ALFAGTV6.COM

[xrad]

what ever happened to this driveshaft experiment?

How is the axial load taken up (ie: when the engine and tranny move away or towards each other)?

[Mats]

In the joint itself, most propshaft joints can plunge about 20mm, often more.

I'm building everything at once right now. I'm looking at making a new flywheel up front with a somewhat nicer interface (less bulk and weight) but I'll probably start off with the stock prop and couplings. No need to change everything at the same time.

[MD]

You blokes are pulling tonsils out through the arsehole. This is how you do it.

The BMW coupling has 14mm crucher tubes that need a 1mm wall thickness bushing to convert the 12mm Alfa bolts to take up the oversized holes. (Not shown in photo)

No noise. No vibration. No shredded donuts. No hassle.Cheaper than refurbishing and original Alfa shaft. Easy to fit and remove.No need to drop transaxle.

[Mats]

I don't understand why you feel the need to tell us that our solution is complete rubbish every post in this thread?
From my point of view my solution is a lot better then yours and from a complexity point of view you still do a lot of redesigning of parts.

NVH on a racecar, are you for real?

[Duk]

Tripped over this on my internet travels. Not exactly applicable, but deffinately different http://www.zip-corvette.com/ProductDeta ... SR&CTitle=&

[MD]

Mats, when you put your theories into practice, we'll talk some more..

[Mats]

Mats, when you put your theories into practice, we'll talk some more..

Yes, pissing contest!

[Giuliettaevo2]

Mats, when you put your theories into practice, we'll talk some more..

I believe i've read somewhere on the forum that Mats designed these things for a living?

If it doesn't work for one person that doesn't mean another person can't pull it off. maybe Mats has some secrets up his sleeve...

[MR2 Zig]

Where is the smilie with the popcorn

[MD]

Yes, pissing contest!

Hey Mats, so that's Dicks at Dawn, 20 paces ??

Or,

How about we battle it out Stars Wars style? You could be Joda and I could be Obi-Wan Kenobi and we could have a piss off contest.

I have a sense that you are fairly primed for it-you could indeed win.

...so may the force of piss be with you.

We need to lighten up just a tad man

[kterkkila]

Are you Mats saying that CV will hold fine on front, and the engine pulsation isn't a problem? I could buy that. Average torque is really low anyway, because gears are on transaxle.

V6 engine uses loose rear mounting, thus the agle changes on front coupling are quite significant. Also transaxle moves quite much. Transaxle mountings generally must keep the same torque you see on tyres.. That's why the front end want to jump up, just like motorcycle front wheel does, in example. I think it may move even 10mm in first gear when using std mountings.

This means that front and rear of the axle are moving and changing their angles compared to shaft line. Thus those need to be fleaxible and not try to resist angle changes. That's probably why Alfa used such a rubbers they did. Center doesn't change angle that much, which means it doesn't need to be able to work angled.

If CV's can take the engine pulsation, then I'd go CV on front setup too. If using flex disc, I'd put it on middle because it has easiest job there. I need to start my shaft project in near future too.

[MD]

KImmo,

I take it we are talking race cars here..
My simple point here which I have said consistantly is the engine firing noise resonating up the propshaft because there is not damping created by a rubber coupling behind the engine flywheel. Particularly so from a 4 cylinder.
Any of these combinations will work as I have experimanted with them all. The only one that is quiet is the one using a rubber coupling up front. This is particularly important for street cars.

Now as for moving engines (and especially race cars) the usual solution for that is to tie the bastards down so they don't ! (if you want to go that far).

GTV27, Have you got any comments here about shaft noises at Morgan Park from certain transaxle cars running there?

[kterkkila]

It's about "half race" car, and 6 cylinder. I'd like to be able to drive it also on road. I agree that there should be at least one flexible joint, not only because of noise, but also to save the transmission. I'd like to use solid clutch discs too.

If the flex disc is mounted on front, that would save all the joints and tranny from engine pulsation. If positioning it to middle, then the front CV would need to take pulsation without any dampening. If there's some play on CV, then it sure starts making noises, but rest of the driveline should be as quite as if the flexdisc would been in front, I think.

If engine stays on it's position and shaft is lined, then the front would be ideal place for the flex disc. Preventing V6 six from leaning back and forth with hard mounting will results lot of noises..

What kind of shaft is there on M3? Is it 2-piece and UJ's on middle and rear? That M3 flexplate goes with 4-cyl guibo mountings, but is there alternative for 6-cyl/turbo shaft? I may think about M3 with smaller diameter also for V6. I need to make new flywheel anyway.

[MD]

If there's some play on CV, then it sure starts making noises

I just want to clarify my point here. The actual components of a new shaft of whatever parts does not appear to be the source of the noise Kimmo. It is seems to be the actual engine firing cycles that create a loud "hammering" sound along the prop shaft which sounds just like somebody striking a hammer on an anvil very quickly. A sharp steel on steel sound. Real bad news. The hollow tube in the prop shaft acts line a skin on a drum that amplifies the engine firing and radiates it all along the length of the prop shaft if it has all "solid" components.

So I say again, to decouple this phenomena, it is necessary to fit some dampening material at the start of the prop shaft which stops the sound transmission instantly. The fact that a rubber coupling will also do the job of a flex joint, that is just a bonus. The key reason it is there is a noise dampner.

As for the engine tie downs, you could use some firm rubber mounted tied downs that produced a semi solid/rigid bracing eliminating some (but not all ) vibrations. But hey let's not forget that it used to be customary for some race cars to have the engines hard mounted without any cushioning whatsoever !!

(They were tough guys in the old days ! )

To be clear on this, I am only trying to make a firm point not to say I am right and everybody else is wrong as there is not point in that whatsoever. I am just trying to save anybody contemplating this some serious grief and bucks from where I went wrong in the first place.

[Mats]

Since you're from Finland ans can probably read swedish (sorry, can't remember if this is true or not) you should go for some Volvo Valp engine mounts. Sturdy bastards and still small. Probably available in Finland too but surely in Sweden.

As for engine fire pulsation: 4-cylinder diesel automatics. I rest my case. Solid drivetrain the whole way, from the crank to the wheels (during lock-up) and way more torque then our rear GB cars, we're talking thousands of NM here.

MD, if you get engine fire related high frequency noise I'd say you need softer (not soft, softer) mounts because normally you don't get pling-noise from the prop unless something hit's it (like small stones). So your bushings/straps probably is bottoming out/goes solid and gives metal to metal condition.
Although the stock alfa props are incredicly much like a musical instrument, sounds like a church bell if you tap it. So I guess you're using the stock alfa tubes?
Also, a sloppy clutch plate with too soft springs can give you all kind of vibrations in the prop, not good. The spring bottoms out and then there are all kinds of issues.

If this is an issue you can always ask the prop-shop to add a liner in the tube, usually a cardboard liner will do the trick, quite normal on factory props actually.

I'm going for a sprung clutch with an organic friction surface. Yes it weighs some more and it doesn't take the same amounts of torque as a puck-type or sintered but I want the sprung hub to spare the gears from the shock-loads and I want to be able to slip the clutch in a controlled manner. Driveability is very important I think, especially in a high-strung racecar.

If you still have problems you can always add a tuned torsional damper at the front of the prop, not too easy to get right but it is very effective.