Moulton TSR rear pivot

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rogerzilla
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Re: Moulton TSR rear pivot

Post by rogerzilla »

I measured that mine, which is currently slop-free, has a minuscule clearance of about 0.1mm (4 thou) on each side, which is about the same as a nice sliding fit for a seatpost.

Thinking about it, the outside of the bushes is a bearing surface too, because the rear triangle will not sit perfectly centred, and the sleeve will wander from side to side within the bushes within its minimal clearance. I think the inside of the "ears" is painted, so you have paint as a bearing surface. Yuck. This reinforces the advice to grease frequently - the grease that oozes up between the bushes and the "ears" is just as necessary as that between the sleeve and the bushes.
fastpedaller
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Re: Moulton TSR rear pivot

Post by fastpedaller »

Without expensive tools. Plan to face ends of tube..... Careful use of a file or wet/dry paper could do it...... maybe abrade with 600 grade (just one 'pass') so that it leaves uniform scratches over the face, then use a finer grade to just remove the scratches evenly, so should still remain square, flat and true
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

gazza_d wrote: 15 Apr 2021, 4:03pm I've read previously in the Moulton club instructions for servicing the rear suspension http://www.moultonbuzz.com/resources/te ... /apb-rear/
It is advisable to get a new pivot bolt, sleeve and pair of phosphor bronze bushes before starting a full overhaul. It is a good idea to service the rear suspension on a yearly basis if the APB is in regular use

1. The TSR doesn't have phosphor bronze bushes.
Oil Filled Bronze Bushes: Made in a variety of styles from bronze, graphite and several other metallic powders formed to shape by the sintering process and then soaked in oil.
Phosphor Bronze bushes are entirely different.

2. The bushes wear, and the bolt and the sleeve do not wear at all.
3. It's advisable to buy new bushes from Simply Bearings at a fiver a pair, and skim them less than 30thou off in a lathe.
4. Service (and by that I mean grease it) rear suspension monthly, and certainly not as long as annually.
5. The APB, I know nothing about, but this thread is about TSR bushes. Perhaps the APB rear pivot is different.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

rogerzilla wrote: 15 Apr 2021, 4:34pm ............... advice to grease frequently - the grease that oozes up between the bushes and the "ears" is just as necessary as that between the sleeve and the bushes.
I agree with this.
fastpedaller wrote: 15 Apr 2021, 5:31pm Without expensive tools. Plan to face ends of tube..... Careful use of a file or wet/dry paper could do it...... maybe abrade with 600 grade (just one 'pass') so that it leaves uniform scratches over the face, then use a finer grade to just remove the scratches evenly, so should still remain square, flat and true
I agree with this too.

Going to chat to my engineering mate tomorrow evening socially distancing in the beer garden. I'll be taking my iPhone and showing my piccies. I'll put it to him about my idea to trim the frame so it'll take standard bushes.
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gazza_d
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Re: Moulton TSR rear pivot

Post by gazza_d »

Mick F wrote: 15 Apr 2021, 8:39pm 5. The APB, I know nothing about, but this thread is about TSR bushes. Perhaps the APB rear pivot is different.
It is essentially the same design for the pivot they just changed the location. The TSR is a refined APB after all. The APB pivot design itself is lifted from the AM so has been substantially unchanged now since the early 80s.

The APB bushes are a little bit longer and there's no grease nipple. The APB pivot is behind the bottom bracket and protected from muck etc by the BB unlike the TSR pivot which is directly in the firing line. The nipple is an addition that should prevent the need for regular strip down and regressing.

I think the description of the material is possibly incorrect as true phosphor bronze seems to be not an off the shelf product unlike the oilite bushes available for a few quid. There's a comparison here [http://www.getyourbearings.co.uk/oilit ... onze.html]. Over the years I've bought and fitted APB bearings from the factory and off the shelf from simply bearings, and the off the shelf are the same size and fit without any need to machine down to a specific flange thickness. The off the shelf bushes don't ride or wear appreciatively differently
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

Good Morning guys.
I woke early - as usual - and suddenly thought of a good idea.

Buy five new bushes - that's two pairs plus one.
Remove the rear triangle and remove the sleeve.
Measure accurately the overall width. Width A.
Replace the sleeve and remove one bush with the grease-gun idea.
Remove the sleeve again.
Clean out the inside.

