Author Topic: Cush Drive Conundrum  (Read 511 times)

Online BagONails

  • A's Good Friend
  • ***
  • Join Date: May 2021
  • Posts: 96
  • Karma: 2
Re: Cush Drive Conundrum
« Reply #15 on: 14.09. 2021 11:46 »
Hi Swarfy, See photos below for what I called the plunger sleeve, I'm not certain exactly what it is but it bears comparison to the part you refer to. I'm calling it Orig. as it is the part that came with the bike. Yes it fits fine on the crank but the 5mm shoulder put the sprocket 3mm offset inboard to the clutch. I guess I could space it out again but I'd be back at 8mm off or the same as my new sleeve. In addition as you have stated the splines are different with much less contact, this is something I had not noticed so thanks for mentioning! I also show the diameter differences which on my parts here are not great but the new part is a slightly closer fit to the sprocket and of course lacks the undercut so does support the sprocket better, to keep things running true. For my money I'd rather stick with the new part I think. On to the sprockets my original sprocket measures 10.2 at the minimum of ramp to the rear face so slightly fatter than yours and the new one is fatter still at 11.6 so this part is also in the mix for sure. If I had your smallest sprocket that would give me 2.6mm straight off!

The parts I have now though are what I have to make work so I think that's about it really. Quite amazing the number of parts the same only slightly different and also the variation between parts that are supposed to be the same...whatever happened to standardisation and interchangeability of parts then?!

Hi John, thanks for this idea, it is something I could consider for sure. I wonder if anyone has any dimensions for this part? 

It looks like it might have a longer threaded section, clearly would allow more movement of the cush sliding sleeve and potentially more room for the spring too. I missed the Degsy thread as I hate to say I am well behind on the forum having been away with the wife for a vacation for the past week.  We are very lucky here in SA being free of the virus currently so we were able to get away up to the NT for some Croc spotting and very careful swimming in warm springs which was nice. 38c was a bit of a shock after leaving here in the morning at 3c. What a difference about 3000km can make.

I'll add some more photos in a following post.
Ian

Nil Desperandum

Online BagONails

  • A's Good Friend
  • ***
  • Join Date: May 2021
  • Posts: 96
  • Karma: 2
Re: Cush Drive Conundrum
« Reply #16 on: 14.09. 2021 11:51 »
More pics, titles on the photos should be self evident.
Difference between the old and new sleeve - fit on splines to the sliding sleeve.
Slight difference in diameter where the sprocket runs
Ian

Nil Desperandum

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1624
  • Karma: 32
Re: Cush Drive Conundrum
« Reply #17 on: 15.09. 2021 08:27 »
Ian. The drive sleeve with the undercut is indeed the plunger version. Using a plunger nut with your S/A drive sleeve is fine in theory, but as you appreciate with the plunger design the slide moves from a splined to a plain section. While the ID of the drive sleeve splines and OD of the nut nose are the same, the internal splines on the S/A cush are shallower as shown, and will not bear onto the plain  nose of the Plunger nut. The S/A slider is also of less depth than the Plunger in comparison and there may be a tendency for it to cant over and jam at full lift.

   As the plunger sleeve has already been ground down to take the S/A Sprocket, a complete plunger cush set up could be used, although the profiles of the cush ramps are a poor match. From your picture the Plunger Sleeve looks to offer enough lift, so should work with the rest of the bits. The poor depth of spline engagement is the stumbling block here, but is obviously enough to take the load as in the later design.

 The reason for the small amount of lift using your "correct parts" still baffles me. Somewhere out there is there a S/A drive sleeve that pokes at least 8mm above your stacked sprocket and sliding sleeve?  The last paragraph of the original post to this thread says it all.

 Chain alignment is taken care of by shimming between the drive sleeve and oilseal spacer, as already mentioned and has no influence on the amount of available cush lift, affecting only the final position of the tightened nut on the crank.

 Swarfy.

Online BagONails

  • A's Good Friend
  • ***
  • Join Date: May 2021
  • Posts: 96
  • Karma: 2
Re: Cush Drive Conundrum
« Reply #18 on: 16.09. 2021 09:13 »
Yep all valid comment Swarfy and much appreciated.

Somewhere out there is there a S/A drive sleeve that pokes at least 8mm above your stacked sprocket and sliding sleeve?  The last paragraph of the original post to this thread says it all.


tell you what when I find one of these spurious sleeves I shall be fitting it but until then...


