Small wheel options

[WarehouseCrew]

Can anyone recommend some smaller wheels to try for the shooting mechanism? I understand team 3847 used Banebot wheels successfully, but I would like to hear if others have used other wheels that have also worked (and where you can buy them from).

If using a non-Banebot wheel, how are you mounting the wheel to your shaft (either gearbox or direct drive on CIM, etc.)? Most of the wheels I've seen are designed with bearings to spin freely on a shaft.

Thanks.

[Garrett.d.w]

http://www.vexrobotics.com/vexpro/wh.../217-2903.html

This is what I'm thinking of using on ours. It would be driven directly off of a CIM using an AM style hub after we mill the nubs off of the built in hub of the wheel.

[WarehouseCrew]

Does the wheel's tread pattern (eg. not smooth) work well for shooting discs?

[Garrett.d.w]

Originally Posted by WarehouseCrew

Does the wheel's tread pattern (eg. not smooth) work well for shooting discs?

I should have been more clear in my original post. We haven't actually tried them yet. Though their size and price ($4.99) make them really attractive.

I don't foresee any problems with the tread pattern (one of our prototypes used a wedgetop pattern). If there are any we can just expedite the wear process by introducing the tread to our sander. The trick would be to take off enough to make the surface even, but leave enough to still get some grip on the disk.

[AllenGregoryIV]

These are the wheels we used before the Banebots and they worked very well but were still a bit big for us. We were looking for them in 1/10th scale but non of the pre-mounts seemed to be foam filled like the 1/8th scale ones. We just drilled the 1.625 hole pattern into it and mounted it to an Andymark Hub.

[TheMadCADer]

Originally Posted by WarehouseCrew

Does the wheel's tread pattern (eg. not smooth) work well for shooting discs?

I haven't seen them tested, so you'd really have to just try it to find out. I would guess that it would not be very good, since the tread pattern decreases the area of the wheel that is contacting the disc as it goes through the shooter.

However, I think the problem with them will be more related to how firm the tread is. If you've ever held one of those VEX Pro versa wheels you'll know that they're very hard to the point that the tread's edges are sharp to the touch. Something that almost all teams have found is that wheels that can compress are better, since they get better contact with the disc.

[pilum40]

We're using the Andy Mark larger pneumatic wheels and straight CIMS. We've got standard sized wheels (6"-standard kit bot wheels from next year). Hopefully our build team has the dimensions correct and the wheels won't be pushing the envelope...ha...the cylinder.

[pfreivald]

We're in the process of trying some colson wheels as an improvement on our design. They're light-weight, come in lots of sizes, and are easy as pie to hex broach.

[WarehouseCrew]

How do you hex broach these wheels? We have very basic tools (eg. our school doesn't have an industrial arts program or shop).

Are these the wheels you are referring to? They don't look like they compress (eg. hard rubber).

http://www.robotmarketplace.com/prod...on_wheels.html

[AlexH]

Originally Posted by WarehouseCrew

How do you hex broach these wheels? We have very basic tools (eg. our school doesn't have an industrial arts program or shop).

Are these the wheels you are referring to? They don't look like they compress (eg. hard rubber).

http://www.robotmarketplace.com/prod...on_wheels.html

colson wheels are 65a, banebots wheels range from 55a to 30a. the green banebots wheels (30a) are super squishy and wear out really fast. colsons will last forever.

coslon wheels are essentially shopping cart wheels

mcmaster also has a pretty good selection of small dia rubber wheels

http://www.mcmaster.com/#caster-wheels/=l2qt4x

[pfreivald]

Originally Posted by WarehouseCrew

How do you hex broach these wheels? We have very basic tools (eg. our school doesn't have an industrial arts program or shop).

Are these the wheels you are referring to? They don't look like they compress (eg. hard rubber).

http://www.robotmarketplace.com/prod...on_wheels.html

Those are indeed the wheels, and you are correct that they don't compress much. This can be but doesn't have to be a problem when it comes to shooter design.

Broaching requires (a) a press of some kind (arbor press or bottle jack press), and (b) a broach. The process is (1) drill hole to correct diameter for broach (if not already that size), (2) insert broach, (3) press through hole -- but make sure things are square, because any side load on the broach will probably shatter the hard steel.

A press necessary for plastic or aluminum wheels/sprockets/etc is less than a hundred bucks. A half-inch hex broach is about $215, but unless you break it you only need one.

A keyway broach is cheaper -- you can get a set of them suitable for FRC-sized applications for around $200 -- but having switched to hex broaches this year I don't think I ever want to go back!

---------

On a side note, over the course of several years we bought a small mill, lathe, arbor press, and bench vise and mounted them on a four-wheeled, heavy-duty cart, and put a bunch of drawers underneath to store hardware (nuts, bolts, rivets, washers, etc, etc). This "machine cart" cost us around $1500 total for everything, and sees near-constant year-round use. It fits through doors, doesn't take up too much space in an FRC pit (or our storage closet), helps with organization, and two people can push it up/down whatever ramps we need to get it up/down.

I would recommend that any team that doesn't have access to a machine shop set about acquiring these things as budget permits. It took us longer than we wanted it to, but it's very, very worth the investment. You go from, "holy cow, how are we going to attach that motor to that wheel?" to "hey, you whip up a couple of motor couplings while I mill out the plate."

[commodoredl]

Patrick, would you mind sharing more information about your "machine cart?" Pictures, product information, etc.
Being part of a team that has never done much machining with the students, I'd love to find an economical solution to get them started in that area.

[pfreivald]

Originally Posted by commodoredl

Patrick, would you mind sharing more information about your "machine cart?" Pictures, product information, etc.
Being part of a team that has never done much machining with the students, I'd love to find an economical solution to get them started in that area.

If you want to come down and check it out any time, you're certainly welcome -- Naples isn't that far from Fairport. (I first heard about FRC while student teaching at Fairport, if you didn't know...)

We'll have it at FLR, too -- it's the same one we had last year.

The lathe, mill, and some tools came from Micro-mark.
http://www.micromark.com/microlux-7x...athe,9615.html
http://www.micromark.com/microlux-hi...hine,9616.html

Looks like prices went up a bit since we got ours, but not a whole lot. In addition to the machines themselves, a good collet set, center finders, parallel bars, cutters, etc can run several hundred to thousands and thousands of dollars depending on what you choose to get. I can't elaborate on those exactly because they were sourced and donated by others -- a machinist willing to donate some time could suggest what a good starting set of stuff would be.

The arbor press was picked up at a garage sale. New ones run under $100 for the same tonnage.

For lathe practice, delrin works great because it's easy on your tools, and if you go this route please don't buy any. I think I have 20934870974326204987 lifetime supplies of 1.5" delrin rod in 12' sections that were donated to us last year.