Dual Mass Flywheel

[Michael GilliganParticipant @michaelgilligan61133]

After more than 100,000 miles, the clutch is finally on its way out

My trusted local garage ‘strongly recommends’ that the flywheel be changed at the same time … this came as something of a shock, but they are probably right.

The mighty Haynes appears to agree:

https://haynes.com/en-us/tips-tutorials/what-dual-mass-flywheel-and-what-does-it-do

The logic, of course, is that if they just replace the clutch … and then the flywheel fails, the job will need doing again [but properly, this time].

Any comments ?

… and is the old flywheel worth salvaging for materials ?

MichaelG.

 

[Neil AParticipant @neila]

If the clutch needs replacing, then I would probably take the advice and change the flywheel as well if it is indeed a dual mass flywheel. The clutch and dual mass flywheel on my last car were still going strong at 215000 miles, mostly long journeys, I had to change the vehicle for other reasons. It depends on the type of driving you do.

There might be some salvageable material in the old flywheel, you can only have a look and decide, you always throw it away later. Usually a case of its too good to throw away, but I can’t think of a use for it at the moment.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Thanks Neil

Clutch is definitely in need of replacement … I first started noticing the latency between engine revs and road-speed in 6th but it’s now evident in 4th

Late 2003 and just over 110k miles … it probably deserves a flywheel change.

Yes, it’s dual mass [in theory at least … I haven’t looked]

It’s booked-in for Wednesday & Thursday

MichaelG.

[Tim StevensParticipant @timstevens64731]

hello Michael

You will of course take no notice of Haynes’s claim: Between the two flywheels, connecting them, are a series of springs which dampen the engine vibrations ….

It is not the springs that do the damping, here or in the suspension system, or anywhere else. Springs can absorb energy and give it back, but on their own they will keep doing this indefinitely. There must be some friction or viscosity to ‘use up’ the energy, turning it into heat (usually).

I make no comment about ‘are a series’

But then, what do I know … ?

Cheers, Tim

 

[Andy StopfordParticipant @andystopford50521]

The Wikipedia page isn’t terribly helpful, but seems to suggest that multiple different springs are arranged to work against each other to provide the damping (with the energy presumably being lost as heat):

https://en.wikipedia.org/wiki/Dual-mass_flywheel

[Maurice TaylorParticipant @mauricetaylor82093]

Hi, Don’t forget to fit all new parts that are inside the bell housing ,ie spigot bearing,slave cylinder etc.

Maurice

[Tim Stevens]

On Tim Stevens Said:

which dampen the engine vibrations ….

It is not the springs that do the damping, here or in the suspension system, or anywhere else. Springs can absorb energy and give it back, but on their own they will keep doing this indefinitely. There must be some friction or viscosity to ‘use up’ the energy, turning it into heat (usually).

I make no comment about ‘are a series’

But then, what do I know … ?

Cheers, Tim

 

Could be they mean ‘smooth’. The springs could introduce a delay / negative feedback type of damping.

[Tim Stevens]

On Tim Stevens Said:

[…]

But then, what do I know … ?

Cheers, Tim

 

You know a lot, Tim … You know that, and I know that

I am, however, happy to take the Haynes statement with the requisite pinch of artistic license …  It gives the right general idea of ‘softening the blow’ of aggressive clutch engagement … although of course the tyres can also  do that for you 🙂

MichaelG.

[SteviegtrParticipant @steviegtr]

My Son’s Golf GTi gearbox failed. The Dual mass flywheel had been clattering for a while. When we removed the gearbox the flywheel was a proper mess. Lots of play. He been a hothead on the pedal decided to go for a solid flywheel. Worked well. I have known many cars with noisy Dual mass, needing changing. The idea was it made the car /van smoother.

Steve.

[Michael GilliganParticipant @michaelgilligan61133]

This might should help a little, but I think even they are struggling to find the right words !

https://clutch-specialists.co.uk/products/cg-motorsport-dual-mass-flywheel-only-700-0140

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Mine still feels as-new … to both me and the mechanic who came out for a short drive to check my diagnosis. But he warned me that when they do fail, it can be sudden and unexpected.

If only HAL was with us, and could be relied upon !

MichaelG.

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Ref. __ https://www.imdb.com/title/tt0062622/quotes/

 

[Robert Atkinson 2Participant @robertatkinson2]

Dual mass flywheels are not the same as the springs used to soften clutch engagement. They are designed to dampen torsional vibrations of the crankshaft. This helps stop resonances at specific engine engine speeds. Somtimes a damper is placed on the other end of the crankhaft. These may be on their own or with a dual mass flywheel and are often built into the auxilary belt pulley. Often a two part pulley with the two parts bonded together with rubber.
Fitting a solid flywheel in place of a dual mass item can put additional stress on other engine components as well as increased noise and vibration.