 Chain alignment is taken care of by shimming between the drive sleeve and oilseal spacer, as already mentioned and has no influence on the amount of available cush lift, affecting only the final position of the tightened nut on the crank.


and therein lies my problem. While I could theoretically fit the plunger sleeve as before, notwithstanding all the other issues we've been discussing; by shimming behind it to move the sprocket back into line I am also running out of threads on the crankshaft so really I may as well fit a spacer ring, turned up to be a good close fit on the crankshaft and with an O/D just under the diameter of the splines, to allow the cush sleeve free movement. Tomorrow I am going to encase my spring inside a thin wall tube with a slit in it so I can chuck it in the lathe and try to turn the ends of the spring back as it feels tough but not too hard. So we'll see how this goes...My fallback plan is to use the ends of the tube as a guide to keep things square and hand grind the end faces! One way or the other the spring is losing 4mm in length *ex*
Ian

Nil Desperandum

Offline chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3584
  • Karma: 50
Re: Cush Drive Conundrum
« Reply #19 on: 16.09. 2021 13:07 »
Hi Ian,
I think you are worrying too much about the required space needed for the spring?
On my A10, there is app 30 mm for the spring, that leaves 4-5mm for the spring to compress before coil bind, at more or less the same compression the sliding cam collar will meet the nut,
Its been like that for a fair few miles and has not caused any problems

John
1961 Super Rocket
1963 RGS (ongoing)

Online Colsbeeza

  • Valued Contributor
  • ****
  • Join Date: Aug 2015
  • Posts: 371
  • Karma: 3
Re: Cush Drive Conundrum
« Reply #20 on: 17.09. 2021 01:42 »
Ian, Mikes in Qld has several sleeves of different types. Here is the correct one for the 1960 Flash

https://mikesclassiccyclespares.com/product/42-0269/
Col
1961 Golden Flash
Australia

Online BagONails

  • A's Good Friend
  • ***
  • Join Date: May 2021
  • Posts: 96
  • Karma: 2
Re: Cush Drive Conundrum
« Reply #21 on: 17.09. 2021 02:55 »
G'day John,
Hi Ian,
I think you are worrying too much about the required space needed for the spring?
On my A10, there is app 30 mm for the spring, that leaves 4-5mm for the spring to compress before coil bind, at more or less the same compression the sliding cam collar will meet the nut,
Its been like that for a fair few miles and has not caused any problems

John

Well really that is the crux of the whole thing John if you check back in my sketch (previous post above). The spring is coil bound at 24mm (squeezed in a vice) and I only have 24.1mm for the spring when the nut is tight against the sleeve bearing. So basically when the nut is tight my sliding sleeve can't move, I have no cush!  In addition even with no spring I would only have 3.2mm available movement.  Hence all the discussion about the various options. I'm literally now going to fit a 4mm spacer and cut/ grind the spring end faces to reduce the coil bound length to ensure I can get 6-8mm travel without binding on the spring.

Hi Col, That is the correct part I am using now.  As you may recall the original incorrect (plunger) part pictured above was the reason for my primary drive being 3mm misaligned. I cured one problem only to cause another. I've also bought a new spring and nut. The issue seems to be either the sprocket (also new) or the sliding sleeve or both but I've had enough now after waiting weeks for parts and finding them wrong or incompatible somehow I am going to have to make it all work together!    *pull hair out* *work*  *eek*

Ian

Nil Desperandum

Offline Sav

  • A's Good Friend
  • ***
  • Join Date: Jul 2011
  • Posts: 186
  • Karma: 2
  • VMCC Men of Kent and BSAOC member
    • Ashley, Ripple & Studdal Enthusiasts
Re: Cush Drive Conundrum
« Reply #22 on: 17.09. 2021 09:54 »
Been a useful thread on the mysteries of the cush drive thanks guys.

My A10SR had the cush drive and rubbers in the clutch mounting. When I took it apart to replace the ailing clutch I found the cush drive spring bound up on the lobe.

Solid new clutch basket and a shim to stop the cush travel enough for binding, always wondered if I had got it right and whether the lobe should be able to pop over the top in case of seizure.

Understand it all now ( i hope) thanks!
1961 A10SR, spent a fortune at SRM
1961 A7SS, finally the right green
2011 New addition 1937 Empire Star, twin port, high pipes. Turned out to be the most unreliable bike I have handled.
2017 finally found the liner/barrel were flexing and causing all the overheating/nipping up. Early B33 barrel fitted and it's reliable at last!
White Cliffs Country

Online BagONails

  • A's Good Friend
  • ***
  • Join Date: May 2021
  • Posts: 96
  • Karma: 2
Re: Cush Drive Conundrum
« Reply #23 on: 17.09. 2021 11:32 »
Hi Sav, good to hear you have got something out of this if only to confirm you made the right decision to go with a cush in the clutch, or maybe you have both, some do I have read.

I am not familiar with the detail of your clutch but I can't imagine any circumstance where it would be desirable for the cush lobes to ride over each other and reset, even in the event of a seizure to be honest, you'd be better off whipping the clutch in I would think.  I think the intention would always be to limit the extreme of cush movement to a hard stop well before that could happen in the interests of road safety and maintenance of clean undies!  *eek*

Happy and event free travels to you.
Ian

Nil Desperandum

Online Greybeard

  • Jack of all trades; master of none.
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 7322
  • Karma: 40
Re: Cush Drive Conundrum
« Reply #24 on: 17.09. 2021 11:42 »
... in the interests of road safety and maintenance of clean undies!  *eek*
😳
Greybeard (Neil)
1955 Golden Flash, sprung frame
Supporter of THE DISTINGUISHED GENTLEMAN'S RIDE https://www.gentlemansride.com

Warwickshire UK


A Distinguished Gentleman Riding his 1955 Plunger Golden Flash