File the parallel section diameter of one of the new bushes so it's a nice finger-fit into the frame.
Measure accurately the overall width again. Width B.
B minus A is how much needs to come off the side with the finger-fit bush.

Trial and error will get B to equal A as well as the finger-fit bush to sit snugly. Softly-softly catchee monkee .......... slow but sure and take your time.
Clean out all the swarf and filings.
Fit the sleeve and fit the rear triangle to check all is well.

Take off the rear triangle and remove the sleeve.
Remove the finger-fit bush and drive out the other bush having removed the grease nipple.
Fit a new bush into the side you've just filed.
Fit the finger-fit bush into the other side check that Width B is the same as before.
Remove it and file that side as per the first side.
When B equals A again, Bob's your uncle.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

gazza_d wrote: 16 Apr 2021, 6:34amI think the description of the material is possibly incorrect as true phosphor bronze seems to be not an off the shelf product unlike the oilite bushes available for a few quid. There's a comparison here [http://www.getyourbearings.co.uk/oilit ... onze.html]. Over the years I've bought and fitted APB bearings from the factory and off the shelf from simply bearings, and the off the shelf are the same size and fit without any need to machine down to a specific flange thickness. The off the shelf bushes don't ride or wear appreciatively differently
Thanks Gazza.
This suggests that Moulton made a cock-up by having to machine the bushes.
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gazza_d
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Re: Moulton TSR rear pivot

Post by gazza_d »

That was my thought as soon as I got and compared the stock bushes to the Moulton TSR ones. I'm not an engineer but I cannot see any advantage in a marginally thinner flange.

Presumably easier and cheaper to trim the bushes than redesign the frame and adjust the tooling etc.

What we need is a tame SST owner to measure their bush and flange as that pivot has supposedly been refined further. I would not be surprised if the bushes are stock sizes again.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

From what you say, it wouldn't surprise me either.

The more I think about this idea of modifying the FRAME instead of the bushes, the more I like it.

Said before, that I'll be chatting to my mate down the pub this evening, but instead of showing photographs, I'll remove the rear triangle again, remove one bush and the spindle, clean it all up, and take it with me.

Fifteen minute job to do. It takes longer putting it all back on and re-threading the cables and adjusting the gears! It's worth it I reckon.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

rogerzilla wrote: 15 Apr 2021, 2:38pm Mick, was the paint already cleaned off the ends of the tube?
It's all stripped down, and one bush out, ready to take down the pub this evening.

Show and tell eh? :D

As you can see, no paint.
IMG_0516.jpg
Mick F. Cornwall
rogerzilla
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Re: Moulton TSR rear pivot

Post by rogerzilla »

Is there paint on the inside of the rear triangle "ears"? That doesn't really affect clearance - unless the sleeve digs right in - but it will rub against the bushes.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

Yes, there is. Both sides.

IMG_0517.jpg
IMG_0518.jpg
Mick F. Cornwall
rogerzilla
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Re: Moulton TSR rear pivot

Post by rogerzilla »

You can see how the bush wears it a bit there. I wonder if it would move a bit better with the paint cleaned off (to the diameter of the bush)? It won't rust as it'll be slathered in grease.
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

Good idea maybe.
Five minutes with emery or something. Can't do any harm.

One anomaly I noticed, is that all the four angled connections where the centre bolt goes through to hold the two halves together, have no paint. It must mean that the frame halves were joined together during the painting process. It's not paint that's been removed, but a place the spray gun never got to.

Similar subject, why is the frame number only on the front half?
It can only be that they are a matched set ....................... or am I wrong?
Can the rear half of one TSR properly and correctly fit with the front half of another TSR?
Perhaps not.

It's only when you look at how the five bits of the frame and forks are made, you realise why they're so expensive.
(1)Rear triangle, (2)Rear section, (3)Front section, (4)Steerer and fork, (5)Suspension fork.
Are they all made as a complete bike, or can we mix and match ALL the bits?
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Mick F
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Re: Moulton TSR rear pivot

Post by Mick F »

We need five like-minded TSR owners to get together to swap bits. :D :D
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