The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: smartsx1x on 21.06. 2018 17:45

Title: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 17:45
Hi i'm new to this board thank you for letting me join
having bought a goldflash 1959 i soon found out that all that glitters is not necessarily gold,
so i am in the process of removing 9 peoples worth of hobby time from the engine etc,
my question is has any one thought about shimming the outer race on driveside roller bearing this would eliminate the need to fit those flimsey shims that i hear alot of horror storys about,the outer race would only stand proud an extra .05mm i would remove .05mm from the outer race protruding side to keep a good gap from crankshaft to allow oil flow ,the inner roller has a lot of clearence to the outer edge so dont see any problems .
has this been done before ? your thoughts advice would be appreciated
regards martin  *smile*
Title: Re: I have an idea re: shims
Post by: Greybeard on 21.06. 2018 18:25
Hi Martin  *welcome*
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 18:46
cheers
ps 62mm od shims same as bearing od available on a well known website
Title: Re: I have an idea re: shims
Post by: berger on 21.06. 2018 19:33
hi and welcome, *welcome* the answer from me is no. the inner race must be tight up sandwhiching the shims to the web by means of the engine sprocket sleeve etc. if you do it the way your thinking it will tend to dance with vibration causing problems. my two penneth anyway. edit,

 engine sprocket bearing I keep calling it a sleeve cos well, to me  its long like a sleeve
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 19:36
thanks for advice
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 19:54
just looked at it again i see what your saying but the sleeve would push inner race tight up against crankshaft and the .05mm clearence would be taken out by shimming outer race the only thing i can see might need extra shim to lift cus drive cog up to align up with clutch
with respect thats how it looks to me i could be wrong  *conf*
Title: Re: I have an idea re: shims
Post by: berger on 21.06. 2018 20:01
I have not been to the pub, you are still giving the inner race a license to dance on the crank shaft . I thought out your idea many moons ago.  be careful *warn* if you go with your idea .... when moon come over mountain white man die. edit there will be some wise people along to speak on this but I do see what you mean, so who's done it this way over the years? ignore me i'm going to the pub cos i'm now talking shite with a house full of loons doing my head in, cheers
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 20:07
i here you :)  will tread very carfully
Title: Re: I have an idea re: shims
Post by: Servodyne on 21.06. 2018 20:32
Sorry to jump in, but I can't really see to advantage of what you are trying to achieve. If the correct shims are fitted to the inner race, the whole assembly is clamped up solid to the crank by the retaining nut.
If you delete these shims and shim the outer race, the crank assembly will still be clamped up solid, but you will need the same shim you deleted, fitted between the crank seal spacer and the shock absorber sleeve, in order to keep your sprockets in line.
It seem to me you are trying to fix a none problem.
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 20:37
having heard a lot of storys about the shims being found in bits in the sump i just thought this could stop that but wonder why so many stories of shim breaking whats the root cause
thanks for your input
Title: Re: I have an idea re: shims
Post by: Servodyne on 21.06. 2018 20:49
Possibly incorrect shims (ID too big or wrong material) or slack retaining nut?
Title: Re: I have an idea re: shims
Post by: edboy on 21.06. 2018 21:55
some bsa engine builders used to recommend the shim behind the bearing outer to case as small shims can be spat out from the crank webb at high revs. finding the size of shim is the major problem. the next one down is the bloke who posts a picture of his engine post explosion and blames this mod and me who recommended it.
Title: Re: I have an idea re: shims
Post by: smartsx1x on 21.06. 2018 22:02
i have seen suitable ones on UK Bearings Ltd i do like the idea  but not heard any thing on reliabilty just thought i'd throw it out there never hurts to ask
Title: Re: I have an idea re: shims
Post by: chaterlea25 on 21.06. 2018 22:04
Hi All
You guys are thinking too hard   *conf*
once the cush drive nut is tight, shims or no the bearing inner will be clamped solid
The sprocket alignment is secondary and needs to be addressed no matter where the shims are fitted
The downside of shimming the outer race is that it might require several attempts to get correct
this means heating the cases to release the bearing, this could lead to the interference fit being lessened
BSA picked shimming the inner bearing for a reason  *ex*

