Dual Mass Flywheels

[Cyker]

I'd imagine a solid flywheel would be okay, but it would have to be significantly heavier to smooth out the 'shocks' compared to a dual-mass wheel, with all the corresponding effects on response and performance, unless the whole drivetrain is strong enough to cope with the extra stresses.

The way I grok it, the whole point of a DMF is a compromise between the smoothing effect of a heavy flywheel and the responsiveness of a lighter one, but the compromise is that it has more moving parts and I imagine it is a lot more delicate (If you ram your foot down on the accelerator, I imagine the springs would not be strong enough to prevent the two plate flanges from colliding with each other!)

[anchorman]

I'd imagine a solid flywheel would be okay, but it would have to be significantly heavier to smooth out the 'shocks' compared to a dual-mass wheel, with all the corresponding effects on response and performance, unless the whole drivetrain is strong enough to cope with the extra stresses.

The way I grok it, the whole point of a DMF is a compromise between the smoothing effect of a heavy flywheel and the responsiveness of a lighter one, but the compromise is that it has more moving parts and I imagine it is a lot more delicate (If you ram your foot down on the accelerator, I imagine the springs would not be strong enough to prevent the two plate flanges from colliding with each other!)

Yes absolutely. In fact if the flywheel weight was increased to the point which it smoothed out all of the pulses (which as you say would be unacceptable) then all of the shock would be taken by the crankshaft and the vibration confined to the engine itself. Where do you stop with it? More main bearings, stiffer crank case, beefed up pistons, con rods, engine mountings........

Apparently the springs are designed as such that they should never be fully compressed even under full load and so they can still absorb the shock under these conditions. Maybe it would be possible for them to bottom out if you "drop" the clutch or abused it in some other way???

[HEMI]

The solid flywheel IS heavy and it has taken abuse from me and it has the smoothest operation that I've felt in ages,it reminded me of the first jap car I ever drove and I thought the clutch had failed in that till I let the pedal up.The springs in the clutch are heavy duty-read-massive,there are no vibe issues whatsoever.My wife gives me a daily report on the clutch and so far she says its still smoother than ever before.I will keep giving you reports on "vibe" issues (wtf) and if my "crank" fails (wtf)

[Fujisan]

In this respect you have to have a little respect for the DMF and the life v abuse it endures. there is no doubt that as with all things mechanical it will either be developed to give longer life or more likely it will be phased out as manufacturers move to auto transmission only vehicles. That is certainly an aspiration of Toyota and if it sounds ridiculous it isn't so long since we were saying you could never replace a manual choke. The point is that the only way a vehicle designer can absolutely guarantee how a vehicle behaves is to remove more of the functions and control from the driver and it will be emissions that finally drive this change.

I believe, from what I read, last year was the first time that the worldwide sale of automatic transmissions (which I think includes semi-auto and double clutch DSG type gearbox's), exceeded the sale of conventional manual transmissions.

[Cyker]

Yes absolutely. In fact if the flywheel weight was increased to the point which it smoothed out all of the pulses (which as you say would be unacceptable) then all of the shock would be taken by the crankshaft and the vibration confined to the engine itself. Where do you stop with it? More main bearings, stiffer crank case, beefed up pistons, con rods, engine mountings........

Haha! Indeed! Then suddenly you find you have a bus engine in your car!

Apparently the springs are designed as such that they should never be fully compressed even under full load and so they can still absorb the shock under these conditions. Maybe it would be possible for them to bottom out if you "drop" the clutch or abused it in some other way???

Yess.. I was thinking about that after I wrote my last post; You'd assume they know the sort of force the springs would have to cope with and would build in a safety factor accordingly, but looking at the torque stats on some of these diesel engines... that's a lot of instantaneous force to deal with by a single ol' spring!

I'd love to see one of those Horizon-style cutaway animations of a real one being stressed!

[HEMI]

Look,all I know that in all my years as a mechanic(from the ground up)solid flywheels have worked in all sorts of motors but some bright spark invented a DMF only recently(to impress his boss no doubt-and make some money too)so how come all the powerful motors of yesteryear(right up to when the "DMF" was invented)had solid flywheels and how come one of my cars which has 450hp has a solid flywheel and has never suffered "vibes" or "crank failure"even when the "button" is pressed?.The saying goes"you can dazzle people with diamonds just like you can baffle people with bull *****". Proof is in the eating,as they say.No I dont have any respect for the DMF or the person/people that devised it,if it aint broke dont fix it.

