cush drive nut and sleeve

[RogerSB]

That SRM nut is pretty but is it's only advantage that you can put a socket on it?

My main reason for buying it was that the original sleeve nut was knackered beyond further use by being chiselled on and off by previous owners - and then further brutalized by me when I had to do the same because there was no way I could get a C spanner or anything else on it to move it due to the damage. The SRM nut was easy to torque up to 65 with a socket, and I would imagine it would be the same to remove it.

[Greybeard]

I was using a pair of Stillsons, (pipe wrench) on my original nut but bought one of those special adaptors with pegs so I can use a socket in my rattle gun.

[RichardL]

Guys,

Thanks for your confirming thoughts on this.

Two assemblies back, I left out the washer for not thinking about it and everything was fine torqued to 65 ft-lb. In the last assembly, I made the mistake of looking at the parts book and thought, "Hey, I should put that in," despite the fact that I saw no locking function. Sure enough,when I pulled open the primary yesterday, the washer was free to spin  (as John seems to suggest could happen), but the nut was basically in place (I assume, because of the Loctite). Also, I found the cush drive to lobe-locked. Besides the fact that no locking function is available from the washer with the SRM nut, I figure leaving out the thickness of the washer will help avoid lobe locking.

Richard L.

       

[KiwiGF]

Guys,

Thanks for your confirming thoughts on this.

Two assemblies back, I left out the washer for not thinking about it and everything was fine torqued to 65 ft-lb. In the last assembly, I made the mistake of looking at the parts book and thought, "Hey, I should put that in," despite the fact that I saw no locking function. Sure enough,when I pulled open the primary yesterday, the washer was free to spin  (as John seems to suggest could happen), but the nut was basically in place (I assume, because of the Loctite). Also, I found the cush drive to lobe-locked. Besides the fact that no locking function is available from the washer with the SRM nut, I figure leaving out the thickness of the washer will help avoid lobe locking.

Richard L.

     

I hate to be the bearer of bad news especially on New Year’s Day.....but it’s not good the washer was loose as this means the crankshaft bearing inner was not being clamped up tight as it should be, only the spring pressure would be making sure the crankshaft bearing inner does not not spin on the crank.

This MIGHT mean any shims behind the bearing would get stuffed. It would be worth a check of crankshaft end float to ensure any shims are ok, maybe a look at the sump plate gauze as well?

[RichardL]

Kiwigf,

I think I'm going to be OK, because the inner race is stuck on with Loctite bearing retaining compound (only intended to come loose with heat) and the race and shims were clamped against the crank web while the compound set up. Nevertheless, I guess I'll take a look in the sump. It is winter, after all, and about 5 degrees F. outside right now. So, it ain't holding up riding.

Richard L.

[Greybeard]

Fingers crossed for you Richard!

[RichardL]

While on the train with wife and daughter heading to a New Years party in Downtown Chicago, what better to ponder than cush nut washers?

Even with the original nut, I don't get the locking function. Are you supposed to jam a punch betaeen the spring coils and somehow smash the edge of the washer into the notches in the nut? That's dumb, or I am.

Richard

[muskrat]

G'day all.
I must be reading this wrong. The original washer has "teeth" that fit into the spline so should not spin even if the nut does come loose (the split pin will stop it going too far). The washer being "fixed" stops the nut from coming loose due to flutter of the spring. When the cush is working the spring is being compressed and relaxed. This could cause the ends of the spring "working" the nut and could eventually loosen it. The washer is a barrier between the spring and nut.
In saying all that I don't have one on the cafe with an SRM nut and only have a plain washer on the plunger with the std nut. Never had one come loose (even racing).
Cheers

[RichardL]

Muskrat,

Like I said, I'm on the train, so it's not in hand, but I don't recall the spring bearing on the washer. I was thinking it might just have been intended to give the nut a surface to land on.

Richard L.

[KiwiGF]

While on the train with wife and daughter heading to a New Years party in Downtown Chicago, what better to ponder than cush nut washers?

Even with the original nut, I don't get the locking function. Are you supposed to jam a punch betaeen the spring coils and somehow smash the edge of the washer into the notches in the nut? That's dumb, or I am.

Richard

Yep, you have to squeeze a punch inbetween the coils to hammer the washer down onto the flat in the nut. Sometimes you have to turn the spring in order to get a punch in. The washer o.d. Is smaller than the spring I.d.

 If the SRM nut has no flat I’m not sure the washer would do much, even though as musket says it’s got “teeth” on the i.d. to stop it turning, so it might do something.

I use the washer AND loctite 

[RogerSB]

Richard, see Andrew's (Priory Magnetos) reply to mugwump dated 5-2-16 on securing the cush drive lock washer:-


https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&uact=8&ved=0ahUKEwjO577w1rfYAhVMBsAKHbpyD7QQFghHMAc&url=https%3A%2F%2Fwww.a7a10.net%2Fforum%2Findex.php%3Ftopic%3D10331.0&usg=AOvVaw2C0o0ad23aI4e0spaR1EIx


My thoughts are, if using the SRM nut, even with the tangs of the lock washer located within the spines if there's nothing else to lock it to it's not a lock washer anymore. If using the standard BSA nut that, of course, is a different situation altogether and then it obviously needs to be locked to the nut by using a punch to be of any use.

[RoyC]

I use one of these and a torque wrench.
Torque to 60 / 65 Ft Lbs.
Saves ruining your nut.

[JulianS]

This is the packing and a shot of the tool on a cush nut.

If the nut has been damaged it is difficult to get the tool on it.

You need a 35 mm socket to drive it.

[muskrat]

I found it difficult to juggle the tool with a socket and the rattle gun so I welded the socket on. A lot easier to use with either a ratchet/torque wrench/rattle gun.
Cheers

[RichardL]

Richard, see Andrew's (Priory Magnetos) reply to mugwump dated 5-2-16 on securing the cush drive lock washer:


My thoughts are, if using the SRM nut, even with the tangs of the lock washer located within the spines if there's nothing else to lock it to it's not a lock washer anymore. If using the standard BSA nut that, of course, is a different situation altogether and then it obviously needs to be locked to the nut by using a punch to be of any use.

Roger,

Andrew's explanation of how an original nut was originally tightened and locked with the washer is, of course, excellent, but does not mention SRM's 65 ft.-lb. figure. It seems that if an original nut is tightened to 65 ft.-lb. (if we accept that number) the lock washer is no more necessary than with the SRM nut, but has "belt and suspenders" status.  One thing about Andrew's comments I'm not sure I understand, is he (Andrew, are you) saying that "shock tightening" creates a better lock of the components than tightening to a measured torque?

I kwow I'm beating this topic to death but, as Kiwigf has emphasized, the repercussions of getting it wrong are serious.

Richard L.