G'day playmates!
Bergerman, you crack me up. I've not been to the pub for what seems like ages either although only locked down since last Tuesday night...hopefully we will be out of this by Weds. All new cases found to date have been directly linked and already in quarantine so we are going well. I would gladly buy you a beer if it was possible maybe when we next get to travel home though it could be sometime...In terms of just "banging it back together" I think this is what the PO did and it hasn't gone well..anyway I shall continue my investigations for now.
i have not been to the pub for ages so i am swigging on the back garden and my personal opinion is bang it together after that effort, my dad hated people wanting a latherer job doing when he had set the 4 jaw up so cheers to you, good work . also i ended up with the grinding paste thread problem and bought taps and dies that will be used only once by me because of shoddy aftermarket bits and bobs. talking of bobs can anyone lend me a score for my next sesh on the piste you
know you want to
Musky and RD, thanks, good thinking and all valid comment.
After posting I carried on rereading and searching old threads and realised what had been noticed by Col early this year when he posted in this, John O R's treatise on the adapter variation etc. here:
https://www.a7a10.net/forum/index.php?topic=9646.msg70166#msg70166and by Simon (Mosin) in 'Touchy Feely" a decade earlier! here:
https://www.a7a10.net/forum/index.php?topic=2689.45I think I now have the culprit identified; my sleeve bearing is wrong. It has only a 5.15mm wide shoulder and it should be 8mm or thereabouts. Interestingly it is also 5.3mm longer overall than the one John measured in his report. It also has a distinct undercut machined into it and I can't see any reason for this either. This makes it different again to the ones Simon, John and Col have unearthed and potentially a 3rd different design part! (Unless it is a spurious part off something else but that seems unlikely) see attached photos.
This is I believe the root cause of my primary drive self destructing although I have found numerous other issues nothing has been conclusive until now 3.5mm misalignment is pretty significant, either with or without oil!
So now the plot thickens further, do I make it work with this or do I buy yet more replacement parts???
The second photo shows the assembled condition only just possible to get the split pin in.
Third photo shows the cush spring being compressed to being coil bound measures 24mm (free length 42.5mm)
Final photo shows the gap at 4.85mm between the sprocket and the cush drive sleeve when set at the 24mm (coil bound spring) distance. This indicates I can potentially space the sleeve bearing out the required 3.5mm (additional spacer between the existing one and the shoulder on the sleeve brg.) and remove this amount from the end of my sleeve brg (which is 5mm longer than it should be anyway) while still maintaining a gap of 1.35mm (4.85-3.5). i.e. on max cush deflection the spring will become coil bound 1.35mm before the cush drive sleeve is hard up against the nut. If I can do this then I will maintain the current nut position, have all threads engaged and be able to fit a split pin. I could even pinch an extra mm to make fitting the pin easier! I could even take the whole 5.3mm extra length off the sleeve and this would prevent the spring from ever binding up on the coils, maybe a good thing?
I think my remaining question now is how likely is it for the cush drive spring to bind up and will this damage the spring over time? Effectively I'm not changing the condition I had previously if I go this way but that doesn't mean it is correct!