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Thread: 7 1/4" triple disk clutch

  1. #21

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    Quote Originally Posted by Pinnacle View Post
    Great info Jeff, what was done and by whom when you "refreshed" the box ? Did you refresh back to stock parts and config ?
    I sent the box along with the new bearings and synchros I bought from Jetstream to Terry Haines of Haines Motor Sports. Terry's fee was very reasonable, and his extensive experience gave me the confidence to hand the gearbox over to him. He was also a pleasure to chat with.

    Jeff

  2. #22

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    Clutch update and question for the Nobility.

    It has not worked out as well as I had hoped for, but it is going to work. The issue we all have is that the transmission input shaft is very short, and the enhancement drugs don't work. It's easy to get the hub for a single disk clutch onto the input shaft splines, but the splined length is so short that it's hard to get 3 disk hubs completely engaged.

    The trick disk set shown below gets me close. I've measured everything multiple times on different days, so I'm pretty sure that I'll end up with somewhere between 0.9" and 1.0' of spline engagement. However, the hub splines are 1.2" long. All 3 clutch experts told me to go ahead and run this setup. The only limitation may be that uneven wear of the hub splines causes clutch release to get funky before the disks are worn out.

    Question: Are you interested in a triple disk clutch for your car?

    The upsides are:
    (1) excellent torque capability, 900 lb-ft for my 7 1/4" triple disk set
    (2) very light
    (3) much lower moment of inertia than the typical single or twin.

    The downside is that they are not the cheapest option. Steve at Powertrain Tech said that he'd be interested in doing a custom flywheel for the Noble that would fix the lack of spline engagement problem. He would offer a package comprising the flywheel, pressure plate, disk set, and release bearing that is designed to be bolt in. Obviously, though, he'd only do it if there was enough interest among the Nobility to offset his R&D time.

    Regarding cost, I don't know. I'll have about $1700 in mine, which required a made-to-order release bearing adapter and 3 different companies making their profit. Post here, or shoot me a PM or email if you are interested.

    Disclaimer: The only thing I stand to gain from this is a triple disk clutch that fits perfectly, rather than one that fits sorta. I have no stake in any of the manufacturers I've mentioned in this thread.





    Jeff
    Last edited by NobleM400; 05-07-2012 at 06:46 PM. Reason: typo

  3. #23
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    Hi Jeff

    The splines on my clutch exactly fit the splines on the gearbox to the mm... someone has sold you something that is different.

    I will get my clutch and flywheel back from balancing at the weekend so I will do some precise measurements and then you can establish what is not right in what you have bought... I checked and agree with your figures for the gearbox figures for the splines with the spare I have in the garage so we can rule gearbox differences out

    In the meantime why dont you just get powertrain to contact superclutch in the UK and strike a deal to provide the correct clutch the same as mine... seeing as mine is a powertrain item and fits with the flywheel you have (assuming its same as mine) with full spline engagement I see this as a far better solution that developing a whole new clutch package.

    Rgds
    Andy

  4. #24

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    Andy, I've compared the picture of your clutch with mine - I think they are the same. The hub has 1.2" of female splines, the input shaft has 1.3" of male splines, so the clutch will slide all the way onto the input shaft with the transmission sitting on the floor. But the Jetstream flywheel does not locate the clutch deep enough in the bell housing.

    The sketch below demonstrates the problem. The input shaft ends 1.63" from the spacer plate that sits between the engine and the transaxle. The clutch disk hub ends 1.35" from the spacer plate. There is (1.63 - 1.35) = 0.28" of hub spline that is not engaged by the input shaft.

    We need another flywheel that pushes the clutch assembly 0.28" deeper into the bell housing so that the input shaft fully engages the clutch disk hub. The 1.38" dimension in the sketch needs to be at least 1.66".

    Also, Steve at Powertrain Tech did not want me to run a flat release bearing. The diaphragm spring fingers are flat, not cone shaped like a stock clutch. The flat fingers need a cone shaped release bearing to get the right geometry. A flat release bearing is not going to push on the tips of the fingers over the full stroke. As you press the clutch pedal, the fingers are going to form a reverse cone, so the flat release bearing contact point will move away from the tips of the fingers. A cone shaped bearing will always contact the tips.



    Jeff

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    My twin disc set up from Hoover has an aluminum spacer mounted on the flywheel. Looks like that is what you need, but I am no expert.

  6. #26

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    I talked with Craig Hill about making a spacer last week. That's kind of a hack, though. I'd rather have the flywheel made so that the clutch is positioned correctly. We just need to move the friction surface 3/10 of an inch away from the engine.

    Jeff

  7. #27
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    Hi Jeff

    Your sketch below shows your clutch/flywheel assemble differs from mine... looking at it the splines within the clutch plates are not offset as much as the splines for each disc are all gearbox side of their center line... I need to measure them but it looks like it is over 10mm different.

    I stress again that with the clutch and flywheel my clutch splines actually come to 1mm from the inner sleeve on the slave cylinder when all in place... so slide the clutch on the gearbox as far as it will go and that is the possition that it stays when bolted up, It seems you do not believe me on this fact so this is the last post I will make other than to post the dimensions at the weekend so you can find your difference if you wish to.

    Understand what you are saying about the slave release bearing... the shape I have used has been used with my clutch in mid engine cars since 2000 and is in hundreds without an issue... will look into your cover but my one is reliable, light and effective.

  8. #28

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    I'm looking forward to your dimensions, Andy! If you measure 3.10" from the spacer plate to the back of the clutch cover, we probably have the same cover. If your fingers are inset 0.32" from the cover, we can assume we have the same pressure plate. The crucial measurement in my mind is the distance from the cover to the end of the splines. Mine is 0.55" as shown in the sketch. I'm guessing yours must be about 0.25", which means the hub extends through the fingers a little bit.

    My sketch is not to any scale, it's literally a sketch done in Visio. It's just a way to visualize the measurements.

    Jeff

  9. #29

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    Another update in case anybody is interested. The first set of disks I got included two with an offset hub, meaning that the hub is flush with one face of the disk, and sticks out passed the other face. Typically, hubs are centered. I put the offset hub disk against the flywheel and measured the distance from the spacer plate to the end of the hub closest to the transaxle. Measurements taken at 3 different places all were 1.87". The distance from the spacer plate to the end of the input shaft is 1.63". That means (1.87 - 1.63) = 0.24" of the hub is engaged by the input shaft.

    The hub splines are 0.5" long, so only about half of the hub spline is engaged, the other half is hanging off the end of the input shaft. I'm still thinking the flywheel friction surface needs to be pushed 0.3" closer to the transaxle.

    Andy, I really wondering how yours is different. In the meantime, here is a new sketch showing the offset hub measurements and a couple of pics of the disk with the offset hub:







    Jeff

  10. #30

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    I'm going to button everything up today, so here's one last pic to demonstrate why I wanted the triple in the first place. I had forgotten how HEAVY the factory setup is!



    Jeff

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