Rover 75 cdti crankshaft damper pulley

[boofs]

Hi,
Why do they have a CRANKSHAFT DAMPER PULLEY why not a normal pulley ?

[boofs]

Hi,
Why do they have a CRANKSHAFT DAMPER PULLEY why not a normal pulley ?
as it only drives a BELT which is a DAMPER in its self ?.

[Goodtimegaz]

Originally Posted by boofs

Hi,
Why do they have a CRANKSHAFT DAMPER PULLEY why not a normal pulley ?
as it only drives a BELT which is a DAMPER in its self ?.

Thats a very good point, I wonder if anyone has ever hard fastened them together?

[okenora]

it damps out resonance in the crankshaft at certain revs which could otherwise cause damage/failure of the crank.

Rover could have re-engineered the crank to be more robust, but instead went the damper route. It is not simply a pulley to drive a belt on our cars.

[jim lee]

I think the pulley is not a 'damper' as such but a de-tuner. By separating the two parts of the pulley with rubber, the rotating crankshaft feels a continually varying mass on its end. as opposed to a constant mass as with a solid pulley. This variation in mass gives the crankshaft/pulley system a continuously changing critical or natural frequency of torsional vibration. Thus, if the engine is running at a speed where this natural or resonance frequency occurs, excessive torsional stresses are avoided which would otherwise occur if a solid pulley was fitted. So it is not a good idea to fix the two parts of the pulley together.
Just my understanding of the reason behind fitting a 'damper' pulley. Any other ideas?

[T-Cut]

Here's what Wikipedia says about it: http://en.wikipedia.org/wiki/Torsional_damper

TC

[jim lee]

T-Cut,

Look for 'Torsional Vibration' in Wikepedia and you will find a description of the mechanics of these 'dampers'. In essence, its says that a crankshaft pulley containg an hydraulic element is a damper. Whereas one containg an elastic element, i.e. rubber, is a tuned mass 'damper' (also stating that the term damper in this application is not correct).
This description is the essence of my understanding of the front pulley's function on the R75 diesel (other than driving the Aux. belt). Perhaps there is an engine designer in the club who can throw more light on subject.
This does show that Wikepedia cannot be trusted entirely as it has contradicted itself here.
Whatever, I think you would agree that the answer to Goodtimegaz is that the two parts of the pulley should not be locked together.

Regards
Jim Lee

[T-Cut]

Yes I agree. They should be sold as tuned mass pulleys.

TC

[Goodtimegaz]

Originally Posted by jim lee

T-Cut,

Look for 'Torsional Vibration' in Wikepedia and you will find a description of the mechanics of these 'dampers'. In essence, its says that a crankshaft pulley containg an hydraulic element is a damper. Whereas one containg an elastic element, i.e. rubber, is a tuned mass 'damper' (also stating that the term damper in this application is not correct).
This description is the essence of my understanding of the front pulley's function on the R75 diesel (other than driving the Aux. belt). Perhaps there is an engine designer in the club who can throw more light on subject.
This does show that Wikepedia cannot be trusted entirely as it has contradicted itself here.
Whatever, I think you would agree that the answer to Goodtimegaz is that the two parts of the pulley should not be locked together.

Regards
Jim Lee

Glad my V6 has a solid pulley, however if I had a diesel with a duff oulley the temptation to hard fasten them and see what happens would be very strong.

[T-Cut]

Originally Posted by Goodtimegaz

- - - if I had a diesel with a duff oulley the temptation to hard fasten them and see what happens would be very strong.

It would be an interesting experiment as long as you bear in mind that new pulleys are a lot cheaper than new crankshafts.

TC