BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: Caulky on 27 March, 2017, 13:00:58

Title: Nuts
Post by: Caulky on 27 March, 2017, 13:00:58

I am just about ready to put the case-halves together with the crankshaft to check the end float.
I am aiming for .002" float, using two .0045" shims, giving .009".
But there's a problem!
All of the case nuts are 'locknuts', some with spring washers.
Having read lots of stuff about locknuts, it appears that metal locknuts deform the threads.
As these have to be undone and re-fitted, its not a good idea to torque them up and undo them.
These can only be used once?
So I'm thinking to temporarily use plain fullnuts or nylocs.
And why not use nylocs anyway (once) instead of metal locknuts?

I read nylocs can be good for 250lbft torque and must be used with SS, but not used on exhausts, etc.
Some say use nylocs everywhere instead of metal locknuts?
Opinions welcome!
Title: Re: Nuts
Post by: Bess on 27 March, 2017, 17:01:07
Hi Caulky,
There is a mass of information on the web regarding nut locking, its made my head spin over the years. So, I try to use what's specified or modern fixings if I think there's a betterment.

My MO is:

I use plain full nuts when assembling/dismantling during a rebuild and setting the end float.

Nyloc or Aerotight as you say are single use.

If a lock is required and with all probability the fastening is going to be in place until the next rebuild I use Aerotight with a spot of Loctite (Loctite strength determined by the temperature of its location and the outcome if the nut drops off). If it's good for the aero industry it's good for me. It's easy to dress the threads during the next build, I do to all fixings to aid assembly when rebuilding anyway.

If I need to remove items in between rebuilds I use Nyloc and try to avoid spring washers (In my experience there is a lot of poor quality spring washers available). As you said not for exhausts or other hot areas.

I always use washers if I can, to spread the load and to stop the paint chipping (not on con rods though, and other places that are not recommended).

Good luck......

Title: Re: Nuts
Post by: Caulky on 27 March, 2017, 17:43:59
Hi Bess

Thanks for your reply.
This topic about locknuts seems to have been going on for ages.
I think plain nuts is the way to go for (temporarily) for this job in hand.
I'm not too keen on spring washers either.  Or metal locknuts.

Obviously I dont want the case fasteners to loosen, perhaps I'll use nylocs plus plain washers and see how it goes in the final assembly?
I was just wondering if anyone has bad results with them.
Vibration, etc?

Title: Re: Nuts
Post by: DEAN SOUTHALL on 27 March, 2017, 18:29:34
A bit of over egging the pudding in my view.
I've only ever used plain nute and spring washers on crankcases (and most other places on the bikes).
They completed the Maudes with these with needing to turn a spanner and I've never had one come loose.

I check end float using plain washers and fit spring washers when everything is ready for final assembly.

Title: Re: Nuts
Post by: STAR TWIN on 27 March, 2017, 18:57:21
Don't know which model of BSA you have, but my bikes all have plain nuts and washers on the crankcases. No loctite. I've never had a problem with them slackening off. If you look hard enough, you will find the odd nyloc nut here and there elsewhere.
If the nuts are torqued up correctly on clean dry threads you should have no problems.
Title: Re: Nuts
Post by: Bess on 27 March, 2017, 20:20:12
Hi Caulky,
                You will be fine with Nylocs, they are better than spring washers, ask NASA..... ;)

 The typical helical spring washer is made
of slightly trapezoidal wire formed into a helix of one coil so
that the free height is approximately twice the thickness of the
washer cross section. They are usually made of hardened
carbon steel, but they are also available in aluminum, silicon,
brome, phosphor-bronze, stainless steel, and K-Monel.
The lockwasher serves as a spring while the bolt is being
tightened. However, the washer is normally flat by the time
the bolt is fully torqued. At this time it is equivalent to a solid
flat washer, and its locking ability is nonexistent. In summary,
a Iockwasher of this type is useless for locking.
Title: Re: Nuts
Post by: Caulky on 28 March, 2017, 14:47:05
Thanks for the replies everyone!
In essence my original plan seems OK.
Final assemble nyloc nuts and plain washers.
If I'm allowed to mention Triumph, my Bonneville uses mainly bolts screwed into the cases.
Where there are through bolts, it has plain washers and full nuts.
The difference in my 1971 A65L is that the cases use a majority of studs and nuts.