# Dual Mass Flywheels



## sallytrafic (Jan 17, 2006)

I have done a little research on the web about DMFs they seem a very complicated and fragile solution to the 'problem' of high torque engines.

I have found an animation on Youtube (which was very slow to load.)
Youtube animation

Can anyone point to an engineering description of their operation rather than just forum opinions.

Better still can anyone on here give a good description and explanation of their working and perhaps tell me how clutch judder might be made worse by having one. I for example assume they operate as a single mass once above a 1000rpm or so.


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## DABurleigh (May 9, 2005)

http://digbib.ubka.uni-karlsruhe.de/volltexte/documents/724768

Mechanical low-pass filter sums the design up for me.

Dave


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## tinkering (Dec 8, 2007)

*dual mass flywheels*

I have just Googled honest john .co .uk Frank, if you read some of the posts there you might find the anser.

As far as I can make out if the load on the flywheel (torque) exceeds its design load it "lets go" so to speak until the load decreases, so you are probably right, it will cause clutch judder.

Les


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## Hintonwood (Mar 21, 2008)

AAAAAAAAAAAAAAgh!

Just reminded of my £ 1000 bill when the DMF on my 2001 Transit with 38k miles on the clock failed and ripped out the clutch. 

Learned of some people having theirs go three times under warranty.

Sold the van to a builder in Brighton and changed to Toyota.

He rang me up 15 months later to say it had gone again! FORD DESIGN FAULT. 8O

Mondeos have the same problem.


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## olley (May 1, 2005)

Hi old slow reving engines had dirty great flywheels to iron out the power pulses from the pistons, but heavy flywheels consume power and make an engine less responsive.

Modern high speed diesels need light flywheels to be responsive and to improve fuel economy, but without a heavy flywheel at slow engine revs you will feel the power pulses, so along comes dual mass flywheels, problem solved.  

Its just a vibration damper.

Olley


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## sallytrafic (Jan 17, 2006)

Thank you (I had already been on the honest John website). One of the problems with the internet and the way search engines function is that forums like this one and honest john get far too many hits compared to ones that have the real deal. I doubt people twitter about the INSTITUT FÜR MASCHINEN-KONSTRUKTIONSLEHRE UND RAFTFAHRZEUGBAU too often. 
Social networking and marketing have a lot to answer for 

anyway

So it dampens out the speed oscillations in each revolution without changing their fundamental frequency, have I got that right?


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## sallytrafic (Jan 17, 2006)

Further thought if its working properly great, but if not, could it be another cause of judder?


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## rayc (Jun 3, 2008)

sallytrafic said:


> Further thought if its working properly great, but if not, could it be another cause of judder?


Some people believe that the design leads to the springs becoming distorted causing the judder and finally becoming unseated and shaking the clutch to pieces. Incedentally there are many postings on the Practical Caravan website of juddering and overheating clutches when reversing caravans occuring on cars with DMF clutches e.g. Mondeos.


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## petepub (Oct 28, 2008)

*tech/mat chat*

If the flywheel goes will this damage the clutch?


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## tinkering (Dec 8, 2007)

*dmf clutch*

hhp://www.standtransmissom.co/dmfhtml

Having read this article, it seems that there are so many factors that can lead to its failure ,it hardly seems worth fitting it as standard.

To low/high turbo pressure,injector failure, to name a few perhaps much more serious for those who have remapped there engines to increase the engines performamce.

Take care Les :wink:


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## sallytrafic (Jan 17, 2006)

*Re: dmf clutch*



tinkering said:


> hhp://www.standtransmissom.co/dmfhtml
> 
> Having read this article, it seems that there are so many factors that can lead to its failure ,it hardly seems worth fitting it as standard.
> 
> ...


I think there are several mistakes in the spelling of your link but I still cant find it after changing it to http and to transmission


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## DABurleigh (May 9, 2005)

http://www.standardtransmission.com/dmf.html


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## tinkering (Dec 8, 2007)

:stoopyd:  

Sorry Frank I :lol: will go to the front of the class with my dunces hat on, not I expect for the last time

Thank you DABurleigh :wink:


Take care Les :wink:


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## CliveMott (Mar 10, 2008)

DMF are designed to transmit the average torque from the engine without transmitting each individual "pop" of each cylinder. Ideal for transmitting low frequency stuff - like vehicle juddering!

C.

Hang on, Have I just hit the nail on the thumb?


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## Stanner (Aug 17, 2006)

As explained to me by my mate "Walter Mitty" who works at the local VW main dealer, the difference is this.

In the old days before torques were invented flywheels used to be solid lumps of metal but clutch plates were two bits of metal - a hub and a plate joined together with 4 little springs.

Then torques were invented and the people who made clutches decided to tame the torques by moving the 4 little springs from the clutch to the flywheel and making them BIGGER springs, because the torques were strong and kept escaping.
This meant that the flywheel was now two pieces of metal joined by 4 big springs and the clutch plate one piece of metal with no springs.

It's called progress - AKA "a process of continuing development".

Night night.


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## 38Rover (Nov 9, 2006)

I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization 

Its progress Petronius 65 AD


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## sallytrafic (Jan 17, 2006)

You know that Petronious was one person I was not expecting to meet in this thread. 

I can give you another quote which is also quite apposite although I can't remember if it was an ancient Greek or someone more modern who said


If it is not necessary to change, then it is necessary not to change.


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## mikeyv (May 23, 2007)

Ah yes, but if you pay someone handsomely to come up with new systems/ideas, don't be surprised if they never say "this system works perfectly, and need not be changed for the foreseeable future - where do I get my cards?"


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