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TBF clamp fix offer - long

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Old 03-06-2005, 10:00 PM
  #31  
bigs
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Constantine -

So I presume the purpose of the flex plate is to compensate for the tiny amount of driveshaft "shortening" that occurs due to twisting under sudden, hard acceleration by flexing "backwards" toward the rear of the car.

This would allow some "give" in the drivetrain components at that location to prevent relaying of the shortening force directly to the crank, which was Vilhuer's concern. Am I understanding things correctly?
Old 03-07-2005, 07:07 AM
  #32  
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From what we can tell, yes. These are also used in other applications, to include the marine industry.

Constantine

Originally Posted by bigs
Constantine -

So I presume the purpose of the flex plate is to compensate for the tiny amount of driveshaft "shortening" that occurs due to twisting under sudden, hard acceleration by flexing "backwards" toward the rear of the car.

This would allow some "give" in the drivetrain components at that location to prevent relaying of the shortening force directly to the crank, which was Vilhuer's concern. Am I understanding things correctly?
Old 03-07-2005, 02:40 PM
  #33  
Drmark
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Constantine - I have since come across 4 TBFs in the UK and have posted your fix here! Just one other question - you say oil warning during extended trips can be the only sign (fien during short trips) - is that the low pressure or low level warning... and why?
Thanks
Mark
Old 03-07-2005, 07:58 PM
  #34  
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Hi Dr Mark,

The low oil pressure warning is what will be seen *sometimes* since the engine block is compromised and the oil will not flow like it should through the oil channels as well as the fragments from the thrust bearing also blocking the channels. What will be noticed more in the later stages is the deep knocking sounds from the engine. That would be the crank counterweights hitting against the engine webbing. That's what I heard in the 928 with known TBF that I drove.

There have also been reports of people driving their car a while, shutting their car off, and then trying to restart the car while it's still hot. The 928 will not turn over and start until it cools off since the engine tolerances are way off kilter.

Hope I answered your questions.

Regards,
Constantine

Originally Posted by Drmark
Constantine - I have since come across 4 TBFs in the UK and have posted your fix here! Just one other question - you say oil warning during extended trips can be the only sign (fien during short trips) - is that the low pressure or low level warning... and why?
Thanks
Mark
Old 03-07-2005, 08:23 PM
  #35  
rob rossitto
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great research! so are the older equipped cars (w/the circlip), "immune" to the shaft creep, or is it just less pronounced or limited a bit (ie still an issue?)?

thx!
Old 03-07-2005, 09:08 PM
  #36  
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Hi,

The circlip, washer, and bearing at the end of the driveshaft would not let the driveshaft get pulled through the clamp. But, one thing we learned is not to say any 928 is "immune" from TBF, even 5-speeds! Although that is very rare.

It was ironic that when Porcshe decided to discontinue using these parts sometime in 1984, they also upped the HP/TQ significantly on the 85 and up cars worldwide.

Cheers,
Constantine

Originally Posted by rob rossitto
great research! so are the older equipped cars (w/the circlip), "immune" to the shaft creep, or is it just less pronounced or limited a bit (ie still an issue?)?

thx!
Old 03-08-2005, 05:34 PM
  #37  
rob rossitto
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my 85 AT/US has the clip, FWIW... lot's of "irony" on these machines if you look deeply enough...
that's a chunk of metal - how's the balance? or should I get the TT balanced with the the new "super clamp"?
what time frame are you anticipating for delivery? (mine is out waiting for stroker motor wrap-up, so if I do it, it would have to be pretty soon, as my lack of patience is only exceeded by my ignorance)

thx again!
Old 03-08-2005, 09:40 PM
  #38  
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Hi Rob,

No need for balancing, it is balanced as is and the circumference of the weight is small. You will not notice it's there.

Don't know about time. Probably a month or more out once I place the order. The manufacturer would have to get geared up to make the clamp and it's a bit of work to make. But this whole thing might be a moot point since I have not come close the the 25 needed.

