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BugUser Samba Member
Joined: March 02, 2007 Posts: 29 Location: Stuttgart/Germany
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Posted: Wed Jun 04, 2008 4:10 pm Post subject: |
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Jimmy111 wrote: |
Hey great! another with visual aids.
Well not quite right. How do you explain how the oil becomes presurized after it exits between the bearing and the shim?
Note the 5mm drain hole at 7 oclock.
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Hi Jimmy,
my understanding (and what I tried to explain w/ the first picture in my last post) is that the oil pressure doesn't escape between bearing and adjacent shim. Yes, there are scallops on the bearing, but they are simply not large enough (don't reach the bearing's outer radius) to provide an escape route for the oil - they are completely covered by the shim.
They could be a direct exit for the pressure if they were milled deep enough to touch the outer edge (compare first picture in my last post). The oil then would be directly drained towards the area behind the big oil seal and finally be drained to the sump by the hole you described.
In my theory the oil is forced through the complete shim package by oil system pressure... which I think is the most sensible approach to explain the lubrication of that highly sensitive area from an engineer's stand point. As aforementioned, the presence of oil pressure in the sketched area would even explain the importance of an undamaged O-ring inside the Flywheel.
All in all a quite interesting topic to discuss
BugUser
Edit: same point as SRP1 stated, I was 10 minutes too late... |
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Jimmy111 Samba Member
Joined: October 05, 2006 Posts: 2643 Location: Wyoming
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Posted: Wed Jun 04, 2008 4:24 pm Post subject: |
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Hmmm...
ok so what you are saying is that the oil will travel between the crank and the shims in the center then exit thru the shims to the outside.
Ok makes sense
If this is correct then you are saying that it does not exit between the shim and the bearing. This means that the shim is as I said before sticking to the bearing and not turning.
So now we are down to 3 possible channels of oil flow thru the shimms. and like I daid before I think that there are only 2..
Let me think about this. |
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BugUser Samba Member
Joined: March 02, 2007 Posts: 29 Location: Stuttgart/Germany
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Posted: Wed Jun 04, 2008 4:34 pm Post subject: |
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Jimmy111 wrote: |
Hmmm...
If this is correct then you are saying that it does not exit between the shim and the bearing. This means that the shim is as I said before sticking to the bearing and not turning. |
That was not my point. Oil may very well exit between bearing and adjacent shim. But not all of the pressurized oil, just a portion of it! The rest may be forced by pressure to pass the gap between first shim and crank and then exit between first and second shim or even move further and then pass through 2nd and 3rd or finally 3rd and the flywheel.
No need for any friction surfaces to stick to each other (not letting oil through) if the oil flow from the bearing is sufficient to maintain a pressure on the insides of the shim package...
Edit:
In an ideal, lab-like scenario the speed differences between fixed bearing and rotating flywheel sides of the axial thrust package is evenly distributed over all participating contact surfaces. |
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Jimmy111 Samba Member
Joined: October 05, 2006 Posts: 2643 Location: Wyoming
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Posted: Wed Jun 04, 2008 4:41 pm Post subject: |
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Well it cant work both ways...
Path of least resistance and all. If the shim seperates from the bearing, all the shims will be pushed by pressure against the flywheel and tbe oil will exit only between the shim and the bearing because that will create the largest area of flow. |
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kadub Samba Member
Joined: November 04, 2004 Posts: 444 Location: Auburn, Wa
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Posted: Wed Jun 04, 2008 5:05 pm Post subject: |
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Just a gearhead observer opinion here (so take it with a grain of salt) but I think what the illustration shows and what Jimmy and BugUser are saying in that the oil fed to the shim 'pack' is equally destributed into each of them. The oil pressurizes a nearly 'common' area on the inside dia. of the sum of all shims (however many). And as long as an additional .001" is factored into endplay for each shim (however thick), the pressurized oil will have room to flow/lube each one.
Am I close?
Karl |
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BugUser Samba Member
Joined: March 02, 2007 Posts: 29 Location: Stuttgart/Germany
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Posted: Wed Jun 04, 2008 5:06 pm Post subject: |
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Jimmy111 wrote: |
Well it cant work both ways...
