Why aren't more frames built from aluminum?

Why aren't more frames built from aluminum? Is there something about it that makes it a poor choice? I was thinking an aluminum themed T-bucket with a Buick 215 and an aluminum frame would be light and zoomy.

So why not an aluminum frame?

 

Traditionally higher costs for aluminum piece parts were--and still are--a barrier to its large-scale subs***ution for steel in cars. (and frames) Steel auto components are simply easier and cheaper to fabricate than aluminum ones. First, stamping out steel sheet parts with heavy--and costly--steel dies is a well-understood process with a long history. Second, aluminum costs three or more times more per pound than steel, resulting in higher model prices, even though aluminum's lower density compensates somewhat when comparing on a cost-per-weight basis.

 

I don't think there's any really good reason why you couldn't. When I was younger my grandparents had several log trucks with aluminum frames. They did have steel inserts in the frames, but c'mon, if you've ever seen a log truck in action off road you'd understand just how rough a life they live...

 

...and what he said...(wow)

 

There's also the matter of welding it for most home builders.......

 

Take a 32 Ford frame, in aluminum it would have to be quite a bit larger in dimensions to have the same strength and lifespan as the trad 32 frame in steel. That is why Big rigs have 12" tall 3/8ths inch thick aluminum material on their frames.

 

Strength to weight ratio and cost I'd imagine.

 

Very, good points indeed. My last motocrosser had an aluminum frame and it was by far the best handling bike I've ever had. Of course, it was 7000 series aluminum, which is horrendously expensive, even compared to 6061 aluminum. It's also harder to weld, and I would bet it's very spendy to manufacture. But it sure works well, at least on bikes.

 

I seen plenty of early Ford frames formed from flat plates formed and welded together, you could do the same out of aluminum plate. As Tman says, you would want to make the channels deeper, and the flanges wider than a steel frame to conpensate for the lower elastic modulus of aluminum. Because welds in heat treated aluminum are not nearly as strong as the plate, you need to configure the connections/welds differently than a steel frame. Finally, there would be a whole lot of welding. Forget TIG, you would want to MIG, that is if you want to get the welding done in your lifetime.

Bottom line. Do-able, but you need to be pretty sharp.

That is all i think i know.

Piper106

 

Check out this thread over at tbucketeers.............
http://www.tbucketeers.com/forum/f34/sale-cl***ic-t-bucket-reduced-price-2752/

 

They tell me that railroad p***enger cars made from aluminum have a set service life, after a certain age they're prone to developing fatigue cracks from the vibration and flexing of normal use.

I know they used it for some components in locomotives in the 60s and the ones that had it it's all been replaced on the locomotives of that type still in service today, for the same reasons.

Maybe today's aluminum is made better -

 

I don't think it would be a good idea. When people approach you at shows and ask you what your frame is made out of...... you might not be able to pronouce "aluminum" properly.

 

Just curious.. Would an aluminum frame, cage & all, p*** any race body's (NHRA IHRA SCTA etc.) tech inspection?
If not, that's why you don't see them.
Real hotrod's are at least potentially/hypothetically built with the intention of racing.

 

You're probably right, but how many miles do you think those things racked up in that lifespan? I bet it was a bunch.

One of my grandparents KW's had 800K on it with the original aluminum frame. It'd been repaired a few times, but as I said before, log trucks lead a rough life.

 

Exactly! 7000 series is extremely "hard", it has no torsional leeway, and for that reason it would make a poor frame for a car. I bet the majority of your bikes motor case was aluminum also! Those hand levers for the front brake and clutch? Probably aluminum too. People give aluminum a bad rap because they don't understand that it has as many variations as steel does. Alloying and homogenization make huge differences in strength...

"Softer" aluminum (lower maganese content) would work better, allowing some frame flex with less stress atomically.

The biggest reason no one does it? Because it's just too easy to use steel. That, and well, because no one wants to see a repeat of this:

 

I know they aren't HAMB friendly, but the new ZO6 and ZR1 corvettes have aluminum perimeter frames. Weighs 3350 lbs and over 600 horse. Just a thought.

 

A truck frame is straight so it's an easy application.
I would ***ume it's rolled out then drilled because of the varying thickness...i.e. they have heavier flanges than the body of the channel for strength.

A steel car frame is all the same thickness so it can be stamped in most any shape... i.e. humped over the rear axel and tappered in to cradle the engine.

 

The aluminum truck frames I remember were fabricated, the flange being slightly thicker than the body.

