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Silentbloc bushes for swinging arm

Submitted by peter_holland1 on Wed, 31/05/2023
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Nortons - General

I've been asked to source some swinging arm bushes for Lightweights. They look pretty similar to some I've seen on a popular auction site for Norton Featherbed. Are they the same? Suspect S/A spindle on Featherbed is greater than 7/16 ins diameter.

Perhaps someone can tell me if the 7/16 inner bore bushes are the same as other bikes of the era. Obviously Francis Barnett, having the same frame type, used the same bushes, but I'm not aware of a spares scheme for these bikes.

The lightweight bush has the following dimensions and marks.

Inner bore 7/16 ins.

Outer diameter 7/8 ins

Inner length 2.75 ins (2 3/4 ins)

Outer length 2.625 ins ( 2 5/8 ins)

Marked ......Silentbloc B20523.

I haven't found any yet.  Photo attached.

Would be grateful for help.

Peter 

 

Attachments
Lightweight SA bush.JPG

Submitted by tony_ripley on Wed, 31/05/2023

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Hi Peter,

 

Might be worth talking to these people:-

 

https://villiersservices.co.uk/product/metlastic-swing-arm-bush-small-early-type/

Dimensions are: length of outer 38mm, length of inner 44.5mm, od 22.3mm, Id 11.2mm. Greeves part number M/A101

Diameters are ok but the length is wrong, they may be able to point you in the direction of the manufacturer.

Your requirements:

Inner bore 7/16 ins. = 11.11mm

Outer diameter 7/8 ins =22.22mm

Inner length 2.75 ins (2 3/4 ins) = 70mm

Outer length 2.625 ins ( 2 5/8 ins) = 66.675

 

Regards

 

Tony

Submitted by alastair_coventry on Thu, 01/06/2023

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Featherbed spindle and bush are  larger therefore not the same as Lightweight. Try Robush Ltd if you are looking to source a quantity. They list 11.1mm ID 22.2mm OD up to 44mm as standard but they may be able to supply longer as at least they have the stock raw material. G.

Submitted by david_cooper on Thu, 01/06/2023

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Is it in order to ask why they need changing?  It's well known to be a vile job with little if any benefit.  Isn't it?  I bought some for my Dommie years ago, but they are still in a box after I inspected the old ones and thought better of it.

Submitted by john_ward1 on Thu, 01/06/2023

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Is there any point in looking at changing the rubber bushings for line reamed bronze bushes or even needle rollers? 

Submitted by barry_carson1 on Thu, 01/06/2023

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hello,

featherbed swing arm bushes i measured.

external tube diameter = 30.17 mm

external tube length     = 72.42 mm

..............

internal tube. internal diameter = 12.70 mm

internal tube length  = 79.27 mm

think it said clayflex, on them.

 

barry

Submitted by peter_holland1 on Thu, 01/06/2023

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Thanks Alastair,

I think Robush will give me a quote. Helpful company. They are looking.

David,

I absolutely agree with you. The bushes last for ever. Until you send them through the powder coating process. Melt polyester and you cook the rubber. Obvious to you and I but alas not to all.

Ashley,

AMC classic spares had a good look today but nothing doing. No bushes at Fanny B owners club either. Worth a try though. Thanks for the suggestion.

Barry,

Thanks for confirming the featherbed bushes are different. I had hoped against all logic that that L/W bushes might be the same.

I have two companies working on quotes. It appears that once upon a time these imperial bushes were a catalogue item and in stock, but time has moved on in 50 years.

Thanks all

Peter 

 

Submitted by david_cooper on Fri, 02/06/2023

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Lots of people have reported no issues with powder coating temperatures.  Have yours already been ruined?  Rubber is very difficult to destroy.  (There is always paint...)

No David,

On mine the hand painted black enamel is looking well and the 60 year old bushes are functioning well.

On a total restoration of a Navigator I did for a fellow member I removed the bushes and masked all holes with studs and washers. The swinging arm was then blasted, acid dipped, primed and then final powder coat. Finishing off in the oven. The original bushes went back in fine.

I work for the NOC spares scheme and it appears that we need to find bushes to keep the Norton's on the road. A praiseworthy aim of the club, I feel, which I give my time to.

And thanks again to all those above who took time out to help too.

Peter

 

Submitted by ian_richtsteig on Fri, 02/06/2023

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There should be no problem powder coating swinging arms with silentbloc bushes fitted.

I have done 10 with no failures.

The key is knowing your powdercoater.

He needs to know that the bushes are fitted.

Any powdercoater can adjust the cure schedule to allow for the bushes.

It's lower temperature but longer cure time.

When I worked in these plants, I have had lines curing powder from 180C to 400C with the cure time adjusted accordingly. 400C was to maximize the production volumes.

 

 

Submitted by peter_holland1 on Sat, 05/08/2023

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No secret that the NOC are keen to help find these elusive swinging arm bushes.

As your volunteer a quick update.

No new bushes to the AMC dimensions to be found. Anywhere.

Redesign using sleeves, bushes, new spindle with greaseways and nipples considered and rejected. Partly because alignment and roundness of swinging arm mounts not good enough, but is OK for compliant Silentbloc rubber bushes.

Dimension and tolerances agreed with a manufacturer after fitting tests with a swinging arm, using machined test pieces.

And an order has been placed. 

Naturally, I carry a certain risk. Was my swinging arm sample typical? Certainly the two mounts were of slightly different bore size. Disconcerting.

Will the customers expect to just bash them in or use a press tool of some sort? Appreciate they can't push on the inner bush?

In the event the customer's S/A mount is oval or small, I expect the relatively thin outer to shrink or distort. Will take some pushing in.

Time will tell. I hope I've done a proper job and the bushes coming mid/end August will be OK.

I would advise anyone removing or replacing these Silentbloc bushes to use M10 threaded rod and some suitable pushing pieces and tube. If you don't know what I mean, seek help from a friendly engineer rather than hammering away with a trusty socket.

I would like to trial install a few before general sale, so possibly a delay but will then be in a position to advise buyers. 

And if they don't fit.........push harder or squash your S/A mount a bit oval in the vice.

Perhaps 

 

Submitted by barry_carson1 on Sat, 05/08/2023

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hello

on my 19s single down tube i couldnt find any swing arm bushes at the time that would press in. i ended up trying 3 different sets of bushes, they all just pushed in with you finger. got in touch with one of the sellers they said thats the correct part number they should fit. it must be my swing arm worn. i told them i tried them in all three swing arms i had, and they just push in. i got no reply.so left it at that.

 looked in my tool box and spotted a land rover spring shackle bush, tried it in the swing arm looked to be a good fit external wise but the internal measurement was bigger plus the bush length was smaller. anyway i had a spacer made up to take up the difference plus had a spindle altered to fit but that ment drilling the frame for it to fit .i didnt want to do that so just made up the different internal diameter with stainless tube straight through the lot, then fitted the original bolt. i only did it until i could get some bushes that press in then i will change it back.

 

barry

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