Aluminum tubing?

[johndoe]

Ive searched with no luck on finding anybody who used aluminum tubing for
a rail? Maybe that should tell me something right there. I know 6061 t-6 has
about 1/2 the strength of chrome moly but could you just go to a bigger size tubing?
99% of all my experience is welding aluminum so I thought it would be a cool looking
frame.

[Glamisman]

J & J Buggy used to make an all aluminum mid-engine frame for VW's years back and while it was lighter and faster the welds and areas next to the welds cracked...lots of elbow grease involved in keeping it clean.

[minibajaman]

Sure it's possible to use aluminum for a frame with large diameter tubing as you said, but the main problem with welding 6061-T6 is that it needs to be heat treated after welding in order to bring the weld areas back to T6 strength. So you would need to find a heat treater with an oven large enough for a buggy frame, and have some fixturing in place to keep the frame from warping.

While 6061-T6 has a yield strength of about 40 ksi compared to cromoly's 65 ksi, it's annealed strength (in the untreated weld areas) is about 10 ksi, which is why it typically cracks. Anything I have ever made of welded 6061-T6 on a buggy without heat treatment has eventually cracked at the welds. An aluminum like 5052 or 5083 works well for buggy components because it retains most of strength when welded, but the yield strength is lower to begin with at around 25 ksi.

[dillon_b12]

Another big problem with aluminum is that it fatigues badly. Even if you overcompensate for its strength vs. steel it will never have the resistance to fatigue that steel does.

An aluminum tube chassis is constantly weakening due to fatigue. Steel is too, but not nearly to the degree that aluminum does.

[b.c.bugger]

6063 would probably work better than 6061 for a buggy frame, it does not fatigue as much when it is bent. The frame could easily be heat treated if you have a powder coating company nearby with an oven big enough. The guys we use at work have an oven 20' long, 7'high 9'wide for coating our service bodies, flatdecks and such

[K-fab]

If you could do a cast section car, in places where components mounted and then held the cast pieces in place w/extruded tube (shapes and such), then you might have a viable setup. Think modern motocross bikes and street bikes - but don't forget to take into account that each and every piece of the frames on those machines are designed, developed and made for a very specific purpose.

To just weld together tubing, like you would w/mild and/or chromoly, it just doesn't seem to work. I've seen a couple pix of a Honda Pilot styled ride that was all aluminum and it looked totally trick. I heard later that the machine also had issues w/cracking.

Just not the correct material for the application unfortunately.

[standfast]

Just start with a real big chunk of aluminum and make friends with someone with a BIG CNC and....

Modern motorcycles can pull it off with extensive engineering but I doubt anyone is gonna make it happen on a homebuilt buggy, and if can stay together, it is gonna weigh more than it would in 4130. Think of how thick a normally steel 1/4" tab would be in aluminum to have the same shear strength. Probably like 1/2" aluminum tabs. Like Kfab said, unless you are starting with some cast subframes (obviously not realistic), I doubt it's success.

[bdkw1]

If you could get a hold of some tubing made from the age hardening 7000 series aluminum that they use in mountain bike frames, you'd be set.

I think a 6061 frame that was properly gusseted and heat treated would have a very long life span. The aluminum frames I have seen from Mazzone were built with so little tubing, I think they would have cracked even if they were made of steel.

[johndoe]

Thanks for your guys input. I think Chrome moly is in my future.

[MC@ Performance Fab]

There have been aluminum cars for years in the desert. If it were built right it would not be a problem however if you want to go desert running verses sand you would want to stick with steel. In the early years there was an aluminum class 1 car that ran all the big races.