Lightened flywheels / protection

[chrislandy]

I have (hopefully) aquired a lightened crank and flywheel for my Rover T16 turbo engine (crack testeded before and after the machining), I have heard a number of tales and seen videos of flywheel "explosions" where the flywheel has been lightened. In the rare event of this happening, what protection can be used around the bellhousing to reduce the likelyhood of flywheel/clutch fragments escaping and doing some serious damage to my passenger, myself or any passers by/spectators?

Reading various websites there is the suggestion that a ballistic / scatter blanket or a 1/8th" steel plate surrounding the bellhousing can be used. I have looked around a little but cannot find any suppliers of these scatter blankets in the UK.

Chris.

[Guy Croft]

FWIW

I have never heard of a straight four cylinder fw exploding where it has been lightened with good radii and to no less than 12mm thick (thicker in the central region) and balanced as an item and with crank. Certainly on your engine it might be an idea to dowel the crank fw to lessen the stress on the bolts. In fact, regarding balance I used the same Fiat TC lightened/balanced cast iron fw as a 'universal' on dyno testing over a 7 year period under arduous load tests and at speeds over 9000 and it never broke, and that fw had never been balanced as a pair with its mating crank, albeit that the cranks in the engines on test had of course been thru rigorous balance correction.

What bursts a fw? Here are a few things:

1. Severe imbalance of fw or assy
2. Embedding of fw bolts into fw and subsequent loss of preload
3. Incorrect torque setting (over/under) on fw bolts - easily upset by incorrect lubrication regime.
4. 'Swashing' of fw friction face. This can be balanced out - but it puts an fluctuating and very adverse axial load across the radius of the fw every time the clutch is engaged. It can be caused by a poor quality regrind of the item or bent crank/flange out of true.
5. Cracks inherent in fw - precision grind and crack test is advisable on each rebuild.

Bolting failures don't alway cause fw burst, sometimes the fw just comes right off completely intact. That can be far more dangerous than a burst, esp if it's a very light steel fw because the spinning ring gear is like a saw and will cut thru almost anything in its way.

Hope that helps some although it's got nothing to do with shields..

GC