If you dont want my feedback to help you save some money and stress on the DMF just say so and I will gladly go away but it seems to me that a lot of people are afraid of changes,changes back to the "old way",manufacturers are always right,are'nt they?,yeah right

[anchorman]

Look,all I know that in all my years as a mechanic(from the ground up)solid flywheels have worked in all sorts of motors but some bright spark invented a DMF only recently(to impress his boss no doubt-and make some money too)so how come all the powerful motors of yesteryear(right up to when the "DMF" was invented)had solid flywheels and how come one of my cars which has 450hp has a solid flywheel and has never suffered "vibes" or "crank failure"even when the "button" is pressed?.The saying goes"you can dazzle people with diamonds just like you can baffle people with bull *****". Proof is in the eating,as they say.No I dont have any respect for the DMF or the person/people that devised it,if it aint broke dont fix it.

If you dont want my feedback to help you save some money and stress on the DMF just say so and I will gladly go away but it seems to me that a lot of people are afraid of changes,changes back to the "old way",manufacturers are always right,are'nt they?,yeah right

Yes we want your feedback, of course we do and I must admit I never thought that it might have been invented to impress his boss. these boffins are cunning aren't they. The boss must have liked it anyway as they started using them!!!

:P ;)

[HEMI]

dont take the p1ss,just think back to when the dmf was "invented"not long ago ay?Like I said in earlier posts we have fitted s/f's to Hyundais and Fords for years and I suppose they're wrong too,we all cant be wrong,except for them being wrong in the first place and thats why they are slowly going back to SF's and now I can say that Mr T got it wrong as he was going with the flow.I have proof that the S/F works,what proof do yo have that it doesnt?

[Cyker]

Dude, don't get so huffy, we're not putting you or anything!

We're just saying, a solid flywheel will need to be heavier to get the same smoothness out as a DMF which means it will have more inertia, which means it will spin up slower and spin down slower than a DMF because of the weight - That's just basic physics.

In a vehicle with loads of torque, they still use solid flywheels because the transmission is strong enough and usually on a vehicle like that you don't really care about the extra weight.

If I had a solid flywheel on my 1.4 Yaris, I reckon it would noticably affect accelerate if it was a heavy one, or the power delivery would be a lot more jittery judging by the sound of the engine at low RPM!

Hmm, y'know, I suspect this thing with the flywheel is partly why everyone used to say "Don't go near a diesel unless it's 2L or more", and why older diesels have horrible acceleration despite having loads of low-end torque, because older diesels had big heavy flywheels and stronger drive train components to compensate for the stuttery power delivery.

It's only relatively recently you could even buy a small-engine diesel car that didn't suck.

The thing with a DMF is everything can be lighter, but given that the DMF has a lot more moving parts and uses springs (!!) as it's main energy transfer mechanism (Helical springs too! Ugh, I wonder if they even tried a thick ribbon-coil spring...), I have my doubts over how much punishment it can take in larger engines.

It works great in smaller diesels like mine, but I suspect as you go up in torque, the benefit will lessen until the springs are the size of small trees and the thing weighs almost as much as a solid flywheel

Of course, not being a mechanic or anything I could be badly wrong :P

[HEMI]

How much lighter do you think a DMF is compared to a SMF?let me tell you that its not a lot,well I cant notice it when I pick them up for comparison,so it cant be in kg's,must be in grams,next time we do a conversion I will weigh them for comparison,...Huffy indeed,lol

[anchorman]

dont take the p1ss,just think back to when the dmf was "invented"not long ago ay?Like I said in earlier posts we have fitted s/f's to Hyundais and Fords for years and I suppose they're wrong too,we all cant be wrong,except for them being wrong in the first place and thats why they are slowly going back to SF's and now I can say that Mr T got it wrong as he was going with the flow.I have proof that the S/F works,what proof do yo have that it doesnt?

Me??? Seriously, and I mean seriously, I would love to go down the pub with you and get your take on all sorts of issues as you have the ability to look at things from a different angle - a kind of practical version of Bothy's almanak of "How to do things in a way that nobody else thought of".

Are you saying that Ford have gone back to solid flywheels in new diesel cars or the are undertaking a program of re-fitting solid flywheels after a failure?

[anchorman]

How much lighter do you think a DMF is compared to a SMF?let me tell you that its not a lot,well I cant notice it when I pick them up for comparison,so it cant be in kg's,must be in grams,next time we do a conversion I will weigh them for comparison,...Huffy indeed,lol

I think Cyker means that it would have to be a lot heavier to have the same damping affect

When I weigh things by hand I have to swap around and do it again because for some strange reason my right arm is much stronger than my left!

