Author Topic: SRM Gearbox mainshaft nut and oil seal. Torque value?  (Read 343 times)

Offline KeithJ

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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
'59 A10RR + Second engine

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #1 on: 27.09. 2020 22:23 »
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 .

Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #2 on: 27.09. 2020 22:54 »
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
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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #3 on: 28.09. 2020 19:23 »
 *doh* did you read my post about stripping the threads *eek* then backing the nut off. I will have to change my humor  *bash*

Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #4 on: 28.09. 2020 19:33 »
*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
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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #5 on: 28.09. 2020 19:55 »
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.

Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #6 on: 28.09. 2020 19:58 »
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
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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #7 on: 28.09. 2020 20:11 »
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.
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Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #8 on: 28.09. 2020 20:31 »
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
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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #9 on: 28.09. 2020 20:40 »
" usually just do them just right" and a gearbox nut has caused you the concern of how tight *conf2*

Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #10 on: 28.09. 2020 20:43 »
" 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".
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Offline Swarfcut

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #11 on: 28.09. 2020 20:47 »
   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.

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #12 on: 28.09. 2020 21:50 »
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
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Offline KeithJ

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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #13 on: 28.09. 2020 22:08 »
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
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Re: SRM Gearbox mainshaft nut and oil seal. Torque value?
« Reply #14 on: 29.09. 2020 00:19 »
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

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