Bottom Trunnion Thrust Washers

[klm]

On the left are original steel thrust washers and a used original fulcrum pin for the bottom trunnion. I have been told that BL later changed the material of the thrust washers to hard fibre to prevent the wearing of the surfaces of the trunnion in contact with thrust washers. On the right is a replacement pin I purchased recently with two fibre washers. Should I use the original steel washers or the new replacement fibre washers?

[philthehill]

I have never come across the fibre washers but that does not mean they were never used.
I personally would use the steel thrust washers as original and so long as they are kept greased and the sealing ring is kept in good condition there should be no wear to the bottom trunnion or washer. I would suggest that you will get a greater rate of wear to the fibre washer which could result in the trunnion moving fore and aft on the trunnion pin.
The Marina/Ital which used a similar trunnion pin used the same metal washers and I have never come across a fibre washer on those either.
I note that your old trunnion pin has the screwdriver slot in the end of the pin as per original equipment. I have never been able to determine why it was put there because you can tighten the trunnion pin nuts up against each other. No doubt someone reading this will tell me why.

[bmcecosse]

I can't imagine fibre washers being used - apart from breaking up under the load - they would surely soak up water and encourage RUST!!

[klm]

Many thanks for your responses. I myself was surprised to learn that fibre washers were used on fulcrum pins. I will certainly reuse the original thrust washers and pins as they appear to be in good condition. I believe the reason for the screwdriver slot is to prevent the pin rotating when tightening the nuts. As the pin needs to be centralised during installation sometimes it is necessary to hold the pin as the nuts usually run tight on the BSF thread.

[philthehill]

Klm
The trunnion pin shown on the left of your attached photo appears to have had the case hardening worn away and should not be used as it will wear away the bearings inside the trunnion housing. The wear to the trunnion pin may have already resulted in wear to the trunnion bushes so check for play in that area.
I think that you may be right about the screw driver slot for stopping the pin rotating but there is no need to centralise the pin as the pin is not offset from the threads. The slot was omitted on later trunnion pins.

[klm]

Phil,
Thanks for your response. I noticed that there is some wear on the original pin but the trunnion bush appears ok. The pin on the right is a new replacement purchased recently and I found that the trunnion bush needs to be reamed to fit the new pin. This suggests to me that there is minimal wear on the bush. The new pins available have UNF thread whereas the original pins have BSF. Is it possible to obtain pins to the original specification?

[mike.perry]

As usual the RH side of the photo is cut off, is there a cure for this problem?

[MarkyB]

Use another browser?
That picture is hosted elsewhere, you can click on it for another view.

[Boris64]

Klm

It does look like a bit of fore/aft wear on the pin but I'm certainly no expert and there's a lot to go at

I found the link to your photo bucket, where did you get the tech drawings of the damper?

Any idea how I change the oil in there?

Good luck, thanks

Pete

[philthehill]

Klm
I have never had to ream the bushes in the bottom trunnion. I have just tried a new trunnion pin (with UNF threads) in three new bottom trunnions and the pin went into all three without having to ream. No matter the main thing is that there is no wear and the trunnion and trunnion pin have a good fit. There is a tendency nowadays to use UNF threads on the Minor front suspension components and only supply a trunnion service kit which includes the trunnion, trunnion pin, thrust washers, seals and nuts. You can purchase a trunnion pin Pt No: SUS157 from ESM separately if required. You may be able to get a BSF threaded pin from NOS advertised locally to you, on 'e' bay or from another club member. All the spare trunnion pins I have are fitted with UNF threads. You can use the trunnion pin (but not the trunnion) from a Morris Marina/Ital if they are any easier to come by in your part of the world.

[bmcecosse]

There should be NO need to 'ream' - check the pin for burrs on the ends - gently chamfer off with a file.... Why worry about UNF threads?? One less spanner to mix up........

[klm]

Pete, I found the damper drawing in a book on car suspension systems. I scanned it myself to share with others.

Thanks Phil and BMC for the responses. It is possible that the new pin I have is slightly larger than the original. I will measure the diameter and also check pins available with other suppliers.

[chrisryder]

Regarding the slot in the end, I agree it wouldn't be necessary on assembly. But could be useful when dismantling! As you'll always find dirt on the exposed threads that stops the nut coming right off.

The alternative is double-nutting the other end to stop it turning.

Are you sure the new pin you've got is a Minor one, and not just similar?

[Boris64]

klm, thanks - I'll have another dig on the web before I venture to the library

Pete

[philthehill]

The diameter of a Minor new bottom trunnion pin is 17.43mm or 0.685".

[klm]

The pin on the right is not a genuine item, a new replacement for the Minor. I measured the diameter of the new pin with a vernier caliper and it is exactly 17.0mm. The trunnions I have are genuine MOWOG and this pin does not fit. Does the new replacement trunnions have bushes with slightly larger ID?

[philthehill]

Klm
I have just measured the internal diameters of the trunnion pin bushes on three new genuine BMC bottom trunnions and they all measure 17.46mm internal diameter so your 17mm diameter trunnion pin should easily go through the bottom trunnion bushes! If it does not there must be something wrong either with your measurements or with the actual pin/bushes.
There is a floating spacer between the trunnion bushes which if not aligned with the bushes could stop the trunnion pin being pushed right through so check that it is aligned before trying to push the pin through.

[bmcecosse]

But if it IS 17mm - it's going to rattle around inside the 17.46mm bushes...... Better get the correct pin I think.. Note also that the pin can only go through the trunnion (when on the swivel pin) when the groove in the swivel is correctly aligned.

[philthehill]

I would agree with bmc; replace the worn trunnion pin with one that has the same diameter as a genuine BMC one i.e. 17.43mm.

[klm]

I just found that the 17mm pin is meant to be used with replacment bottom trunnions made in India. These trunnions have a bush diameter of 16.9mm and I was advised to 'ream' the bush to 17mm before fitting the pin. This I guess is part of going metric. I purchased the Indian trunnions and pins during a visit to Asia. They look good quality although I didn't realise that they have a different bush diameter. You are correct, the 17mm pin is loose on the original MOWOG trunnion which has a bush diameter of 17.4mm. I should now order two pins from the UK (ESM or Bull Motif). Many thanks to Phil and BMC.