Aluminum frame - Is this a bad idea?

Mr. Roadster had an aluminum T frame about 1970. It was oversize, I think 2x6

 

my motocross bike is ali. dont see why a car wouldnt be able to be made out of it.

like it has been said though, the proportions would have to change. i wouldnt like to be thrashing that one of boyds around.

also it would get damn hot in there becasue it transfers heat so well.

 

The Lotus Elise has an Aluminum frame

 

Enroll in a tafe course and do aircraft construction or repair first. An aircraft fuselage is strong but if it fails it does so catastrophically! Remember even in an aircraft anything that had to be truly strong is still steel!
I know its been said befor but all the factory cars and bikes have had millions spent in design and development, just because they did it dont mean jo blow in his shed can.
I have to agree on that Cotterpin POS, DANGER WILL ROBINSON. Its one dumb fuck, or a brave one that takes that for a ride!

 

Another approach would be a lightweight space frame. My Locost has a frame made of 1" square steel tube. The frame tips the scale at 120lbs. Made from aluminum, it would likely weigh less than 100lbs.

It would not be difficult to adapt a straight axle and crosssprings to this type of chassis.

 

Lotus Elise is a combination composite fibre and alloy extruded Tub,not a frame. Different world entirely.

 

PBY Catalina wing struts were alum, and used for dragster chassis in the 50s. my 158'' top fuel frame made out of 4130 steel weighed 80 lbs, my 134''chassis weighs 82 lbs. more tubes.

 

Maserati Tipo or "Birdcage" has a all tube frame----very graceful and strong.

Rome

 

This is obviously not the same but would suggest usability none the less, Motocross bikes (some) come aluminum framed, and my 250F did several 120' gaps that had the bike easily 20' off the ground, I would say that those types of impact stresses would show a much higher "moment" than any road condition could duplicate, I would build one out of aluminum but I dont have access to a welder for such applications

 

I suppose one caution would be that it might be more difficult to pass tech if the intent was to make a 200mph pass in a locost space frame. While I trust it to putter around on the streets, there would have to be some serious re-engineering to make that thing safe enough to be a really fast racecar.

 

How did this thread get so wiiiiiiiiiiiiiiiiiiiiide? Must be some broad thinking individuals.

 

Check out the Ariel Atom.

 

xlr8 posted a HUGE link to a postage sized stamp of the Alumatruck. It was about 5,926 characters...

Say, since I think about women a lot does THAT make me a broad thinking individual too?

 

If it does, you aren't very exclusive in that.

 

Lots of good insight here on aluminum as structural material. The industrial "frames" I've built had an interesting behavior...as they tended to be far more flexible than a steel structure. As mentioned Al does have a fatigue failure mode...trans: a low but significant stress/load repeated often will eventually cause failure. Even if you go to chrome moly, and we've got some good builders here, who have experience w/tube frames, the wall thickness choices (.065. .090 etc.) mean that you have to estimate the max. stress regions carefully, so you don't have a collapsed joint/tube. The stress skin and Al frame construction is interesting too. For the time and materials required, I'd want to build into it as much "wisdom from experience" as possible. Material quality, weldment, localized stress, shape & thickness deserve time to evolve out a sound approach.

 

Didn't some factory drag car SD Pontiacs in the 60's have Aluminum frames? Thats a big ass car. Of course the stress was just a quarter mile at a time.

 

The inherent stiffness of aluminum is 1/3 that of steel.It also weighs 1/3 of steel. The old story about the airlifted gun comes to mind. They wanted a light artillary gun so the frame was made of aluminum. It was not stiff enough. They kept adding thickness untill it was the same stiffness as original. Guess what. It weighed the same. Aircraft structures do not like penatrations. It gets real hard to move the loads around. Look at the wing stiffners by the wheel wells of a B-24 for scary. I would build out of steel tube.

 

The new Corvettes have aluminum frame rails. They're hydrostatically formed in a permanent die process. Very cool, done all in one machine, starts with a dead soft square tube, roughly bends it to fit in the die, plugs the ends and fills it with fluid, closes the die and pressurizes the fluid to ~4000 psi. The pressure forms the aluminum tube to the die, and work hardens it in the process.

