That kind of bending isn't relevant to a-arms. They see only axial loads. I'm not saying those are strong enough, but unless you stood on the end and that was the tube buckling, it doesn't have anything to do with what the bar will see while on the car.

Also the teardrop tubes are pretty much only beneficial on open wheel cars.

Edit: The A-arm will see a bending moment if you screw up your mounting points, but if you're keeping the stock geometry, I don't think that should happen. It has been a while since I looked at one, though.

 

If there is any type of binding in the suspension they will see loads like that.

Even if there was no binding, or even the chance of binding (which there is ALWAYS a chance) would you use material for a suspension that the leg of a 150lb man could bend? I wouldn't, and that was my point.

Hell, CrackHeadMel mentioned that he's ACCIDENTALLY bent 1" SOLID aluminum. Now I doubt my stomping could bend solid bar stock.

Sean even mentioned that his friends QUADs' suspension was constantly getting tweaked....

 

Thats true, I guess. I wasn't saying he should use that material, or anything, or that it's nearly strong enough. I was just pointing out that bending a piece of pipe over your leg isn't very representative of the types of forces in an a-arm.

 

I help out a local formula SAE team and all our suspension piece are made out of chromoly tubing. Aluminum woundn't stand a chance in there, and this is in a car that only weighs about 180KG. So in a full car, alot more forces. The closest and best thing is actually carbon fiber tubing. The hard part is making the aluminum piece that holds the 2 tubes together firmly with the carbon fiber. Last year we attempted doing them but we believe that someone forgot to clean up the parts properly from all the oils and stuff and hence the epoxy didn't really stick properly to the alumium piece and there went all 4 wheels under the braking test.

 

do anymore hallucinations on subframes ?? I have one in an f body . Had tons of room and saved some weight .

 

Buy Ron Champions book: Build Your Own Sports Car for as Little as £250 and Race It!, 2nd Ed.
He covers building a lotus 7 replica from scratch and he has a section on building racing suspension arms in the 2nd edition. The arms are pretty good, unless you want to radically change something (replace bushings with rod ends) there is no reason to build new arms. If you really want to do it go with steel. Aluminum is harder to weld and much more likely to stress crack.
On the subframe side, I've thought the same thing, that you could lose some weight, but the effort involved is pretty large vs the payoff. For my roadrace FC I've debated dumping the rear subframe completely and just fabricating a front diff mount, some toe rod mounts and some camber lonk mounts off the cage and welding the outer mount directly to the main cage hoop. The main reasons I'd do all that work are to first, raise the rear suspension mounting points to add anti-squat to the rear of the car. Under hard acceleration a lowered FC squats the rear suspension a great deal. If you also throw in a corner at the same time the car pretty much bounces of the bump stops (which are heavily shaved down) on the outside.

The front subframe is a little heavier than it needs to be, but nowehere near the same class and north american built cars. Again, the main reason to modify the front would be to correct a suspension geometry problem. On my FC I've debated notching the main frame rails 2" and rewelding the bottom on 2" higher, allowing me to mount the subframe 2" higher in the chassis (again, trying to compensate for excessive lowering. The sheer volume of work required for a little payoff just doesn't seem worth it to me. So instead I'm thinking about a from scratch 3rd gen tube frame using stock 3rd gen suspension parts. Basically take a straight car, unbolt the suspension and pull a jig off all the mounts. Pull the stock chassis out and then start fabricating the tube frame with the suspension mounts all 3" or 4" higher (effectively lowering the car that amount while keeping stock geometry). That way I'm attacking the subframe and unibody weight at the same time as I create the roll cage as a key structural component. The goal is an FD which is much lighter and pre-lowered while retaining good suspension geometry.

-Trent

 

The OP has not posted in this thread for over two months and there is little we have discovered here that alot of us did not already know. let the thread die or at least cover something like changing the instant center after lowering the car.

as for welding aluminum... its not that hard as long as its to aluminum. hell I've used good old Harris 26 silicon aluminum electrode and a 30 year old stick arc. good for intake fab, but i would never use aluminum for suspension. Before you ask I have never taken a class or had any formal training.

 

figured id at least get a chance to say something before the thread closed.
for doing the a-arms, i also was thinking about making them, after much deliberation, and much research, i found the best way to do it would to use 4130 chromoly, triangulate the arm like they do with scca legal cages, use gm style ball joints (replaceable), and polyurathane bushings.
sure, it wouldnt lower the instant center, change the scrub radius, or the jounce or rebound properties of the suspension, but it would be a hell of a lot better than the cast aluminum with a set ball joint and everytime that damned thing needs to be replaced having to drop 500$ each for a new a-arm

all im saying is that anything is better than having to shell out 1g for new control arms. replace the ball joint, nuff said.
and besides, why not TRY to make new parts available for the fc, fb, fd, why not, i am personally in the process of working out calculations for the rear subframe out of 4130 chromoly. its a matter of time, calculations, and a bit of ingenuity.

Lloyd