I would think you could use extruded aluminum channel as a base for your frame, especially if you were doing a "T" or "A" style frame. That would minimize the amount of fabrication necessary.

 

The current President of the NTBA is building an all-aluminum T. check it out on
www.nationaltbucketalliance.com.

 

If you build identical frames, say from 2x4 x1/8 wall steel and aluminum, the aluminum frame will deflect 3 times as much as the steel frame do to the modulas of elastisity of aluminum is 1/3 of that of steel, also aluminum has a very low endurance limit which is the material trait that you want if you are looking for good fatigue life. Pro stockers throw their aluminum rods away after 75 runs because they know they will fail from fatigue.

The only aluminums that we should ever consider are 3003 for bodies, 5052 for tanks and seats and 6061 for any structure. All of these are very weldable, all go to the "zero" condition after welding so if you are going to make a structure make it really stout or post heat treat it,6061 only. You can weld 2024 and 7075 and it can actually look pretty damn good, it will fail at the weld so don't do it for any thing that you may stake your life on.

Rex

 

Plymouth Prowler has a hydroformed aluminum frame. Some BMWs also have an aluminum frame. There was a build up in one of the magazines about 1960 using an aluminum frame in a T bucket.

 

You mean like an airplane? All the planes I've ever ridden in were aluminum, and I was really hoping they held together, but then again, they are riveted, not welded, but still look out at a jet wing the next time you're in the air, those things flex PLENTY and hold up well past what I would think they should.

 

you would want to make the channels deeper

How much deeper?

THREE times deeper.
To replace 2" × 4" channel, use 2" × 12" channel.
Not so easy now, is it?

Where's the weight saving?
Gone, baby, gone.

 

That's not how it works and a gross oversimplification of material properties. Go ahead and put iron pistons in your engine if you're that leery of aluminum. They ought to weigh the same by your logic, and probably work better than aluminum since they'll match the block's thermal expansion rate.

 

they are not tradional

 

Heres the problem for regular production cars, REPAIR!!! Hitting a deer, for example, bends and buckles several panels that have to be replaced, not repaired. Most bodyshops are not familiar with, or equipped to deal with this kind of welding or repair.

There was an article in car and driver (it was at the dentist office, it was either that or teen beat.) that talked about repairs to an Audi test car that they had wrecked. It was a very involved proccess to get a factory authorized repair that wouldnt void the warranty.

 

That's not how it works and a gross oversimplification of material properties

Fascinating - I especially liked your use of engineering terms and data.

The Young's Modulus of elasticity for most aluminum alloys (10*10^6) is almost exactly 1/3 of that of most ferrous alloys (30*10^6). This is what determines the stiffness or bending resistance of a long unsupported length of tubing.

 

Edit- new and hopefully more constructive answer.

Repair and fabrication techniques have always held a few degrees more voodoo.

Look at all the questions surround welding steel versus iron versus moly, and it's not hard to see why most builders shy from aluminum.

good discussion!

 

Even hardened aluminum rods has less strength than steel rods. That is why aluminum rods are always more m***ive than steel rods for the same application. In the later 1960s, we used Mickey Thompson aluminum rods in our SB Chevy powered Jr. Fuel dragster and the only engine failure was because a M/T rod broke, while the dragster was being push started. The older aluminum rods such as M/T will work harden and break and for that reason they should be replaced at the end of every racing season. Modern aluminum rods are 6061-T6 (hardened) aluminum and can be used in race engines and even in engines driven on the street. I don't think the advantage of aluminum rods would not be worth the risk compared to using aftermarket H-beam steel rods. ***anium rods would be the way to go, if money was no object.

In the fall of 1962, Pontiac Motor Division developed and made an all aluminum frame identical to the steel frame for their 1963 Pontiac 421 Super Duty Catalina FX drag race cars. The so-called "swiss-cheese" steel frame in those FX race cars was drilled and sawed full of holes to reduice weight. That weakened the steel frame and it would start cracking in a different location after nearly every run and the frame had inspected by the crew and welded. In a desparate attempt reduce vehicle weight to be more compe***ive against the Z-11 Chevrolets and light weight Dodge FX drag cars, Pontiac developed and produced an aluminum frame. In January 1963, Pontiac Motor Division was taken out of NHRA and NASCAR racing and the aluminum frame was never tested. Pontiac Super Duty racer and restorer P.J. Heck in Galli-police Ohio had the only 1963 Pontiac aluminum frame that was made at least he had it the last time I heard.

 

Prowlers had aluminum frames. The low weight and size of the car hauled *** for a V6 car.