Lightened Flywheels

Author
Discussion

GnuBee

Original Poster:

1,272 posts

216 months

Thursday 26th July 2007
quotequote all
Ok there's a discussion going on about this within the Track Day Heads thread but to avoid the thread drifting to far off the course of the OPs question I thought it best to start a new thread...

I've a mid engined car with the engine mounted transversly. The original flywheel is being removed and a new one fabricated in lighter material but clearly a common concern is that the failure mode of a flywheel tends to be catastrophic and has a nasty habit of sending fragments of metal firing off in all kinds of directions at very high speed.

In my case the first thing those fragments will meet is the fuel tank and then shortly after that the firewall followed by any unfortunate passenger's body. Are there commonly used measures to help protect/reduce the risk to the occupants of the car?

Cheers

rev-erend

21,421 posts

285 months

Thursday 26th July 2007
quotequote all
Yes - the car is made of steel and the gear box tunnel is often double skinned.


CNHSS1

942 posts

218 months

Thursday 26th July 2007
quotequote all
some people use the dragster-style 'ballistic blankets' around the bellhousing to contain any flying shrapnel.

Snake the Sniper

2,544 posts

202 months

Thursday 26th July 2007
quotequote all
Personally, I wouldn't bother if the flywheel has been designed and made correctly it's almost certain not to explode. The things we are discussing in the other thread are few and far between, and normally only happen with high power/stressed engines. I've certainly only ever heard of 1 near standard going, and I'm not even sure that one hadn't be buggered about with, it was in a chavalier.

GavinPearson

5,715 posts

252 months

Friday 27th July 2007
quotequote all
Snake the Sniper said:
Personally, I wouldn't bother if the flywheel has been designed and made correctly it's almost certain not to explode. The things we are discussing in the other thread are few and far between, and normally only happen with high power/stressed engines. I've certainly only ever heard of 1 near standard going, and I'm not even sure that one hadn't be buggered about with, it was in a chavalier.
I have personally seen a flywheel fail when a clutch started to slip, basically it built up so much energy in the cover and flywheel they turned blue and fell apart.

It was messy. But thankfully nobody got hurt.

Bottom line, when the part is designed the material chosen needs to be carefully selected, and you need to think about shielding in case of failure.

GnuBee

Original Poster:

1,272 posts

216 months

Friday 27th July 2007
quotequote all
Ok thanks all - looks like a search for "ballistic blanket" is on order...

rev-erend

21,421 posts

285 months

Friday 27th July 2007
quotequote all
More to the point - you should chose very carefully who does this work !

GnuBee

Original Poster:

1,272 posts

216 months

Friday 27th July 2007
quotequote all
Got the choosing carefully bit covered - Im not having the existing flywheel lightened (I don't like the idea) I'm having a new one fabricated by Tilton IIRC...

Snake the Sniper

2,544 posts

202 months

Friday 27th July 2007
quotequote all
GavinPearson said:
Snake the Sniper said:
Personally, I wouldn't bother if the flywheel has been designed and made correctly it's almost certain not to explode. The things we are discussing in the other thread are few and far between, and normally only happen with high power/stressed engines. I've certainly only ever heard of 1 near standard going, and I'm not even sure that one hadn't be buggered about with, it was in a chavalier.
I have personally seen a flywheel fail when a clutch started to slip, basically it built up so much energy in the cover and flywheel they turned blue and fell apart.

It was messy. But thankfully nobody got hurt.

Bottom line, when the part is designed the material chosen needs to be carefully selected, and you need to think about shielding in case of failure.
I didn't say it couldn't happen,. just that's its not very likely. If it were OEM's would make shielding on tin tops. Or just change the material so it didn't go bang. From what you've said, it sounds like the engine was buggering about and the driver decided not to stop and/or sort out the clutch as I doubt that the flywheel blued in a matter of seconds.

tr7v8

7,196 posts

229 months

Sunday 29th July 2007
quotequote all
I've only ever heard of 2 flywheels failing, the first was on a Terrapin single seater (David Goulds I think) at Gurston which failed big time! The other was when Cortina Mk3s were around & was on a newish car & had gone bang on the M3. My mate worked at the Ford dealers (Jacksons of Basingstoke) at the time & he said the owner wasn't too happy, but bits hadn't come through the tunnel!
My 7 V8 runs a lighter flywheel aka a machined standard one, never worry about it as A> It was done by by Progress Engineering, aka Rovercraft who had done hundreds with never a failure & B. I don't rev the nuts off it, as 4000RPM in top is highly illegal anyway. If I raced it I might think about it.

A lot of the Yanks worry because I suspect in the early days some of the V8s were over lightened & went bang, also some US V8 engines are externally balanced which makes it a no-no.