Author Topic: Broken Cush Spring  (Read 812 times)

Offline BSA_54A10

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Re: Broken Cush Spring
« Reply #15 on: 12.10. 2021 08:10 »
Mine is bigger than Cols but it in not polite to brag
Also phneumatic
So like most hernia tight nuts it is drive till the nut stops turning then 3 hits for 3 clicks
No idea what the actual torque is but nothing has ever come loose
No washer and blue locktite
Same for the clutch nut
Bike Beesa
Trevor

Offline Swarfcut

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Re: Broken Cush Spring
« Reply #16 on: 12.10. 2021 08:26 »
   To add to Col's observations, the force required to tighten the nut is composed of an element necessary to compress the spring, as well as overcoming the friction on the threads. In fact the "degree of tightness" on the nut itself  against the drive sleeve could well end up far less than we all expect using the conventional methods, and I endorse RD's thoughts on this as it is a reasoned explanation as to why a supposedly gut bustingly tightened fixing comes undone.  Thread locking compound and the rattle gun look to be the most successful and foolproof method. In the absence of such luxury, a peg spanner and a big hammer run a close second, assuming the crank can be locked without damage.

  Swarfy.

Offline Colsbeeza

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Re: Broken Cush Spring
« Reply #17 on: 12.10. 2021 11:10 »
Hi Trevor,
  I am not very tall either!
Col
1961 Golden Flash
Australia

Online berger

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Re: Broken Cush Spring
« Reply #18 on: 12.10. 2021 13:07 »
i am back! been away with blooming interference with 02 UPGRADE!!!!!!! and because i haven't got wifi  i could not top up my sim card in the dongly device i use on the computer *pull hair out* *bash*. well back to the post , i bash my original crank nut with a brass drift until i get that lovely sound it makes when it can't get any tighter then put my home made locking nut on that has a small hole drilled into it for me to punch it up tight, it fits snuggly into the nut recess of the original nut

Online RDfella

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Re: Broken Cush Spring
« Reply #19 on: 12.10. 2021 18:58 »
Further to my previous post, can't understand people who want to introduce modern methods (eg torque wrench settings) instead of original procedures when there is no discernible benefit. Take the Villiers flywheel for example. Only known method of tightening that nut is with a hammer. Pictured is the factory tool.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

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Re: Broken Cush Spring
« Reply #20 on: 12.10. 2021 19:51 »
G'day RD.
Depends on what size "knockometer" is used.
Or tighten till it strips and back off half a turn.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online KiwiGF

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Re: Broken Cush Spring
« Reply #21 on: 12.10. 2021 20:44 »
   To add to Col's observations, the force required to tighten the nut is composed of an element necessary to compress the spring, as well as overcoming the friction on the threads. In fact the "degree of tightness" on the nut itself  against the drive sleeve could well end up far less than we all expect using the conventional methods, and I endorse RD's thoughts on this as it is a reasoned explanation as to why a supposedly gut bustingly tightened fixing comes undone.  Thread locking compound and the rattle gun look to be the most successful and foolproof method. In the absence of such luxury, a peg spanner and a big hammer run a close second, assuming the crank can be locked without damage.

  Swarfy.

I know not everyone has a rattle gun but I use a battery operated dewalt one which has two settings, low and high, one about 80 ft lb (from trialing it against a proper torque wrench) and the other (supposedly) 450 ft lb stated by the maker.

So I use the lower setting for the cush drive, and 243 loctite, I didn’t use to use loctite (I don’t like using it on larger threads) but a cush nut once loosened on my B31 at a very inconvenient time  *problem* and actually that was what encouraged me to convert it to belt drive. The tab washer inside the cush drive did not stop it coming loose.

To UNDO a cush nut I have to use the rattle gun on full noise, which worries me a bit about damaging internal engine components, even the crank thread, but it shows the strength of loctite, come to think of it I should probably heat it up first.

