I am considering replacing the Lucas E3 dynamo on my M20 with a modern Alternator. What I have in mind is installing a unit that is taken from a small Kubota diesel farm tractor (link enclosed). I have seen on the web that this has been made before by some Vincent, Velocette and Douglass owners (unfortunately with minor explanation). I am willing to "pay the price" of the authentic look as far as I will be able to ride the bike in a safe manner, with all lights on.
But, I still cannot understand, whether this is a dynamo or an alternator? What is a "permanent magnet alternator", as it is sometimes described as? Is it really a benefit to install one of these?
Have a nice weekend.
I think it is a simple alternator, much like the rotor and stator set up on many British bikes. The rotor is spun by a belt as opposed to the rotation of the crank.
You will need an external voltage regulator/rectifier to not only convert AC to DC, but also knock down the voltage to around 14V.
I would guess you are considering running the bike 12V.
If you are in the UK Kubota parts are quite expensive. You can get Chinese stuff, but it can take around 6 weeks to arrive.
ps What you are trying to achieve is quite an expensive modification.
You will need to find a way of mounting the alternator somewhere on the engine and then try to run a belt from the end of the crank to the pulley housing on the alternator. You would need a way of adjusting the belt tension.
I guess you may need to machine the crank and cut the primary chaincase. That's a lot of work. I wouldn't know how to fit a pulley on the M20 crank.
Personally, I would spend the money on getting your existing dynamo reconditioned and the headlight reflector re-silvered.
You can then choose if you want to run a 6 or 12V system. The downsize of 12V is the plates in the battery are very small and can deteriorate very quickly.
The Kubota alternator is a permanent magnet alternator,
Much like the "Alton" and the "Powerdynamo" are.
The good thing about it , is that you do not need the stator coils, so it is much compact, with powerful
Permanent magnet, but on the other side, it always has some resistance for turning, whether the battery needs charging or not.
Whilst traditional alternator, like the dynamo, rotate smoothly when not charging is needed.
I saw at the past an E3L Lucas with a "window" cut on the side, (on the "width" of it, on one side)
The internal coils where gutted, and replaced by a small pulley.
At the time of putting the "dynamo" together, a belt inserted from the "window", the internal axle
(What was previously the armature) inserted, with the belt now on the pulley,
And after all was mounted, the other side of that short fan belt, drove a small Suzuki alternator
Which was mounted above the dynamo.
I was quite a while ago.
Wish I had taken a picture…
Thanks a lot to you all.
I'm located in Israel. These small alternators are also fitted on other engines and generators.
I will think it over again.
I intend to take the drive from the magneto.
I will post as soon as something will proceed.
