Proper impeller play on a Union (Con-tec)dynamo?

On Wednesday, November 18, 2020 at 12:28:24 PM UTC-8, Tosspot wrote:
On 18/11/2020 10:43, Rolf Mantel wrote:
Am 18.11.2020 um 10:07 schrieb Tosspot:
On 17/11/2020 19:01, Mark J. wrote:

snip

Spinning modern dynamo hubs with fingers at the axle *greatly*
exaggerates their drag. Take the same wheel and spin it mounted to a
frame. It will spin far longer than one would expect from the
finger-axle-spin test.

I *think* what is going on is that the dynamo greatly resists motion
for some small fraction of a turn *then* propels the axle forward a
similar small distance. The ?stator? ?rotor? nearly "snaps" from one
position to the next. On *average*, over a full rotation, there's
only a small drag, but nowhere near as much as one feels during that
first small bit of twisting the axle.

I always wondered about that, but now you mention it I think that is
what is happening. I also note with no load the voltage wll rise
quite a lot. Lick your fingers and put them on the terminals. That
ain't 6v :-(

Sure, the dynamo is approximately a "current source": output 0.5A,
voltage depends on the resistance (i.e. infinite resistance gives
infinite voltage), IIRC you can expect 30-50V with no consumer.
I think I was that consumer :-( I would have guessed over 50V tbh, but
I am not going to do it again! Shimano hub dynamo.

You look pretty close One thing - notice how slowly the wheel runs down on the stand with no load but the wheel and tire. While the voltage does go extraordinarily high in my opinion, (45 volts) due to improper design ( you should ALWAYS have a voltage regulator on a generator if it is making this sort of voltage open circuit ) This could easily destroy lights that you place upon it with the initial switch-on. Since 6V and 3 Watts is only 12 ohms of resistance. So this would be an instantaneous load of some 169 watts on a 3 watt bulb. One would think that such a shock loading would burn out any filament bulb. Now surprisingly a lamp filament has a resistance ratio of about 15:1 hot to cold. This means that the initial resistance at turn on of a filament lamp would be about. 2.4 ohms which at 45 volts would be a shock loading of 845 watts for a 3 watt bulb. In this demonstration you can't see any significant loading and the light is turned ON. So there is a full power draw.

Ralph Barone writes:

Tosspot wrote:
On 17/11/2020 19:01, Mark J. wrote:

snip

Spinning modern dynamo hubs with fingers at the axle *greatly*
exaggerates their drag.Â* Take the same wheel and spin it mounted to a
frame.Â* It will spin far longer than one would expect from the
finger-axle-spin test.

I *think* what is going on is that the dynamo greatly resists motion for
some small fraction of a turn *then* propels the axle forward a similar
small distance.Â* The ?stator? ?rotor? nearly "snaps" from one position
to the next.Â* On *average*, over a full rotation, there's only a small
drag, but nowhere near as much as one feels during that first small bit
of twisting the axle.

I always wondered about that, but now you mention it I think that is
what is happening. I also note with no load the voltage wll rise quite
a lot. Lick your fingers and put them on the terminals. That ain't 6v :-(


The phenomenon is called cogging and is the result of stator and rotor
magnetic paths aligning in a state that has reduced magnetic energy. You
can greatly reduce it by “twisting� either the rotor or the stator so that
one pole of the rotor bridges two adjacent stator poles, but that costs
money.

That would make it feel nicer when spinning by hand, but do you think it
would make any real performance difference? I have my doubts.

On Saturday, November 14, 2020 at 8:49:22 AM UTC-8, landotter wrote:
I put a rear triangle dynamo on my retro roadster with a 50 lux Cordo LED lamp and it's the tits. Works great, weighs eh nuttin, and you can switch it 100% off. Cost about 12 bucks for the dynamo and 25 for the lamp. Oh boy.. Big spender, but it kept the front wheel looking bulgy hubbed and new fanglish. 50 lux is fifty lux. works fine, but I wanna dial it in to get that edge riding across town to pick up fava beans, ya know?

These days if you want a new silver olde timey looking jobber it's an AXA 8201 or the Con-tec DL-150. Both are a tenner and a bit. The Con-tec appears to be a rebranded Union-Marwi and the "U" on the spring cover is kind of a giveaway AND it comes with a little impeller cover, so it won out.

