[Cloud9...68]

[quote name='Monstrous4Banger' timestamp='1335111158' post='125893']

This is why I have a spare one with no slit on the shelf.

[/quote]



Smart move - hold onto it - could be worth serious money some day...

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[MB968]

[quote name='flash' timestamp='1335105335' post='125882']

thanks - yeah - glitch in the software. i'll record that here accordingly.



i am really trying to figure out where they changed it. the slit is a fairly serious design complication. while it reduces resonance, it also reduces the ability to retain concentricity. this presents itself as a real problem if you introduce things that will cause deflection, such as higher output engines, or repeated hard shifting, as in the case of track use, both of which would be seriously increased when in conjunction with a single mass flywheel.



a solution is in the works, but it isn't going to be cheap.

[/quote]



Have you considered just beefing up the area just where the bearing sits. Placing a ring or the like around that area and thus eliminating the slit right at the bearing. Since torsion is additive (it is a linear function with length) beefing up one or two areas won't have a very significant effect on the torsional stiffness. You could eliminate say 3 inches of the 20 inch split, and the torsional stiffness of that section (not the whole tube which would change even less) of the TT would only go up by 17.6%. And since the natural frequency is proportional to the 1/2 power of the stiffness, you'd see even less of a change in the torsional natural frequency. So, you may be able to keep some of the isolation created by the split tube, while actually beefing up the area that the bearing sits, making it even less suceptable to issues than the solid TT.

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[tamathumper]

[quote name='MB968' timestamp='1335141496' post='125933']

...Since torsion is additive (it is a linear function with length) ... the torsional stiffness of that section ... would only go up by 17.6%. And since the natural frequency is proportional to the 1/2 power of the stiffness,...

[/quote]

I'm impressed with your knowledge of physics! It just leaves me feeling like:

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[flash]

of course that was considered. the problem is that there is no way of doing that, and still being able to install bearings. you can't weld the slit, as you can't control the inside diameter well enough as the steel expands and contracts from the welding. the best you could do is clamp it, and even that allows some movement. i had a tube all set to go, but when they installed the shaft, even after bonding the bearings in place AND clamping it, the bearing moved. not good.



a solution is in the works, and being done by the best in the business, but it won't be easy or cheap.

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[Monstrous4Banger]

Ill be holding on to it....cause its going in the 968 with super bearings when I do the engine build.

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[Monstrous4Banger]

http://www.blacksear...11&limitstart=2



The Black Sea R&D Solution

We initially tried to pin our 944 Super Bearing within the split area and thought we had done a good job. Unfortunately the 944 Super Bearing was pinned at an angle and came apart in the exact same way as the original bearing insert. This necessitated another fix which could capture the front 944 Super Bearing concentrically within the torque tube so this problem would not happen again.

After some initial designs and testing we designed a fix which alleviated all the problems of other possible fixes and which positively captured the front bearing unit in the middle of the 944S2 torque tube.

This is a picture of the finished solution. It is not easy to execute correctly since the torque tube can be further damaged in attempting this fix during the welding process. The end result worked as designed and we believe it is an elegant solution for this problem.

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[flash]

yeah - that's what they tried on the one i was going to exchange with them (they weren't aware that 968s had both kinds of tubes either). when i first called, they said they had a 968 tube, and i figured i could have them do that one, while i yanked mine and sent it, saving me at least a week.



they got it all done, and it didn't work as well as they wanted it to. they were pretty bummed. they were going to bail on the job because they didn't think it would hold up to what i was going to put it through. i had to respect that. very professional. i then took a look at mine (i should have done that in the beginning) and found it to be a solid tube. that made them much more comfortable.



there is an upgraded fix in the works though. they were determined to work it out. i'll see if i can get more info on it. they were working on it when i decided to go with the solid tube.



the fix shown above would be fine on a stock car though, and probably even for a supercharged car with a DMF, but not a car with a single mass flywheel, and certainly not a single mass flywheel and a supercharger. p.s. that job is over $1000 plus shipping. great work though.

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[MB968]

[quote name='tamathumper' timestamp='1335142386' post='125935']



I'm impressed with your knowledge of physics! It just leaves me feeling like:

[/quote]

Not helping me much right now with my wife's Subby. Today it decided that if would give one cylinder a break and run on only 3 of the 4 cylinders.

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[Monstrous4Banger]

Yeah mines gonna run a bit North of 1k. Im in norcal right now, my 951 is in phoenix still at the shop. Im just paying them to drop it, and send it to Constantine. I too have been impressed with their dedication, and progress. Without their research, this Porsche breed could become extinct prematurely, seems to me anyway. The TT used to be the one structural grey area so to speak once upon a time. The more of us increase power, and the older they become, seems many would fail, and basically total out a lot of cars. The only other real choice is buying a new one from Porsche. Thats no fix for us with gobs of power though. 1500 bucks to just have to replace it again soon....no thanks. So far Constantine has been great to deal with. I expect the end result to be superb.

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[flash]

lol - i just priced out a new one for the 968. a whopping $3k and there are only 3 of them, and all in germany.

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[Monstrous4Banger]

Holy crap....that has doubled since I last checked....that was for the 951 though.

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