C: Clutch Twin Primary Chain PD1

bmetcalf

Well Known and Active Forum User
VOC Member
I wonder if the crank and clutch shafts are ever just a little too far apart to allow installation?

From the Newby site:

vincent_twin.jpg
 

timetraveller

Well Known and Active Forum User
VOC Member
If it turns out that this is a real problem and that, looking into the future, chains of adequate quality are likely to become unavailable then there is another solution. That is to replace the whole of the chain and sprocket or belt arrangement with three spur gears. One on the engine main shaft, one (an idler) on a pivot supported in the tunnel provided for a left hand kick starter shaft and the third acting as the base for mounting the clutch. If you look at the system on some Japanese bikes they drive their gearboxes via a helical gear on the engine output shaft and a larger helical gear on the gearbox main shaft (no intermediate idler). The clutch is mounted onto this gear via a plate with two sets of springs, one to take the drive forces and the other to take the overrun forces. This is the same idea as most cars. The springs replace the E.S.A. Nothing to wear out except gears and a wonderful ready made interface for a starter motor mounted where the dynamo normally resides, or, drive the central idler gear via a shaft that goes all the way through to the kick start cover and use a modification of the French starter system to drive this shaft, but this time please, with a Bendix or pre-engagement system.
 

greg brillus

Well Known and Active Forum User
VOC Member
Yes a bendix type starter is what I'm looking at for my next project..........The Bob Newby clutch/primaries are excellent save one small feature. The center clutch bearing is a non sealed set up that uses tiny BB's and some grease to lube it all. This needs periodic attention or else the set up will start to self destruct, as it is not actually sealed and dirt can get in, plus any water/moisture. Not a big deal on a racer, that you should be mindful of stripping and servicing perhaps annually if you are racing several times per year, but a road bike is probably not going to get attention in that area too often. If this was sorted with a large sealed bearing then the assembly would be an excellent choice for a road bike.
 

kettlrj

Well Known and Active Forum User
VOC Member
If you are worried about the tensioner blade, you should change over to the series 'D' type that has two thinner blades. You need to change the end abutment parts as well. The thinner blades are more flexible and less likely to break.
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
I think you will find they are the same blades and end abutments are widened to take two blade thickness, I've seen several blades that have kinked, usually at the rear end but this was because they were run as a single blade. Angle grinder to widen slots nowadays but 50 years ago it was Silver Steel machined to suit and hardened then tempered to straw colour.
 

stumpy lord

Well Known and Active Forum User
Non-VOC Member
I've got the primary side of my Rapide in bits. Its got an original Renold England chain. The tension adjuster looks to have about 3/16 of adjustment left and the blade is in good condition. I cant decide whether to replace it. Normally i would, but i'm unsure of the quality of the available replacements. and wonder if this one is better quality than the new ones, and still serviceable?
If not, is there a preferred make of replacement. Thanks.
how about the rubber coated ones that are made by V3 products. See the rear pages of the M P H.
stumpy
 

Pete Appleton

VOC Hon. Editor
Staff member
VOC Member
VOC Forum Administrator
VOC Forum Moderator
Perhaps we should get together and organise a supply of these chains and other parts that we may need. We could set up a supply company and pay someone to administer it... Oh, hang on a moment!

That is only partly a sarcastic answer. I like saving money as much as any of you but last time I needed a primary chain I got it from the spares company. I could have saved a few quid by shopping around but my logic was....

1. The guys ( and girls) there have already researched the best product so I am getting the benefit of their experience in supplying loads of them.

2. Ask their advice on fitting it and make sure that you follow this advice. You could even get photos of the other components in there as you fit your new chain.

3. Be reassured that they have a proper product liability insurance in place. If the chain turns out to be not up to standard and causes an expensive snarl up you can expect to be compensated. Try asking the stall holder down the autojumble what they will do if their chain fails.

4. Bulk chain suppliers may have liability insurance but are they specifically stating that their chain is suitable for our application?
 

oexing

Well Known and Active Forum User
VOC Member
You could buy any brand of triplex chains, these are basically extremely strong for that primary drive purpose. Many bikes have a lot weaker chains, duplex or single chains. After all, a 1000 cc V-Twin is only two 500 cc singles flying in a close formation when chain stress is calculated. BUT: You have to ditch that miserable ESA or block it because it is the root of the problem of breaking chains: NO ESA is a lot easier on the chain than having to cope with all that slamming of ESA components when they hammer onto full compression as the springs cannnot possibly prevent that due to the completely wrong design of the ESA cams - way too flat and no progressive action to fight the full lock. That bang-bang behavior has been watched by other Vincenteers like Hamilton. Even when you find a chain that does not break you still have the stress by shock waves from ESA into chain and onto the main bearings and more so onto the gearbox input ball bearing. No way I´d accept that knowing how to prevent it - by fabricating my own ESA cams with progressive character, see my picture below. We had this discussed some time ago but frustratingly the club gods did not even want to look at this in ignorance (or pride?) for including in a future production, which would be a bit cheaper as the positive lobes are a simple 6mm radius that any cnc mill does in minutes. The corresponding negative shape requires a cnc mill with cnc dividing head for two axes milling. I could do it on my manual mill and DRO plus rotary encoder on the dividing head at first try so any bright cnc guy should be able to copy when I could do that with my 65 year old brain.
Anyway, I´d suggest blocking the ESA with a big o-ring replacing the springs to prevent full compression and its shocks. What is missing in my photo is a steel cup covering the spring holes and keeping the o-ring from expanding by cenrtifugal forces. It is worth a try, the o-ring is easily replaced by bigger size or rubber plate or some such when trials say so. Even welding up the ESA would be better than the original misery.

Vic
P1060633.JPG


P1060635.JPG


P1060644.JPG
 

vibrac

Well Known and Active Forum User
VOC Member
there has been a revision (or perhaps just a new drawing) of the cam profile about a year or so ago by the VOC drawing committee (I guess thats who are referred to as 'Club Gods' above) I am not sure of the details but I think as normal policy it was to ensure it was exactly to Vincents original design, whether that implies some non drawing committee cams perhaps from outsiders previously available had strayed from the original I could not say
 
Top