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Trunnion Repair Kit

Posted: Mon May 21, 2018 5:20 pm
by scimjim
They should be the same on the one side - they are offset to the front or rear of the car to accommodate the difference in trunnion angles so both sides should be offset the same way (front or rear depending on PAS or non-PAS).

If you look at the numbers above, the LH brackets on a PAS car (211306 Qty 2) are the same as a RH brackets on a non-PAS car.

Trunnion Repair Kit

Posted: Tue May 22, 2018 10:28 am
by spegru
Thanks that is what I expected but what I seem to have is this
Left hand side of left wishbone
2018-05-22 09.06.25.jpg
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Right hand side of left wishbone
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2018-05-22 09.06.33.jpg (177.01 KiB) Viewed 522 times
The left one has its mounting bolts offset to the left but the right hand one is offset to the right. Thus if I swap with the other wishbone it will presumably make no difference. If I swap front to back I can alter the spacing between the mountings by about 1 inch which will mean the wishbone itself wont fit any more!

Is there more to this than the mounting bolt offset?

Note that I only raised this because when I refitted the new trunnion / kit it was difficult to get the top ball joint to go in - but it seemed out of line by about 7mm....

Trunnion Repair Kit

Posted: Tue May 22, 2018 10:34 am
by scimjim
Presumably the other side is equally wrong?

If so, you need to swap side to side.

PAS needs the bolts offset to the rear - so currently, your LH rear bracket is correct.

Trunnion Repair Kit

Posted: Tue May 22, 2018 11:22 am
by spegru
Thanks. Yes the other side is the same. As far as I can tell the car was made this way albeit with manual steering.
I cant' see how the wishbone will fit with the both brackets offset to the rear though. I do not think there was that much slack (~1") in the spring plate.

I presume the intention of all this side to side swappery that also includes the top wishbone, is to increase caster angle, which increases the unassisted weight/effort of the steering - without which PAS would make the steering effort too light and floaty
Do you by any chance know what the caster angle is actually meant to be?

Trunnion Repair Kit

Posted: Tue May 22, 2018 11:24 am
by gtcse8
11 degrees

Trunnion Repair Kit

Posted: Tue May 22, 2018 1:00 pm
by scimjim
Yes, manual is 4 deg, PAS is 11 deg. The trunnions sets the angle but of course it can be moved slightly by brute force and/or ignorance as you’ve found. You’ll need to slacken everything off to allow it to reseat properly.

It’s highly unlikely that the car was built like that - a previous owner has refitted them incorrectly.

Trunnion Repair Kit

Posted: Tue May 22, 2018 3:08 pm
by spegru
Ah Scimjim thanks for the comment about the LH Rear being correct, as it's being a pain to get off. The problem is with so many of the nuts on this car is that they were never very deep and now the rust has attacked them too so there's hardly anything to get hold of. Just to avoid all doubt it's the bolts that are offset to the rear so actually bracket is offset to the front thereby making the upright lean backwards more (which is essentially what caster angle is)
Odd that it should be wrong on both sides though why would they even have come off? The only reason for me doing it is the PAS conversion.

Those caster figures sound about right - similar figures to an electric PAS conversion we did on a Dutton last year - had to remake the lower wishbone in order to increase from ~3deg to about 9. Actually it would be quite something to get rid of all this trunnion stuff on the Scim and go to proper ball joint lower arms/wishbones with adjustability

On the wishbone width question it does not seem quite as bad as I had feared even though I am sure the mounting concerned will have moved by nearly 1". A trial fit shows that I just need a few mm of slack in the wishbone plate.

Trunnion Repair Kit

Posted: Tue May 22, 2018 3:12 pm
by gtcse8
Getting rid of Trunnions has been discussed to death over the years, I once looked at making new uprights that accepted the top ball joint and a lower swivel.

Could not get them done at a reasonable price so shelved the idea.

Trunnion Repair Kit

Posted: Tue May 22, 2018 3:15 pm
by scimjim
Yep - bolts to rear.

GW designed a ball joint system but never went into production. TBH I don’t understand why anyone would want to change to a system that fails every few years (assuming you replace the rubber gaiters which also fail regularly in normal use) and was only designed to reduce build costs - they certainly don’t reduce long term costs?