Utility Cycling - 29er Ute bike build? + Welding Aluminum?

Have been looking around for a cheap older cromoly frame or bike in my area - Craigslist, garage sales, etc. Haven't had any luck.

What I want to do is take a frame, get a rear triangle from another cheap/scrap bike and weld it onto the frame, and then fab a rack and weld that on.

But all the bikes I"m finding are aluminum frames. So, I have a couple q's.

First - obviously aluminum can be welded, but is welding aluminum a capability I should be able to find at a small local shop? Or does it take pretty specialized equipment?

Second - would doing this with an aluminum bike be a bad idea? Why?

Third - assuming it's ok to do this with an aluminum bike, what do you think about doing it with a relatively cheap 29er frame (i.e.- Nashbar frame for $99), and running a 26" wheel in the rear and 29 in front? I'd try to get components cheaply from season end sales and ebay.

Most shops do not have a TIG welder, the usual requirement for welding aluminum. If they do, be prepared to pay significantly more than for welding steel.

:)ensen.

Have been looking around for a cheap older cromoly frame or bike in my area - Craigslist, garage sales, etc. Haven't had any luck.

What I want to do is take a frame, get a rear triangle from another cheap/scrap bike and weld it onto the frame, and then fab a rack and weld that on.

But all the bikes I"m finding are aluminum frames. So, I have a couple q's.

First - obviously aluminum can be welded, but is welding aluminum a capability I should be able to find at a small local shop? Or does it take pretty specialized equipment?

Second - would doing this with an aluminum bike be a bad idea? Why?

Third - assuming it's ok to do this with an aluminum bike, what do you think about doing it with a relatively cheap 29er frame (i.e.- Nashbar frame for $99), and running a 26" wheel in the rear and 29 in front? I'd try to get components cheaply from season end sales and ebay.

When aluminum is heated above [roughly] 500 degrees F it becomes soft . . . any previous heat treatment is removed. Welding takes place at a much higher temperature than this. So what you'd end up with is an un-heat-treated frame which would probably not last long.

I've owned a welding/machine shop for 35 years. I don't know where you live but most of the shops in my area have TIG welders. But it doesn't matter: none of them [including mine] have the necessary skills or equipment to heat treat the project AFTER welding.

Years ago I was involved in the manufacture of a new bicycle design. It involved forming 6061-T0 [which is soft] aluminum in a hydraulic press, forming two halves of a frame, which were later welded together. Then the whole frame was sent off [somewhere] and properly heat-treated.

Find some old steel frames and have fun!

Thanks guys...I figured I'd have read about people using alum frames if it were doable.

That $99 29er frame is at Performance, not Nashbar (yeah, I know they're the same ownership).