3 to 9W VPG … variable power generator

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SA_SA_SA
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Re: 3 to 9W VPG … variable power generator

Postby SA_SA_SA » 27 Feb 2018, 11:55pm

Mick F wrote:.....From what I remember, the BB dynamo was just that .......... a dynamo ......... and produced DC. I was never able to strip it down to see or maintain the brushes.
...

I had one (Soubitez BB gen) which was indeed reliable but was unfortunately unable to remove it when the bike frame was damaged but I can't see why they would make it a DC dynamo: surely unnecessarily complex compared to the usual claw-pole generator around which the Stzvo voltage curve is based... Some modern dynamos (lite spin / 12V axa spoke / sun-eco spoke) are not claw poles and use electronics to meet the Stvzo curve ).
CJ used to comment that the Stzo was based on slower German utility cyclists so speedy sporty UK persons could improve bulb life by fitting a pulley cap to bottles and/or fitting a inverse-series-zener clamp regulator like the Reflectalite presumably was.

I have just bought a Soubitez BB generator on ebay to (attempt to) make a maus-style top roller for my folder....
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kwackers
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Re: 3 to 9W VPG … variable power generator

Postby kwackers » 28 Feb 2018, 9:24am

NATURAL ANKLING wrote:Hi,
The way to do away with no load drag is to dispence with permanant magnets, and use a electro magnet armature, but it would need brushes, vary easily controlled output....................

And a power supply to get it 'started' and so you're back to batteries again.
No need for brushes either, you can easily make an ac alternator with electromagnets but you still need power to power up the electromagnet...

It's a red herring anyway, with no load the drag is negligible. I remember spinning my new Son front wheel and the old wheel, the Son stopped first but not by much and even that could have been down to differences in the bearing.
Now short out the Son terminals and it barely span at all...

MikeF
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Re: 3 to 9W VPG … variable power generator

Postby MikeF » 28 Feb 2018, 9:49am

kwackers wrote:
NATURAL ANKLING wrote:Hi,
The way to do away with no load drag is to dispence with permanant magnets, and use a electro magnet armature, but it would need brushes, vary easily controlled output....................

And a power supply to get it 'started' and so you're back to batteries again.

No need for brushes either, you can easily make an ac alternator with electromagnets but you still need power to power up the electromagnet...

Not necessarily so. I have built a generator (not for a bike) from an old 3 phase squirrel cage motor by connector capacitors across the phases. The small amount of residual magnetism is sufficient to start it producing electricity. But then I don't think anyone has made a 3 phase generator for a bike yet.
"It takes a genius to spot the obvious" - my old physics master

Brucey
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Re: 3 to 9W VPG … variable power generator

Postby Brucey » 28 Feb 2018, 10:03am

an example of this is with car alternators; normally they are first excited (on start up) by the current flowing through the charge warning circuit. Once running normally the excitation current flowing through the warning light circuit would drop to zero and the voltage regulator would provided the current for the magnetising (stator) windings.

For years on many cars if the charge warning light blew, the alternator would not work correctly, because there was no excitation current to start the process. However in nearly all cases if the rpms get high enough (typically about 4000rpm on the crank) the residual magnetism in the soft iron is enough to excite the alternator anyway. Ironically better soft iron might make the alternator 'worse' in this respect.

But.... carbon brushes and lubricants don't mix. The brushes have to be close to bearings and the bearings need grease or oil. I'd anticipate that this would cause problems in bicycle use.

cheers
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kwackers
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Re: 3 to 9W VPG … variable power generator

Postby kwackers » 28 Feb 2018, 10:17am

MikeF wrote:Not necessarily so. I have built a generator (not for a bike) from an old 3 phase squirrel cage motor by connector capacitors across the phases. The small amount of residual magnetism is sufficient to start it producing electricity. But then I don't think anyone has made a 3 phase generator for a bike yet.

I did think about residual magnetism, but I thought that might not be enough although I stand corrected.
My initial thought was a 'poor' permanent magnet, just enough to kick the whole thing off.

I don't think there's any good technical reason to not make 3 phase generators, I just don't see the point. I think people worry far too much about the negligible drag.
I don't even turn my lights off, after much fumbling with the on/off switch I concluded I couldn't tell (although it makes a fair difference if you're just spinning the wheel on the bike stand).

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Mick F
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Re: 3 to 9W VPG … variable power generator

Postby Mick F » 28 Feb 2018, 10:37am

Brucey wrote:an example of this is with car alternators .............
Talking of which ..........
Thread drift warning! :shock:

In the mid 70's we had a 1966 Humber Sceptre Mk2 and it had an alternator. Unusual for a car in those days. One day, the ignition light didn't go off, and I traced the fault to a small alu pot - like an indicator pot - and unplugged it and pulled it apart to see if I could fix it.
It was knackered, so I did away with it, and the light went out.
No probs, we had full instrumentation and you could see the charge on the ammeter.