I dripped a single drop of oil down the impeller shaft and then put a glob of red Sta-Plex grease on top of the bushing before putting on the roller and lock nut. Friction really ain't anything now. Spins like the dickens. Doesn't get hot. It's happy on a real dynamo track on a Schwalbe tire without too much pressure.

But it still rattles a bit. I reckon it's the simple bearing whacking against the bushing. Would adjusting play even matter? I'v got it at a generous couple millimeters.

My solution has been to listen to quiz shows at a medium volume and enjoying that the rattle has probably extended the life of my Crane bell as pedestrians seem very irritated by it.

Forgive me for getting angry at you. I can plainly see what is coming if the Democrats gain any serious control and I don't believe you understand what exactly is going on. You seem to be running with the Hate Trump pack rather than actually looking at what happened and what Trump did and why.

On 11/18/2020 3:15 PM, Tom Kunich wrote:
On Wednesday, November 18, 2020 at 9:26:41 AM UTC-8, Frank Krygowski wrote:

Tom, would you PLEASE just put a voltmeter on an unloaded dynamo outlet?
It would give you a chance to know what they hell you're talking about,
which would be a nice change.
Sheesh!

--
- Frank Krygowski
I don't believe that you even know how to use a voltmeter.

What nonsense you believe doesn't matter. If _you_ know how to use one,
grab it and do what I said.

And a reminder for this group's ignoramus: Make sure you switch it to AC
volts, not DC volts.

--
- Frank Krygowski

On Wed, 18 Nov 2020 08:21:35 -0800 (PST), Tom Kunich
wrote:

On Tuesday, November 17, 2020 at 4:25:24 PM UTC-8, John B. wrote:
On Tue, 17 Nov 2020 09:02:49 -0800 (PST), Tom Kunich
wrote:

On Tuesday, November 17, 2020 at 8:54:15 AM UTC-8, Frank Krygowski wrote:
On 11/17/2020 11:45 AM, Tom Kunich wrote:
On Monday, November 16, 2020 at 11:14:15 AM UTC-8, Frank Krygowski wrote:
On 11/16/2020 1:55 PM, Tom Kunich wrote:
On Monday, November 16, 2020 at 9:31:59 AM UTC-8, Frank Krygowski wrote:
On 11/16/2020 11:36 AM, Tom Kunich wrote:

Unless you're drawing current from generator hubs they shouldn't be offering any drag at all. They have no friction surfaces and like all generators only offer resistance when they are in use.
"Shouldn't be offering any drag at all" is true only in the aspirational
sense. They all have some drag (usually minor) when off, due to eddy
current losses if nothing else. This is documented through many tests by
many different investigators. There are have even been a few models that
have less drag on than off.

Really, Tom, you should do a _little_ study before posting.

--
- Frank Krygowski

Really Frank, you should know that in a properly designed generator there would be no eddy currents generated unless and until there was an actual current flow pathway.
You're talking about the difference between theory and practice.

In theory, they're they same. In practice they are not.
Not having use the Shimano generator in a long time I was unaware that they were improperly designed.
But you have no reluctance about posting, of course.

See https://www.cyclingabout.com/dynamo-...g-lab-testing/ along
with many other articles on the subject.

It seems by your standards, even the best are improperly designed. Could
it be the designers know more than you do?

Tell us Frank, why do you think that Tesla's do not have regenerative braking or decelerate when you pull your foot off the pedal? You're an engineer and you're saying that in practice you can't avoid eddy currents. So HOW has Tesla done it?
Tom is once again babbling away in an attempt at deflection.

Focus, Tom, focus! You said bicycle hub dynos have no additional drag
when turned off. You're wrong, as every relevant test has shown.

I'm sure that somewhere in your fantastic resume you have the part where
Elon Musk personally hired you to completely eliminate drag from
coasting Teslas. But that's not what we were talking about.

Just admit you were wrong (yet again) and stop typing.

