E30 Zone

I was just day dreaming and wondering if you could skim some wieght of an M30 vibration damper like you can skim the fly wheel ?

A stock one weighs 4.8kgs, what about taking it down to 2-3kgs and getting it balanced again ?

I'd say try getting one made from alloy but it starts getting expensive !

I'm guessing my tick over might be a tad less smooth ?

I've got a spare vibration damper to play with if needs be.

It's more of a harmonic frequency dampner so skiming could cause problems,
Iv'e heard of crank nuts shaking loose or in a worst case the crank shaft self destructing!

Graham

I've chopped the air con belt part off of my crank pulley with an angle grinder!

And Theo325's!

Surely, as long as the rubber part is still there (or partly there) it can't be that bad?

The way I look at it is, if you replace the clutch you only have the trust of the clutch manufacturer that their product is 100% accurately balanced.

If it isn't (and you probably wouldn't even notice unless it was out by a reasonable amount), are you really going to take the crank, flywheel and front pulley off and have them balanced every time you fit a new clutch ?

I say go for it, chop away!

The crank pulley nut on an M30 is supposed to be tightened to 440nm!

That is feckin' tight, they take some undoing!

DRIFTBOY wrote:
Surely, as long as the rubber part is still there (or partly there) it can't be that bad?

You've lost me mate, which rubber bit ?

next you will want to skim he prop shaft down . . . . . . wait a minuite looooool . . . .

No thats so council dude, C/F all the way !

Andy335Touring wrote:

DRIFTBOY wrote:
Surely, as long as the rubber part is still there (or partly there) it can't be that bad?

You've lost me mate, which rubber bit ?

Ooh, am I talking nonsense?

I thought there was some rubber somewhere in the damper..?
Maybe I got that wrong then, sorry!

yeah, it's solid metal i think, the good news it the big crank nut doesn't need to come off, just the 8 pully bolts and it comes off leaving the hub on the crank

They're usually a metal hub bonded to the damper with a large amount of flubber.

although it's quite heavy, the diameter isn't great (compared to the flywheel / clutch) so it's not going to make a massive difference as it's all about the radius of gyration of the mass. eg, if it was twice the diameter but the same weight (mass), it would store more energy and hold back engine pickup more.

that said, i was looking at one at theo's the other day and it's fecking silly big for what it is! attack it! unlike a flywheel, at least if it explodes you won't lose your legs!

The pully is that size for a reason, Take a look at the difference in dimentions between
an M20 2.0 and an M20 2.7 front pully.
You prob would not feel the vibration, but if you run your car hard most of the time, you WILL damage the crank.
Dont get me wrong I am a great believer in the carroll shelby school of winning (for speed add lightness!!)
I once spent a weekend removing individual wires from the loom on my E30 track car!
But skiming the dampner is not the right way.

Graham

Are you all running lighter flys already? I'm intrigued to see the difference that makes - I've never run mine with anything other than the E28 M535i jobbie!

Bim wrote:the carroll shelby school of winning (for speed add lightness!!)

Wasn't that Colin Chapman ?

Shelby stuffed a stonking V8 in everything!


Ziggy - the E28 M30 flywheel is the lightest standard one any of us are likely to get hold of in this country, although I'm reliably informed that the clutches for these are a little heavier than for the E34 / E32 set up.
I've had many flywheels lightened, never found it to have made a huge difference really.

that's why I'd be interested to compare it to one with the E34/32 fly...

im running e34 flywheel if your at the pod this year il let you have a drive

Turbo-Brown wrote:They're usually a metal hub bonded to the damper with a large amount of flubber.

I've just dug it out to double check and it's a solid lump of metal.

gareth wrote:although it's quite heavy, the diameter isn't great (compared to the flywheel / clutch) so it's not going to make a massive difference as it's all about the radius of gyration of the mass. eg, if it was twice the diameter but the same weight (mass), it would store more energy and hold back engine pickup more.

that said, i was looking at one at theo's the other day and it's fecking silly big for what it is! attack it! unlike a flywheel, at least if it explodes you won't lose your legs!

It was more a general weight saving i was going for rather than a lighter fly wheel effect, due to it's location right at the front of the engine in front of the front axle it more beneficial to lose wieght there.

I'm not overly bothered about being a tad nose heavy because the tourings fat arse counter balances it. It started off as an idle thought which is it's pretty easy to lose weight in the mid-rear of the car by losing the interior but it's a lot more difficult to lose wieght from in front of the axle line.

Graham, is the vibration damper some kind of external blancing for the crank ? i.e. they have to be balanced together ?

you could always remove your headlights and 'use the force'!!!

The vibration damper is exactly that.
but I´d like somebody to give it a try so why not .
But does your crank sensor input come from the front or the back?
I think they aren´t solid through as they are sandwiched plates via rubber that
covers the thing.

jaffro wrote:im running e34 flywheel if your at the pod this year il let you have a drive

I'll be there!

Bugger, after a closer look it has got some rubber in it, unless you dig your nail into it or clean it thoroughly(sp?) you wouldn't notice it was there

It won't be possible to lighten it because of the way it's constructed, the hub and the back of it are one bit of metal, rubber inner then front toothed part with the belt pully is another single piece of metal.

What is the rubber in there for ?

It's the rubber which gives it it's 'damping' quality?

It's nothing to do with balance, the crankshaft damper is there to reduce vibration that naturally occurs, even with a balanced crankshaft / engine.
It's to do with cylinders firing and others being in compression etc. causing the crank to try and flex.
The vibration is rotational and if not damped can cause fatigue and even failure of crankshaft and other components due to the stresses.

The rubber in the damper allows the hub to wind and unwind, removing most of the vibration.

And yes, I did look it up!
My old college books come in handy sometimes!

i cant see it causing a prob on an m30 six cylinder engine, but thats just wild guessing

surely theres more crank issues with simply droppping the clutch

Hey Andy, Yes it does have to be on the crank when it is ballanced along with the flywheel and clutch.

Driftboy, I wont argue who actually quoted "For speed add lightness" because Chapman and Shelby were both god's in my eyes.

Bim wrote: Chapman and Shelby were both god's in my eyes.

I certainly agree with that!