Alloy Flywheels

[Kev_205]

I need to get a custom alloy flywheel made up for my 205 - the steel flywheel for the tilton clutch is far too heavy!

For a N/a car can you go too light??

[Cameron Winton]

Let me know where you get it. I have my 205 stripped at the moment and one possibility is a lighter flywheel

[graham bahr]

for a n/a race car its difficult to go too light, but you'll soon know if you do with a race clutch you wont be able to get out the paddock without either stalling or wheelspin.

if you already have a steel flywheel you could get it lightened, by turning in a lathe, drilling or milling slots in it, you can make a steel flywheel almost as light as an alloy one, due to the fact that alloy is weaker than steel you need much more of it to get the same strength, how thin can you go in steel? look at a torque converter flex plate, they are waffer thin, although you will need more material for the clutch face its self

my steel flywheel which was already quite light had some machined off it in a lathe, i'm now going to put slots in it.

[COLIN STUBBS]

hey up!! be very careful if your going to start chucking flywheels in lathes. some are made of really crappy stuff. saw one explode in a manta rally car once and it broke the co drivers foot,but the best was a mustang in a phtc race i was in at mallory had it break in practice.it sheared through both chassis rails,bellhousing and bonnet. then,bizarrely we were lining up for the race and someone noticed the missing half of the flywheel stuck in the bridge!!

[graham bahr]

agreed it has to be done with care and understanding on stress raisers and points,

however if you have a proper steel competition flywheel in the first place you shouldn't have a problem provided its lightened sensably.

done correctly a lightened flywheel can be stronger as it will exert less stresses on the centre where its bolted to the crank

lightening cast flywheels has to be done very carefully, but even then is a no no once you start going to 7,000 rpm

[COLIN STUBBS]

exactly,but lots of people think cast is steel.. gets more complicated on v6 with the balancing weight in it. now youv got me thinking about my honda engine......

[graham bahr]

[QUOTE=COLIN STUBBS]exactly,but lots of people think cast is steel..QUOTE]

yes i suspect the flywheels you mentioned earlier were probably cast, and probably being used at too higher revs to be safe, in fact the only thing really holding them together at high revs was the ring gear.

unfortunatly if you have a flywheel thats machined all over it can be very hard to tell if is cast or not until you try to machine it.

i know i'm safe with mine its made from a steel billet

[dtype38]

I looked at an alloy flywheel for mine, but all of them had a steel ring screwed to them for the clutch to run on. Personally I was very dubious of having lots of little fixings like that on a flywheel, and they didn't seem much lighter than a full competition steel one. In the end I went for the latter, which has the outer ring held by spokes, like an alloy rim. Its half the thickness and about 1/3rd of the weight of a standard a one. I do get a bit of wheelspin around the paddock though :-)

[graham bahr]

D type i wondered how long before your jag engine crept into the tread!

only joking,

from memory 6cyl XK jag flywheels used to have hardened ring gear teeth cut directly into the flywheel itself, instead of having a seperate ring gear, making them even more likely to explode than normal cast flywheels, although i guess with the massive strokes and long conrods they dont rev like most race engines

[dtype38]

Originals yes, but the racing ones have shrunk on ring gear.

This is mine http://www.tkracing.co.uk/brands_aug05_ken/pic_2.JPG

I'm only trying to show that steel ones can be nearly as light as alloy ones

[graham bahr]

Originally Posted by dtype38

I'm only trying to show that steel ones can be nearly as light as alloy ones

argreed, but then i think that what i said several posts ago

[dtype38]

True..... but I did it with visual aids

[graham bahr]

yes also it has to be remembered that its only the mass towards the outside of the flywheel that has any effect, so any weight saving an alloy flywheel has at its centre is almost wasted, exept that i suppose it makes the car itself a bit lighter

[ian_w]

What you are actually interested in doing is reducing the 'inertia' of the flywheel, this is a product of Mass * Radius^2.

So what you need to do is reduce the mass at the outside of the flywheel. Go for something with a strong centre and the ring gear supported with a few thin spokes. As regards size then my F3 flywheel is approx 7 inches in diameter, this is probably as small as you want to go. With an 'in or out' style 5.5" twin plate clutch its a little difficult to pull away without stalling or leaving black lines!

I wouldn't bother with aluminium, its a very poor choice of material for a flywheel. As pointed out, its strength:weight ratio is no better than steel so you need more of it for the same strength. Its strength properties also fall off rapidly if you get it above about 150 degC - like when you start slipping the clutch. You can't run the clutch directly on the aluminium so you need to add a steel insert. Finally, aluminium also has a finite fatigue life ( unlike steel ) so it will eventually fail no matter what you do to it - as noted, flywheel explosions can have devastating consequences.

