Sooo, here are my latest findings from the test set with 48 V three phase brushless motors. Actually I got a lot more power from the mid size motor than I will ever need, starting from low speeds and with no temperature problems in my workshop and no cooling.
My previous tests were tried with same motor but typical brushless permanent magnet alternator motorcycle voltage regulator. That was NOT a great set up just as timetraveller had suspected: The technology with one - or most of - these is simply to earth one or more phases to keep voltage within limits. I observed some groaning in the motor once speed exceeded the specified voltage and in that state the regulator plus the motor started to heat up quickly to unacceptable temps so I had to stop when some Lucas wire smoke appeared from the motor. By doing some Google reading I learned that this type of regulator is widespread in motorbikes when excessive heat gets cooled down in oil bath generators - so no choice for a Vincent.
New idea was to get a standard voltage converter 48 V to 13.8 V to go with the three pase rectifier. I blew up two 55 W quartz bulbs before when I exceeded the voltage limit with a 24 V to 13.8 V converter when I did a quick high speed test to 5000 rpm and the converter blew up two capacitors and the bulbs in a second. The 300 W motor in the photos does 55 Volts AC at 5000 rpm so no surprise really.
When I got the 48 V converter recently I hooked up all components , rectifier for single phase DC and converter to 14 V and got these numbers after half an hour test run, no cooling :
cold motor 55 W bulb sees 14 V at 2450 rpm - 1960 rpm at crank
100 W bulb 14 V at 2520 rpm - 2020 rpm at crank
155 W (100 + 55 W bulbs ) 14 V at 2670 rpm - 2140 crank speed
I then hooked up three quartz bulbs to have 210 W on the motor and did half an hour run, with little reduction of performance at higher temperature:
210 W 14 V from 2820 rpm - 2260 at crank
after a 10 minutes run at 3200 rpm and 210 W load the motor temps came up to 47 degrees C , after half an hour at 210 W load and 3200 rpm at the motor I got 55 degrees on the motor, NO cooling.
The rectifier and voltage converter had practically no temperature rise , so no worry on a bike at all. So my conclusion from that is the mid size 300 W motor is more power than I´d ever need . You can get four sizes from Aliexpress, all same size but different legth, from 100 W to 400 W 48 V , 14mm shaft.
When playing with the generator I fabricated some type of friction clutch for the dynamo so as to post some idea for owners who may run a geared Alton on the triplex chain and old ESA. I do not believe to really need it with my own design ESA but it does not hurt. The mass of the permanent magnet rotor is a lot lower than say a miller dynamo armature so even less critical anyway.
I placed some friction material at both sides of the sprocket and loaded the unit with wave type spring washers. Only road tests will show if I need to add another washer due to too much slip at higher loads from the alternator, no problem.
An Alton is certainly the easiest way to replace the Miller dilemma. But for those who love lathe jobs the cost of all the China hardware is around € 100.- depending on size of motor. So for the difference to the Alton version you may want to mess around in your workshop instead and be creative . . . .
Vic
48 V brushless
48 V converter