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Featherbed swinging arm bushes

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Featherbed swinging arm bushes

Posted by brian_sheekey at December 01. 2015

how can I remove swing arm bushes please.

Re: Featherbed swinging arm bushes

Posted by paul_webb at December 01. 2015

The silentbloc bushes are a real pain to remove. I have tried a number of ways over the years but I find burning the rubber with an oxy torch or similar till the inner bushes fall out then carefully with a hacksaw blade slit the outer part and with a long sharp edged drift hammer each of them out from the opposite side. 

Good luck. Paul.

Re: Featherbed swinging arm bushes

Posted by Bruce Mitchell at December 01. 2015

I had mine removed with a 10 ton press, even then it was a challenge.

Re: Featherbed swinging arm bushes

Posted by robert_tuck at December 01. 2015

Are you sure they need to go?, They do seem to be almost indestructable in use.

Re: Featherbed swinging arm bushes

Posted by Jonathan Soons at December 02. 2015

Previously robert_tuck wrote:

Are you sure they need to go?, They do seem to be almost indestructable in use.

Let me guess. The spindle has rusted solid in the bushes. Right?  I had to burn mine out for that reason.

Re: Featherbed swinging arm bushes

Posted by robert_tuck at December 02. 2015

I seem to remember mine was like that in1986 so I painted it all with the SA in situ ,Its  still working perfectly. Good luck with finding the right new bushes.Some wrong ones about.

Re: Featherbed swinging arm bushes

Posted by brian_sheekey at December 02. 2015

Previously Bruce Mitchell wrote:

I had mine removed with a 10 ton press, even then it was a challenge.

Thank you for your information have decided to leave well alone.

regards Brian

Re: Featherbed swinging arm bushes

Posted by brian_sheekey at December 02. 2015

Previously robert_tuck wrote:

Are you sure they need to go?, They do seem to be almost indestructable in use.


I will leave alone. thank you .  Brian

Re: Featherbed swinging arm bushes

Posted by brian_sheekey at December 02. 2015

Previously robert_tuck wrote:

I seem to remember mine was like that in1986 so I painted it all with the SA in situ ,Its  still working perfectly. Good luck with finding the right new bushes.Some wrong ones about.

 

Am going to leave well alone.  thank you

Brian

Re: Featherbed swinging arm bushes

Posted by lionel_yexley at December 05. 2015

They will even stand stove-enamelling without damage! I had my frame and S/A done.  The main prob seems to be that the spindle seizes on the bearings such that the S/A isn't free to rotate but uses the bonded rubber as a kind of spring.  Still works OK though! I was thinking of putting a grease nipple in the S/A.

Re: Featherbed swinging arm bushes

Posted by robert_tuck at December 05. 2015

Hi Lionel, I think the spindle is not designed to turn in the tube so if its seized its still works as god intended. The Rubber does it all.

Re: Featherbed swinging arm bushes

Posted by David Cooper at December 11. 2015
As Robert says - when the spindle is tight, the nuts squeeze the central steel tube and from then on the design requires the rotation of the arm to twist the rubber. Which is why the books say you are supposed to have someone sitting in the saddle when doing up the nuts so that as the rear wheel moved up and down on the road the extreme positions are similar both ways so the extreme stress is smallest. Rubber springs bonded to steel are used in shear all over the place in industry - from bridge bearings, train suspension systems to 'Indespension' units in trailers and caravans. Zero maintenance and very long life and very stiff radially but flexible in shear - just not quite as radially stiff as needle rollers etc. and they might shear side to side also (in theory). Don't oil or grease them or the rubber will rot. The three things that ruin rubber are ultraviolet light (not much sunshine down there...), ozone, and oil (but they are quite thick and mostly protected behind steel). (On reflection - maybe boiling in oil would get the rubber out - eventually?)

Re: Featherbed swinging arm bushes

Posted by Jonathan Soons at December 11. 2015

Does anyone know of a bronze bush conversion I could copy?  I prefer to make all the bits myself.  Can the Commando system be adapted to the featherbed?

Re: Featherbed swinging arm bushes

Posted by james_brierley at December 11. 2015

Previously Jonathan Soons wrote:

Does anyone know of a bronze bush conversion I could copy?  I prefer to make all the bits myself.  Can the Commando system be adapted to the featherbed?

Mike Hughes at Royton Road and race does a neat conversion, (see attached) It costs £89 for the bits or £107 fitted. It does require machining of the sides of the swinging arm to get it to fit but I suppose you could use the same basic design without having to.

Personally, I'm thinking of the rather tasty Alloy box section swinging arm that he also supplies, to complement my Norton Cafe racer project, as it takes the BSA/Triumph conical hub. I just hope the wife's let Father Christmas know that that's what I want for Christmas.   

Products - Royton Road And Race

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Re: Featherbed swinging arm bushes

Posted by laurence_king at December 11. 2015

Hi Jim

I have an alloy swing arm in cupboard, never used, had a lot of grief over getting it made!  If interested  let me know

I had a steel one made by the guy I asked to remove my silentbloc bushes, he trashed the arm in process and gave me a good deal on new one!