[Al Weyman]

Colin, was you at Snetterton when Ray West's Manta 400 engine let its flywheel go. spectaular or what! It lifted the bonnet and put a huge gash into it. It also severed the oil hose spilling oil onto the hot manifold which resulted in a fireball which only the quick work of the ever efficient Snet marshalls saved the car. This was a lightened flywheel (I know as I sold it to him unmodified).

Back to lightweight flywheels a subject I have had a bit of experience with (sorry Chevys I am as bad as dType). I am at this moment fitting the Tilton button clutch back into my Historic Camaro after the conventional type clutch I tried to run it with proved not to be man enough. Now one of the reasons I did not put the clutch in previeously is that they are a sod in the paddock as I outlined in another post. However on the track and at the start they are great. I tell you what I run and maybe you can addapt the Pug the same. I use the Tilton button clutch (7.5 inch triple plate) and for the flyweel (well actually the Tilton is the fllywheel) I use an automatic drive plate which does not have much weight and merely carries the ring gear.

On my other car I have a McCloud twin plate set up with an alley flywheel which has a steel driven surface for the clutch plates (sintered) to run on. This has been very reliable as well. I also have a third clutch here called a 10000 rpm clutch and that is a triple plate with a conventional cluch material and an alloy flywheel, this time the clutch drive plates run directly off the alloy flywheel with no steel surface.

[graham bahr]

Originally Posted by Al Weyman

that is a triple plate with a conventional cluch material and an alloy flywheel, this time the clutch drive plates run directly off the alloy flywheel with no steel surface.

i guess that works because as a triple plate clutch only 33% of the drive is taken directly on the face of the flywheel , the other 66% will be going through the intermediate plates which drive against the clutch cover itself.

tell me Al do you ever get the spec between your fleet of cars mixed up, you seem to have sooo many different options on what seems like 20 cars to the rest of us not 3

[dtype38]

Originally Posted by graham bahr

i guess that works because as a triple plate clutch only 33% of the drive is taken directly on the face of the flywheel

Don't want to be pedantic, but wouldn't that be 16.5%?

Yeh, ok so that was a bit pedantic, sorry

[graham bahr]

you could say, in which case with a std clutch only 50% of the drive is put through the flywheel itself.

maybe i should of just said the triple plate puts 33.333333333333333333333333% less torque into the flywheel face?

[dtype38]

Something like that. But it sort of begs the question as to why the clutches have to run on the flywheel face at all. If they had a rear cover plate as well as a front one, it could simply be bolted to the flywheel and it wouldn't matter what the flywheel material was. It would save having to mount a steel plate on alloy ones.

[graham bahr]

dont see why not except perhaps cost, and the ability to shed dust which needs to find a way out

[dtype38]

I was thinking of a sort of cage like multiplate item with the springs at one end and a similar cover at the other, but with a bolt hole ring in the middle rather than springs. Then you could just bolt it straight to the crank. But then you'd need to mount a ring gear.... and that could be on an extended flange on the back face of the clutch... and that would be a.... err... flywheel.

I think I'll just shut up now

[Al Weyman]

dType that is exactly what a tilton button clutch is like, which is why between the clutch unit which bolts direct to the flywheel you have am automatic transmission drive plate which is basically a thin flat piece of tin cut in a circle that carries the ring gear. if you did not need a starter motor you would not even need that.

Graham I do only have the thre cars thank God and that is probably two too many. The yellow car is the one the Tilton is going in, the black 3rd Gen is the one with the McCloud and the 10,000 rpm unit will go in the Penske IROC space frame car eventually. I was gonna put the Tilton in that but there you go it has to go in the yellow car now.

[johnny yuma]

Would not 100% of the torque always go through the flywheel no matter how many clutchplates then shared the later friction and torque transfer to the gearbox? This being the case I could see an alloy flywheel giving srructural/heat problems on big torque engines.

[TEAM78]

Originally Posted by graham bahr

maybe i should of just said the triple plate puts 33.333333333333333333333333% less torque into the flywheel face?

errors are creeping in, maybe it should be writen as 100/3
id get shot for that

[johnny yuma]

dont forget bolting a triple plate setup onto the [lightened] flywheel is probably adding mass back on so where does it get you if a single plate clutch is ok,unless all you want is less spinning mass with the clutch depressed.Am I right???