Primary drive sprockets

[alan.moore]

Just going through my recent WNG and the engine sprocket is 20T...which seems correct...but the clutch sprocket is 42T. The parts book for the WNG I have says 44T. I cannot find a reference to a 42 tooth clutch sprocket on the Drags site (they list 40 and 44)

The primary chain as fitted has 79 links...which makes sense with the 42 tooth sprocket fitted as the standard 20T & 44T is 80 links.

I have the gearbox apart and it has the standard CP final drive gears fitted (30T and 20T) . In fact it has the roller bearings on the camshaft as opposed to the plain bearing so may well be a civilian gear set.

So....was the 42 Clutch sprocket a WNG specific part, if not where does it come from?

Also, what effect will it have on performance if I leave the primary gearing at 20T/42T.

Any observations gratefully received

Cheers
Alan

[pete.collings]

The 42t chainwheel was fitted on the early Huntmasters, but they soon reverted to the standard 44t chainwheel as it was found to be slightly overgeared.
I don't know if it was used in any other Ariels of that period (early to mid 50s), but would have thought it post dated the WNG.
It is possible someone fitted it to use in conjunction with a 19t engine sprocket.

[nevhunter]

It's a 44 T in my 1941 W/NG parts list and as far as I know all my chainwheels are that size. It's an under 5% variation so the more important thing is not to have a 1/2 link in the front chain if possible. Nev

[alan.moore]

........ so the more important thing is not to have a 1/2 link in the front chain if possible. Nev

Re the 'half link' Drags 'odd number of link' chains (79, 81 etc) have a cranked link and there are quite a few models that are specified with odd link chains both front and rear. So is a half link different to a cranked link?

[nevhunter]

it would be the same thing I reckon. They are a weakness in a chain and to be avoided if possible. (even the joining link is). More important on worked bigger engines where the chain is doing a harder job. Nev

[Simon.Gardiner]

To most bike people a cranked link seems to be a half-link but if you're a chain person they're very different animals...

http://forum.arielownersmcc.com/viewt ... 3&start=30

SG

[alan.moore]

So.... if the cranked link is a weak point why oh why did Ariel end up with so many models that required an odd number of links in both primary and final drive chain?

[bevanclark]

I cannot speak authoritatively for Ariels, but I have another make of bike (Panther) which also have Burman boxes - they often need half links or cranked links to get the right primary chain tension, because they were really intended as sidecar tugs. As is usually the case, in solo trim for better rideability the engine sprocket needs to be increased. On another forum, this subject seemed to arouse many vehement opinions, with people claiming they should never, ever be used, would inevitably break and cause catastrophic damage. As a newby, this caused me considerable anxiety since I had no choice but to fit one, however I also got feedback from others saying they had done many, many thousands of miles without problem.

While the ideal is an endless, riveted chain I guess, most of our old road bikes are pretty low powered and I think that a good quality cranked or half link should be fine for the type of loadings our bikes produce. Both my chain the additional cranked link are DID brand, so hopefully will be robust.
Fingers crossed.
Cheers,
Bevan

[nevhunter]

As far as the weakness is concerned both links have the same issue The non flat (offset) side plates, which is extremely poor design from an engineering standpoint. I'm not racing my stuff, so IF it cannot be avoided I do use them but not necessarily too happy about it. Split rollers are even worse if one wants to look around for another problem. I've had a handful of spit rollers end up in the bottom of the primary chaincase and would recommend to NEVER ever use that type of chain .A single row chain is already doing a big job if it's a side car machine with a VH 500 and If the gearbox bearings are loose the rear chain will make the front one go too tight especially in the lower gears on any model. That's a common cause of premature primary chain problems. Push the rear chain runs closer together and watch if the primary one gets tighter. Nev

[alan.moore]

Thanks gents for the info.
I get my chains from Drags and the odd number of link ones have the cranked link fitted by them so hopefully they are decent quality. Having said that I've just checked the primary chain they sent me for the VH and the cranked link has been riveted on too tightly so the link does not fully articulate
so it will have to go back.

The problem with the primary tightening up after adjustment can also happen if the bottom gearbox pivot bolt hole is oval or oversize, which can happen over time if it has not been fully tightened. Symptoms are that both primary and rear get correctly adjusted and after a run the primary is very tight and the rear chain too slack. One way round this (I think this may be one of Nev's tips) is to put and maintain a fair bit of pressure on the bottom run of the rear chain while you set the primary chain tension and tighten the gearbox bolts (two pairs of hands are helpful). The only permenent remedy is to drill and then sleeve the gearbox pivot to restore a good tight fit with the pivot bolt.

Cheers
Alan