I've not seen a print of an entire chassis, but I do know the frame in those Corvettes is all aluminum. Rivets or welds is anyone's guess, though I'd imagine welding would be faster, but without a head treatment, that may not be as strong. I dunno for sure about the assembly aspects.

I think you could build an alum frame that would hold up for a good while, but do be aware that aluminum cannot be designed for infinite service life like steel can be. It will crack eventually, it's just a matter of time and location.

Personally, I'd opt for the small dia round tube (mild steel) space frame. Much easier to fabricate, and much more forgiving of neglect than alum or 4140 (which will also crack if not welded correctly). The weight differences will be very small on a vehicle that size, if you design the structure well.

Andy is also right, steel's modulus of elasticity is three times that of aluminum, so it's gonna be a whole lot more rigid for a given section. That can be overcome, but it's a lot of trouble and a lot of extra material. All of a sudden, that weight savings isn't there anymore.

 

The general consensus seems to be that while an aluminum frame could be done it's not that feasible for what I plan to build. I really hadn't given too much thought to a space frame but that concept intrigues me.

Which ever way I go, ladder or space frame, it's going to be steel. I've got the experience with welding that and the weight savings are so minimal that it makes sense to be safe and use steel.

 

Dude! Those things are rad. Well, everything but the cost!

 

the rails i`ve seen clearly state DO NOT WELD in large letters on them.

gary

 

That's 'cause those rails were cold formed after heat treatment.

They depend on the cold work they've received through the forming process for most of their hardness and strength.

When you weld on cold worked material, the heat effected zone around the weld cools slowly enough to anneal that material, making a weak spot on either side of your weld. It's a guaranteed failure zone.

Oddly enough, the same thing is true for cold worked steel, it's just not as stark a change in strength as the heat treatment in mild steels doesn't change the properties as greatly as it does in alum. There are many grades of alloy steel that will react similarly though, so you do need your wits about you if you're gonna go welding on alloy stuff.

 

I would be thinking thin wall steel tubing too. Check out the 'clubman' style sports and kits cars, Lotus 7's, Caterhams, Westfields etc. Westfield in England build a Buick V8 powered clumban that's apparently the second fastest accelerating production car in the world, and it's built on a steel tube chassis.

Cheers, Glen.

 

Steel Alert!!!

Comparable strengths to mild steel can be had in chromemoly with lesser wall thickness, generally saving 1/3 to 1/2 the weight.

It can also be welded easily at home. Aluminum welding is sensitive, often requires preheating the work piece and generally should be left to those with advanced skills.

1", .058 wall CM would make an exelent space frame or belly tanker chassis, provided you didn't need the protective cage.

An aluminum skin would be far more durable than aircraft fabric, but cloth is cool! Do I sound like I have put some thougt into this idea myself?

 

How does the weight of Chrome Moly compare to Mild steel for the same size material?
0.058" is pretty close to 16ga isn't it?

 

chrome moly weighs the same as mild steel or even stainless steel.
the only weight savings you will have is using a thinner tube,or smaller ID tube.
but why?
are you building a racer,or a space shuttle?
build it out of mild steel and it will last.

 

Mine is primarily built out of 1" square .065 ERW steel tubing. While not as strong as chrome moly, many, many Locosts have been built and successfully raced with this material.

 

Three words...

Zee Ohh Six


My company makes the frames in Hopkinsville, KY. One person can lift the entire frame.

Rich

 

I want a protective cage since this would see street use and we all know how careful most drivers are these days. A space frame with a driver's cage may be the way to go.

Cloth covered would be up my alley since I am an upholstery and awning guy. I know I could make the covers easily.

 

For you nay-sayers I have two words: Sport Bikes.

The Suzuki Hayabusa and the Kawasaki ZX-12 each have aluminum frames, ~160 HP and weigh ~ 500 lb. Performance is sub 10-second quarter-mile ET's and top speeds of ~190 mph.

Read more here:
http://www.sportrider.com/bikes/146_0110_hayabusa_zx_12r_compared/