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sideshow wrote:..I don't see why internet keyboard experts insist it can't be done...

Of COURSE it can be done. I've got decades of actual racing & chassis design experience upon which to base my judgements, so if that "keyboard expert" crack was directed at me, it's way out of line.
Just because an antiquated design can be dug up and flogged doesn't mean it's smart to do so (unless, of course it's for a class which is intended to celebrate the obsolete). Nostalgia's wonderful but it seldom wins a race.

Hi Sideshow,

Marc is right about the technology. The XCAR isn't up to 917 tech, and if we wanted to, it could be ... but then it would be a 917, not a strange little twin-engine Bug with all the Bug's mechanical quirks.

Now here is a bit of philosophy. The more 917 in the car, the less driver you need. A Bug needs a hero driver who makes up -- where possible -- for tech with balls and brains.

It's something like the days of iron men and wooden ships.

FJC

My criticism of keyboard commanders is directed at all of them. If I hated any one in particular I wouldn't be subtle about it.

What will one killed in a swing axle car FIRST isn't axle tuck (unless its a corvair those things are death traps), it is other drivers. I guess the most famous case study is Jame's Dean 550. A live axle leaf sprung farm truck coupled with indifference to others, is no match to a swing axle no matter how refined.

I have a different view of racing, it is far more important to finish. It bothers me little the competitor used far more technology to “beat” something so old.

Now I am going to do some more wild ass speculation; FJC has driven a swing axle car beyond 75mph enough times to notice that something “funny” is happening behind him. He isn't building a car for an average driver.

FJ,

I was reading the PDF's about the fitti-fusca last night.

The connection between the two engines was thru a "giubo" coupler, which was standard on a Brazilian car named "JK" - a 2000 CC V8, a mix betwen an alfa romeo and a simca.

Some info on the "giubo" joint : http://en.wikipedia.org/wiki/Giubo

This is how it looked:
Another interesting details:

-The car had no alternator or generator, it had a fully-charged battery for the race, and it used an external 24V battery to start, and the starter was rewired for more power to start both engines.
-I got the weight wrong - IT WAS 420 Kilos ! Dam thing had almost 1 HP/Kilo
-It had no fan - As I said before, it had a false ceiling with was a scoop to drive air into the engine for cooling, the driver's head was about 6 inches lower than a regular bug, and the windshield was at a 45 deg angle in relation to the original position, this way air made it's way into the scoop above the driver's head.
-The crankshafts on the two engines were out-of-phase by 90 degrees.
-the cams were very hot with a narrow power band, they used a 5-speed Porsche 550 gearbox with all gears changed to be optimal for these cams.
-Front suspension was also from a 550.

I don't know if people saw it yesterday, this is a drawing how it looked:
Please let me know if you need more. I have more.

LCV

sideshow wrote:...He isn't building a car for an average driver...

We're aware that there's talent on that team, but I still say that's no reason to hamper them with a death-trap suspension design so inherently flawed. I cut my teeth on swingaxle Bugs, but when IRS came along I became a total convert and vowed never to use swingaxle again unless it was mandated.
There's going to be a significant amount of fabrication involved in building a subframe to carry the engines and reversed transaxle, improving the suspension while you're at it just seems logical to me.
The drivetrain layout of the twin-engine car would make it difficult to employ a trailing/diagonal-arm IRS setup, so the options I see are Chapman strut, twin A-arm, or DeDion. Any would work, but the latter appeals to me because of its relative simplicity and ruggedness (it should be inexpensive to build as well, and could be built using the stock torsion bar/springplate arrangement if desired). There's no "technology" involved (DeDion's been around since the 17th century, after all) - just pragmatism.
http://www.worldwizzy.com/learn/index.php/De_Dion_tube

I became a total convert and vowed never to use swingaxle again unless it was mandated.

We race swing axle beetles as well and honestly when setup right it handles real good. Maybe one day I'll try irs... but up until now swing axle has been good to us

interesting!

I was at the Spa Bugshow last month. a Formula Vee racer present had this suspension. Very interesting to see, I hope someone with more swingaxle knowledge can give the full explanation.

Hi Volkscris,

The car is equipped with a highly modified type of swing axle suspension that is great for racing but not well suited for street cars.

The effect of this design is to allow body roll while keeping the axles as parallel to the pavement as possible, and adding no roll resistance at all while performing that function.

Remember, for a swing axle you want to increase front roll resistance and reduce rear roll resistance, like the Porsche and then VW factories did as their cars got faster.

Nice side effect of the racing suspension in the photos you've posted is much lighter weight, and more centralized inboard weight. Beefing up such a system to support the weight of a street car is possible but impractical.

To sum this up, the design took a 1930's suspension, modified by decades of racing development, and married it to some genuine Formula 1 inboard shock technology.

FJC

Not quite, Frank. That has the typical "0 roll" design, but they have added another shock between the coilover and the chassis, so that it does have adjustable roll resistance.

Hi OneBadBug,

Yes, you're right. I glossed over that for brevity, where it would have only taken the insert of the word "adjustable."

Nice to have someone else proofreading!

FJC

I think I have it right, but one odd thing is that the roll resistance shock has a bump stop, I don't quite get that.

Hi OneBadBug,

No mystery about the bump stops. There has to be a limit to the lateral motion, and the stop would just dampen the jolt if it occurred.

FJC

Oh, I just noticed there are 2 roll resistance shocks, with stops each way.

I was at the Mitty with my '55 Porsche 356 racer and was talking to the Ghia Guru in the tech shed about my Devin D race car build. Many thanks for the advice given there but of course I have more questions.

On the 356s we use link pin spindles that are made in the US by one of the VW guys. They give us 3.25* camber and take the Porsche hub, disc, and caliper. Pic attached. I see 2* spindles for VW but not 3+*. The VW parts are cheaper so what is usually done on a link pin VW to get a good road race camber?

The 356 races best with a ZF bean limited slip. The next best is the GT diff since the ZF is no longer made. The Ghia, I think, is running an open diff. Rancho offers a limited slip...so what is best? I have a spare 356 race geared transaxle(I am running a 356 engine) but they do break from time to time and parts are VERY expensive. Am I correct to assume that a race VW trans is sturdy?

Many thanks!