PD: Primary Drive Make your own Generator

[oexing]

Laverda twins had a dynamo 12 V 150 W at the front of the engine, belt drive. The extra small motor starter was via a sprag clutch drive and chain plus planetary gear in the starter motor behind the cylinders, don´t know about MVs.

All brushless motors have no windings in the rotor, just permanent magnets there. So I cannot see a problem with high revs, quite unlike the old dynamos and their brushes on collectors. There you can expect to find burnt soldered contacts and flung out tin solder when something broke in the windings. The armature really is the weak point in a dynamo, the field coils rarely fail.
I honestly got my wattage numbers from my own tests and loaded the motors by hooking up a few bulbs, quartz too and noted the voltage on a digi voltmeter. That is why I wrote, don´t trust any numbers in ads but do your own tests and see what that shows. I just ordered another brushless from Aliexpress, said to be a 400 W type, 48 V. Length is no problem on the Vincent, but I want to keep the 68 mm diameter. So in a few weeks I can tell if that big motor might be suitable. It has a massive 14 mm shaft, so a decent ball bearing to go with it I guess.
Hmmm, don´t see an easy way to have a starter/dynamo combo at this place. You´d need some gear reduction for the starter to make it over TDC but then you don´t get the speeds when asking for the generator function. The starter/dynamo combos I know from BMW Isetta 250 and 700 cc flat twin car or some scooters from Zündapp had veeery big diameter armatures and 12 batteries plus direct drive sitting on the crankshafts.
What I noticed in my tests, you get high voltage at very moderate revs with no load but when loaded this goes down a lot. So only an actual load test will be helpful.
Bill, your Lithium battery is a LiFePo4 type - hopefully ?? Not the explosives as in notebooks ?? I would not expect to get problems with electronic step-down converters then, batteries should not be as critical as tablets or the like and I believe truck drivers will have lots of them for operating all sorts of electronic devices on these.
Below another brushless on back order from Ali today, possibly a bit too big, will see.

Vic
48 V 400 W brushless

 

[JustPlainBill0]

After thinking a starter/generator over, I came to a similar conclusion Vic. Maybe when there's a hybrid Vincent.

It seems to me that the test of a generator is whether it makes enough power to keep the battery charged with whatever lights, ignition, etc. are being used. And therefore, a proper test would include a converter, battery and maybe a quartz H4 light bulb to approximate the electrical load. My problem in that regard, is that the highest speed my (floor) drill press can achieve (2850 RPM) is lower than the speed at which my generator reaches 12V (3000 RPM) and it's lower than the generator RPM expected when on the road. I'm not sure how big a problem that will be, since when the output voltage reaches 10 VDC, the converter will boost it to 13.8 VDC. Maybe if I knew anything about electricity...

Another concern: except for measuring battery voltage at the start of the test and at the end of the test, I don't know how to determine whether the generator was able to maintain the charge or not. I suppose putting an amp meter between the generator and battery would be helpful too. Any other ideas?

 

[oexing]

Well, when looking at your test findings I´d think your strategy on motor choice was not optimal. See my tests above, I get about 14 V at 2050 rpm crank speed. And this with motors of 24 V type at 3000 rpm in the descriptions. My thinking was you might arrive at 14 V with a nominal 24 V motor at lower speeds than with a proper 12 V type. So I am very curious to get the new 48 V motor in a few weeks for tests. I am expecting 14 V with it at even lower speeds.
My test setup had no converter included, just a three phase rectifier for the brushless as you cannot connect all phases to one single wire. You can drive a bulb with one phase of course, AC power in that case. And from this you can guess what power to expect with all phases but then my tests appear good enough for me to have an idea about performance on the bike, a connected battery will most likely not have a bad effect at all. From above a certain motor speed at 14 V you´d need a step-DOWN converter to limit the system to max. 14 V when picking a 24 V or 48 V type. So really I cannot see a problem to keep the battery charged when having a stepdown converter in the setup.
The present Alton type has no longer any gears in it to get higher speeds for the rotor like in the older type - as far as I have learned. So in consequence they must have changed the diameter of the rotor to a smaller size to keep the radial offset of the shaft for simple installation, no machining required. Nobody here who could point me to performance numbers at various speeds with these ?
I only came to looking for alternatives because I just would not accept any noisy gear drive in Altons then - which did not prove to be very durable - or so I found in this forum somewhere. So to this day for lack of info about performance of the present Alton it seems to me a modification plus some minor machining for the China brushless types may be very worthwhile to do. At least all tests appear to be better than what I know about Altons.

Vic

 

[JustPlainBill0]

You're probably right about my choice of motors, but it's easily corrected. I do like the brushless motors you're testing/considering. But one of my reasons for choosing a 12K RPM motor was that there was no chance of exceeding the maximum speed it's rated for on the Vincent. I don't know what happens to a motor rated for 3000 RPM when you turn it 7500 RPM, but it can't be good.

