Aluminum frame sports racer?

In reply to PeteWW: Success depends on what alloy of Aluminum. And what is 'success'? Just because the pieces are physically joined, does not mean the the joint is mechanically strong or tough enough for chassis duty.

Carter-

I wish we were having this conversation over a beer. You sound like someone I could get along with. I dig your reasoning- and I concede most of your points. I take issue I guess, whenever someone says something about "million dollar presses". I think it's total bs to assume that the unibodies created today are "optimized". Bull-effing-e36m3. They are built to a price point. It could be a BMW/Audi/Mercedes point or a Kia price point, but they are all built to a price. Case in point- there are no down sides to a flat bottom from a safety/performance standpoint- except that it costs more to build them and maintain an inexpensive packaging for the exhaust etc. There aren't any (as far as I know) companies building a steel or aluminum unibody with a flat bottom. Small point, yes, but one of many that an enterprising person in their garage could overcome and build something greater than is commercially available at a price that a blue collar worker could afford.

The luxury a homebuilder has, that car manufacturers don't, is time and complete design freedom (under their own constraints). Sure, safety should be a constraint in anyone's plans, but there is so much information on the interwebz now that building a safe, fast, light, aluminum monocoque shouldn't be outside the realm of a person willing to put in a little time and effort.

The aircraft stuff wasn't meant to condescend, and I think it came out that way. My bad.

Some good discussion here. I'm not sure where anyone really said it couldn't be done. OP asked for thoughts and got some.

Check out this book It gets into aluminum chassis a little bit Mostly a bonded honeycomb chassis which will be lighter than a tube chassis http://www.amazon.com/gp/product/images/1845841239/ref=dp_image_0?ie=UTF8&n=283155&s=books

Jensenman wrote: If you are set on such a project, there are structural adhesives out there to bond aluminum together. That and some serious rivets (like aircraft rivets) would make for a very strong tub.

The Elise is bonded and riveted. I've used a similar substance (Lord Adhesive) at work on DiBond and it's quite impressive. My boss used it in some projects at his old job where aluminum sheet was bonded to a frame. The welders in the shop were convinced it was crap until one of the finished projects fell off a fork lift. They were going to peel the sheet off the frame and attempt to repair the sheet. It tore off and the glue did not let go. That one was scrapped and a new one had to be made (they must not have known that many things like this can be chemically debonded).

I've been dreaming up a motorcycle/scooter frame made of aluminum tubing and cast joint connections. The tubes slip in with adhesive and are riveted to basically clamp the joint together until the adhesive cures, as well as prevent shear in some circumstances.

Bonding and riveting are now a very accepted practice given the technology behind the epoxies available today. If you look at the Lola's of the 60's and 70's you'd find a lot of thin alloy sheeting that's buck riveted much in the same manner as aircraft of the day. You can braze Aluminum, but the filler is very soft and weak - I would not trust it to anyone not having a booth at the state fair (if you know what I mean)..

My project car is an all alloy monocoque chassis with billet alloy suspension. Not cheap by any stretch, but will be worth it in the long run. The chassis is exceptionally stiff )more so than a steel tubular space frame) and I believe it to be competition worthy. We'll see...

Here's my build site - although I haven't made may updates lately - you'll get the general idea;

http://www.GT-Forty.com

Regards - Randy

Brust wrote: Case in point- there are no down sides to a flat bottom from a safety/performance standpoint- except that it costs more to build them and maintain an inexpensive packaging for the exhaust etc.

There are many downsides to a large flat panel-poor strength in all but one plane being the biggest.

I don't want to get in the middle of engineers in a pissing match because it's fun and also educational... but the OP is going to put a cast iron lump in his sports racer.

The wisdom over on the locostusa board is: Don't focus on eliminating weight and increasing complexity on what is going to be a small percentage of overall weight, esp when other components are going to be heavy.

Go chromoly or even mild steel for the chassis and focus weight savings $$$ on aluminum heads (or different drivetrain), superlight wheels, etc.

Also, consider your spindles and seats. Don't construct an aluminum chassis and then put 40lb passenger car seats in or spindles from an S-10 (or a Dana 60).

-James

jamscal wrote: or spindles from an S-10. -James

That's exactly what the Stalker uses.

www.Dpcars.net

look at the work he's done on the spindles for his Atom.

In reply to Brust: Yah, I think beer is a excellent idea. No condescention taken (or intended). Your point about the 'build price-point' is dead on. I think that's why they spend so much design time on the unidodies, it's an exercise in industrial design, not chassis design. It's not about designing a stiffer chassis, it's about designing something that can lower the total delivered unit cost, by reducing the amount of build time labor by being the ultimate bracket, ie everything bolts onto it or into it with as few extra pieces as possible, and is just good enough to meet all the requirements. As you say, the home builder has no such constraints, and can spend as much time and money as desired to achieve his goals.

Carter

Um, if y'all haven't checked out Big_Foot's site, do so. Very nice work!

Back to the OP's question: the more I think about this, the biggest stumbling block I can see is the size of sheet metal brake which would be needed. That kind of stuff gets expensive. With some thought it's possible to work around that, for instance when I make the 20 gauge sheet aluminum dash for the Jensenator (48" wide) it will be done using the edge of my workbench and some 2x4's as a crude brake. It worked well when making the Abomination's spoiler from .080 sheet, no reason it won't work here. You'll have a bend radius of around 1/4".

The small Harbor Fright brakes can be used for smaller stuff, but a word of caution: they will flex and this makes the corners less than sharp. They are made of angle steel with no bracing, the flex can be minimized (but not eliminated) by welding a piece of flat bar stock across the open part of the angle steel. This has to be done slowly ('skip welding') so that the angle steel will not bow due to heating/cooling.

Kinda surprised no one has posted this thread

Thanks for ALL the great feedback!

I was about to post that I'm now thinking more old school Can Am with a steel frame. But you've posted some new links I need to check out.

Stay tuned!

too bad you don't have enough money laying around for TiAl, now that would be impressive...