LAST Wheel question

[sdcantrell56]

I see that a lot of teams use lawnmower wheels, and I want to know are they using plastic or metal wheels, and do most teams just drill holes to mount sprockets. Also how do lawnmower wheels hold up?

[greencactus3]

we tried metal ones in OCCRA a couple years back. drilled holes to bolt the sprockets onto..... we'll just say we won't be going back to that design again.
the rubber tread just wasnt even close to grippy enough to be competitive in that sense. and we had duallys too. but then again we mightve pickesd the wrong type. ive seen many teams succeed very well with them. but i just dont like them anymore.

[EricH]

Originally Posted by sdcantrell56

I see that a lot of teams use lawnmower wheels, and I want to know are they using plastic or metal wheels, and do most teams just drill holes to mount sprockets. Also how do lawnmower wheels hold up?

You don't use straight metal wheels in FIRST. If you use metal wheels, make sure you put belting around the edge as a traction device. There is a rule in Section 4 about no damaging the playing field with a traction device (and no metal on carpet). Also, I think most FIRST teams use wheelchair wheels.

[sdcantrell56]

I know that you can't just use metal wheels, but what wheels can you use to put conveyor belt material on. Also how can I attach caster wheels to a drive shaft?

[EricH]

Originally Posted by sdcantrell56

I know that you can't just use metal wheels, but what wheels can you use to put conveyor belt material on.

Any you like. Metal wheels are fine with belting, Skyways are often modified with belting. I'd go with a Skyway. Grind down the tread 'till it's flat and close to the plastic. Use screws and drive them as deep as you can get them (or come up with your own unique way of attaching).

[sdcantrell56]

for doing six wheel drive would it be easier to use a keyed shaft or drive the wheels?

[Biff]

Originally Posted by sdcantrell56

for doing six wheel drive would it be easier to use a keyed shaft or drive the wheels?

It's a loaded question, first determine what wheels your going to use, then your desired speed.(s) your wheels will tend to drive how you mount them, The Skyway 6 and 8 inch will only work with a 3/8" shaft unless you do some serious custom mounting. The Skyway's with an inner tube only drive with a 5/8" keyed shaft. If going with a shaft pay attention to what the shafts will be mounted in. Steel pillow blocks get heavy very fast (we built our own out of "cutting board" plastic one year) Search the forums for the Atwood gearing xls spread sheet it's a big help in picking sprockets and gears with out redoing the math every time. The wheels from IFI let you decide how you are going to go, If you are willing to spend the money. Hope this gives you some ideas.

[TimCraig]

Originally Posted by sdcantrell56

I see that a lot of teams use lawnmower wheels, and I want to know are they using plastic or metal wheels, and do most teams just drill holes to mount sprockets. Also how do lawnmower wheels hold up?

Our second robot used 8 inch plastic lawnmower wheels (Home Depot @ about $10 per wheel). We just drilled 3 holes and mounted the sprocket using 1/4-20 bolts and spacers. That robot just went through it's third build and those wheels still have tread on them. Even being run on asphalt several times. We've also used wheelchair casters when we needed something very light and have moved up to go-kart wheels last year.

[sdcantrell56]

I think I am going to try lawnmower wheels just based off of cost. Our team has a really small budget so if they work it will save us a lot of money. Are there any specific things to look for in lawnmower wheels.

[sanddrag]

Colson wheels are cheap, maybe even cheaper. But you'll have to make hubs for them.

[TimCraig]

If you're going to attach the sprocket to the wheel so the wheel spins on the staft (rather than firmly attaching the wheel to the shaft and driving the shaft), I'd spend the few extra dollars and make sure I got the wheels with the ball bearing hubs. I'm not sure I'd trust broaching a plastic wheel and using a key to keep it on the shaft to drive it. It probably will work as I broach plastic gears and generally they're fine but wheels can take a bit of shock. If you're going to drill through the wheel disk to attach the sprocket, don't get the wheels that have open spokes.

[sdcantrell56]

Yeah I'm planning on getting the ones with bearings and drilling through the wheels. How is the traction with the wheels?

[TimCraig]

If you're building a 4 wheel drive robot, the traction on the 8 inch wheels we used is pretty good. Not so much grip that you can't turn relatively easily. 4 wheel drive is always a pain because of the tradeoff between traction and turning, not to mention the odometry problems when you start getting fancy.

[sdcantrell56]

What do people think about the skway beadlocks or the 8x2 skyway pneumatics?

[Biff]

Originally Posted by sdcantrell56

What do people think about the skway beadlocks or the 8x2 skyway pneumatics?

The pneumatics we have both with the standard and the larger tread and tube on them. They give good grip with and the standard are pretty easy to turn, They do bounce. The larger tires have tremendous grip and take two motors a side to turn tank style. The hubs we used only drove with the 5/8" keyed shaft, they have an aluminium insert and take abuse very well. The beadlocks tend to be heavy and have a large amount of slip in all directions on carpet. On the plus side, they don't bounce