500W alternator stator (again)

Maestro, SEI-V
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: 500W alternator stator (again)

Post by penman »

Hi all,

Just a follow-up on the re-wound stator saga. I finally ended up with 50 turns of 0.8mm wire on each coil. It was just too difficult to wind that many turns of 1.0mm wire by hand on the short bobbins. I think a professional with a coil winding machine could do it, but the wire is too thick and too stiff to do it by hand. I did the winding with the plastic bobbins in place and using a single continuous length of wire, reversing the direction of winding after each coil. This is by far the easiest way to do it by hand, in fact the whole winding operation only takes about 15 minutes.

Anyway, this arrangement gave a much better cut-in rpm and with lights on, the alternator would maintain 14.4 battery volts from around 2500 rpm. I didn't have time to do any proper load test because by then I was just a few days away from leaving for the Moto Piston Rally. Still, the bike was running well, the lights were bright and I'd even fitted in a 10 mile shake-down test. What could possibly go wrong?

In fact nothing did go wrong. I covered about 1300 miles on the rally as usual, the Sachse ignition was brilliant, the electrics gave no trouble at all and much fun was had.

So what's the conclusion? Well this re-wind is a practical proposition if your stator is in a bad way as mine was. If I had time, I would probably use a professional coil-winding service and go for 1.0mm wire, but 0.8mm works fine and bends a lot more easily! If I get around to it (probably not!) I might do a load test just so that I know how many watts I have to play with, but the experience of the 2022 Piston Rally is that it is adequate anyway.

Now on to the clutch problems....!

Joe.
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: 500W alternator stator (again)

Post by mbmm350s »

Hi Joe
Brilliant and thanks for updating.
This kind of information would have been long lost on facebook.

So I think you made use of all 6 bobbins (as now you don't need the CDI bobbin) and that you wound as one continuous winding.
Winding in place meaning you therefore eliminated a lot of the soldered connections and improved reliability!

Only a specialised winder would be able to wind the coils on the former directly, but this is how it is done for later Morini/Cagiva stators, well indeed most motorcycle stators.

With the 0.8mm wire you will get more I^2 R losses compared to 1.0mm , The losses will be approximately to the ratio of 100/64 and max power output will be less.

The interesting measurement is the rpm at which the current to/from the battery with all lights on is zero, i.e load balance, ideally this is tickover speed or just above.

This modification is only for those who do not need the CDI generator winding!

Mark
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