Myself having no experience in stepper motors I´d think you might try one for generator use. You got one with four wires ? So you would get two phases from two sets of field coils. Basically a stepper motor is designed - well, for steps, so the feel you get when spinning the rotor is not so smooth compared to a nine pole ac brushless as in my tests. This is no factor for the bearings as they are designed for it - and the load onto the primary chain is negligible. The motor will draw half an hp at best and the chain has to handle 50 , 60, 100 hp any day. The "power" required to drive the dynamo/alternator from the middle rollers is simply nothing , at maybe one quarter or half of a hp really, no issue at all, never ! Sorry to repeat myself, the root of all troubles in the primary drive is the Elastic Shock Generator - definitely .
I guess, even with the old "high power" 6 V Miller 50 W dynamo owners will have seen worn middle rollers in the triplex chain - and you are not saying it was too much power that the Miller had asked from the chain ?? Really the single factor in all that drama is the mass/inertia from the armature/rotor in the generator that f***s up the chain rollers. The impulse for the shocks from inertia comes from the triplex chain when the ESA slams onto its stops because the shape of the lobes is completely wrong for the purpose and no progressive and smoother action is designed into them. So any shocks get into the triplex chain and along it into the rotating armature that wants to keep its speed against the harsh acting chain. It is easy to see that a lighter rotor will be less of an issue than a heavy type, the wattage not being ANY factor at all. No surprise for me that a geared Alton will never stand a decent mileage with its tiny gear teeth inside,lubrication just one aspect. But really any harshness from the ESA compromised triplex chain will be multiplied by the ratio in the Alton and observed in broken bits inside. So in one way a generator at the old magneto place is a better proposition than hoping for survival in the ESA primary environment.
The best way to overcome this dilemma is to throw out the ESA or weld it up. No ESA is a lot milder on the chain than with it. There have been lots of broken chains and engine cases in the event just because of this very flawed ESA, even though the chain without it would transmit a lot more power than most engines got. In my photos below you can see a duplex chain from a Horex 400 cc, 460 in my case - next to the triplex. The added cross sections of all links are a tad more in the duplex than in the triplex. But the rollers are metric at 6mm , 1/4 or 6,35 mm in the triplex. Yet there have never been broken Horex chains in a production run of more than 50 000 in 5 years - and that with no ESA there and SPLIT rollers in them. Just some poor rubber elements in the clutch sprocket included. There are photos of the Horex gear box contents next to the very strong Vincent gears, so what to worry about throwing out the horrible ESA , never a problem with these gears, I say. A big Vincent is just two 500 cc singles flying in close formation, after all.
Brian, don´t worry, be happy - with your belt drive and the Alton ! You will never have a problem with the alternator, non geared, i guess. Your drive has no longer the ESA so a smooth primary in your bike. But certainly any load on a dynamo chain sprocket or toothed belt gear must be prevented for a silent operation.
Don´t know much about Vespas but I guess the Hegeler sytem got its design from a starter motor planetary gear like in my photo. BUT this is a REDUCTION gear , not for speeding up a rotor. And in this role that will put quite a bit higher load onto timing gears as you can test by spinning said alternator via the planetary gear in its role as multiplier. Myself, I would not like this - nor would I like another gearbox on the alternator to care for . I got something similar on my twenties BMW in the Bosch type of magdyno - and I hate it. No great lubrication in there possible and a bit noisy too. The armature spins about five times faster than the input from the timing side, at just 30 W 6 V output.
Vic
I guess, even with the old "high power" 6 V Miller 50 W dynamo owners will have seen worn middle rollers in the triplex chain - and you are not saying it was too much power that the Miller had asked from the chain ?? Really the single factor in all that drama is the mass/inertia from the armature/rotor in the generator that f***s up the chain rollers. The impulse for the shocks from inertia comes from the triplex chain when the ESA slams onto its stops because the shape of the lobes is completely wrong for the purpose and no progressive and smoother action is designed into them. So any shocks get into the triplex chain and along it into the rotating armature that wants to keep its speed against the harsh acting chain. It is easy to see that a lighter rotor will be less of an issue than a heavy type, the wattage not being ANY factor at all. No surprise for me that a geared Alton will never stand a decent mileage with its tiny gear teeth inside,lubrication just one aspect. But really any harshness from the ESA compromised triplex chain will be multiplied by the ratio in the Alton and observed in broken bits inside. So in one way a generator at the old magneto place is a better proposition than hoping for survival in the ESA primary environment.
The best way to overcome this dilemma is to throw out the ESA or weld it up. No ESA is a lot milder on the chain than with it. There have been lots of broken chains and engine cases in the event just because of this very flawed ESA, even though the chain without it would transmit a lot more power than most engines got. In my photos below you can see a duplex chain from a Horex 400 cc, 460 in my case - next to the triplex. The added cross sections of all links are a tad more in the duplex than in the triplex. But the rollers are metric at 6mm , 1/4 or 6,35 mm in the triplex. Yet there have never been broken Horex chains in a production run of more than 50 000 in 5 years - and that with no ESA there and SPLIT rollers in them. Just some poor rubber elements in the clutch sprocket included. There are photos of the Horex gear box contents next to the very strong Vincent gears, so what to worry about throwing out the horrible ESA , never a problem with these gears, I say. A big Vincent is just two 500 cc singles flying in close formation, after all.
Brian, don´t worry, be happy - with your belt drive and the Alton ! You will never have a problem with the alternator, non geared, i guess. Your drive has no longer the ESA so a smooth primary in your bike. But certainly any load on a dynamo chain sprocket or toothed belt gear must be prevented for a silent operation.
Don´t know much about Vespas but I guess the Hegeler sytem got its design from a starter motor planetary gear like in my photo. BUT this is a REDUCTION gear , not for speeding up a rotor. And in this role that will put quite a bit higher load onto timing gears as you can test by spinning said alternator via the planetary gear in its role as multiplier. Myself, I would not like this - nor would I like another gearbox on the alternator to care for . I got something similar on my twenties BMW in the Bosch type of magdyno - and I hate it. No great lubrication in there possible and a bit noisy too. The armature spins about five times faster than the input from the timing side, at just 30 W 6 V output.
Vic