Author Topic: Silent bloc  (Read 882 times)

Offline Norsa1

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Silent bloc
« on: 27.10. 2014 09:44 »
I am just about to undertake the removal and replacement of bushings in the swingarm. 
Can anyone suggest a method to remove the existing bushings?

Offline bsa-bill

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Re: Silent bloc
« Reply #1 on: 27.10. 2014 10:10 »
Pay someone to do it  *smile*

It can be a pain, I drilled out as much of the rubber as possible, the middle sleeve will then press/knock out.
then cut the outer sleeve long ways as far as you can (padsaw or better air type hacksaw), then collapse it in on itself and knock or draw it out
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online terryg

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Re: Silent bloc
« Reply #2 on: 27.10. 2014 12:25 »
I burnt out the rubber using a blow lamp. Then, as noted above, carefully hacksawed a slot in the bush outer sleeve ( pad saw, of course) and drove a thin steel spike between the sleeve and the s/a to collapse it.
The second one came out quicker, as usual.
Terry
'57 'SR', '59 SR, '63 RGS

Offline Norsa1

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Re: Silent bloc
« Reply #3 on: 27.10. 2014 17:11 »
Is there a shoulder inside the housing? If I use a saw to cut through the outer case would that cause damage to this inner shoulder

On another note what is the purpose of the rubber bushing? Should this design be a solid bronze bushing?

Online beezermacc

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Re: Silent bloc
« Reply #4 on: 27.10. 2014 17:38 »
There is a very good method on the www.cheshirebsa.co.uk website. basically drill down the rubber with a drill slightly under a quarter inch, I think their website says 1/4" but 7/32 might be better to avoid scoring the inside of the swinging arm as well. You'll be able to tell how close to the swinging arm you are as soon as you start drilling because you can see the end of the sleeve. Using the correct drill size is important. The drill should be big enough to score the inside edge of the outer sleeve so, after burning out the rubber the outer sleeve collapses. I've used this method a number of times and it works well, no drama! When pressing the new bush in you need to be aware that the inner sleeves butt up against each other when properly fitted. It's a good idea to press them in with the swinging arm spindle in place so the bushes line up, i.e they don't miss each other at the join or you'll have problems fitting the spindle later. Also be aware that the spindles don't always fit the bushes supplied (Wassell again!). Check before fitting. I have to skim them out on the lathe before supplying (PITA). Rubber bushings are commonly used on car suspension and were an improvement on previous bronze bushes which needed greasing and still wore out progressively.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline bsa-bill

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Re: Silent bloc
« Reply #5 on: 27.10. 2014 18:07 »
It seems some S/As do have a shoulder halfway along, others don't, mine certainly does.
It amazed me that they last so long when I heard how they work, basically the same as a torsion bar on a cars suspension, the rubber takes the twist so they need to be tightened up in the position that the arm will be in when ridden normally ( one rider or two ).
Get someone to sit on the bike while you pull up the cross tube nut
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online beezermacc

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Re: Silent bloc
« Reply #6 on: 27.10. 2014 18:14 »
I think they need to be tightened up in the 'at rest' position, I. e. bike on stand otherwise the rubber is under stress when the bike is not being used which is 99% of its life, rather than 1% of its life, which would rapidly decrease the life of the silentbloc. Also, the tension in the rubber is intended to assist the suspension, I think. Maybe others think differently...here goes !
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Online terryg

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Re: Silent bloc
« Reply #7 on: 27.10. 2014 19:27 »
Mine did have a shoulder but with a new hacksaw blade the outer sleeve cut quicker than I expected. It's only mild steel, after all.
 'Pay someone to do it'?  Why would I want to do that?
Terry
'57 'SR', '59 SR, '63 RGS

Offline bsa-bill

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Re: Silent bloc
« Reply #8 on: 27.10. 2014 23:13 »
Quote
'Pay someone to do it'?  Why would I want to do that?

intended as jokey comment Terry *smile*

Quote
the tension in the rubber is intended to assist the suspension
Think that is what I said " basically the same as a torsion bar on a cars suspension,"

Quote
I think they need to be tightened up in the 'at rest' position,

yes I see the logic beezermacc although I've read otherwise a few times - debatable maybe *conf*

All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online KiwiGF

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Re: Silent bloc
« Reply #9 on: 27.10. 2014 23:34 »
http://www.a7a10.net/forum/index.php?topic=4293.msg31755#msg31755

Lots of infoi and pics on that thread...might be useful?



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Online muskrat

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Re: Silent bloc
« Reply #10 on: 28.10. 2014 10:11 »
DOH. *conf*
Both Richard and I just put posts on that one.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline unclerob

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Re: Silent bloc
« Reply #11 on: 28.10. 2014 11:43 »
Replacing the silent blocs was the first major job I ever did on the first A10 I ever owned and despite it being over 40 years ago I can still clearly remember thinking that they were too big to fit in the swingarm and was convinced I had the wrong parts....after watching me struggle for some time one of the more experienced mechanics did most of the work for me!
He also pointed out that there was nothing at all wrong with the original bushes (before I'd butchered them anyway) and the reason for the MoT failure was the oval hole worn in the mounting....!
I can understand that the idea of mounting a suspension component this way seems a little imprecise but in my experience it does actually work very well, granted most of that experience is with cars but, for example, if you were to replace the 8 silent blocs on say, Triumph Spitfire front wishbones, with the much harder pu bushes now available you definitely notice the change is not for the better and if you used solid bushes I would imagine the car would be very unpleasant to drive....so some degree of compliance is a good thing!
Also, and again from car experience, its very rare to ever see any evidence of the inner sleeve turning on the mounting bolt, its far more common for them to be totally seized together....
One last thought, I suspect that the method of actually bonding the rubber to the steel is not as good as it once was in some instances, and though it would be hard to notice on an A10 I have seen it happen more often nowadays on cars where the part is more visible....

Online Triton Thrasher

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Re: Silent bloc
« Reply #12 on: 28.10. 2014 18:17 »

He also pointed out that there was nothing at all wrong with the original bushes (


I hope Norsa1 considers that.