Small wheel options

[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.