Oh man... I just love contraptions!!!
Elliot wrote:
Sorry, so far as I know, steel and aluminum can not be welded together. But you don't need to. Steel rims and hubs are plentiful and don't weigh much.
Word is, a wire-feed welder (MIG) is the easiest to learn and not expensive.
I use a "stick" arc welder, but it is a rather crude tool, tricky on thin materials. (I burn a lot of holes!)
Top of the heap is a TIG (tungsten) welder, but those are expensive and require more skill. This is the only realistic way to weld aluminum, though.
No, you can’t weld aluminum and steel. Brazing might be an option, but finding steel wheels seems much more reliable. Here's some stuff I thought would be worth sharing with you all:
Some welding info and tips for welding thin stock:
Stick, or Arc welding (technically known as Shielded Metal Arc Welding) is tricky with stuff 1/8" or less. Look for the smallest rods you can find (some places still sell 1/16" rods, but they are getting fewer) and keep your amps low, low, low. Some stuff is just too thin to weld with a stick and even if you can weld it, you will blow holes. When you do, simply let the spot cool down, then start to weld with short beads, welding on one side, stopping, then welding the other. Let them cool a bit and repeat. You’ll eventually fill up the hole... just watch the weld puddle and try not to get it too hot. This “hole plug” technique works with MIG welding too and is much easier since you have a trigger (some bigger units even have a “pulse” feature that does it for you).
Welding thin stock with a stick:
Keep your arc gap close (the arc gap is the distance from the end of the rod to the base metal that the arc jumps). By stabbing the rod down into the molten puddle, you shorten the gap and cool the arc down. This is tricky, since it’s a small change from shortening the gap to sticking your rod. With practice you can do it, so don’t give up.
MIG Welding:
Wire, or MIG (Metal Inert Gas) welding is much more forgiving, both in general terms of use and in the learning stage. It uses an inert gas to shield the weld puddle from oxygen (usually Argon or an Argon/CO2 mix). It’s a much better choice for thin stock, since it’s stable to lower amperages. The small units work great for thin stock. If you can, spring for the 220V version, since you can get a little more amps from it and it doesn’t stress the machine when trying to weld thicker stock. You can weld 1/4" or even 3/8" with multiple passes, but the puddle starts to get cool with the thicker stuff and you risk lack of good weld penetration (bead humped up rather than spread out smoothly). If you can spring for a full sized roll-around 250 amp model, you’ll love it. But keep in mind, with those extra amps come extra abilities and that means extra ideas to spend money on.
You can use a flux-core wire in a MIG welder (if I remember correctly, technically changing it to Flux Core Arc Welding). This replaces the inert gas with a shielding gas produced from the burning of the flux, similar to stick welding. It also makes for more spatter and stuff to clean up, but doesn’t force you to buy a bottle of gas and tote it around everywhere.
As far as grounding both work pieces, I’ve never done it. I’ve always done as Gravity Mike has pointed out... that being start on the grounded side and lay the bead over to the ungrounded side. Both pieces are then connected and thus grounded. Then you can start down the middle of the gap and begin to fill in the weld.
Welding Aluminum:
TIG (Tungsten Inert Gas) welding is the best choice, but is much more expensive to get setup with. It is also the best choice of welding steel when clean joints and tight, controlled weld beads are required. It’s very stable at lower settings, with some units holding a steady arc down to the fractions of an amp. I knew a guy who did welding repairs for Tool & Die shops and he routinely welded under a microscope.
But for most general applications, you can get a couple of slightly more affordable options.
One is a spool-feed gunthat hooks up to any standard arc welder. It’s like a mini-MIG and they work fairly well. You can also get aluminum wire for a standard MIG, but I’ve never had first hand experience with it. I’ve heard it can “bird-nest” on you at the drive rollers. Incidently, I’ve also seen aluminum rods for a stick welder, but I’ve not used those either.
Regardless of the process, compared to steel, aluminum is a big ol’ fickle bitch and takes practice... but it can be done and done well.
Quick Change Helmets:
Worth every penny. But it should be noted that I've never used any of the cheaper ones and can't speak for their quality. They may well be just fine, but I know without a doubt that Jackson makes good shit that I trust my eyes to every day.
The New and Improved Black Cat... now with 25% more blather
What picture hoster is simple and cheap -- Photobucket??? 