They are also found on some stepper motors as used on CNC machines and 3D printers.
https://www.phytron.eu/products/mechanics-equipment/dmp-20-29-37-inertial-damper-for-stepper-motors/

[bernard towersParticipant @bernardtowers37738]

Dual mass flywheels do not suit everybodies style of driving so can get some bad press from some drivers and a lot of those have benefitted by changing to solid type, which must be ok to fit as they are an option in most parts lists

[Michael GilliganParticipant @michaelgilligan61133]

Whatever … having driven approximately 94k of those 110k, I will be happy if it retains its original specification … it works for me.

Thanks for all the input … hopefully I will report back on Thursday evening [‘though one can never predict what might be found]

MichaelG.

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P.S. __ given that this straight-six is one of the sweetest engines that I have ever sat behind … some of the reasoning on that Wikipedia page does seem a little superfluous.

[Dave HalfordParticipant @davehalford22513]

It sounds like a harmonic balancer moved to the other end of the crank. They are just two rings of metal with rubber bonded between then.

I had a dual mass flywheel quit after the car cut out at 30mph with a fuse box fault.

Something went clang like a bell and everything started working again.

6 months later it started slipping in top going up hill, then the auto box gear shift effect. Only 12k of motorway miles, new clutch, new flywheel.

If any flywheel has a slipping clutch it needs refacing these days.

 

[dodmoleParticipant @dodmole]

My VW trained and recently retired AA man said that dual mass flywheels are proof of the “if it ain’t broke don’t fix it” saying is perfectly true and the old fashioned solid flywheel option appearing is surely proof of overcomplicating something that has served well for probably a century.

[SillyOldDufferModerator @sillyoldduffer]

Taking a clutch apart to replace the plate is a fair amount of work, hence expensive, plus VAT.  Thus it makes sense to replace a time-worn flywheel when a new clutch plate is needed because the labour cost is halved compared with doing the flywheel and plate separately.

A couple of posts suggest the Dual Mass Flywheel works by absorbing energy.  Not so.  Rather it stores energy such that shocks are spread over time, smoothing sharp hammer blows into smoother pushes that are much less likely to damage the engine and drive train.

As a general rule replacing a DMF with a solid flywheel isn’t smart.   Although solid flywheels also reduce shocks, they’re not as effective, causing more hammering.  The exception is performance driving, where it’s accepted that the car will be damaged.   Whilst expensive Formula 1 engines are happily rebuilt by their owners after every race, I choose to minimise maintenance costs by driving within my car’s ordinary design envelope.   Though I do dream of removing the silencer and painting on a Starsky and Hutch go-faster stripe!

Dave

 

[SillyOldDuffer]

On SillyOldDuffer Said:

A couple of posts suggest the Dual Mass Flywheel works by absorbing energy.  Not so.  Rather it stores energy such that shocks are spread over time, smoothing sharp hammer blows into smoother pushes that are much less likely to damage the engine and drive train.

It seems to be rather more complicated than that, with both smoothing, and damping (i.e. energy absorbing).

This is by the people who appear to be the developers of the thing:

http://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/symposia_1/downloads_11/luK_kolloquium_en.pdf

I’ve only glanced through it so far, but page 69 onwards apparently tells all in reasonably comprehensible language.

Or, in short:

http://www.luk.de/content.luk.de/en/products/clutch_systems_new/zms_new/zms_new.jsp

[vintage engineerParticipant @vintageengineer]

Dual mass flywheels are cheaper to make than decent crankshafts. They are only there to cut manufacturing costs.

 

[duncan webster 1Participant @duncanwebster1]

I thought Frederick Lanchester invented these 100 years ago, although he used a viscous damper rather than rubber

[Michael GilliganParticipant @michaelgilligan61133]

Not quite the same thing, Duncan

… With a Fluid Flywheel, there is no clutch.

MichaelG.

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Ref. __

https://simple.wikipedia.org/wiki/Fluid_coupling

https://www.jaguarheritage.com/frederick-lanchester/

https://www.jaguarheritage.com/daimler-history/daimler-engineering/pre-selector-gearbox/

 

 

 

[duncan webster 1Participant @duncanwebster1]

Who mentioned fluid flywheels?

[Michael GilliganParticipant @michaelgilligan61133]

Only me, Duncan

… They’re what I usually associate with Lanchester.

Oops! … I evidently misunderstood your reference to “these”

MichaelG.

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Incidentally … have you read my P.M.  ?

[Howard LewisParticipant @howardlewis46836]

I have always thought that dual mass flywheels were intended to reduce the resonant frequency of the  driveline, rather than absorbing energy.

If a resonance occurs within the operating range of the system, the effects can be quite disastrous.

(Which is why some of the early B R railcars had a propshaft consisting of three shafts, with a rubber coupling between each element. )

It can be quite important to decouple some parts of the system from the others.

Howard

[Michael GilliganParticipant @michaelgilligan61133]

[ a brief update ]

I delivered the car to the garage just before 09:00 this morning … and they hoped to get the job done today.

Things have not gone to plan.

More anon

MichaelG.

[Author]

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