[HEMI]

I know what Cyker means,Ford themselves aren't swapping flywheels but a lot of independant specialists are.The Transit for example is the worst culprit,a mate/customer of mine bought a brand new Transit and after about 6 months he had flywheel issues and so have a lot of my mates/customers with their Transits,its going that way with the Mondeo methinks as it uses the same lump and flywheel.On the other hand our local Hyundai dealership do swap flywheels for SMF's,we know this cos we do some for them as I mentioned before.I serviced a Kia Sedona yesterday and he has the same lurch my Rav had before I swapped flywheels,we also MOT'd an 05 TDV6 yesterday and that had a terrible lurch in 1st gear as you let the clutch up and its the DMF slipping round(doing its job,although in my eyes a not very good job)before everything can catch up,once it stopped lurching it was sort of ok but not as drivable as my wifes Rav-if you get what I mean-

[Davrav]

I know what Cyker means,Ford themselves aren't swapping flywheels but a lot of independant specialists are.The Transit for example is the worst culprit,a mate/customer of mine bought a brand new Transit and after about 6 months he had flywheel issues and so have a lot of my mates/customers with their Transits,its going that way with the Mondeo methinks as it uses the same lump and flywheel.On the other hand our local Hyundai dealership do swap flywheels for SMF's,we know this cos we do some for them as I mentioned before.I serviced a Kia Sedona yesterday and he has the same lurch my Rav had before I swapped flywheels,we also MOT'd an 05 TDV6 yesterday and that had a terrible lurch in 1st gear as you let the clutch up and its the DMF slipping round(doing its job,although in my eyes a not very good job)before everything can catch up,once it stopped lurching it was sort of ok but not as drivable as my wifes Rav-if you get what I mean-

Found this to be interesting:

LINK

Especially the bit in 'Function and Operation' about starting and stopping. Implies that actual driving is less likely to cause problems than start up/shutdown. Should we all be depressing the clutch when switching off as well as when starting up?

[anchorman]

I know what Cyker means,Ford themselves aren't swapping flywheels but a lot of independant specialists are.The Transit for example is the worst culprit,a mate/customer of mine bought a brand new Transit and after about 6 months he had flywheel issues and so have a lot of my mates/customers with their Transits,its going that way with the Mondeo methinks as it uses the same lump and flywheel.On the other hand our local Hyundai dealership do swap flywheels for SMF's,we know this cos we do some for them as I mentioned before.I serviced a Kia Sedona yesterday and he has the same lurch my Rav had before I swapped flywheels,we also MOT'd an 05 TDV6 yesterday and that had a terrible lurch in 1st gear as you let the clutch up and its the DMF slipping round(doing its job,although in my eyes a not very good job)before everything can catch up,once it stopped lurching it was sort of ok but not as drivable as my wifes Rav-if you get what I mean-

Found this to be interesting:

LINK

Especially the bit in 'Function and Operation' about starting and stopping. Implies that actual driving is less likely to cause problems than start up/shutdown. Should we all be depressing the clutch when switching off as well as when starting up?

A very good question. My transmission makes a lot of noise when it is not under load. Wait until the engine is hot and then just keep pressing and releasing the clutch and you can hear all the backlash. Just how much is in the gearbox and how much is in the DMF I don't know but something is clattering away in there.

I suppose as the engine slows down then the intensity of the "pulse" increases as there are fewer to keep it running smoothly. When I first got it I stalled it on a couple of occasions and it is the worst teeth rattling horrible bang you can imagine as the last power stroke is confined.

I tend to start mine without pressing the clutch (I think) but as you say, maybe it would be a good idea.

[anchorman]

I know what Cyker means,Ford themselves aren't swapping flywheels but a lot of independant specialists are.The Transit for example is the worst culprit,a mate/customer of mine bought a brand new Transit and after about 6 months he had flywheel issues and so have a lot of my mates/customers with their Transits,its going that way with the Mondeo methinks as it uses the same lump and flywheel.On the other hand our local Hyundai dealership do swap flywheels for SMF's,we know this cos we do some for them as I mentioned before.I serviced a Kia Sedona yesterday and he has the same lurch my Rav had before I swapped flywheels,we also MOT'd an 05 TDV6 yesterday and that had a terrible lurch in 1st gear as you let the clutch up and its the DMF slipping round(doing its job,although in my eyes a not very good job)before everything can catch up,once it stopped lurching it was sort of ok but not as drivable as my wifes Rav-if you get what I mean-

It can't slip but yes I see what you are saying, it can twist as it takes up the tension in the springs. In this case I guess when you remove the DMF you can move it back and forth by a large amount (they all move to some extent);

Toyota say 8 - 10 degress for new and 10 to 12 degrees for used. How much do these "lurching" ones move?

