Dual disk clutch does not shift slower than a single.

YES!!!

Please.

That would be fantastic. It would be a HUGE help.

what do you need, the disc are actually 13.875" in both, the flywheel's weigh about the same at 61lbs, the single plate clutch weighs 41lbs and the dual disc weighs 59.will the friction material need to be measured as well.
 
what do you need, the disc are actually 13.875" in both, the flywheel's weigh about the same at 61lbs, the single plate clutch weighs 41lbs and the dual disc weighs 59.will the friction material need to be measured as well.

Okay, disks 13.875.

Flywheel stock is about 61lbs...

You said the single disk weighs about 103 pounds?

And the dual disk weighs about 120 pounds?

The single plate weighs 41 pounds.. Does EACH of the dual disks weigh 59 pounds? Or do both together weigh 59 pounds? Do those not include friction material?

This is just going to make the math more realistic.. Which is a good thing.


JasonCzerak said:
your right. I'm wrong.. I need to stop thinking at the end of the day so much ;-)

1st gear is 1:1
2nd gear is .73

3200rpm
Top Speed in 1 gear = 83.484 MPH
And changes into 2 gear at 2336 RPM dropping 864 RPM
Top Speed in 2 gear = 114.361 MPH

6400rpm
Top Speed in 1 gear = 166.967 MPH
And changes into 2 gear at 4672 RPM dropping 1728 RPM
Top Speed in 2 gear = 228.722 MPH
Today 03:27 PM

I think I'm starting to see why flywheel weight isn't as big of a concern in a diesel application.. What do you think? That is a pretty significant difference in RPM change.

Maybe that is why a lighter flywheel has never been offered. Since the engine has to fall less than half as far in RPMs as in an equivalent gas engine it isn't worth the drivability loss to lighten the flywheel. Just thinking out loud here..
 
God I hate math.

Do this:

Take a trans, hang 2 disks on it, then figure out how to spin it to 4000rpm an pull the power away.

Measure how long it takes to return to a stop.

Do the same with a single and triple.

That will eliminate if we are dealing with kinetic energy or drag on the shifts.
 
I don't know how this is even a argument, both drag and kinetic energy are going to go up with rpm's and weight, this is loose loose for most of the DD's for our diesel's from the syncro side of it.

Most diesel's that are in need of a DD arn't looking for lighting shifting speed, they want it to hold.


And on the keeping it simple stand point.....

Between both my ton's, from idle they both go into first pretty much instant, the DD is maybe a little more,
But rev them both right up, then at the point of dropping the rpm's "feel" for first, and the DD is slower, no question.
 
I don't know how this is even a argument, both drag and kinetic energy are going to go up with rpm's and weight, this is loose loose for most of the DD's for our diesel's from the syncro side of it.

Most diesel's that are in need of a DD arn't looking for lighting shifting speed, they want it to hold.


And on the keeping it simple stand point.....

Between both my ton's, from idle they both go into first pretty much instant, the DD is maybe a little more,
But rev them both right up, then at the point of dropping the rpm's "feel" for first, and the DD is slower, no question.


The question isn't if the kinetic energy goes up (it does).

The question is if the synchros are capable of dealing with the extra energy. If we can find a real world example where the synchros deal with more energy than what the addition of a second clutch creates, then obviously they are up to the task.

You say the dual disk "feels" slower. There are pleanty here that say they "feel" exactly the same. Some even say they "feel" faster.

If there is an actual measurable difference in shift speed, there has to be a reasonable explanation. No one can come up with a reasonable explanation, other than "feel." If they truely shift slower for any reason, I'd like to see the math behind it to show why. We can have different opinions, but the math doesn't lie. :)
 
When I say "feel" for the gear, I mean moving the shifter so you can feel when the gears are ready to line up, not "feeling" as in "MAYBE".

Its not a feeling......simply fact, I can tell the DD takes longer to spin down, from the extra weight.


Reasonable explanation, wow....don't know how to make it any more clear, the syncros HAVE to work harder, when there is more drag on the disks, OR the weight of the clutch disks goes up. And in this case both go up.
 
Just another thought...

Has anyone else noticed their DD is slowest to shift the lower the gear ratio is?

For example, if I start off in first, rev to 3000 rpm and shift to second, it is a lot harder to shift than doing the exact same thing between the 3-4 gear change...even though the shifting motion is identical.

To further illustrate, what is everyone's results when in 4-Lo? There's been plenty of time off-roading that I've started out on a steep hill in 1st gear in low-range. No matter how hard I try, it's almost impossible to get it into 2nd gear before you start rolling backwards...

--Eric
 
Just another thought...

Has anyone else noticed their DD is slowest to shift the lower the gear ratio is?

For example, if I start off in first, rev to 3000 rpm and shift to second, it is a lot harder to shift than doing the exact same thing between the 3-4 gear change...even though the shifting motion is identical.

To further illustrate, what is everyone's results when in 4-Lo? There's been plenty of time off-roading that I've started out on a steep hill in 1st gear in low-range. No matter how hard I try, it's almost impossible to get it into 2nd gear before you start rolling backwards...

