Quote:
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!
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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."