making wheels

metal circles are really useful, but how do you make them?
for wheels, bike rims...

Anyway, I'm thinking of this again, because I recently visited Haystack Observatory, and they have this giant metal circular track that's bent railroad track. [edit: and by giant I mean 50'+ diameter GIANT) And because of imperfections in the circle which come from bending railroad track, the concrete is actually cracked as the antennae rotates. Is that the state-of-the-art of giant metal circle making?

1. Maker Faire NYC:
giant 5 ft wheels: apparently they just picked the rim up as trash from electrical work around the city

2. Mars's Pennyfarthing: http://en.wikipedia.org/wiki/Penny-farthing
which sits rider-less at MITERS because he miscalculate and his legs won't reach the pedals-
apparently, there was round table of the right-ish diameter (3 feet?), so he just took the ?steel? and literally rolled it with his hands...

relatedly, http://en.wikipedia.org/wiki/Velocipede

3. Bend some conduit? They... probably wouldn't stand up to use though, if you can bend them that easily. http://www.instructables.com/id/How-to-bend-tubing/step4/Ready-to-bend/

4. Plastic instead of metal -- melt plastic bags and form as appropriate (Star has this up on Instructables somewhere)

Would metal casting work? For small wheels, I guess there's no reason why not.
Make induction furnace to melt aluminum (Josh is building this). Pink styrofoam insulation cut out in the shape of a wheel with a bit sticking out. Sand to bury the styrofoam except for a small bit. Pour Al, melt styrofoam to nothingness.

The internets hold few answers.

Machine 'em: some amazing model train wheels here: http://www.clag.org.uk/bill-newton1.html
(details here: http://www.mmrs.co.uk/technical/wheels.htm)

The English wheel threw me for a bit, but it's more for planar curved surfaces, not rims:
http://en.wikipedia.org/wiki/English_wheel
(see pics here: http://www.tinmantech.com/html/fine_art_of_metal_shaping3.php)


anyway, I should stop punting (aughhh 2.005, I just want to throw in the towel and fail the final and go on my merry way.... >.<)
http://en.wikipedia.org/wiki/Direct_drive_mechanism
http://en.wikipedia.org/wiki/Hubless_wheel
http://en.wikipedia.org/wiki/Yike_Bike (is it a hub motor? O.o)

[edit 16 dec 2010 -- yay finals punting] Well, yike bike's hubless so it's clearly not a hubmotor ^^;
Also, page 25 on this guide says custom wheels can be made with "three plates: Two outer flanges, one (or more) slightly smaller middle."