I can spin mine with no resistance whatsoever,

 

however!

 

would the uV output from those type be at all worthwhile at over say 50 miles??

 

That's the point, the output isn't anything like adequate for charging our batteries. It would just reflect the input you gave when you spun the wheel, a small effort for a small output.

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You mean turn the lights on, lol?!!

Yes, isn`t that what i`ve been saying for goodness sake!!? The wheel spins effortlessly.

 

please try and keep up d8..

 

the effort you talk about expounding is already being put in anyways when you are riding the bike so its not an extra effort,

haven`t you ever ridden a bike with these front hubs??

 

anyway having said all that its questionable that the current produced would be worthwhile to the modern battery..... although something is better than nothing as they say

I don't think that yours is working.

I have just tried to turn mine

1 Unbridged=distinct cogging.

2 Bridged.=Cogging is even more pronounced.

if its not working then why do the lights work when i spin up the wheel??

if its not working then why do the lights work when i spin up the wheel??

Well the only way the lights can work is if they are taking energy out of the spinning wheel. That means that the wheel cannot spin as freely or as long as if there was no dynamo attached.

Bike lights hardly take any electricity. But to recharge an ebike battery will take a lot.

d8veh, not true, don`t you remember those old front hub dynamos? You could hold the bike off the ground and spin the front wheel, it would go on for ever,

 

similar to this...[ATTACH=full]18460[/ATTACH]

.. the SA hub dynamo is a lovely bit of kit. They were highly reliable, still are, if you have one on a bike, and with very little mechanical drag as compared with the bottle dynamo . However once they are connected up to a load .. a bulb , there is an electromagnetic drag and a spinning wheel will slow down faster than if the bulb is switch off. If you think otherwise, I have these magic beans I could sell you. As a youngster you would have had buckets of energy, and putting 150watts into propelling the bike would be typical. You would not be noticing the 9 watts going into rotating the SA , but you would have noticed the 20watts going into a bottle dynamo.

 

 

According to the SA Dyna hub publicity handout it produced 2watts of electric power at 6 volts . Presumably at a sedate pace. If the bike was going faster the voltage would rise and the bulb s glow brighterThe bulbs front and back were rated 1.8w I do recall blowing bulbs on a number of occasions.

Edited March 31, 20179 yr by Danidl

The newest generation of bike dynamos that come with lighting systems from such as Busch & Müller and Shimano may well have much lower outputs to suit the greatly reduced demands of their LED lighting.

 

That in turn will mean much lower drag.

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I changed my standard heavy Shimano dynamo on my Kalkhoff for a lightweight Shutter Precision weighing less than 400g.

The output is quite low at about 3 watts but as Flecc mentioned, that's enough for a good LED light.

 

It spins smoother than the Shimano, with very little drag, but off course, you still don't get something for nothing.

You mean turn the lights on, lol?!!

Yes, isn`t that what i`ve been saying for goodness sake!!? The wheel spins effortlessly.

No I don't. I mean what i said: bridge the two terminals.

 

The wheel cannot spin effortlessly when the lights are on. The SA hub-dynamo is taking power from the wheel and convertijng it into electric power, which slows it down. If you had 2 watt bulbs, you'd have to put in about 6watts to produce that. A casual cyclist pedals with an average of about 100 watts, so that means, you have to pedal 6% harder to get the light out of the dynamo. It's simple physics. the energy for the light has to come from somewhere. That somewhere is you.

Tommie

Why not connect your magical dynamo directly to a motor...set it spinning, connect elec terminals...and hey presto...perpetual motion...

Or how about reading the thread from the beginning, it`s about putting a current back into the battery if possible, and i can assure d8 i didn`t have to put an extra 6% effort into my pedaling just by switching the lights on! Thats in line for `silly statement of the year`! I can also confirm i noticed NO difference whatsoever in cadence or effort,.. possibly you had tightened your front wheel bearings up too tight d8??

Thats in line for `silly statement of the year`! QUOTE]

QUOTE]

 

Why? have you invented perpetual motion? You cannot get something out without putting something in.

Or how about reading the thread from the beginning, it`s about putting

So where

Or how about reading the thread from the beginning, it`s about putting a current back into the battery if possible, and i can assure d8 i didn`t have to put an extra 6% effort into my pedaling just by switching the lights on! Thats in line for `silly statement of the year`! I can also confirm i noticed NO difference whatsoever in cadence or effort,.. possibly you had tightened your front wheel bearings up too tight d8??

 

 

Please tell us where the energy for the lights is coming from ??? And if it makes no discernible difference to pedalling it certainly wont charge a 400w/h battery.

 

If folk want longer range on ebike ( the whole point of regen) isn't it cheaper , easier, lighter, and less expensive to simply fit a larger battery...or buy a spare.??

Regen can only make any sense ( and even then debatable) if it is only used during braking..if not Merc, Red Bull, Ferrari have all got it wrong ??!!

Or how about reading the thread from the beginning, it`s about putting a current back into the battery if possible, and i can assure d8 i didn`t have to put an extra 6% effort into my pedaling just by switching the lights on! Thats in line for `silly statement of the year`! I can also confirm i noticed NO difference whatsoever in cadence or effort,.. possibly you had tightened your front wheel bearings up too tight d8??

Well, if I were you, I would present that dynamo to the Nobel prize committee. You'll probably win the prize for physics because, until now, nobody has ever managed to make a machine that could output more energy than that which was put in. Your name will go down in history and you'll get loads of money, plus all sorts of development grants to improve it.

You could build a perpetual motion machine aswell. There,s a big prize for that...

Tommie

Why not connect your magical dynamo directly to a motor...set it spinning, connect elec terminals...and hey presto...perpetual motion...

