Bent Clutch Diaphram fingers, how does it happen?

phaeton

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Jan 2, 2012, 11:13:28 PM1/2/12

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A friend of mine's gf has a VW Jetta (fully manual transmission), I
think an 05 or around that vintage. He goes to 'rescue' her because she
can't shift out of 1st gear- depressing the clutch doesn't disengage it,
and once she pulls it out of gear she can't put it into any other gear
with the engine running.

So he took it apart, and the fingers for the pressure plate were bent.
This isn't the one he pulled out of his VW (some random web pic), but it
looks pretty much like this:

http://imageshack.us/photo/my-images/293/0410091553.jpg/sr=1

He put in a clutch kit (also converted the flywheel from dual-mass to a
standard solid one) and the car drives like a dream. Better than
before, actually (none of us like the dual-mass flywheel). But we're
both baffled as to:

1) How the springs can get bent suddenly. The car drove just fine right
up until the point when it didn't. This isn't a slow-onset condition,
like it got worse and worse due to metal fatigue.

2) How the engine torque is *not* removed from the transmission input
shaft, even though putting the clutch to the floor has normal
resistance, you can see the little arm on the bellhousing pulling the
throwout bearing to disengage position, and such. The 'connection'
between engine and clutch was very positive- you could drive the car up
a hill with the clutch pedal to the floor and no slippage.

3) In spite of the pressure plate being toast, everything else in the
clutch assembly looked ok. It all had normal wear on it but it's not
like the whole thing was trashed.

What say you, sirs?

thanks

-J

Steve W.

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Jan 1, 2012, 11:39:59 PM1/1/12

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That isn't bent fingers. It's a broken wave spring inside the cover.
They get metal fatigued, cracks start and then you press the pedal and
they break through. When they break the fingers drop and you have no clutch.

--
Steve W.

jim beam

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Jan 2, 2012, 1:21:31 AM1/2/12

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what he said.

--
nomina rutrum rutrum

hls

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Jan 2, 2012, 10:33:50 AM1/2/12

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"Steve W." <csr6...@yahoo.com> wrote in message news:ozaMq.54326>

> That isn't bent fingers. It's a broken wave spring inside the cover. They
> get metal fatigued, cracks start and then you press the pedal and they
> break through. When they break the fingers drop and you have no clutch.
>
> --
> Steve W.

Interesting. Do you think the metal fatigue is intrinsic with this type of
spring application, or do they just use poor metallurgy, manufacturing
technique, etc?

hls

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Jan 2, 2012, 10:38:32 AM1/2/12

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"Steve W." <csr6...@yahoo.com> wrote in message

news:ozaMq.54326$cN1....@newsfe12.iad...

Re Wave Spring failure

Should have looked this up before I asked.
http://www.smalley.com/engineering/spring_design_performance.asp

jim beam

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Jan 2, 2012, 4:00:57 PM1/2/12

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there's a good deal more corrosion on that than you'd typically want to
see. most likely therefore, failure is rust pitting initiating fatigue.

that said though, they could have better protected the spring, so
production spec and manufacturing definitely contribute.

--
nomina rutrum rutrum