You were asked a question and you speak of me deflecting? If a dyno hub has drag when no current is being drawn, it has been improperly designed. Could I design one that works without drag? Yes, it is NOT very difficult. You separate the magnets from the conductors when it is not in use. But you didn't even know that did you? Instead you blabber on as the all knowing freak of nature you consider yourself.
See
https://www.cyclingabout.com/dynamo-...ision-shimano/

You ignorant oaf.
--
Cheers,

John B.
Tell us John, how many bicycles do you have set up with generator hubs and lights.

None at present as I don't need them. Which has nothing to do with the
reference I posted (above). I was simply replying to your post stating
that "If a dyno hub has drag when no current is being drawn, it has
been improperly designed".

The posted reference demonstrates that you (again) didn't know what
you are talking about as all generators posted do exhibit drag.

Yes, Sir! Tommy's battle cry is, "Hey Guys, I don't know what I'm
talking about but I'm gonna post anyway".
--
Cheers,

John B.

On Wed, 18 Nov 2020 08:25:12 -0800 (PST), Tom Kunich
wrote:

On Tuesday, November 17, 2020 at 4:38:33 PM UTC-8, John B. wrote:
On Tue, 17 Nov 2020 21:16:57 +0100, Tosspot wrote:

On 17/11/2020 17:45, Tom Kunich wrote:
On Monday, November 16, 2020 at 11:14:15 AM UTC-8, Frank Krygowski
wrote:
On 11/16/2020 1:55 PM, Tom Kunich wrote:
On Monday, November 16, 2020 at 9:31:59 AM UTC-8, Frank Krygowski
wrote:
On 11/16/2020 11:36 AM, Tom Kunich wrote:

Unless you're drawing current from generator hubs they
shouldn't be offering any drag at all. They have no friction
surfaces and like all generators only offer resistance when
they are in use.
"Shouldn't be offering any drag at all" is true only in the
aspirational sense. They all have some drag (usually minor)
when off, due to eddy current losses if nothing else. This is
documented through many tests by many different investigators.
There are have even been a few models that have less drag on
than off.

Really, Tom, you should do a _little_ study before posting.

-- - Frank Krygowski

Really Frank, you should know that in a properly designed
generator there would be no eddy currents generated unless and
until there was an actual current flow pathway.
You're talking about the difference between theory and practice.

In theory, they're they same. In practice they are not.
Not having use the Shimano generator in a long time I was unaware
that they were improperly designed.
But you have no reluctance about posting, of course.

See https://www.cyclingabout.com/dynamo-...g-lab-testing/
along with many other articles on the subject.

It seems by your standards, even the best are improperly designed.
Could it be the designers know more than you do?

Tell us Frank, why do you think that Tesla's do not have regenerative
braking or decelerate when you pull your foot off the pedal? You're
an engineer and you're saying that in practice you can't avoid eddy
currents. So HOW has Tesla done it?

That's weird because Tesla supply the cars with regenerative braking.
Can you have it removed as an after market option?
To be honest, I know nothing about electric cars but I thought that I
read something about them generating power when coasting that served
to partially top up their batteries.

https://www.greencarreports.com/news...car-completely
Apparently the Tesla does exactly that.

John, tell us when you bought a Tesla.

Gee, I didn't tell you? Of course I didn't.

I mean here you are so improvised that you have to buy all that cheap,
secondhand **** off the net. It would probably ruin your whole day
(month?), if I told you I bought a Tesla.

Tommy you really are a twit.

(noun: twit; plural noun: twits - a silly or foolish person.)
--
Cheers,

John B.

On Wed, 18 Nov 2020 08:25:12 -0800, Tom Kunich wrote:

On Tuesday, November 17, 2020 at 4:38:33 PM UTC-8, John B. wrote:

Apparently the Tesla does exactly that.

John, tell us when you bought a Tesla.

Good lord, you don't buy Tesla, you build them, or more correctly wind
them.

Radey Shouman wrote:
Ralph Barone writes:

Tosspot wrote:
On 17/11/2020 19:01, Mark J. wrote:

snip

Spinning modern dynamo hubs with fingers at the axle *greatly*
exaggerates their drag.Â* Take the same wheel and spin it mounted to a
frame.Â* It will spin far longer than one would expect from the
finger-axle-spin test.

I *think* what is going on is that the dynamo greatly resists motion for
some small fraction of a turn *then* propels the axle forward a similar
small distance.Â* The ?stator? ?rotor? nearly "snaps" from one position
to the next.Â* On *average*, over a full rotation, there's only a small
drag, but nowhere near as much as one feels during that first small bit
of twisting the axle.

