PD: Primary Drive Rapide Chain Problem

[bmetcalf]

The new chainwheel arrived and I checked the overall length. I measured mine on a granite surface and the old one is 1.475" and the new is 1.440"!

I stuck the shoe carrier through the old chainwheel and it is flush on the back side. I thought that I had a C19 shim on the nut’s flange, but it isn’t there now. I’ll look through the pile of nuts and bolts from stripping the primary to see if it is there.

Also, looking at my copy of Clutch drawing MO28/2. I am thinking that appropriate C19 shims between the C2 spacer and the flange of the rear chainwheel bushing would fix me up, unless the backside of the drum rubs on the inner primary cover. It would be kept centered by the end of the clutch nut sticking through the shoe carrier or would the chamfer on the nut end spoil that? The bore of the front chainwheel bushing is a bit tight, but that is easier to solve.

Any suggestions on the shim idea?

 

[Bill Thomas]

Bruce, The last chain wheel bushes I fitted, The one at the back was too thick !,
I spent ages flatting it to make it narrower so that the carrier would stick out a bit and give some free play,
Or else it will lock up when you do the Big nut up, And you will have trouble !.
Good Luck, Bill.
In Mikes Video, The one he tried to fit was too loose inside the wheel, And he had to refit the old one !.

 

[vibrac]

Bill has stirred my grey cells as I recall Reynold changed the rollers from solid to butt welded which is why the advice was to go to Japanese chain with solid rollers (solid as in bored out bar). That Reynolds change was instigated it was said because the triplex chain was increasingly used for OHC car engines and the market became more competitive on price. Obviously in that car use chain runs in ideal conditions without so much the alternating stress and forming strip into rollers and butt welding was cheaper as production volume increased.

 

[Bill Thomas]

Only to add , Back then most of us were still using old Dynamos,
So you can't blame , The hard to turn, Like an Alton ?,
So we are back to too much mesh ?.

 

[Peter Holmes]

Yup, I also had the middle row of the primary chain taken out completely whilst running a Miller dynamo, but I completely blame myself for that occurrence, I had undertaken a complete engine tear down and rebuild with zero mechanical knowledge, using only the Richardson book for guidance, along with the enthusiasm and confidence that only youth can possess, on that occasion, and for not the last time, I was rescued by someone totally unknown to me at that time, one Marcus Bowden, who just happened to be riding through Looe on his magnificent, highly polished Vincent, and the year was 1966, why had I torn the engine down you may well ask, well rather topically the G39AS had shed its ears and I had lost all gear selection, back then my bike was a dog, and I mean a dog, someone in the past had had the ESA punch or wear its way through the primary chain case, and then simply repaired it using a patch of roofers lead, nice!

 

[bmetcalf]

Further to my post #61 https://www.vincentownersclub.co.uk/threads/rapide-chain-problem.17596/page-7#post-156733

I have convinced myself that a C19 shim of the right thickness will do the job. The orange pieces are the bushes in the chainwheel and the narrow blue line is the C19. It serves the purpose of making the adjacent bush (PD24) flange thicker so that the end of the shoe carrier is not proud of the face of the bush and shim. I talked to Coventry Spares and all their C24 bushes have near enough to the same flange thickness, so knocking out the bush and replacing it with a new one with a thicker flange isn't an option. For assembly, a bit of grease should hold it in place while I offer up the chainwheel with the shoe carrier in place to keep the shim centered.

 

[greg brillus]

Bruce are you shiming this because the chainwheel has too much end float.........If that is the case you can simply put a thin shim on the C3 carrier spigot, then do up the C20 nut and see how much end float you have then.......In other words the shim is outboard of the chainwheel.

 

[Gene Nehring]

Hi, I don't know if you noticed the "Fretting" on the face of the hardened dynamo sprocket. There could have been movement there causing a problem with the rollers. However it just could be the "chicken and egg" mystery. Luckily the chain stayed in one piece.
Roy

Roy,

This is an interesting point as when I set up my sprocket the back lash was the first thing that came to mind based all the threads and talk here on the forum. Yet in actuality I had to spend much more time getting the sprocket centrally located in the middle of the centre link. This is only something like 8-12 thou a side clearance. So side loading on the sprocket over time could be an issue too.

Best,

 

[Monkeypants]

Those Alton's are hard to turn ?,
I am hoping my Mcdougleator with a slipper clutch, Is a bit more kind to the chain ?.
Cheers Bill.

I think its the other way Bill, the Mcdougallators take more to drive and are probably a bit tougher on the chain, even with the slip clutch.
They also produce a lot more power than the Altons, but the Altons do get the job done, if you keep your power requirements fairly low.
I'm speaking of the last version of the Alton, the single phase direct drive unit.
I've had one of those on the bike for about 30,000 miles now.
According to my notebook, this Tsubaki primary chain was installed 36,000 miles ago (bottom of first photo). It still looks perfect and the side curve is only slightly more than it was when new.
The chain that was removed 36,000 miles ago is at the top of the photo. It has roughly twice as much side curvature as the 36,000 mile chain. It might have done 100,000 miles or more as the bike was used for huge mileages in OZ back in the 80s/90s
The lower photo shows the rollers on the 36,000 mile chain. They look very good, shiny but no visible wear.
Steel sprocket on the Alton.
I briefly tried plastic but it was quite noisy, put the old steel one back on.

 

[Bill Thomas]

I don't do many miles now, But John said in his instructions there would be noise , Clacking at low speed ?,
But I have not heard any problem,
One of our lads said the drive can lose oil ?,
But I have checked mine and it's OK.
I am pleased with it, Lot of money at the time , But I had had a good few weeks work,
So treated myself .