4.3_DMF_check_procedure.pdf

[HEMI]

well,mine moved to about 70-80 then it would jam,all that backlash you can hear and feel is the DMF,I had that same noise/feel before I swapped F/W's now I have no lurch,backlash or noise

[hertsnminds]

I tend to start mine without pressing the clutch (I think) but as you say, maybe it would be a good idea.

Could this be a reason for Toyota putting the push button starter in their cars? You cannot start the engine unless the clutch pedal is down.

[MarsKy]

I tend to start mine without pressing the clutch (I think) but as you say, maybe it would be a good idea.

Could this be a reason for Toyota putting the push button starter in their cars? You cannot start the engine unless the clutch pedal is down.

I think it's a safety feature so that you (or the kids playing about) can't accidentally start the car by just pushing the button. Interestingly I did deliberately push the button while the car was in motion on an empty road to see if it would cut the engine - and it did.

[three5]

I know what Cyker means,Ford themselves aren't swapping flywheels but a lot of independant specialists are.The Transit for example is the worst culprit,a mate/customer of mine bought a brand new Transit and after about 6 months he had flywheel issues and so have a lot of my mates/customers with their Transits,its going that way with the Mondeo methinks as it uses the same lump and flywheel.On the other hand our local Hyundai dealership do swap flywheels for SMF's,we know this cos we do some for them as I mentioned before.I serviced a Kia Sedona yesterday and he has the same lurch my Rav had before I swapped flywheels,we also MOT'd an 05 TDV6 yesterday and that had a terrible lurch in 1st gear as you let the clutch up and its the DMF slipping round(doing its job,although in my eyes a not very good job)before everything can catch up,once it stopped lurching it was sort of ok but not as drivable as my wifes Rav-if you get what I mean-

It can't slip but yes I see what you are saying, it can twist as it takes up the tension in the springs. In this case I guess when you remove the DMF you can move it back and forth by a large amount (they all move to some extent);

Toyota say 8 - 10 degress for new and 10 to 12 degrees for used. How much do these "lurching" ones move?

4.3_DMF_check_procedure.pdf

Anchorman,

the way I see it, the springs in the DMF store part of the energy from every power stroke. The failure mode of the springs is likely to be through fatigue rather than outright overload. I think that you said in a previous post that you tend to drive at about 2500rpm. Anyone who is attempting to get the best fuel consumption ( i.e. me ) is likely to drive at less than that. I have a feeling, haven't fully analysed the problem yet, that my flywheel is likely to fail before yours as we would be both driving with the engine running at the top of it's ( very flat ) torque curve. My DMF springs would therefore be subject to a lower frequency higher amplitude load than yours which is likely to be bad news

[anchorman]

Not sure when the amplitiude becomes critical Chris but the info suggests it will be very low revs rather than you might use for economic driving. I think I was saying there is no point driving at much more than 2500 rpm and when I get it moving I get it in 6th where I can where the revs are actually down toward 1000 rpm. I have to keep a close eye on things down there as I don't like loading the engine if I need to open it up a bit - it is uncomfortably close to idle speed! In that case I'd rather see the revs up a bit.

[Cyker]

Argh, you're making me even more paranoid now!

I'm often idling along in slow traffic in 2nd at 800-900rpm, up and down hills, over speed humps and pot holes!

I would have hoped that whoever designed the DMF would have picked springs with enough of a safety factor that they wouldn't wear out that quickly 'tho...

[anchorman]

50k equated to engine revs must be astronomical - those springs must have been pounded millions and millions of times.

[HEMI]

Argh, you're making me even more paranoid now!

I'm often idling along in slow traffic in 2nd at 800-900rpm, up and down hills, over speed humps and pot holes!

I would have hoped that whoever designed the DMF would have picked springs with enough of a safety factor that they wouldn't wear out that quickly 'tho...

Whoever designed it didnt thoroughly tested it,or did he and didnt give the correct results just to be smart and rich.Dont forget that the clutch didnt wear out,the DMF failed-it fell apart,rattled,banged,etc,etc but the clutch faces themselves didnt wear.I bet anyone thats had a DMF failure never had clutch slip but just had the clonking etc before the failure

[HEMI]

just an update on my solid mass flywheel,its been fitted over a month now and has done over 1000 miles and still with no problems,no vibes etc just a smooth take up and drive