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.
