Temperature of alternator flywheel/crankshaft a factor in PMA design?

BBS360

BBS360

XS400 Guru
Top Contributor
Messages
1,974
Reaction score
196
Points
63
Location
BC, Canada
With the stock, and rather ingenious, brushless alternator the temperature of the flywheel is fairly irrelevant but with permanent magnet alternators it might be a factor.

I believe most PMA flywheels use ceramic magnets which might indicate that temperature is a factor in flywheel design as they are not as temperature sensitive as neodymium magnets.
Or it could be because they're cheaper.

Neodymium magnets are pretty common in wind turbines and even a few aftermarket automotive alternators. In both cases temperature is not being directly conducted to the rotor by the drive shaft.
It is in our bikes.

Anyone care to guess at the maximum temperature seen by the rotor and/or crank shaft?
Pondering an alternative PMA design.
Neodymium magnets could provide a better source of flux and greater alternator output, but they might crap out at temperature.
 
The pamco system is awesome and is much more efficient at conducting energy from the ignition coils to the spark plugs than points systems, but it should be the coils (in relation to RPM) that dictate the current draw of the ignition system.
Power in the sense of bhp at the wheel would be slightly improved but I dont think actual alternator consumption/capacity would be affected in any way.

The idea of the custom PMA would be to hopefully increase voltage output by increasing the number of poles on the rotor, drop some weight by eliminating the field coil and maybe to simplify the overall PMA conversion procedure by allowing the stock stator to be used.
The issue is getting strong enough magnets to accomplish the voltage increase that can also handle the heat.

If enough voltage can be produced the next step would be to rewind the stator for an even higher current capacity. I'm pretty sceptical about whether the voltage could be increased that much though.
 
Last edited:
After looking at Pete's videos in the other thread I think it's conceivable that the PAMCO ignition might consume slightly more power because it runs that much more reliably than points.

Once I reinstall my mufflers I'll run the bike for a while and see if I can get a decent temperature readings under the timing cover.
Can't do any significant road riding right now but it might give me an idea of the temperature range the stock rotor experiences, and what strength of magnets can be used.
 
Back
Top