Clutch Preasure Plate Repair

[Frank.61]

Andy,

If you could be so kind, aks the old man what material he used for brazing the pressure plate.
There are a couple of options there and I'm curious -as always- which one he did use.

Frank

[Frank.61]

Oh, and I don't think the springs have anything to do with it: the plate is fixed to the aluminium back pressure plate pillars once the bolts are tightened.
Also checked my springs and they had all exactly the same length, 41mm.
Still my steel pressure plate has 3 out of 4 welds cracked (right in the middle of the welds).
I wanted to ask a material specialist if this was due to fatigue or else.
If your old man says it could be due to different materials, I tend to believe him.

Frank

[Mc tool]

I thought both bits were steel ,but anyhow if that was really the issue it wouldnt take 30 years to show up . I think that its down to a thin steel plate that obviously flexes during use and we are looking at metal fatigue ( very common on things that have seen a bit of use a probly a bit under spec in the 1st place ). Probly should have been braced ( washer) or made out of thicker plate and welded right round . I aint so sure that if sticking with the same thickness plate as original it still wouldnt crack round the edges of that set up either . The steel plate and pin look a bit half arsed ,Im not that surprised it gives trouble .

[Frank.61]

Mc tool,

Yes they are both steel, but I thought a cause could be different alloys.

But in the meantime I've asked a professional welder and his first/immediate reaction was: "that is the work of a layman, most likely autogenous welded without adding any metal. Almost sure that the crack is just a shrinkage crack (due to lack of adding sufficient metal)".

He said that the fact that it is a longitudinal crack right in the middle of the weld together with a very thin and superficial weld gives it away.
"Just carefully grind the remaining weld away clean it and weld it properly and done".

According to him it is very likely that those cracks started to appear quite early on (he said the cracks would appear even if they were left on a shelf without additional stress.).

Well then we know that again.

Frank

[Mc tool]

When I consider things like the possiblity that uneven springs could have an effect I think about the extreme , like what would happen if you removed 2 adjacent springs ,and Im sure that would cause the pressure plate to lift unevenly ,so if all the springs were fitted and 2 adjacent one were weak if must have an effect, although how much could lead to a whole nother bun fight. I have a friend with an old Triumph and he disengages the clutch and puts a dial gauge on the pressure plate and then shims the springs so the pressure plate is even at full lift ....he dont care about even pressure when clutch is engaged . Its the same but different.
The cracked welds makes sense ,some of them welds may not even survive cooling down according to your welder . Ha , had to laugh when he sez " the work of a layman" Im thinkin well yeah , its Italian made . :-)

[AndyK]

Andy,

If you could be so kind, aks the old man what material he used for brazing the pressure plate.
There are a couple of options there and I'm curious -as always- which one he did use.

Frank

Hi Frank, I saw him yesterday and he used Sifbronze 101 because he had some in stock but Sifbronze No1 would also work.

Hope that helps, Andy

[Frank.61]

Thx Andy.
That's what I wanted to know!
Please keep us informed if it stays in 1 piece.

Frank

[AndyK]

Sometimes coming back to this site is like meeting an old friend or even a lover.
The clutch is fine, there was a little bit of "Pulse" on the lever initialy but that faded over mayby 3 - 4 days of town traffic and it's been sweet ever since