Path of least resistance and all. If the shim seperates from the bearing, all the shims will be pushed by pressure against the flywheel and tbe oil will exit only between the shim and the bearing because that will create the largest area of flow. |
If you argue like that, the whole lubrication system of an engine wouldn't work. The key should be the volumetric flow that maintains the oil pressure. If flow is sufficient and at the same time the oil pressure on the insides of the shims is greater than the pressure applied to the axial surface via throwout bearing and pressure plate, the oil should not only escape the path of least resistance (which should of course be between bearing and 1st shim), but also take the route to the rest of the surfaces...
Everything seems to be possible... but the fact that an old or crushed flywheel O-ring causes oil leakage through the gland nut (against centrifugal forces!) at least seems to support the "pressurization theory".
I'm out for today, it's way too late now for me... 2AM.
BugUser |
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HBRag Samba Member
Joined: April 29, 2005 Posts: 735 Location: Huntington Beach, CA
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Posted: Wed Jun 04, 2008 5:07 pm Post subject: |
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Just an update on how the thread got started;
Since the out come of the discussion appears to be a ways off, I decided to pull the flywheel and head over to DPR and have the crank depth cut a couple thousands deeper.
Luck would have it that Jose was on the lath turning flywheels when I arrived. He looked at the flywheel, recognized it as one of his, and took it immediately to the lath and trimmed .003" off it. When I asked him how much I owed him, he said, "Nothing. Take care of me next time".
All I can say is that I am very fortunate to live 20 minutes from DPR, and that Jose is one stand up guy. What I thought would be 2 day delay, turned out to be a 45 minute trip up the street.
...and now back to the four shim discussion...
HB |
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Jimmy111 Samba Member
Joined: October 05, 2006 Posts: 2643 Location: Wyoming
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Posted: Wed Jun 04, 2008 5:10 pm Post subject: |
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Yea Jose is a good guy. You like his shop? Just two guys and 5000 cranks |
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Nater Samba Member
Joined: June 19, 2006 Posts: 493
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Posted: Wed Jun 04, 2008 5:40 pm Post subject: |
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Great topic discussion. I am quite sure VW had many such, but the bottom line is they settled on three (3).
Carry on! |
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Blaubus Samba Member
Joined: October 25, 2003 Posts: 5153
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Posted: Wed Jun 04, 2008 5:57 pm Post subject: |
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hmmm, why do you think the type 4 return port is at 6 o'clock? why did they change this? |
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Terry Cloyd Banned
Joined: March 23, 2004 Posts: 2218 Location: Valley Center "SO CAL"
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Posted: Wed Jun 04, 2008 6:10 pm Post subject: |
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Nater wrote: |
Great topic discussion. I am quite sure VW had many such, but the bottom line is they settled on three (3).
Carry on! |
Oh my I only run two shims and no o ring and no gasket with no problems |
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Nater Samba Member
Joined: June 19, 2006 Posts: 493
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Posted: Wed Jun 04, 2008 6:17 pm Post subject: |
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Terry Cloyd wrote: |
Nater wrote: |
Great topic discussion. I am quite sure VW had many such, but the bottom line is they settled on three (3).
Carry on! |
Oh my I only run two shims and no o ring and no gasket with no problems |
Gee Terry, did you read that again after you posted it. Do you also hold your pinky out when you drink a beer? |
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SRP1 Samba Member
Joined: January 06, 2007 Posts: 4340
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Posted: Wed Jun 04, 2008 6:21 pm Post subject: |
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Jimmy, there is no constant load on the shims. The crankshaft is in a constant state of load and unload moving back and forth as conditions change, so the oil will pass threw any or all of the shims at the same time no matter the number of shims. I don't think any one shim will necessarily stop spinning nor begin to spin at any given moment, only load can dictate that. |
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bugninva Samba Member
Joined: December 14, 2004 Posts: 8858 Location: sound it out.
