It is a great shame that the original ESA cannot be retained on the Comet when an electric starter kit is fitted, despite all the flack that the original ESA is receiving, I am sure on a standard Comet it is more than adequate. I do wonder if the culprit in the first instance are the ESA springs, and whether they are of the same quality of those that were originally fitted by the works, same goes for the C45, how is the standard and quality of an aftermarket spring checked?
PD: Primary Drive Rapide Chain Problem
- Thread starter bmetcalf
- Start date
It might be worth going back over the history of the ESA. It was clear within few years that the original had problems and this lead to the redesign for the Series ‘D’s. More springs and a better locking mechanism but no change in basic design. Then came the Australian one which had even more springs. Experience by Dick Sherwin on his sidecar outfit showed that even with the addition of a heavy Russian sidecar there was not much movement of this ESA and it paid to remove some of the springs. All these ESAs have a similar design in that the ESA cam design is such that compression of the springs versus rotation is more or less linear and if one uses normal coil springs, which have a linear force to compression ratio, then one is applying a linear resistance. The design advocated by Vic (Oexing) has a different cam design in that the movement between compression of the spring and the rotation of the ESA is not linear. In fact the resistance to compression rises much more rapidly than linear.
Then we have Stu Spalding’s contribution of bothering to get springs made wherein one spring gave the same, or similar. characteristics to the pairs of springs used in the original ESAs and clutch shoe centralising I have no idea why it was thought that two springs could be used when one could have the same characteristics. Perhaps post war availability was a problem. Even acknowledging the Spares Company’s wish to produce parts to the original specification I still do not understand why they continue to provide spring pairs but I am prepared to believe that there is something here that I do not understand.
Now to the failure of primary chains and dynamo drives. About eighty of the Walkernators are out there, generally being used by the long distance riders who value output and reliability over originality. So far as I am aware there has never been a failure of either the chain or dynamo sprocket when the Walkernator is being used. The only failure at all that I am aware of is that on some of the early ones it was possible for the bearing at the driven end of the dynamo replacement to start to turn on the shaft and in its housing. A redesign by father and son, John and Peter Appleton solved this problem by trapping a steel tube between the two bearing inners, thus forcing them to rotate together. All Walkernators now have that built in. During the development of the Walkernator, by Dick Sherwin and myself, I did originally design the drive with the same multi vee belt as is use in all of them but with the driven sprocket plain, that is no grooves, to reduce the need for alignment of the two pulleys. Such a system is used on some Flymo grass cutters. It did not work in that enough power is being taken by the alternator that the belt slipped on the driven pulley, even when the belt was overtightened. I mention this to emphasise that even with a modern alternator design there is still sufficient power being taken to potentially cause problems with the original design of chain and sprocket and yet none has ever manifested itself. I put this down to two things. One is the inherent shock absorbing nature of the multi vee drive belt. The second reason is the fact that modern alternators do not produce maximum power at all times. Instead the magnetic field is controlled by the field windings which themselves have their electric feed current controlled by the alternator controller. The originally used Iskra alternators could produce 30 amps, the more recent Nippon Denso items can produce 40 amps. At 14 volts that is 420 or 560 watts of power, call it half a kilowatt which is near enough half a horsepower. So the mechanics of the system can take plenty of power.
Then we have Stu Spalding’s contribution of bothering to get springs made wherein one spring gave the same, or similar. characteristics to the pairs of springs used in the original ESAs and clutch shoe centralising I have no idea why it was thought that two springs could be used when one could have the same characteristics. Perhaps post war availability was a problem. Even acknowledging the Spares Company’s wish to produce parts to the original specification I still do not understand why they continue to provide spring pairs but I am prepared to believe that there is something here that I do not understand.
Now to the failure of primary chains and dynamo drives. About eighty of the Walkernators are out there, generally being used by the long distance riders who value output and reliability over originality. So far as I am aware there has never been a failure of either the chain or dynamo sprocket when the Walkernator is being used. The only failure at all that I am aware of is that on some of the early ones it was possible for the bearing at the driven end of the dynamo replacement to start to turn on the shaft and in its housing. A redesign by father and son, John and Peter Appleton solved this problem by trapping a steel tube between the two bearing inners, thus forcing them to rotate together. All Walkernators now have that built in. During the development of the Walkernator, by Dick Sherwin and myself, I did originally design the drive with the same multi vee belt as is use in all of them but with the driven sprocket plain, that is no grooves, to reduce the need for alignment of the two pulleys. Such a system is used on some Flymo grass cutters. It did not work in that enough power is being taken by the alternator that the belt slipped on the driven pulley, even when the belt was overtightened. I mention this to emphasise that even with a modern alternator design there is still sufficient power being taken to potentially cause problems with the original design of chain and sprocket and yet none has ever manifested itself. I put this down to two things. One is the inherent shock absorbing nature of the multi vee drive belt. The second reason is the fact that modern alternators do not produce maximum power at all times. Instead the magnetic field is controlled by the field windings which themselves have their electric feed current controlled by the alternator controller. The originally used Iskra alternators could produce 30 amps, the more recent Nippon Denso items can produce 40 amps. At 14 volts that is 420 or 560 watts of power, call it half a kilowatt which is near enough half a horsepower. So the mechanics of the system can take plenty of power.
