Vibration damper flywheels

[Tom Coates]

I have been in contact with a manufacturer of "rattler" vibration damper flywheels and the price seems to be not outrageous (probably less than 1k€) in view of the potential benefits - ie running a relatively hi C/R without harshness. My car has a Ricardo head and although it is fully balanced and runs nicely, the vibration through the steering wheel starts to be unpleasant on a long run.

Does anyone have experience of these?

A second question, do new (pheonix) cranks come dynamically balanced out of the box? If so then it should be possible to fit a new balanced flywheel without having to take everything to pieces to rebalance the whole assembly - right? or am I just being naive?

[Bela]

The whole assembly is not only crank and flywheel. Pistons and conrods are disturbing balance too.

[Charles P]

Tom

Sounds like you need to investigate the Nick Beck/ Rob Beck "Floppy Flywheel"
Rob swears by it, and argue against his engineering solutions at your peril.

Charles

[John Mason]

I have heard of flexible flywheels for sevens which help with the flex of the crank allowing the centre of the flywheel to move with the bowed crank. I believe this is achieved by parting off the centre in a lathe then rejoining the centre to the outer part with flexible steel straps bolted between the two. Some years ago I went on the Molentocht rally and met a seven enthusiast and engineer from March in Cambridge who had done this modification.

John Mason.

[Malcolm Parker]

The new Phoenix type cranks that I have come across are definitely not dynamically balanced 'out the box' and in most cases a considerable amount of metal needs to be removed.
As a new crank is much sturdier than the original I would not expect it to flex as much which to my mind makes the need for the flexible flywheel questionable.

[Paul N-M]

Hi Tom,
I take it you are talking about a crank damper and not the flywheel/clutch assembly?

I have some experience of the rattler type of crank damper. Suggest you PM me with the company you have been in touch with. Possibly the same one I have been dealing with.

Paul N-M

[Bob Culver]

Whilst 2 brg Seven engines and esp high cr ones are harsh is it usually very evident as physical vibration at reasonable revs or mainly as din? Do others encounter significant steering wheel vibration? Is the engine token rubber mounted? The simple RP mounts make a big difference. The fact that cranks so often fail at the rear journal implies major involvement of the flywheel as the direct bending there should be minimal. (Bridges do not fail at the ends) The life of the phoenix crank is due mainly the fatigue protection provided by nitriding. Whatever the steel the rigidity is the same for the same shape. Torsional vibration problems are usually assocaited more with high rpm and multi main bearing carnks with many heavy counterweights.
Ideally crank dynamic balance error should not be corrected in the flywhee but the presence of the key complicates matters somewhat.

[Chris KC]

Could someone please point me in the direction of a write-up / pics on the 'floppy flywheel'?

I thought there was an article in The Companion but perhaps I remembered wrong.

I have tried Google but it throws up lots of expired links.

[Charles P]

Could someone please point me in the direction of a write-up / pics on the 'floppy flywheel'?

I thought there was an article in The Companion but perhaps I remembered wrong.

I have tried Google but it throws up lots of expired links.

Try this thread or dig out Grey Mag 2006C
http://pub25.bravenet.com/forum/static/s...8&cmd=show

If the link fails search Nippy Crank and Rods on the old forum
The archive version here seems knackered but Google will find a better version


c

[Chris KC]

Thanks Charles, 2006C met my needs.