The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: KeithJ on 27.09. 2020 19:18
-
Just assembling the gearbox and primary side and want to tighten the SRM mainshaft hex nut with oil seal. Have looked on their web site but can't locate the torque setting. Think I had a value when I last did it but that was some years ago. Would anyone happen to know please? Would like to assemble it tomorrow.
Thanks
Keith
-
keith that nut needs tightening until your grunting and sweating and the threads strip *eek* then back it off 1/2 a turn and fix the lock washer on any flat or corner you like. only joking , 45 rpm should do it then hit the lock washer ,erm lbs/ft --- ft/lbs .
-
Thanks for a quick reply. 45 rpm is good, I’d struggle at 78! Not quite there yet though.
Keith
Just had a reply from SRM: Sleeve Gear Nut
"The torque setting for the A10 gearbox nut is 65ft/lbs. I hope this is a help. Kind regards, Mark"
No mention of "backing off"?
ATB
Keith
-
*doh* did you read my post about stripping the threads *eek* then backing the nut off. I will have to change my humor *bash*
-
*doh* did you read my post about stripping the threads *eek* then backing the nut off. I will have to change my humor *bash*
Sure did , that's why I posted the reply I received from SRM and said "no mention of backing off". I didn't realise the humour in your post. Difficult to distinguish between what some folks actually do and a light hearted comment.
By the spelling of "humor" I guess you are in the USA? If it had been humour, I'd probably had got it. Haha.
ATB
-
I use an 18 inch 1 1/2 AF ring spanner, lock the sprocket to hydraulic work bench with a short length of chain, loctite the nut (I dont use a lockwasher) and do up very tight. Never found it easy to use a torque wrench in this position.
-
I use an 18 inch 1 1/2 AF ring spanner, lock the sprocket to hydraulic work bench with a short length of chain, loctite the nut (I dont use a lockwasher) and do up very tight. Never found it easy to use a torque wrench in this position.
Just used a torque wrench with deep socket. Chain around rear wheel sprocket, applied the rear brake and torqued up ok, also undid it that way. ATB
-
Don't get the present facination with torqueing everything. What's the point - BSA didn't issue torque figures (at least not as far as I'm aware on older models) so it's all based on a guesswork anyway. Basically there's four settings: nipped up, tight, very tight and bloody tight.
-
Don't get the present facination with torqueing everything. What's the point - BSA didn't issue torque figures (at least not as far as I'm aware on older models) so it's all based on a guesswork anyway. Basically there's four settings: nipped up, tight, very tight and bloody tight.
It's not a fascination and don't usually bother. With a standard retainer for the sprocket, would not/could not. The point is, this is an SRM gismo not a BSA part, so why not try to do it up "properly". Would always torque big end bolts. Never used the four setting you mention. Usually just do them just right.
ATB
-
" usually just do them just right" and a gearbox nut has caused you the concern of how tight *conf2*
-
" usually just do them just right" and a gearbox nut has caused you the concern of how tight *conf2*
That's why I said "usually".
-
Many mainshaft keys and keyways are damaged by shearing forces between shaft and clutch centre due to inadequate tightening. I look on a keyed taper as simply a location to prevent rotational movement in the initial stage of tightening. Once the tapers grip that's when the key has done its job and you can put some real force on. In practice the required torque is as much as you can swing on a breaker bar.
Swarfy.
-
Hi All
Over tightening the SRM nut can make the end of the sleeve gear contract and lead to seizure of the mainshaft to the sleeve gear bush *eek* DAMHIK *red*
It's the same principal as re boring a cylinder with and without a torque plate
John
-
Hi All
Over tightening the SRM nut can make the end of the sleeve gear contract and lead to seizure of the mainshaft to the sleeve gear bush *eek* DAMHIK *red*
It's the same principal as re boring a cylinder with and without a torque plate
John
Hello and yes, I read your post, thanks.
Received this from SRM "The torque setting for the A10 gearbox nut is 65ft/lbs". So as long as I don't exceed this, all should be well?
ATB
-
I do mine up to 80ft/lbs and check it at 1000Ks and again at 5000Ks, first check it went up 1/8 to 1/4 turn and about 1/8 second time. last time I checked it at 20000K it was all good.
Peter
-
Don't get the present facination with torqueing everything. What's the point - BSA didn't issue torque figures (at least not as far as I'm aware on older models) so it's all based on a guesswork anyway. Basically there's four settings: nipped up, tight, very tight and bloody tight.
I guess that for those of us who spent our formative years practising whilst we either stripped threads or parts just fell off along the wayside - 'just so' is now good enough.
When my daughter was doing her mechanics badge in the Scouts with me (we used her Mother's Bantam for the exercise), she asked me how hard to tighten up something, and I said something like - so it feels right. And I realised this was of course absolutely no help at all.
-
I think some are missing the point - well, two points actually. Firstly, in the era machinery we're talking about, torque figures weren't supplied except for things like big ends - and then not in all cases - and so guessing a torque setting is no different to choosing how tight to do something 'by hand'. And secondly if one doesn't know how tight something should be then maybe working on old machinery is not for you?
-
At the end of the day, there is no argument against torque wrenches and quoted figures. Nobody had a torque wrench in the 1950s? So what!
I only use them on the cylinder head and the big ends, but others may use their clicky bar on the inner tube dust cap and the dipswitch, if they like.
-
I think some are missing the point - well, two points actually. Firstly, in the era machinery we're talking about, torque figures weren't supplied except for things like big ends - and then not in all cases - and so guessing a torque setting is no different to choosing how tight to do something 'by hand'. And secondly if one doesn't know how tight something should be then maybe working on old machinery is not for you?
Doesn't everyone start not knowing how "tight" something should be? I know when I left school all I had experience of tightening was on a push bike. I learn from there. Everyone has to start somewhere. I guess the advantage today is if unsure of tightness, standard torque values would be a good guide. Just my ha'porth.