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Posted: Wed Jun 04, 2008 6:26 pm Post subject: |
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SRP1 wrote: |
Be honest please. I say this because I have done this many times and it has worked just fine. Not to say VW or anyone else is wrong this is just a special circumstance. |
that's rich, Steve.... really is.... especially when you insulted me over pulling the restrictor plug that i've done "many times" and it worked just fine... guess it's different when it's *your* point of view.... LOL... _________________
[email protected] wrote: |
With a show of hands, who has built over 1000 engines in the last 25 years? Anyone? |
GEX has. Just sayin |
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SRP1 Samba Member
Joined: January 06, 2007 Posts: 4340
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Posted: Wed Jun 04, 2008 6:27 pm Post subject: |
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dansvans wrote: |
hmmm, why do you think the type 4 return port is at 6 o'clock? why did they change this? |
I admit to drilling several type 1 cases for an oil return in this position, the thought was to allow a better oil return to the sump and relieve the seal of so much pooling of oil that could cause the seal to leak or weep. I don't think it helped at all to be honest. |
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SRP1 Samba Member
Joined: January 06, 2007 Posts: 4340
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Posted: Wed Jun 04, 2008 6:28 pm Post subject: |
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bugninva wrote: |
SRP1 wrote: |
Be honest please. I say this because I have done this many times and it has worked just fine. Not to say VW or anyone else is wrong this is just a special circumstance. |
that's rich, Steve.... really is.... especially when you insulted me over pulling the restrictor plug that i've done "many times" and it worked just fine... guess it's different when it's *your* point of view.... LOL... |
Is your engine a special circumstance? That is what we are talking about here. BTW I apologize if I insulted you, I need to learn to get my point of view across a little better. Sorry bought that. |
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bugninva Samba Member
Joined: December 14, 2004 Posts: 8858 Location: sound it out.
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Posted: Wed Jun 04, 2008 6:37 pm Post subject: |
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SRP1 wrote: |
Is your engine a special circumstance? That is what we are talking about here. BTW I apologize if I insulted you, I need to learn to get my point of view across a little better. Sorry bought that. |
no big deal, i wouldn't dish out insults if i couldn't take em...
to answer the question, what would "special circumstance" entail? in this case it seems to be a a need to work around a (possibly) incorrectly machined crank... so special cirucustance would actually equate to needing a shortcut or way to compensate... as far as the restrictor plug, i'd guess all the engines i pulled that thing out of were special circumstance because i never had any of the (potential) problems with those....
my vote, for the OP of the thread is that you really only have two options in my mind... either maching the crank, or use more than three shims... the shim thing has been debated nearly as much as a thermostat on a vw... some say three, exactly three, and no other way... i subscribe to this, but probably because that is what was beat into my head...others say, at least three, but more is okay(and actually this is the first thread i can recall where it went in depth enough to actually have the critical information of additional oil clearances, so thanks guys for that, the archives will have more information now)..... then in one thread that i recall another poster(can't remember who) that is familiar with old porsche engines pointed out that the porsche of the era used a single spacer/shim....... who knows...i do know you can't go wrong with three...hehe _________________
[email protected] wrote: |
With a show of hands, who has built over 1000 engines in the last 25 years? Anyone? |
GEX has. Just sayin |
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SRP1 Samba Member
Joined: January 06, 2007 Posts: 4340
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Posted: Wed Jun 04, 2008 6:51 pm Post subject: |
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The difference I think is the fact that I don't make this a daily habit to install or recommend the use of 4 shims. Pulling that restrictor plug from a case seems to be your constant build practice. I merely pointed out an option for this circumstance that works and is viable, maybe not "by the book" but still viable non the less. |
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Terry Cloyd Banned
Joined: March 23, 2004 Posts: 2218 Location: Valley Center "SO CAL"
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Posted: Wed Jun 04, 2008 6:59 pm Post subject: |
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Jimmy111 wrote: |
Hey great! another with visual aids.
Well not quite right. How do you explain how the oil becomes presurized after it exits between the bearing and the shim?
Note the 5mm drain hole at 7 oclock.
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Jimmy that's a drain hole and has zero pressure. It goes into the case at a 45 degree angle. |
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bugninva Samba Member
Joined: December 14, 2004 Posts: 8858 Location: sound it out.
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Posted: Wed Jun 04, 2008 7:25 pm Post subject: |
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SRP1 wrote: |
The difference I think is the fact that I don't make this a daily habit to install or recommend the use of 4 shims. Pulling that restrictor plug from a case seems to be your constant build practice. I merely pointed out an option for this circumstance that works and is viable, maybe not "by the book" but still viable non the less. |
i understand... and until you had a problem like someone is suggesting can/will/might happen using four shims, it's an option when needed.... same here, i've always pulled the plug as have others...honestly, always knew the plug was "different" but never knew why, nor had a reason to try and find out... i've also never had the problems that have been brought to light as potential issues... not everone does things the same, and really folks sharing ideas is wonderful and a great resource and what makes these forums great... insulting each other is just a bonus...haha _________________
[email protected] wrote: |
With a show of hands, who has built over 1000 engines in the last 25 years? Anyone? |
GEX has. Just sayin |
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