--Eric

Mine is the same way, although I can't comment on the 4-lo, as the real slow shifter is a 2wd. 2-3 is brutal, 3-4 isn't too bad, I can hit the 4-5 pretty good. I just float the gears in that truck, only use the clutch for starting and stopping.
 
When I say "feel" for the gear, I mean moving the shifter so you can feel when the gears are ready to line up, not "feeling" as in "MAYBE".

Its not a feeling......simply fact, I can tell the DD takes longer to spin down, from the extra weight.

So, when driving a gasser manual trans, you can feel that trans is slower to shift than a diesel? The specs show the gasser has to work harder to match speeds in a gasser shifted at redline than a diesel at redline...

Merrick
 
So, when driving a gasser manual trans, you can feel that trans is slower to shift than a diesel? The specs show the gasser has to work harder to match speeds in a gasser shifted at redline than a diesel at redline...

Merrick

Its been about 20 years since there has been a gas job around here, but in theory yeah, if the weight of the disks is the same, however....

A gas engine will dump rpm's a lot quicker than a diesel as well, due to the throttling. So there is a big gain there.

Anyone who's spent some time driving a semi, knows if you need to speed shift in the bottom gear's, you dump rpm's with the jake, and you can pretty much shift as fast as you can operate the lever.

Again, to the semi's try and put one with out a clutch brake into first gear, and you either need to wait for that disk to spin down, OR crash it into gear.

Now, rev it right up, put the clutch in (Not far enough to use the clutch brake) and see how long it takes to spin down.

Check out any sport performance clutch builder and I'm sure you'll find low inertia of the clutch disks is well thought out.

Hyper Series : Exedy Clutch Europe, Performance Clutches
 
Its been about 20 years since there has been a gas job around here, but in theory yeah, if the weight of the disks is the same, however....

A gas engine will dump rpm's a lot quicker than a diesel as well, due to the throttling. So there is a big gain there.

Anyone who's spent some time driving a semi, knows if you need to speed shift in the bottom gear's, you dump rpm's with the jake, and you can pretty much shift as fast as you can operate the lever.

Again, to the semi's try and put one with out a clutch brake into first gear, and you either need to wait for that disk to spin down, OR crash it into gear.

Now, rev it right up, put the clutch in (Not far enough to use the clutch brake) and see how long it takes to spin down.

Check out any sport performance clutch builder and I'm sure you'll find low inertia of the clutch disks is well thought out.

Hyper Series : Exedy Clutch Europe, Performance Clutches

Right! So, why haven't we seen a light weight flywheel offered in the high-performance diesel work?

There is more energy at gas engine RPMS levels with a single disk clutch than there is at diesel RPM levels with a dual disk clutch. If you're right, it should be a lot slower to shift a 5-speed gas engine dodge than a 5-speed diesel dodge.. Unless, the synchros are capable of handling the additional energy without comprimising shift speed. Once again, it isn't a question of if there is additional energy. It is a question of whether or not the synchros can handle that additional energy. We have a real work example where they are subjected to more energy then we are dealing with at our RPM levels in the gas application. Do you think the engineers planned on that? I do.

Further, if you're right, you should have ZERO issue finding thousands of examples of folks in the gas engine world installing dual disk clutches and complaining about shift speed. Fact is, I can't find any... Which I find really strange.

We can keep going back and forth on our opinions. I'm looking for the numbers. Still hoping Tate will chime in again on the kinetic energy thoughts.

By the way, are you using a lever style dual disk or a diaphram style?... I have some more thoughts on the lever style shifting slower. ;)
 
When shfting to a higher gear, the clutch discs, input shaft, countershaft and all the gears on the main shaft will have to slow down. The mainshaft it self will maintain speed since it is directly connected to the driveshaft/axle shaft/wheels. So, for the work the synchros absorb is the speed change multiplied by its mass. The mass change between a single disc and a dual disc is a second disc, which may weigh more than twice a single (12" single to 13" dual), and a slightly heavier input for those who upgraded to the 1-3/8" input. Considering the amount of mass already spinning, the extra mass added isn't huge.

The bigger issue in my mind is that the single disc has more room to float between pressure plate and flywheel, allowing much more positive disengagement, reducing drag. Dual discs with a floater plate that doesn't have straps on it has no means of seperating the the two clutch discs and the floater plate, thus increasing the drag. A good test for this (although not terribly practical) would be to have a single disc mounted to a flywheel with an input shaft that you can put a dial torque wrench on. Disengage the pressure plate, rotate the single clutch disc, record the torqe reading. Do the same with the dual disc. That will give you how much work it takes to overcome the drag of each clutch.
 
just had a thought:

The dual disk setups I've seen for cars use smaller diameter components than the single disk for the same application. I'm not sure on the floater plate design they use because I've never paid attention.

Seems 2 7" disks will have a the same mass as an OE 9" after you figure in the lightweight guts in the dual.
 
just had a thought:

The dual disk setups I've seen for cars use smaller diameter components than the single disk for the same application. I'm not sure on the floater plate design they use because I've never paid attention.

Seems 2 7" disks will have a the same mass as an OE 9" after you figure in the lightweight guts in the dual.