My Alton plastic sprocket (Comet ESA) has lasted a season but I also have a Honda clutch and I guess that also has a shock absorber in it, I will keep an eye on the set up but I am sure changing the bushes even yearly is a small price to pay for that button press - my knees certainly agree.
I have not heard of Harleys breaking primary chains and they are now around 2 litres, this is what they use.
When a tightly mounted dynamo can produce split rollers in the triplex chain I´d be worried a lot about wrecked bearings in the dynamo ! At least in the Miller type the bearings are not particularly massiv so I would not think they´d last long in this situation.
What is current thinking about snapping chains and the reason for this ? Would not imagine it is the power of the engine. Same types of chains in Commandos and Laverdas but different ESAs or none . In case of Laverdas they have gone to 2 single row chains as triplex types no more available. No choice for Vincents as you want a dynamo drive from the middle rollers. They change chains in 20 000 km intervals for safety aspects - cheap enough I´d think.
The Harley ESA is old logic still, not overly great. There is no good reason to have same lobe shapes for both sides as you don´t get the space for geometrically progressive lobes with springs not responsible for providing a stop. That is why Japanese engines don´t adopt this old design - instead go like BMW for half a century. So in that design you don´t get same side loads from very hard springs as the steep ramp of lobes does the job. High spring forces in Vincents eat into the sprocket and ball main bearing inner race faces , no thrust bearing in there.
The springs look like Belleville dished washers ? I was thinking about these in my engines but was not quite sure about lifetime in engines. So I kept the small standard springs. See the HD dupex chain sprocket in photo above, obviously good enough there. So what is the root of snapped chains in Vincents - very long use , no changes in decades ??
Vic
What is current thinking about snapping chains and the reason for this ? Would not imagine it is the power of the engine. Same types of chains in Commandos and Laverdas but different ESAs or none . In case of Laverdas they have gone to 2 single row chains as triplex types no more available. No choice for Vincents as you want a dynamo drive from the middle rollers. They change chains in 20 000 km intervals for safety aspects - cheap enough I´d think.
The Harley ESA is old logic still, not overly great. There is no good reason to have same lobe shapes for both sides as you don´t get the space for geometrically progressive lobes with springs not responsible for providing a stop. That is why Japanese engines don´t adopt this old design - instead go like BMW for half a century. So in that design you don´t get same side loads from very hard springs as the steep ramp of lobes does the job. High spring forces in Vincents eat into the sprocket and ball main bearing inner race faces , no thrust bearing in there.
The springs look like Belleville dished washers ? I was thinking about these in my engines but was not quite sure about lifetime in engines. So I kept the small standard springs. See the HD dupex chain sprocket in photo above, obviously good enough there. So what is the root of snapped chains in Vincents - very long use , no changes in decades ??
Vic
I have a McDougalator. It worked great for about 2000 miles, then the clutch started to slip. I adjusted the pressure on the Belleville spring wtih a file but I filed it to much and didn't have enough slip. It is a very sensitive adjustment. Then after about 500 miles I ruined the primary chain and the dynamo sprocket. Once I got the tension right with the new spring though it has been fine for 12,000 miles. I think that you need a bit of slippage on this type of alternator drive to prevent the inertia of the alternator causing to high a load on the chain. It's not the electrical load it's the inertia. Even some modern motorcycles have slip clutches in the alternator drives when they are gear driven from the crank. Probably you could have problems from too tight a mesh or also to loose a primary chain.
Funny how I have seen a few Primary chains which have lost the centre rollers,
And had no damage to the dynamo bearings,
Another one of those strange mechanical results !.
And had no damage to the dynamo bearings,
Another one of those strange mechanical results !.
Bill, do you remember how the center rollers looked when you found them in the sump ? Mangled as in this thread by obviously finding their way between the remains of the shredded sprocket ? Still I am not clear if the mess starts with broken ESA springs finding same place between dynamo sprocket and middle rolles and breaking teeth or rollers from this. So what is your opinion why rollers break and dyno teeth shredding ? It cannot be the "power" of the dyno , rather the mass of rotor. But this seems a bit with question mark as it takes a lot of force to break them. I would not think this would come without wrecking dyno components ?? Still mysterious story to me . . .
Vic
Vic
Hello Vic, Not sure but I think the rollers were split, When made ?,
ie have a join ?, And when they break, They just break in half ?.
It happened often in the old days , Mostly due to too much in mesh.
It never happens to the 2 sets of outside rollers !! ??.
These are Funny old Bikes, They can go on for years, If rode gently,
I remember my first Twin with a sidecar 1965, Still got the Bike !,
The Cams were so worn the valves were hardly opening !, But it would still pull like a train up to 70 mph.
I agree there is lots that can be made better, On these Bikes , But on a good day , I have had a lot of FUN .
Cheers Bill.
ie have a join ?, And when they break, They just break in half ?.
It happened often in the old days , Mostly due to too much in mesh.
It never happens to the 2 sets of outside rollers !! ??.
These are Funny old Bikes, They can go on for years, If rode gently,
I remember my first Twin with a sidecar 1965, Still got the Bike !,
The Cams were so worn the valves were hardly opening !, But it would still pull like a train up to 70 mph.
I agree there is lots that can be made better, On these Bikes , But on a good day , I have had a lot of FUN .
Cheers Bill.