MIG welding aluminum rim with spool gun, tips for Al newb?

[Chuck78]

I'm swapping my narrow factory steel spoked wheel rims to wider aluminium rims for weight savings and to run wider tires around 140/150 rear and 110 front. Now I can find used drag bike rims for KZ's and GS's for the rear in the 3.50x18 WM6 size I'm looking for, as my buddy and I did on my GS750 and his KZ1000, but drag bikes go skinner on the front, so a wider front rim is harder to find used. I found a very cheap front match for my 3.50x18 DID rear, a 2.50x18 DID rim, but then I realized when mocking up some spare KZ spokes into my GS front hub that with motorcycle wheels vs the familiar bicycle wheel lacing, the much larger spoke nipples need a very specific angle drilled into the rim hole. The rim I got had the spoke hole angles drilled for a larger diameter rear hub, so I need to have Woody's Wheel Works redrill the rim for larger nipples at the correct angle, or I could make up a jig and do it myself but for $30 plus shipping both ways, I'll opt to have them do it.

The other problems I realized - the rim was on a rear setup, and it had two rimlock holes drilled in it!!! those aren't two extra valve stem holes! I figured I could just very gently do several tack welds to plug up the holes without overheating and distorting the rim, and then grind and file them smooth and flush. I also noticed when handling the rim an annoying rattle when rotating it. The welder at the DID rim factory dropped some big globs of aluminum in the hollow sections on the sides of the rim when welding the seams shut!!!! I drilled a 1/4" access hole on the bead seating area inside the rim and fished/dremeled/pried these noisy chunks of aluminum out. Now the tire probably will seat okay, but I figured I'd weld these shut now as well.

I got a Spoolmate 185 with my used Millermatic 185 MIG, but have yet to use it on aluminum. I have the Argon tank and aluminum wire. I'm looking for some tips from you guys on welding thinner aluminum, and your feedback if you think I am being a foolish tightwad in not buying a similar used DID 2.50x18 rim with no extra holes in it straight from Woody's Wheel Works for $100 or $120... I'd save $45-75 shipping them this rim I have. This rim is in perfect shape other than the holes I propose to weld shut, and a perfect match.

Any Al. welding tips and/or comments and suggestions?

[bwringer]

Honestly, a motorcycle wheel that I or a loved one would be depending on strikes me as the world's worst possible way to get acquainted with welding a new material. A great way to get to know your local coroner, though.

I'd spend a few more bucks on the rim from Woody's, and practice welding aluminum on something else for a good long time.

[Chuck78]

My machinist buddy tells me that welding cast aluminum is like welding cast steel or iron, much harder. So aluminum mag wheels probably will be only for the experienced, but this spoked wheel rim I hope would go much easier.

Two vids from this guy are all I've gotten thus far in the way of aluminum welding education:

http://youtu.be/KCxGeyJvQsU

How do I embed videos, anyone know???

[Chuck78]

I've got a lot of practice pieces and insignificant projects like a broken mountain bike frame, cracked cast aluminum lawnmower deck, etc... Since I'm just filling some small holes, I figured it wouldn't be much of a problem at all since it's not affecting the structural integrity of the rim as something like rewelding a cracked rim seam would be. I wouldn't attempt it if I were doing a structural damage repair

[GateKeeper]

you cannot embed videos on this site....

[Sadsak]

Just plug the extra holes with valve stems! I'll bet you a nickel no one will notice and it will balance out nicely.

[Chuck78]

Well, Woody's Informed me that the identical rim they have also has rim lock holes, but they make nice little billet aluminium plugs specifically for this purpose of plugging unused rim lock holes! I can't comment on Buchanan's, but Zach at www.WoodysWheelWorks.com in Colorado are very great deal with for custom made spokes, rims, wheel building, & other wire wheels needs.

I have gotten out of this a whole lot of useful tips for tig welding and mig spool gun welding aluminum.
-Use a pushing motion instead of pulling
-aluminium does not make sizzling bacon sound due to it being a splatter weld spray transfer instead of a direct contact short circuit like welding steel
-Use more wire stick-out on mig to avoid burning the wire back too far
-Must use a spool gun if mig'ing Al
-Use a zap-drg-zap-drag technique & you can mimic the"stacked dimes" appearance of a tig bead with spool gun
-Clean metal well with acetone or similar
-Must use ONLY stainless steel wire brush for heavier cleaning, must not have ever been used on other metals. Same with grinding stones, discs, etc
-Aluminum is prone to cold starts & burn through at the end of a bead.