This is a lot lighter than alloy but I suppose it might twist more with mega ergs

Laurence

Re: Featherbed swinging arm bushes

Posted by mark_savage at December 11. 2015

I've got a swing arm ready to try in this winter that Royston R&R have worked on. Mike gets one of his mates to take the old bushes out with a horizontal borer. I'd heard they were hard to get out so I thought that £18.00 wasn't a lot of money to save the hassle.

Re: Featherbed swinging arm bushes

Posted by Jonathan Soons at December 12. 2015

Previously Jim Brierley wrote:

Mike Hughes at Royton Road and race does a neat conversion, (see attached) It costs £89 for the bits or £107 fitted. It does require machining of the sides of the swinging arm to get it to fit but I suppose you could use the same basic design without having to.

Products - Royton Road And Race

 

That's exactly what I want. I wonder if the spindle can be made in one piece.

Re: Featherbed swinging arm bushes

Posted by james_brierley at December 12. 2015

Previously Jonathan Soons wrote:

 

That's exactly what I want. I wonder if the spindle can be made in one piece.

I think you would be better off making it with two stub tubes as the photo, as each end is flanged. Also it would be easier to get the end float right and assemble, after you have manoeuvred the swinging arm into place through the frame.

Good luck with the project.

Re: Featherbed swinging arm bushes

Posted by mark_savage at December 12. 2015

What is the advantage of having the Manx type bushes over the standard silent block type?

Re: Featherbed swinging arm bushes

Posted by james_brierley at December 12. 2015

Previously mark_savage wrote:

What is the advantage of having the Manx type bushes over the standard silent block type?

Well, they're expensive, they wear out, they require continuous maintenance but they do give you a feel good factor.

The silent block bushes are just boring. They do the job and last forever.

Unless you ride like Michael Dunlop, you would probably never know the difference.

Re: Featherbed swinging arm bushes

Posted by lionel_yexley at December 13. 2015
Previously David Cooper wrote:
As Robert says - when the spindle is tight, the nuts squeeze the central steel tube and from then on the design requires the rotation of the arm to twist the rubber. Which is why the books say you are supposed to have someone sitting in the saddle when doing up the nuts so that as the rear wheel moved up and down on the road the extreme positions are similar both ways so the extreme stress is smallest. Rubber springs bonded to steel are used in shear all over the place in industry - from bridge bearings, train suspension systems to 'Indespension' units in trailers and caravans. Zero maintenance and very long life and very stiff radially but flexible in shear - just not quite as radially stiff as needle rollers etc. and they might shear side to side also (in theory). Don't oil or grease them or the rubber will rot. The three things that ruin rubber are ultraviolet light (not much sunshine down there...), ozone, and oil (but they are quite thick and mostly protected behind steel). (On reflection - maybe boiling in oil would get the rubber out - eventually?)
I'm surprised at yours and Robert's comments on how they are supposed to work. I am very familiar with metal/rubber bonded items in cars. "Metalastik" is the most common brand in British cars, but they are often used in the way that I have said. This rubber is to reduce vibration and make a softer suspension/transmission - as with Jaguar cars with which I am very familiar - from the road to the driver everything is insulated by rubber. Most often the bushing allows rotation, such as in suspension wishbones. As a retired Civil Engineer I also know the properties of rubber when used in shear and as a general rule I would avoid it due to its limited lifespan before perishing. As a former Bridge Engineer/Inspector I am also fairly knowledgeable about bridge bearings. In my experience they are normally used in compression, although longitudinal expansion will put them into shear, but that is not their primary loading. The same goes for vehicle engine mountings. I think that a fully rotational S/A rubber-bonded bush will still be effective and cannot see the need for the spindle to be "fixed" to the bushes. Hence people going for bronze bushes I presume - giving free rotation? I agree with the comment about not using oil-based products with 'rubber' but most modern rubber has oil-resistant additives. I.e. it's not natural rubber. Alternatively you could lubricate with a silicon grease.

Re: Featherbed swinging arm bushes

Posted by james_brierley at December 13. 2015

Previously lionel_yexley wrote:

I think that a fully rotational S/A rubber-bonded bush will still be effective and cannot see the need for the spindle to be "fixed" to the bushes. Hence people going for bronze bushes I presume - giving free rotation? I agree with the comment about not using oil-based products with 'rubber' but most modern rubber has oil-resistant additives. I.e. it's not natural rubber. Alternatively you could lubricate with a silicon grease.

 

The swinging arm spindle when tightened, firmly clamps the frame gussets to the inner steel bush that is bonded to the rubber bush. Therefore there is no 'free' rotation and consequently no need for any form of lubrication other than an anti seize grease to prevent the inner bush seizing onto the spindle.

Re: Featherbed swinging arm bushes

Posted by David Cooper at December 14. 2015
Thanks Jim....as you say..the nuts squeeze the gussets against the inner bushes. Lionel... most reinforced concrete bridges of moderate spans sit on rectangular rubber bearings. There must be thousands of them under UK motorway bridges. They are very stiff vertically but they shear sideways typically by something in the order of 50mm on a thickness of maybe 100mm to allow the bridges to shrink with age and to expand and contract with temperature. BS 5400 part 9 gives design criteria. Free on Highways England web site. They last for decades. Indeed I have failed to find any evidence of failures from my colleagues. (Bridge engineer over 40 years).

