABS plastic are both very dense plastics that work great for wheel applications. We used UHMW 2006-2007 and had very little problem with it, it is critical to remember you are working with a plastic when toleranceing these parts however that is where you run into trouble. http://www.chiefdelphi.com/forums/sh...ght=1251+wheel Here is the thread on our 06 wheels and the next year they were redesigned with a flange for the wedgetop to sit in. We reccomend sheet metal screws with a mushroom head to attach the tread and not rivits. I know the 07 was a 4 in dia wheel and the 06 I think was 6 in dia. When machining this plastic use coolant as the UHMW especially does not like excessive heat. 1251 has had custom wheels since 06 and dont ever regret making them. Making wheels is great if you have the time, resources money etc, if you don't buy them or modifiy the kit wheels with some high traction material as Arefin has showed us many times. The AndyMark FIRST kop wheel is a good product in the first place.

[RMS11]

Originally Posted by techtiger1

UHMW or ABS plastic are both very dense plastics that work great for wheel applications. We used UHMW 2006-2007 and had very little problem with it, it is critical to remember you are working with a plastic when toleranceing these parts however that is where you run into trouble. http://www.chiefdelphi.com/forums/sh...ght=1251+wheel Here is the thread on our 06 wheels and the next year they were redesigned with a flange for the wedgetop to sit in. We reccomend sheet metal screws with a mushroom head to attach the tread and not rivits. I know the 07 was a 4 in dia wheel and the 06 I think was 6 in dia. When machining this plastic use coolant as the UHMW especially does not like excessive heat. 1251 has had custom wheels since 06 and dont ever regret making them. Making wheels is great if you have the time, resources money etc, if you don't buy them or modifiy the kit wheels with some high traction material as Arefin has showed us many times. The AndyMark FIRST kop wheel is a good product in the first place.

Those look slick. And i assume you used the incline conveyor belting for traction. Ya, for us that little weight could matter a lot. About 300 holes later this year, our robot clocked in at 119.8, afterreplacing the sponsorship material And to mount the incline conveyor belting do you use rivets, screws, or something else? Thanks

[RMS11]

O, and how much did those wheels actually weigh?

[David Guzman]

Originally Posted by RMS11

O, and how much did those wheels actually weigh?

I think our 2006 wheels were like 0.28 lbs a piece, those are the ones drew posted. They were 5" in diameter and 2" wide.

Our 2007 wheels were 0.18 lbs a piece, 4" OD and 1" wide.

Since 2006 we have been making our own wheels and will probably continue to do so. For us, it is much cheaper to make them then to buy any of the ones that are in the market right now. They are also much lighter.

Overall UHMW worked good, but after some time the bearings began to get a little lose on the counter bores. The wheels were very tough, in fact in my opinion they handle impact better than our new aluminum wheels.

Best picture I could find of our 2007 wheels: http://www.chiefdelphi.com/media/photos/27927

For 2008 we decided to go with aluminum because we wanted to run them on live axles with a 1/8 key. There aren't any good pictures of them online. I will try to find one and upload it.

[=Martin=Taylor=]

Originally Posted by RMS11

Wood vs. Metal and also what is the best material to use for traction. Website please. Thanks

My favorite wheels have got to be the colson wheels (found here and a billion other places). They have lots of traction, they're very thick, so as the tread wears down nothing needs to be replaced, they're light, and they're dirt cheap to boot. We used the 7/8" wide variety and they had plenty of traction.

Many people will say that the conveyor belting material offers more traction. I am dubious of this.

Although the conveyor belting material does have a higher coefficient of friction than the colsons, you must remember that it was designed to move food.... Food usually isn’t dirty (I hope), and it also doesn't offer much wear.

Colsons on the other hand were designed to be used as castors for heavy equipment. They are meant to work in dirty environments. As a result, Colson designed them to be resistant to dirt and wear slowly (they brag about this on their site).

We never had to change the wheels all season.... But we did replace two of them with omnis since they offered too much traction