I always wondered about that, but now you mention it I think that is
what is happening. I also note with no load the voltage wll rise quite
a lot. Lick your fingers and put them on the terminals. That ain't 6v :-(


The phenomenon is called cogging and is the result of stator and rotor
magnetic paths aligning in a state that has reduced magnetic energy. You
can greatly reduce it by “twisting� either the rotor or the stator so that
one pole of the rotor bridges two adjacent stator poles, but that costs
money.

That would make it feel nicer when spinning by hand, but do you think it
would make any real performance difference? I have my doubts.


Not much, unless the vibration from the cogging really annoyed you, but it
would sure feel more impressive when you spun it by hand, which might sell
one or two units.

Ralph Barone writes:

Radey Shouman wrote:
Ralph Barone writes:

Tosspot wrote:
On 17/11/2020 19:01, Mark J. wrote:

snip

Spinning modern dynamo hubs with fingers at the axle *greatly*
exaggerates their drag.Â* Take the same wheel and spin it mounted to a
frame.Â* It will spin far longer than one would expect from the
finger-axle-spin test.

I *think* what is going on is that the dynamo greatly resists motion for
some small fraction of a turn *then* propels the axle forward a similar
small distance.Â* The ?stator? ?rotor? nearly "snaps" from one position
to the next.Â* On *average*, over a full rotation, there's only a small
drag, but nowhere near as much as one feels during that first small bit
of twisting the axle.

I always wondered about that, but now you mention it I think that is
what is happening. I also note with no load the voltage wll rise quite
a lot. Lick your fingers and put them on the terminals. That ain't 6v :-(


The phenomenon is called cogging and is the result of stator and rotor
magnetic paths aligning in a state that has reduced magnetic energy. You
can greatly reduce it by “twisting� either the rotor or the stator so that
one pole of the rotor bridges two adjacent stator poles, but that costs
money.

That would make it feel nicer when spinning by hand, but do you think it
would make any real performance difference? I have my doubts.


Not much, unless the vibration from the cogging really annoyed you, but it
would sure feel more impressive when you spun it by hand, which might sell
one or two units.

I get the impression that most hub dynamos are actually sold in complete
bikes. Building one's own wheels with hubs bought in a shop where you
could fondle them ahead of time is right up there with using a hook to
button one's shoes.

On 11/18/2020 6:31 PM, Radey Shouman wrote:
Ralph Barone writes:

Radey Shouman wrote:
Ralph Barone writes:

Tosspot wrote:
On 17/11/2020 19:01, Mark J. wrote:

snip

Spinning modern dynamo hubs with fingers at the axle *greatly*
exaggerates their drag. Take the same wheel and spin it mounted to a
frame. It will spin far longer than one would expect from the
finger-axle-spin test.

I *think* what is going on is that the dynamo greatly resists motion for
some small fraction of a turn *then* propels the axle forward a similar
small distance. The ?stator? ?rotor? nearly "snaps" from one position
to the next. On *average*, over a full rotation, there's only a small
drag, but nowhere near as much as one feels during that first small bit
of twisting the axle.

I always wondered about that, but now you mention it I think that is
what is happening. I also note with no load the voltage wll rise quite
a lot. Lick your fingers and put them on the terminals. That ain't 6v :-(


The phenomenon is called cogging and is the result of stator and rotor
magnetic paths aligning in a state that has reduced magnetic energy. You
can greatly reduce it by “twisting� either the rotor or the stator so that
one pole of the rotor bridges two adjacent stator poles, but that costs
money.

That would make it feel nicer when spinning by hand, but do you think it
would make any real performance difference? I have my doubts.


Not much, unless the vibration from the cogging really annoyed you, but it
would sure feel more impressive when you spun it by hand, which might sell
one or two units.

I get the impression that most hub dynamos are actually sold in complete
bikes. Building one's own wheels with hubs bought in a shop where you
could fondle them ahead of time is right up there with using a hook to
button one's shoes.


There's probably some local/regional difference, as the
'buttonhook' method is popular here, no bikes with dynamos
out of the carton at all.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971