John

Title: Re: I have an idea re: shims
Post by: duTch on 21.06. 2018 22:16

 Hiya smartsx1x , there was a discussion of this not very long ago- if you do a search you should find it....might save carbon-copying the stories  *smile*
Title: Re: I have an idea re: shims
Post by: Greybeard on 21.06. 2018 23:05
smartsx1x, please will you mosey on over to Introductions and er introduce yourself with pictures of motorcycles, if possible. Ta muchly.
Title: Re: I have an idea re: shims
Post by: KiwiGF on 22.06. 2018 01:07
Hi i'm new to this board thank you for letting me join
having bought a goldflash 1959 i soon found out that all that glitters is not necessarily gold,
so i am in the process of removing 9 peoples worth of hobby time from the engine etc,
my question is has any one thought about shimming the outer race on driveside roller bearing this would eliminate the need to fit those flimsey shims that i hear alot of horror storys about,the outer race would only stand proud an extra .05mm i would remove .05mm from the outer race protruding side to keep a good gap from crankshaft to allow oil flow ,the inner roller has a lot of clearence to the outer edge so dont see any problems .
has this been done before ? your thoughts advice would be appreciated
regards martin  *smile*

In my humble opinion the best solution is to get a single thick shim made up, to fit on the crank.

I know the shims get bolted up tight on the s/a engine, I’ve no experience of the plunger set up, and if that also bolts up tight, or relies on the pressure from the cush drive spring, others can chime in on that.
Title: Re: I have an idea re: shims
Post by: groily on 22.06. 2018 07:09
imho too kiwgf.
I tried a few years back a different wheeze, which didn't end well - before adopting a one-off single shim in the usual place.
The failed wheeze was to have the outside face of the left hand web behind the inner race built up with weld and finished for a perfect fit. It failed for a stupid reason - because we didn't extend the 'finish' quite far enough out radially from the centre line, and the bearing cage picked up a shard of new material and deposited it in the sump gauze.
Shame, 'cos I thought it was a good idea while the crank was out.
Single shim has been good ever since. (After unmachining the extra dollop of metal!)
Title: Re: I have an idea re: shims
Post by: groily on 22.06. 2018 07:10
and here's what came adrift!
Title: Re: I have an idea re: shims
Post by: duTch on 22.06. 2018 08:29
 
Quote
.... I’ve no experience of the plunger set up, and if that also bolts up tight, or relies on the pressure from the cush drive spring, others can chime in on that.....

 Without getting technical , it's much the same setup, except for the seal spacer (pre '54 had no seal, post '53 had a wider flange on the 'sprocket/ sleeve bush' for a seal), and a few different shapes/dimensions...

 groily, sounds like a good idea, and reminds me of an old buddy's Dad said when he was talking about the Hardly Flathead chopper with Chev Pistons...." (Aussie drawl), Dave- that would'a been a good bike if it'd 'ave had brakes".... *eek*
Title: Re: I have an idea re: shims
Post by: Greybeard on 22.06. 2018 09:19
My first thought when I saw the first post was: How often do the standard shims cause a problem?
Title: Re: I have an idea re: shims
Post by: Butch (cb) on 22.06. 2018 09:34
My first thought when I saw the first post was: How often do the standard shims cause a problem?

Well we do seem to spend quite a lot of time chewing over the premature demise of these things, which is probably why we're discussing alternatives again.

Seems to me - from reading at least, the main problems stem from too skinny or too big a stack of too skinny shims; one thick one being best. And pulling it up tight enough on assembly.
Title: Re: I have an idea re: shims
Post by: groily on 22.06. 2018 12:09
Yup. Mine hadn't been tight enough on the big nut I think.  There was about a millimetre of float - ouch! - when I got to it, so it was pretty bad, though the shims hadn't disintegrated. One had split though iirc.
So a big 4-pegged monster-weapon was knocked up with an inch 'n a 'arf hex  for a 3/4 drive socket to make sure I could do it up tight in future.
Seems to have stayed put since, although I don't make a habit of taking the primary case off to inspect it, I have to admit, because since following the wise advice of Brian down-under from on here to invest in Surflex clutch plates on the 4-springer on there, I haven't had to get the primary side open in years, literally.