Locking Plates Question

[stableblock]

Hello, can someone satisfy my curiosity. 

There are at least two areas on these cars where Lancia have used 'locking plates', under the flywheel bolts and under the driveshaft bolts. 

There arent any tabs or spring action on these, they appear to be flat pieces of steel and I am curious to understand where the locking action comes from.  Can anyone shed any light on this?

I do see that the driveshaft plates will help keep the relatively thin boot top hat flat and sealed but the thin flywheel plate wont add any value in that department.  I have read online about incidents when the flywheel plates were ommitted so I expect they do something.

thanks

Peter

[peteracs]

Hi

I am guessing they prevent rotational movement which could happen with a simple washer?

Peter

[SanRemo78]

I would agree with Peter. I had an incident when fitting an engine built by the late Guy Croft into a Hawk Stratos (many years ago). It arrived as a full drivetrain so was a simple fit but required plumbing in. On first start up it was fine for 20 seconds and then a death rattle that turned out to be a missing flywheel lock plate. An easy fix once identified but a day to remove and refit the engine. It ran just fine once the plate was fitted and retorqued.

[WestonE]

The Plate is essential with the flywheel as are new bolts. I was told long ago by GC how it works, but old age means I have forgotten.

[stableblock]

Thanks All
I agree plates are essential.  Just curious to understand why a separate plate is different to the face of the flywheel.  I can see a simple washer could rotate  but the flywheel is rigid between the bolt holes as is the cv boot sleeve.  One of lifes mysteries?

Peter

[peteracs]

Hi

Maybe they are viewed as sacrificial. Ie the tightening of a turning bolt could damage the flywheel surface whereas any problem with the plate is an easy replacement ?

Again just a guess

Peter

[stableblock]

That would make sense except that I doubt the bolt removal rate for most engines is that great.  I suspect the clue is in the name but I am guessing too.