Transaxle/Engine Mis-Alignment; Custom Drive-shaft!

[junglejustice]

OK, so let's talk turkey here. The motor is twisted to the left (flywheel bolts point to the right-rear) and the gearbox - I would assume pointing forward towards the right - maybe to allow for a mid-way kink at the center towards the right where the shifter comes down to make room for it to the left of the shaft...?

Is that why they did it? -And also why the one shaft-section has that extreme skinny section right there...? I heard that there is also an up/down mis-alignment of the engine too - greeaatttt.....

I am having new custom-made couplers produced (from the marine world) with a simple single-section aluminium drive-shaft in the middle and no break or kink - if at all possible! See: http://www.vulkanusa.com/megiflex.htm

Yes I am reinventing the wheel. Yes, because I believe that it is crap as it is. (For what I want to do with it any way.) No, not everything produced OEM has the best design tolerances in the world. No, not everything produced by the AR engineer was put there "for my own good" (as with the 164 wheel-lug conversion thread next door...) It is crap and we all know it, so please - let's not get in the conversation about "why" and rather in to a discussion on "how" to do this... I would like to improve on it - if nothing else only for myself, but maybe others would benefit from it too - we all know that the donut-design is a weak-point - even with stock 150-odd horses - I would be happy to share in the success of it...

Bottom line; the couplers that I am looking at utilizing can be mated to anything, carry any imaginable amount of power (many different models) and will handle some degree of mis-alignment. I would prefer to straighten out the engine/driveline though and move my shifter if I had to - what points where at this stage?

Also, I could go with Allen's ( member: "Realle"???) carbon-fiber drive-shaft but there is a cost consideration here as well as a time/materials availability issue. Driveline-shops that will whip up an aluminium drive-shaft are a dime a dozen!

[AR4me]

I know you don't need to hear this. But... I believe practicing smooth driving techniques will make quite a difference in the longevity of many of the Milano/75/GTV6 OEM components that are often bashed as inferior designs.

Having said that, it would be great if you could come up with an even better and more robust design. Is this for your street car or your track/race car?

Jes

[junglejustice]

Tell that to the drive-shaft on my simple - pretty stock - street car that gave up at 175 RWH on the dyno... (Judy? Is that you...?)

JES!!!! You of all PEOPLE!!!!

For the two 3.7s - I thought - since we would probably have to modify the shifters however, if we can make it street-applicable without TOO many other mods - then great - for the street cars too! (Hence the reason for the questions about the engine-to-transaxle alignment and the shifter-fit too...)

I was blown away by how easy that forward coupling sheared! Must fix that with the new motor coming soon!

[AR4me]

LOL I knew I could get you going

I hate to play the devil, but what was the condition of the front coupling? If it already had cracks you might just have pushed it over the edge with a dyno pull with 175 RWHP.

Ok, back to your question regarding a single piece affordable alu drive-shaft and the (mis-) alignment - hmm...

Jes

[loach1]

I spent a few years with GKN making props and have some thoughts on why the Milano prop is the way it is:

1. The rubber couplings combined with pilot bushings are the best combination for eliminating unbalance. Anything with metal moving parts needs a running clearance, hence contributes to non-correctable unbalance. Given the speeds that the Milano prop runs at, it needs to have rubber couplings to keep vibrations low. In a race car, it's a different matter altogether.

2. The necked down portion is likely for rear impact protection, aka a crash feature. The idea is that the tube will telescope inside itself rather than shooting through the floorpan into the passenger compartment. If you don't plan on getting rear-ended, this doesn't matter either. It could be for packaging, but I haven't seen one first-hand (yet).

For high torque CV joints are hard to beat and they can handle much higher angles than a rubber coupling (couplings are good for about 3 degrees). The problem with CV joints is that they get hot themselves at speed and when they are close to the exhaust they can fry the grease.

A UJ or Cardan joint is good for torque and small angles and probably is the best compromise. Aftermarket folks make nice aluminum joints, but the corresponding tube might not fit easily under a Milano. So, a practical, cheap way to go is steel UJs and a single piece steel tube. Be prepared for driveline shock and more vibration than you are used to, but sized correctly it should handle all the torque you'll ever need. Weight might even be the same as stock since you will be deleting the center joint, stub, bearing and 3-arm flanges.

Most important is balance at the right speed - about half of the max running speed is a good ballpark. A good machine, good calibration and a skilled operator has a huge bearing on the end result.

[Craig]

G'Day Guys,

First off, despite the quotes I'm not aiming this at anyone in particular.

Let's kill a few of these half truths.

Quote:

Originally Posted by loach1 Given the speeds that the Milano prop runs at, it needs to have rubber couplings to keep vibrations low. In a race car, it's a different matter altogether.

[darth dino]

Someone on the Alfa Racing Digest had a one piece carbon fiber driveshaft made for his GTV6 last year. The engine and gearbox mounts needed to be shimmed to obtain alignment. I seem to remember that he did have some vibration issues. I do not remember if there were shift linkage issues . . .

[Greg Gordon]

JJ may be onto something with the better donut idea. A carbon fiber driveshaft is expensive and it's total overkill. Has anyone ever broken a driveshaft on one of these cars? I doubt it. If they did I suspect it's because it was bent first. Plenty of people have blown guibos (they don't seem to blow for me, but that's another story) so that's the part that needs improvement. Another problem with the factory guibos is the high cost.

If JJ can get a better donut for close to the price of the stock part who wouldn't buy it?

[AR4me]

Quote:

Someone on the Alfa Racing Digest had a one piece carbon fiber driveshaft made for his GTV6 last year.

[PSk]

Serious GTV6 race cars in the New Zealand and Australia (I think) replace the rubber donuts with CV joints.

They rattle and bang, etc. but never break . This is what they did to the Group A GTV6's ... so why re-invent the wheel.
Pete
ps: I also know of an extremely quick GTV4 with the CV joint conversion ...

[75evo]

PSk,

This is not for serious race cars. Possibly this is for powerful street cars or double duty cars (some track and lots of street).

[PSk]

Quote:

Originally Posted by 75evo PSk, This is not for serious race cars. Possibly this is for powerful street cars or double duty cars (some track and lots of street).

[loach1]

[quote=Craig]

First off, despite the quotes I'm not aiming this at anyone in particular.

QUOTE]

I'm feeling victimized, so I have to reply :-)

The Milano prop is not unique, but it is unusual for non-TA cars to actually see the higher running speeds since they have to be driving very fast. A TA car's prop runs at engine speed every time you drive it in every gear, so special care is needed to keep vibration low. The Milano prop is excellent at keeping vibration low thanks to the rubber couplings having virtually zero non-correctable unbalance.

Thanks for the pic of the swaged section - it is definately to clear the shifter, but it could double up as a crash feature. Not sure what the requirements were in the 80's for crash (probably not much). Just wanted to throw it out there since sometimes props look strange for no apparent reason, but it's actually for your safety.

[slyalfa]

Just a thought but has anyone ever had the smaller flexdisk go bad?
They seem to be used on a lot of other cars too. It is the big doughnut that seem to blow up all the time. The rubber seems to not have any thing else inside like string/cords and the large size seems to add more outward stress on it. How about just making somthing so that the smaller disk can be used in the other 2 places. What is the part BMW use on there big cars. it looks more like the center disk to me. As far as I know only alfa use the big doughnut and only alfa have the problem of the blowouts. but there are a lot of other cars with flex disks on them with much bigger motors.