Re: Featherbed swinging arm bushes

Posted by lionel_yexley at December 16. 2015
Previously David Cooper wrote:
Thanks Jim....as you say..the nuts squeeze the gussets against the inner bushes. Lionel... most reinforced concrete bridges of moderate spans sit on rectangular rubber bearings. There must be thousands of them under UK motorway bridges. They are very stiff vertically but they shear sideways typically by something in the order of 50mm on a thickness of maybe 100mm to allow the bridges to shrink with age and to expand and contract with temperature. BS 5400 part 9 gives design criteria. Free on Highways England web site. They last for decades. Indeed I have failed to find any evidence of failures from my colleagues. (Bridge engineer over 40 years).
Thanks David - been there, done that, got the T-shirt! When inspecting bridges/structures as an engineer, my area covered the A31 from Bere Regis to J1 of the M27; All of the M27; A3 & A3(M) to the M25; south end of the M3; M4 from M25 to Junc. 15; A404(M); A329(M) and others as required, so I do know my job! Regardless of what you have read in any specs, most of the standard concrete beam bearing pads do not shear anything like 50mm because they are usually sub-25mm thick in the first place, designed for simple bearing loads. Composite steel/rubber bearings are much thicker and are similar to the items we are talking about. In any case I didn't say that bonded bearings fail easily or at all - my 1959 S/A bearings have withstood stove-enamelling! What I am puzzled about is the need to have them in shear - indeed I would see an advantage to allowing free rotation, as they would be if bronze bushes were used. The rubber part with these types of mounting is primarily there to provide vibration insulation.

Re: Featherbed swinging arm bushes

Posted by David Cooper at December 17. 2015
I think that's the point - rubber bearings end up being designed to move a great deal further than they really do in practice. But the swing arm is much the same - the actual amount of angular movement is quite small, so the rubber strains are quite small most of the time. Which is why it's a good idea not to tighten it until it is roughly in its mid position. If the spindle is tight then it must squeeze the gusset plates against the central bush. If it is not tight, then the bush could slip and rotate back and fore against the gusset plates and eventually wear holes in them. And of course if the nuts aren't tight, they would fall off in the road. There is no provision to oil the spindle inside the steel bush inside the rubber bush - and not many designers would run steel on steel anyway. I cannot remember off hand but I think the shear movement limit used in design is a distance of about half the thickness of the rubber. If the bush is has about 6mm of rubber, that allows about 3mm of circular movement at a radius of maybe 20mm. So at about the length of the swing arm of perhaps 400mm, that allows an extreme movement of roughly 400/20x3 = 120mm up (or down). That's a total of 10 inches overall range, which is plenty. But it also suggests why modern bikes use 'proper' bearings because they want a lot more movement than the old Featherbed gives us. So they would need thicker rubber and the back wheel would wobble about all over the place.

Re: Featherbed swinging arm bushes

Posted by malcolm_baker at August 30. 2017

I've seen a video somewhere, possibly you tube, but I can't relocate it, does anyone know where it is in the great wide web ??

Re: Featherbed swinging arm bushes

Posted by David Cooper at August 30. 2017
Is this it? https://www.youtube.com/watch?v=jC2xmp15WZ0 But he does not remove the outer sleeve because he re-uses it without bonding to it - it seems to be a generic system that seems to claim to substitute an alternative product for what looks like a very similar duty. No idea if it would work...or if it's available in a suitable standard size, or if it would be stiff enough.

Re: Featherbed swinging arm bushes

Posted by Andy MacKenzie at September 03. 2017

When I bought my '65 Atlas from a club member who had rebuilt it from the ground up to a point where it was on the road, MOTed and had been used a bit, but needed finishing touches like proper chrome tank badges rather than the odd alloy ones fitted.  He owned an Inter and seemed knowledgeable, so i assumed he knew what he was doing - oh, how naive........

As I worked my way round the bike after getting it home, some things started to ring alarm bells - swinging arm play being one. To cut a long story short, I stripped the bike and amongst the horrors, found metric pistons in imperial bores, 2 broken valve springs, a 7" front wheel spindle instead of 7 3/8" (the nut was on by about 2 threads) and the swinging arm?  New bushes had clearly been fitted, but without the spacer between them - doh!

I ended up taking the swinging arm to Dave Degens and he cut off most of the cross-tube, and attached a larger diameter one to take taper roller bearings on a 5/8" rather than 1/2" spindle. Apart from the slightly larger spindle nuts and approx. 3/8" rearward positioning of the swinging arm, it is an invisible mod.  he had wanted me to junk the swinging arm because he said that they are far too flexible, but I wanted to maintain a standard look as much as possible.

The bike is not on the road yet (far from it!), so I have yet to find out how the new bearing arrangement and ever so slightly increased wheelbase works in practice.

Andy

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