Moon plates / cv washers what's the story.

[alex g]

Can anyone give me an explanation why these are used. or some history behind them??



Cheers

[h100vw]

They are just washers AFAIK Al.

[Stuwey]

They're locktabs more than washers yeah?

Lock up your bolt/nut/fastner then knock the side over to stop the bolt vibrating loose. This happened a lot on my brothers' old Alfasud. Sudden rattle, folled by the 'thump' when the driveshaft fell off...

[h100vw]

Never seen them knocked over Stuwey, for one they are like 2.5mm thick and two the CV bolts are spline drive and the heads are round. You can't tell that from the photo though.

Gavin

[alex g]

Yer really puzzled me , still does ,it's not like the tension needs to be spread out either as the casting is sufficient to deal with anything a m8 bolt can muster.
The plot thickens.

[OEM G60]

Joined to stop the washer turning as you tighten the nut/bolt??

[h100vw]

Best plan Al is to just fit them and forget all about them.

Gavin

[alex g]

Yer just gotta find some 100mm variety Gav, for a reasonably price that is.

[Jace]

Maybe to help prevent the head of each bolt shearing off? One strengthening the other?

Dunno, i understand what i mean.

[ryana89]

It spread's the torque of the bolt head over a larger area? Than individual washers?
:S

[roccodingo]

Maybe to help prevent the head of each bolt shearing off? One strengthening the other?

Dunno, i understand what i mean.

I would say most likely correct, Socket head cap screws ( torx etc) and other higher strength fasteners are usually made with a rolled radius under the head, the plate or washers allow clearance for the radius as to not bind on the item being clamped together. There exists a greater chance of fastener failure if the radii under the head is interfereing with the bore of whatever is being held together.

Check the head bolts on your VW head, hardened washer to give clearance , spread the load and minimise galling of the alloy head.

HTH.

Just had a quick read of Carroll Smith's nuts, bolts ... - Google Books

And he says that its purely spreading the bearing load of the fastener. You should get a copy and have a read Al, good book along with the rest of his literature 'thumbup icon'

[alex g]

I would belief that that radius would actually aid the tension as it's an increase in surface area ala countersunk hardware. Having said that that still doesn't explain the paired format.

Maybe

[alex g]

Finally a definitive answer, I just saw the solid state and mass of the flange not to benefit from such load spreading, and come to think of it the torque numbers aren't that high.

Yer will have to check that one out.

[Peter Jones]

The CV boot flange it's bolting to is pretty thin. if a bolt or washer rotated against it it would likely tear or buckle the metal.

Might would be a way to stop the bolts ripping up the flange, preventing the grease having any way to get out.

[Jace]

They just look ****ing awesome.