Really? I've only personally seen 1 or 2, but they where exactly the same size as a stock clutch.. There are some crazy floater plate setups in gas engines. I just did a couple google searches and found stuff like this:

Corvette Dual Disc Clutch - Textralia LS Exo-Skel Series - FREE Shipping!


tate said:
When shfting to a higher gear, the clutch discs, input shaft, countershaft and all the gears on the main shaft will have to slow down. The mainshaft it self will maintain speed since it is directly connected to the driveshaft/axle shaft/wheels. So, for the work the synchros absorb is the speed change multiplied by its mass. The mass change between a single disc and a dual disc is a second disc, which may weigh more than twice a single (12" single to 13" dual), and a slightly heavier input for those who upgraded to the 1-3/8" input. Considering the amount of mass already spinning, the extra mass added isn't huge.

That's pretty much what I've been getting at. Valair was getting some hard numbers for us, but I think we are going to see the same thing.. There just isn't a big enough difference to justify "slower shifting." We agree on the kinetic energy measurement then?


tate said:
The bigger issue in my mind is that the single disc has more room to float between pressure plate and flywheel, allowing much more positive disengagement, reducing drag. Dual discs with a floater plate that doesn't have straps on it has no means of seperating the the two clutch discs and the floater plate, thus increasing the drag. A good test for this (although not terribly practical) would be to have a single disc mounted to a flywheel with an input shaft that you can put a dial torque wrench on. Disengage the pressure plate, rotate the single clutch disc, record the torqe reading. Do the same with the dual disc. That will give you how much work it takes to overcome the drag of each clutch.

It would be interesting to see the difference, but I'm pretty sure it would end up a mute point. There is no pressure pushing against the clutches or the floater plate. They don't have to completely disconnect from each other, they just need to move far enough to slide past. That, and the flywheel/floater is going to be dropping at a different speed than the clutches...

Now, if something failed or warped. I could easily see a big difference. If the flexplate got warm enough to warp, it would bind up and not allow it to release. That would cause major shifting issues.

And, once again, if this is the answer, we should see the same problem in every application. The gas engine guys should be having the same problem, and they should all be asking each other "why does this dual disk shift slower?" Not all of the gas engine applications have the metal tabs to pull the floater plate, either..

This is entirely my opinion so take it with a grain of salt: I noticed 0 difference between the stock clutch, the haisley with the tabs, and the SBC without the tabs. I'm certain you're not looking for opinion any more than I am, but I don't think the tabs play as big of a role as we are giving them credit for. Purely opinion.

Finally, why do only some folks report that dual disks shift slower, and not everyone? If there is a universal cause (weight, drag, clutches sticking, etc) then why doesn't every dual disk owner report slower shifting?

Tone is difficult to get through the internet, so don't think I'm talking down to anyone here. I'm just stating my opinion again: if I installed a dual disk clutch, and I noticed slower shifting, I would assume something was wrong with either the clutch or the install, and I would probably take it apart to try and find why. Since there is no universal cause any of us can come up with, I'd have to assume something wasn't "right." Just my humble opinion.
 
AWSOME READ:


Heavy Duty Clutch

And they even talk about smaller disks, just like Roachie mentioned!!

(Let's leave them alone about the centrifugal force though, eh? LOL)
 
Another great read:


Q. What are the causes of poor shifting quality or notchy shifting?

A. Poor shifting may be the result of any number of problems. Possible causes are as follows:

Improper clutch release caused by faulty linkage and/or improper release linkage adjustment.
Improperly installed shifter.
Improperly adjusted shifter or shift linkage.
Damaged transmission parts–bent shift fork.
Worn transmission synchronizer rings.
Improper transmission lubricant–check factory service manual for proper fluid type and viscosity.
Pilot bearing/bushing binding on transmission input shaft.
Clutch disc hub spring pack hitting flywheel or flywheel bolts.
Damaged or defective pressure plate drive straps.
Bellhousing misalignment.


http://www.mcleodind.com/faq.html#top_questions

I think I'm going to shoot them an e-mail and see if they have any interest in posting in this thread. Always nice to get some more expert opinion.. Even if it may prove me wrong. :D


I tried registering on their forum, but they don't like my e-mail address.. :hehe:

Here is an entire forum dedicated to twin disk clutches.. I didn't see any thread specifically about shift speed though. :(

Multi Disc Units (Street Twiin, Mag Force, RST/RXT, etc.) - McLeod Industries Forum
 
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I know most automotive units use the smaller flywheel because they cant physically fit one as large as the OEM like we can.

Hope McLeod can shed some light on this. I highly doubt that they are used to our needs LOL
 
When you engage a clutch in the real world, it slips a little and creates heat. I imagine that if you could replicate the heat during a normal fast takeoff and add some torque to really seat the grains of the friction disk into the flywheel and floater plate or pressure plate on single disk, then you could perform the torque on input shaft test to see how much torque it takes to overcome disk drag.

In my opinion, disk drag is the number one factor for shift speed. Has anyone else noticed that it takes longer to shift a single FE than a stock oraganic?
 
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