I guess loctite make weaker versions for larger threads?
New Zealand

1956 A10 Golden Flash  (1st finished project)
1949 B31 rigid “400cc”  (2nd finished project)
1968 B44 Victor Special (3rd finished project)
2001 GL1800 Goldwing, well, the wife likes it
2007 KTM 950 Adventure, cos it’s 100% nuts

Online RichardL

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Re: Broken Cush Spring
« Reply #22 on: 12.10. 2021 22:00 »
Surprised no one has commented about the bolt blocking the crank through the inner-case hold-down holes. Is it that risky that it doesn't merit comment? It takes very little thread protruding into the case to reach the crank web, so I THINK not a lot of leverage on the bolt to distort the threads in the case, nor enough to break off the bolt into the case. Anyway _________ (fill in the blank with name of person about to tell me horror story from doing this), what is the horror story from doing this?

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Online RichardL

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Re: Broken Cush Spring
« Reply #23 on: 13.10. 2021 06:27 »
Whoa! I hope I didn't break the forum with that last question.

Anyway, as one of my mentors (Chaterlea John) suggested, I checked end float following the extensive lobe-over-lobe running. Appears to still be about 0.0015", thanks, I'm sure, to another mentor (Muskrat), who, 6000 miles ago, told me to clamp my inner race and shim stack together while the semi-permanent Loctite on the bearing race set up. As another check, I'll be pulling the sump plate and checking on top of the screen, though I don't expect to find trouble there.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Online RDfella

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Re: Broken Cush Spring
« Reply #24 on: 13.10. 2021 10:55 »
As you say, Richard, with little protrusion I'd guess the bolt would resist bending and do the job. Must admit hadn't thought of that possibility of locking the crank. If said bolt undoes OK after required amount of tightening of crank nut then I guess all is OK.
 
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

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Re: Broken Cush Spring
« Reply #25 on: 13.10. 2021 11:30 »
G'day Fellas.
Not wanting to go too far off topic.
Another way to lock the crank is to wind it up to tdc backwards then back 1/4 turn. Then feed in a foot or two of cord through the plug hole. Now wind it back till she stops. Do the nut up and retrieve the cord.
Do it like this everyday at work on chainsaws etc.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Greybeard

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Re: Broken Cush Spring
« Reply #26 on: 13.10. 2021 11:43 »
Surprised no one has commented about the bolt blocking the crank through the inner-case hold-down holes.
That idea worries me. If the thread on the bolt were to get even slightly damaged it is very likely to mash the case threads on its way out.
Greybeard (Neil)
1955 Golden Flash, sprung frame
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Offline Peter in Aus

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Re: Broken Cush Spring
« Reply #27 on: 14.10. 2021 01:06 »
Surprised no one has commented about the bolt blocking the crank through the inner-case hold-down holes.
That idea worries me. If the thread on the bolt were to get even slightly damaged it is very likely to mash the case threads on its way out.

That is what happened to me want do that again.
Peter

Busselton West Australia
49 A7 longstroke
58 A10  SA

Online RichardL

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Re: Broken Cush Spring
« Reply #28 on: 14.10. 2021 01:20 »
Peter,

Very interesting. May I ask, did you let the crank web come fast and hard against the bolt or nudge it up slowly? I have doubts about the web causing a slow crush of the threads on the stop-bolt, but can easily picture it when there is considerable inertia. I just looked again at the bolt I used and see no apparent thread crushing. Granted, I only tightened to 65 (or so) ft-lb, not the three or four hundred hinted at earlier. I DO believe this is a worthwhile topic for continued discussion because, if the method is harmless, it can be an easy and effective method for getting the bastard tight.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline Colsbeeza

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Re: Broken Cush Spring
« Reply #29 on: 14.10. 2021 09:56 »
Hi Richard L,
  I have read that others have done just what you did, but for me it is not a method I would be comfortable with. No-one can say it isn't a good idea though. Personally I would not like to subject the end of the bolt to a sideways force of that magnitude when it is screwed through the alloy crankcase. I am a bit squeamish when it comes to steel threads in alloy, and I might have a nightmare out of all proportion to the risk. :o. Is that a cold sweat coming on?? *pull hair out*
Col
1961 Golden Flash
Australia