No build-link yet. We have the donor 1969 VW Sedan, three 914 engines, a pile of new and used parts. The big issues are coupling the engines, and we think we have that solved, plus having access to all the right places with a body on the car.
The original bi-motor was coupled wih elastromeric rubber donuts, which failed. We've got a few good coupling options, all rigid or semi-flexible. This means a very strong engine subframe that supports them both.
Two engines, one starter. And we will be swing axle, hydraulic clutch.
(Shuddderrr) I know you've done well enough with swingaxle to date, but if I was to set about building an entire new subframe I'd be trying to incorporate something better...which IMO is just about anything. Have you looked into DeDion? Caterham, Locost, et al have shown that it can work with outboard brakes. In a transaxle application I would envision the DeDion tube needing to go over the trans in order to maximize ground clearance. It'd be heavier than swingaxle, but depending upon the materials used it shouldn't be worse than IRS, and it would avoid the diagonal-arm clearance problem inherent in IRS. You'd have no evil swingaxle-tuck, and the rear roll center could be significantly lower. Springing could be stock torsion bar, coil-over, or a combination of the two.
FJ, I'll be honored to help you in any way I can. My brother has seen the original and is friends with one of the designers. We have ties to the Fittipaldis.
They have built a replica new one , with diferences:
I think we all agree the only way to make a swing axle handle is to keep it from swinging.
We'll call this a modified swing axle.
The main reason we're using the swing axle is ease of adaptability and lots of parts available. The axles will be on coilovers, and have limited downward movement (no tucking under) but fairly soft rear roll so as to make the front end work harder, and some wide tires.
Tuck isn't the only issue; with swingaxle the rear roll center height will always be at the center of the differential. Nothing you do with the suspension can change that. Combined with a trailing-arm front end (which has a roll center height of zero) the roll-center axis is pitched downward; since the car's mass must rotate about the RCA, the rear will always be "hiking up" under body roll. It's a hopeless arrangement, at its very best it can only be mediocre.
Yes, everything you say is true. I'm minimizing rear roll center lift by physically limiting downward axle movement. I know that if I give it two inches of downward axle movement, it will try and take three.
To keep control of what may be a 300 HP racer, the rear axle is restricted so it is almost a straight axle, with just a couple of inches of upward suspension movement before it hits the bump stops.
By keeping this chassis low and the tires wide, we have a smooth-track go-kart.
Remember, if we were doing all this for any reason other than we love it, we wouldn't be racing cars with basic 1930's technology!
A swing axle is more true to the era, same goes for a lack of radiator, same goes for points, same goes for carburetors, I don't see why internet keyboard experts insist it can't be done.
Let them type furiously...while you do. It will just make them more mad.
Yeah some may call it overkill, but you can't have too much overkill.
Fj, later i will try to write a small reader's digest of what i know of the twin engine, aka 'fitti-fusca'...
Some small things..
-it was based on a formula superv chassis and suspension.
-body was in plastic, weighted 17 kg
-it weighted 550kg in total.
-was named fittipaldi vw 3200, but at the end it had 2200cc in each engine, very hot cams designed by ricardo divilla. Approx 400hp total
-in rio it outqualified much more famous cars, such as lola t70
-was inspired by the movie love bug
-it actually handled extremely well.
You'd only need one generator/alternator so one of the two from the engines could be eliminated. You could then couple the two fan shafts together and run them from one belt.
Thank you. I'd really like to know details of the original engine coupling.
We're not trying to build a reproduction of the original Bi-Motor, but a similiar type car with a steel body, keeping the original wheelbase. Our original plan was a fiberglass body with the rollcage bonded to the body. This has evolved to an extremely lightened steel body shell on a tube frame so we have some repairability.
The rear suspension is a copy of a FV, but made stronger, especially so we can bolt in twin engines.
And CobraJet, yep, we're aware we can get by on one starter and one alternator. Anywhere we can cut weight we're happy. Two engines weight twice as much, and you have to carry twice the fuel.