Some months later, the alternator started whining from the driven bearing. I took it off and stripped it down and replaced the bearing. The back end was a bronze bush, but I saw that there was a slip ring disc there too. Two concentric tracks. By looking at the Haynes(?) Manual, I saw that this was a DC output via brushes with the sole purpose of controlling the alu pot to turn off the ignition light. That's all it was for, so I ignored it. The ignition light stayed off.
Mick F. Cornwall

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ConRAD
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Re: 3 to 9W VPG … variable power generator

Postby ConRAD » 28 Feb 2018, 11:28am

MikeF wrote:... but then I don't think anyone has made a 3 phase generator for a bike yet.

... apparently they did, in the picture below a SunUp MaxiDyn threephase spoke dynamo c/w usb output :roll: :roll: :roll:

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SA_SA_SA
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Re: 3 to 9W VPG … variable power generator

Postby SA_SA_SA » 28 Feb 2018, 12:12pm

ConRAD wrote:.... 3 phase generator......... apparently they did, in the picture below a SunUp MaxiDyn threephase spoke dynamo c/w usb output :roll: :roll: :roll: ....

A review:
https://swhs.home.xs4all.nl/fiets/tests/verlichting/dynamos/Sunup_eco_ds/index_en.html

CJ made some suggestions to them to make it better (ie simpler to fit and lighter) and so a nice modern alternative to the FER spoke dynamo but it seems they have so far ignored them .... :(
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MikeF
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Re: 3 to 9W VPG … variable power generator

Postby MikeF » 28 Feb 2018, 3:06pm

It's not clear to me if it is 3 phase. Their website is a little confusing and the output is given as DC.
Power output of 20W, but that all has to come from the rider, of course, and I think gearing would be needed to achieve 2400rpm! :shock:
"It takes a genius to spot the obvious" - my old physics master

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ConRAD
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Re: 3 to 9W VPG … variable power generator

Postby ConRAD » 28 Feb 2018, 3:18pm

MikeF wrote:... their website is a little confusing ...

I've sometimes got the impression that those people simply don't know very well what they are talking about.
They mix watt with volt, volt with ampere, rpm with km/h, threephase with single phase, dc with ac, etc.
I had just once the chance to have in my hands one of their dynamos and remember that it was labeled with an adhesive paper sticker stating a power of 8W !!! when I asked them some clarifications they explained to me that 8W was referred to 40km/h !!!

ps: the output is however 6Vdc, that at least what I can understand
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MikeF
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Re: 3 to 9W VPG … variable power generator

Postby MikeF » 28 Feb 2018, 5:17pm

kwackers wrote:
MikeF wrote:Not necessarily so. I have built a generator (not for a bike) from an old 3 phase squirrel cage motor by connector capacitors across the phases. The small amount of residual magnetism is sufficient to start it producing electricity. But then I don't think anyone has made a 3 phase generator for a bike yet.

I did think about residual magnetism, but I thought that might not be enough although I stand corrected.
My initial thought was a 'poor' permanent magnet, just enough to kick the whole thing off.

I don't think there's any good technical reason to not make 3 phase generators, I just don't see the point. I think people worry far too much about the negligible drag.
I don't even turn my lights off, after much fumbling with the on/off switch I concluded I couldn't tell (although it makes a fair difference if you're just spinning the wheel on the bike stand).
I'm not sure if you can use that with single phase, but maybe. (Note to self - more reading required! :lol: )
"It takes a genius to spot the obvious" - my old physics master

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ConRAD
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Re: 3 to 9W VPG … variable power generator

Postby ConRAD » 28 Feb 2018, 7:05pm

Brucey wrote:... might be worth mentioning what model hub generator you used for the tests ...

I've been using a very basic Shimano DH-3D32 mounted on my usual test bench; table numbers may slighly differ from "algebric" application of Ohm's law since all readings have been taken with indipendent multimeters

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Brucey wrote:... how does the current vary if the load is reactive (eg if there is a capacitor fitted ...

... I think that it will depend on how much the load is reactive, output indeed is so far AC and therefore full impedance shall have to be considered

Brucey wrote:... there are some generators which are more draggy on an open circuit than when connected to a resistive load ...

... what ???
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Brucey
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Re: 3 to 9W VPG … variable power generator

Postby Brucey » 28 Feb 2018, 8:05pm

some older Nexus models, some sanyo models, and notably the SA generators all manifest high drag into an open circuit load.

cheers
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ConRAD
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Re: 3 to 9W VPG … variable power generator

Postby ConRAD » 28 Feb 2018, 9:24pm

Brucey wrote:...all manifest high drag into an open circuit load ...

... something must be wrong :shock:
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Re: 3 to 9W VPG … variable power generator

Postby ConRAD » 2 Mar 2018, 6:58am

MikeF wrote:... I think gearing would be needed to achieve 2400rpm! :shock:

Considering that 20km/h is roughly equivalent to 150rpm, well yes I think too that some "gear" must exist !!

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