PD: Primary Drive Rapide Chain Problem
- Thread starter bmetcalf
- Start date
I have had two primary chains shed the center row of rollers. Both Tsubaki seamless rollers. Diagnosis by local guru, chain much too loose.
Ken Horner did some exhaustive checking of primary chains available now, and found non are made of high tensile materials like they use to be........remember the near catastrophic failure they had at Goodwood with their twin racer back in 2014........So keep a regular check on your chain for condition and correct tension........It also pays to change the primary oil annually....... the oil gets dirty quite quickly........you can suck most of it out with some form of pump or syringe, then poke some paper towel or something very absorbent down and to the rear with a piece of wire with a hook bent on the end, or a pair of long surgical pliers like I do........ The primary chain is the mostly "Set and forget" part of the engine, but its failure we all know about.........preventative maintenance is the key on this one.
I had the middle rollers taken out at the 1999 IOM lap. I should have remembered that back in the day I took the dynamo sprocket off the twin at silverstone after the scrutineers had checked the lights (later the whole dynamo question was avoided but thats another funny story) For road use a question of a good quality chain (not car cam drive chain) and attention to the dynamo tooth engagement
Once again, a typical case of crap ESA and its effect on chain and dynamo sprocket failure. So my advice, weld up the crap ESA or get a belt drive - which got no ESA at all. Or else, as long as the Spares Co is ignorant for redesigning the non-working ESA for a real thing you could do a cush drive for the dynamo sprocket. Speaking about cush drive, you don´t need any in an all chain drive on a motorbike. What exactly do you want to protect with this ?? Chains are nowhere hard in action so not much reason for having them. In a Vincent the gearbox teeth are extremely solid and I have never seen proof of worn teeth in there. BMW or Guzzi got no chains anywhere so all gears which may be harsh from wheel loads or from crankshaft "shocks" . But still no cush drives on these, just effective ESA in gearbox input shafts - well, not so much on some Guzzis, similar to the Vincent design.
Anyway, the wrecked middle row of chain rollers is not due to "high" loads from the dynamo - just 1/4 hp max, but from the mass of the rotor/armature, loading the rollers from shocks entered into the triplex chain by the ESA bashing onto its stops each time you open or close the throttle.
What you could do for alternative to unavailable effective ESA, do a cush drive for the dynamo sprocket. I did an exercise on a "limited slip" sprocket hub for the brushless alternator, just for the fun of it. Would not actually need one as I did my own ESA in BMW style. But maybe the wave washer loaded friction drive in the sprocket hub could lead to ideas for your mod. Another design could include some fat o-rings in holes in the sprocket for damping peak loads from the rough operating conditions in the triplex chain.
So when taking care of the dynamo drive there should be no more troubles like seen here and split rollers are quite acceptable basically as the outer rollers are fine with all power from the crank. Quality chains in high tensile steel - who would produce anything low strength for trade use ? I would not think you could keep costs much lower by having "cheap" steel types for substandard chains ?
Vic
mass of rotors comparison, small diameters are brushless motors, one Miller armature, one 3ph alterator BMW:
"limited slip" cush drive with phenolic paper friction material plus wave washers:
BMW style ESA :
some shaft drive Jap ESA - they copied my BMW inspired three lobe mod !!
Anyway, the wrecked middle row of chain rollers is not due to "high" loads from the dynamo - just 1/4 hp max, but from the mass of the rotor/armature, loading the rollers from shocks entered into the triplex chain by the ESA bashing onto its stops each time you open or close the throttle.
What you could do for alternative to unavailable effective ESA, do a cush drive for the dynamo sprocket. I did an exercise on a "limited slip" sprocket hub for the brushless alternator, just for the fun of it. Would not actually need one as I did my own ESA in BMW style. But maybe the wave washer loaded friction drive in the sprocket hub could lead to ideas for your mod. Another design could include some fat o-rings in holes in the sprocket for damping peak loads from the rough operating conditions in the triplex chain.
So when taking care of the dynamo drive there should be no more troubles like seen here and split rollers are quite acceptable basically as the outer rollers are fine with all power from the crank. Quality chains in high tensile steel - who would produce anything low strength for trade use ? I would not think you could keep costs much lower by having "cheap" steel types for substandard chains ?
Vic
mass of rotors comparison, small diameters are brushless motors, one Miller armature, one 3ph alterator BMW:
"limited slip" cush drive with phenolic paper friction material plus wave washers:
BMW style ESA :
some shaft drive Jap ESA - they copied my BMW inspired three lobe mod !!
Since installing a new chain and adjusting it properly and checking that adjustment periodically I have racked up 10's of thousands of miles with no discernable wear so far. I have the D type ESA. Not touched the ESA since last engine overhaul 50000 miles ago. I do use a hardened dyno sprocket from Maughns and a PD9 from Vindean.
When I thought the problem was somewhere else and needed to deploy the front stands, I managed to remember the bungee trick (I think from Bill Thomas). The hook on the stand is temporarily kept in place by zip-tying it to the permanent zip-tie double loop that is a cushion between the stand and the engine plate.
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