The voltage converter I have in hand, is a step up/step down unit and converts 10-32 VDC to 13.8 VDC. I got it when I was looking at 60 watt motors; it's only rated for 4 amps and all these China motors we're discussing make 5 or more amps.

 

[Dave61]

So do any of these devices provide a possibility of a through drive to magnetic pickups? and would one be found where half engine speed would produce enough current? If so the ultimate goal of nothing in the dynamo position to stuff primary chains would be achievable and we could run both electrical power and electronic ignition from the mag position.
And perhaps? make a path for improved electric start from the dynamo position....

Tim,
Didn`t Ernst Hegeler do exactly what you`re describing ? I think there were some concerns over whether the timing gears were strong enough to cope with driving a charging system.
Looked like a very neat set up but would want to be sitting down if I was asking for a price.
Cheers
Dave

 

[JustPlainBill0]

Just one of those FYI posts. In anticipation of the arrival of my 12K spindle motor, I decided to test fit a Yamaha FJR1300 starter motor to my drill press/vise set up. It's a four brush, permanent magnet 12 VDC motor. It looked pretty good, so so out of curiosity, I hooked up a sealed beam headlight and a digital voltmeter:



Running the drill press at top speed (2800 RPM) the starter motor barely managed to generate 2.6 VDC and make a faint glow in the headlight. Clearly not a candidate for generator use, though it is a perfectly functional starter.

This does not bode well for home testing the 12K spindle motor.

 

[oexing]

Don´t confuse a nominal rating of, say, 3000 rpm and 12 V or 24 V at maybe 200 W with a speed limit . This is not the speed limit of the motor. The good old 6 V dynamo did 7500 at 6000 rpm crank speed - and that with brushes, collector and windings. So when putting a brushless motor at the same place, where´s the problem ?
I operate a three phase hf spindle motor on the lathe for a few grinding jobs when CBN hard turning is not suitable. That 48mm watercooled spindle has a nominal 2800 rpm speed at 50 Hz, 75 V. The inverter for it does 1000 Hz, so I can have around 60 000 rpm for small bores to grind. So 10 000 rpm is no big thing for these brushless motors, I guess.
Running a dynamo off the timing gears would not be a big load really, you get just 100 W smooth load at best, nothing compared to valve gear pulses. But the half time very low speed there is not great to generate some wattage. Why not keep the dynamo at its old place? The dynamo is really only the victim of the triplex chain, not the root of the problem. Most forumites will know my thinking of what causes the primary troubles and it is not the little dynamo at 60 W . There is only some higher load on the dynamo drive and motor when blipping the throttle and the inertia of the rotor is some factor. I could put the Miller armature on scales and compare it with the brushless permanent magnet rotor weight, my guess , the magnet is less weight, so a bonus for the brushless.

Vic

 

[timetraveller]

Gentlemen, I have been hovering over this thread for some time and in the back of my brain I have some queries. These result from when I was a school boy and learning about Fleming's left hand and right hand rules. My memory, which is very vague on this, is that there had to be some phase difference between the poles if one wanted to use a system as a motor or a generator. Can one of you electrical pundits refresh the memories of those of us of a certain age as to whether this applies to what is being attempted here and if not, why not? Thank you in advance.

 

[JustPlainBill0]

Can't help you timetraveller - my knowledge of electrical theory is limited to "don't put a fork in the power receptacle at home or you'll frizzy your hair". My practical knowledge is to throw money at an electrical problem until it's fixed. That said, if there's a way to avoid throwing $650 at an Alton, I'd like to pursue it.

Meanwhile, back to the issue of turning a motor rated for 3000 RPM some higher amount. My concern was not aimed at the mechanical aspect, but since voltage increases as motor speed increases, wouldn't there be a risk of frying the battery, lights, ignition, etc. when those components are hit with significantly higher voltage?

 

[oexing]

For limiting the voltage in a generator system you have a constant voltage device. The old dynamo had a relay type non electronic voltage and current limiter . Without it you could get way above 6 V from the dynamo, the higher the speed, the higher the voltage. With state of art electronics I guess these electronic CV units use PWM to feed the 13.8 V for battery charging and lights.
A starter motor is no good for a job of dynamo: It has a very low number of windings, but very massive wires for hundreds of amps when hitting the start knob. For higher voltage like 12 or 24 V you´d like to have many windings in the rotor. But these can be finer wires as current will be only 10 to 20 A . Basically many types of electric motors can be run as a motor and a dynamo as well. A big difference is only obvious when looking at an engine starter motor: In this very specialised application you will find extremely heavy wiring for hundreds of amps but only for one minute or two runs, any more and you will burn out the motor.

Vic