Kind regards,
Constantine

Originally Posted by rob rossitto
my 85 AT/US has the clip, FWIW... lot's of "irony" on these machines if you look deeply enough...
that's a chunk of metal - how's the balance? or should I get the TT balanced with the the new "super clamp"?
what time frame are you anticipating for delivery? (mine is out waiting for stroker motor wrap-up, so if I do it, it would have to be pretty soon, as my lack of patience is only exceeded by my ignorance)

thx again!
Old 03-09-2005, 05:03 PM
  #39  
rob rossitto
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thx again! sounds like a good item for a big 3 to stock....hint, hint...
Old 03-09-2005, 05:08 PM
  #40  
bigs
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Originally Posted by rob rossitto
thx again! sounds like a good item for a big 3 to stock....hint, hint...
I was wondering the same thing. Have you talked at all to any of the major 928 suppliers? This may be an item that not everyone wants (or can afford) right now, but if they could be manufactured, then stocked for future sale, it might make more sense.

And it would seem one or more of the major suppliers would be the logical choice to at least talk with.
Old 03-09-2005, 05:18 PM
  #41  
Bill Ball
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I agree with bigs. Trying to find 25 takers via Rennlist for anything at one point in time, be it stroker cranks, cam cover bolts or this, is highly unlikely. These clamps will sell over time. The Big 3 should be able to buy enough to meet the MOQ. I know that asking them to assume some risk, but they do it all the time already and that is why we appreciate and use them. Am I off-base?
Old 03-09-2005, 09:20 PM
  #42  
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I agree with you three! But I already asked one of the Big Three and he could not afford to stock 25 at one shot, too much invested in inventory. Made sense to me really. I guess if they heard about this and people made some noise about them stocking such a product it would be helpful.

I, as I'm sure other makers of specialty parts for the 928, will never recoup my costs on this venture. I did it since it was a challenge to do and I learned quite a bit about the 928 AT driveline. Would be great for this to get out to owners to use and potentially save 928 engines.

Kind regards,
Constantine


Originally Posted by Bill Ball
I agree with bigs. Trying to find 25 takers via Rennlist for anything at one point in time, be it stroker cranks, cam cover bolts or this, is highly unlikely. These clamps will sell over time. The Big 3 should be able to buy enough to meet the MOQ. I know that asking them to assume some risk, but they do it all the time already and that is why we appreciate and use them. Am I off-base?
Old 03-09-2005, 09:50 PM
  #43  
rob rossitto
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don't think any single distributor would want to shoulder the entire load, but a few here, a few there...25 doesn't seem that high if you agree to not sell direct/compete for sales to end users so they can make a $$ or two, and there are orders pending w/them from the gang already... just has to be structured to make sense for them, and they have to feel comfortable w/the technology, IMO...

ps - selling starts with the 1st objection/concern - if you can effectively deal w/it, you are on the road to success for all...
Old 03-10-2005, 01:33 AM
  #44  
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If the MOQ stays at 25 after the first order, then yes, there is a problem. If the Big 3 each took 8 (and I took one, as I offered already), then the part gets made. What happens when one of the Big 3 gets low and needs to re-order? I saw that problem when I agreed with bigs, so I left that out. If the MOQ is 25 then one needs to assume the risk for the whole lot or it won't work.
Old 03-10-2005, 07:42 AM
  #45  
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Hi Rob,

Sounds good to me. Like I said I'm not into this line of work and would rather let the Big Three sell this clamp to 928 owners. Would make sense since as you three said, people can buy them as needed. I have no interest to compete against anyone in selling this.

Thanks for the kind words at the end of your message. There have been many cool products made for the 928 owners, many by 928 owners themselves. Can't think of belonging to a better enthusiast group!

Constantine

Originally Posted by rob rossitto
don't think any single distributor would want to shoulder the entire load, but a few here, a few there...25 doesn't seem that high if you agree to not sell direct/compete for sales to end users so they can make a $$ or two, and there are orders pending w/them from the gang already... just has to be structured to make sense for them, and they have to feel comfortable w/the technology, IMO...

ps - selling starts with the 1st objection/concern - if you can effectively deal w/it, you are on the road to success for all...


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