Aluminum Frame

a1airboat · #1 (**permalink**) 07-08-2003, 02:17 PM

Anyone have any information on a aluminum frame. I'm looking at a car for sale with one. I'm concerned about the frame cracking with the stress of the big block. Thanks Darrel

David Kirkham · #2 (**permalink**) 07-08-2003, 07:37 PM

Aluminum frames are EXTREMELY difficult to work with. (We are talking about tube frames here...NOT monocoque structures.) The weight savings is worse than minimal at best. The Porsche 917's went to EXTREMES to save weight. They finally resorted to welding a bicycle valve into the tubes to detect cracks because they were so terrible for fatigue cracking. If the frame didn't hold air, it was cracked.

BE VERY CAREFUL.

David

Richard Hudgins · #3 (**permalink**) 07-08-2003, 08:04 PM

a1airboat,

I will have to fully agree with David on this one. Aluminum tube frames are a nightmare at best. (Alloy monocoques are also a problem as they age.)

6061-t6 is in the 70k tensile area and cheap old mild steel is in the 125K area. Therefore. sections and wall thickness of an alloy frame have to be quite larger and heavier to match the structure of the worst of steel alloys. (Of course the chassis will be a bit lighter for equal strenght, but it will be much bigger in all ways.)

Not to mention the problems of annealing around the welds, the changing of temper, and self aging timing, etc, etc, etc.

I would not recommend a Aluminum chassis for a Cobra type car unless you have a penchant for repairing welds and replacing tubes every 2000 or so miles.

Woodz428 · #4 (**permalink**) 07-09-2003, 04:02 AM

Aluminum also has a finite number of cycles it cam go through before fatigue. The sport bike road racers replace the frame every so often because of this.

CowtownCobra · #5 (**permalink**) 07-09-2003, 05:48 AM

David,

Didn't the 917's also cap the frame tubes and route oil to the coolers through the frame itself?

Fred Douglass · #6 (**permalink**) 07-09-2003, 01:08 PM

...stated very clearly the DISadvantages of aluminum for things like suspensions! It was in a marine-engineering magazine, but it covered a lot of the disadvantages of aluminum--even in old cook-ware! Despite the tremendous range of tensile strength etc. available in different grades of aluminum, the authors said that even with numerous safe guards (shock settings, spring-rates, the tires-acting-as-springs [they do!] effect, etc.) aluminum suspension parts would either deflect without 100% rebound or simply fatigue, especially around bushings and mounts. Gives one pause when we see everyone from Corvette to Audi rushing towards aluminum suspensions. About the only aluminum "frame" I would look at is Herb Adams' VSE ("very Special Equipment"). It looks like it will do! I dunno if he's still making them, but they were awesome for things like rigidity, etc. FFR started making aluminum frames (despite people saying that they weren't, they WERE! I think that idea went quietly away.

It might pay to talk to vintage aircraft rebuilders. Practically all the "warbirds" racing and displaying aeronautic stuff nationally have had their aluminum main "booms" (guts of the wing strut system) replaced.

My advice on a standard tube (non-monocoque)aluminum frame is----DON"T DO IT!

Brent Mills · #7 (**permalink**) 07-09-2003, 02:34 PM

Just curious.....What about the underpinnings of jets? Don't they use mostly aluminum (I'm guessing) for weight savings (or is it steel)?

David Kirkham · #8 (**permalink**) 07-09-2003, 02:48 PM

Brent,

Yes, but that is a very different process. Airplanes are not made out of welded aluminum tubes. Modern airplanes are monocoques. Older airplanes were welded steel tubes.

Cowtowncobra,

Yes...like I said, they went to extremes. I even have a picture of the Scherader (sp) valve welded on the back of a 917 somewhere. They were nuts. Aluminum front hubs, aluminum cam gears, titanium everything else...

Fred,

Aluminum suspensions have been around for years and years without any problems. The problem is welding (and losing all the heat treat) aluminum tubes for frame structures. (Remember aluminum wheels take a tremendous beating but last the life of a car.) Strange, and others, have made aluimium pinion flanges for the Ford 9 in differential for years.

The props on almost all airplanes are made out of aluminum. Boat props are made out of aluminum. It is a great material...If you know what you are doing. It's all a matter of alloy choice and process.

However, welding aluminum changes the whole world. There are few who can do it right and it does save weight when done properly. (Just look at all the Japaneese Superbikes.) It is not something I would trust to be done by many people.

David

Steve R · #9 (**permalink**) 07-09-2003, 03:38 PM

Lotus Aluminum frame.http://www.sandsmuseum.com/cars/elis...ng/pictsl.html

Sizzler · #10 (**permalink**) 07-09-2003, 03:52 PM

Isn't the Space Shuttle aluminum-framed?

Don't know whose argument that would support exactly.

How about Titanium frames then? USSR is flooding the market right now to raise hard currency. Which leads to the thought of Titanium bodies...