 

That would be very dangerous Zlatan. After powering the motor, the surplus of current from the dynamo would have nowhere to go and would heat up the system and destroy it. It's possibly why we haven't achieved perpetual motion yet, the self-destructiveness of closed loop generating and use systems.

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That would be very dangerous Zlatan. After powering the motor, the surplus of current from the dynamo would have nowhere to go and would heat up the system and destroy it. It's possibly why we haven't achieved perpetual motion yet, the self-destructiveness of closed loop generating and use systems.

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..... Would that be like the brexit thread debate?

Or how about reading the thread from the beginning, it`s about putting a current back into the battery if possible, and i can assure d8 i didn`t have to put an extra 6% effort into my pedaling just by switching the lights on! Thats in line for `silly statement of the year`! I can also confirm i noticed NO difference whatsoever in cadence or effort,.. possibly you had tightened your front wheel bearings up too tight d8??

Tommie , this is an argument you cannot win. Opinions no matter how strongly felt or expressed cannot withstand facts. Please go back and read my previous postings on this topic.

The only scenario where regenerative braking and power harvesting would make any sense is there a person was going down a mountain in the outward run and going back up it on the return. The braking effect of the power generation would reduce the amount of energy turned into heat by the brakes.

 

stick the motor on a rack and take off the disc rotor and replace it with a sprocket and a chain or belt.

 

now if yo got a 12v charger @2a then it would take about 10hrs to charge up a 500w batt.

Dan, I think you`re missing my point here...

Many years ago i used to have a bike that had that SA type front hub, i rode it night and day, and i can assure you it made no difference to effort/input on whether i switched my little front light on or off, certainly not to the extent of a whopping 6%. It was a puny little bulb not the floodlights at Old Trafford on the handlebars!

Now trying to ignore our resident `merchant bankers` in here my serious question was to the effect - would that current from the hub dynamo (or the better dynamos of today), which was turning anyway as i pedaled, be of any use if routed into our ebike batteries over the course of say 100 miles?

 

Being able to spin this hub up freely by hand gave me the impression there was energy going to waste when i was riding normally and not using the lights

no because 1 the voltage is to low and 2 not enough constant current / amps.

 

even if you up the motor to 12v you then have to maintain that speed for 100 miles with all that extra waight going 20mph.

 

there is no way you can put in what you take out off the batt in the first place unless you have a 100 mile down hill run.

 

if a f1 car cant do it going 200mph+ then you have no chance as both will run out of fuel in the end 1 way or the other, knackered or ran of petrol lol

yeah, know what you mean SW, but i`m not after perpetual motion, only the possibility of adding a little time, say 15mins to the battery life over 100 miles or so

you could charge a 5v batt with it but not the one on the bike as would need a 12v motor to power a charger and then the extra waight is just not worth it.

 

http://uk.gpbatteries.com/uk_en/powerbank/f-series/fn03-1?gclid=Cj0KEQjwn_3GBRDc8rCnup-1x8wBEiQAdw3OAdI71z-26qscYMnAjKHtgTmWMEfZ6ZjXWXVmGNE8PUMaAnp88P8HAQ

 

charge that via the dynamo and you will see what i mean as to how long it will take

Dan, I think you`re missing my point here...

Many years ago i used to have a bike that had that SA type front hub, i rode it night and day, and i can assure you it made no difference to effort/input on whether i switched my little front light on or off, certainly not to the extent of a whopping 6%. It was a puny little bulb not the floodlights at Old Trafford on the handlebars!

Now trying to ignore our resident `merchant bankers` in here my serious question was to the effect - would that current from the hub dynamo (or the better dynamos of today), which was turning anyway as i pedaled, be of any use if routed into our ebike batteries over the course of say 100 miles?

 

Being able to spin this hub up freely by hand gave me the impression there was energy going to waste when i was riding normally and not using the lights

... A fair question deserves a fair answer . The SAdynahub, and it's more recent successors are brilliant devices. They have very low mechanical friction... Certainly compared with the bottle dynamo. They were able to produce about 6 watts of electrical power when cycled at a very high speed. They produced at a voltage 6v at 0.18amp to drive the two special bulbs, at normal speeds This is a load of about 2watts. . All this energy came from the rotation of the wheel. If you were to spin the wheel by hand say 1 push, and did not have the bulb connected, the wheel would spin and after a length. of time slow down and stop. If you pushed the wheel with exactly the same push, with the bulb connected, it would take less time for the wheel to stop. The reason the wheel slows is due to friction between the bearings and cones, the air resistance of the spokes . When the bulb is connected there is also a slight extra load due to the magnetic field created when current flows in the bulb reacting against the magnets in the dynamo..

As a youngster, you were energetic and could put maybe 150watts if power into the bike .. maybe 200 watts when you were sprinting. The extra loss of a couple of watts when the lamp was on was not really measurable.Most of the energy lost was to air resistance ,wind.

An electric bike consumes around 200watts. The amount being consumed at any instant depends on the load.. higher consumption when going faster or uphill less on downhill. The EU law allows 250watts. Even if one were to take the energy from a dynahub, increase its voltage from 6 to 38 V, and feed it into the battery, it would only be giving about 2 watts of power or 1% of the consumption. There would only be a value in doing so when one would otherwise be braking e.g going down hill. If one were to use this energy to charge the battery while on the level, you would either need to pedel faster or use battery power.

You might consider using a much more powerful dynamo, but that merely makes the numbers bigger. Don't change the principle

Most people have no idea about how large or small a watt is. We talk about a 2kilowatt kettle or heater and 100 watt bulbs. If you lift a 1kg bag of sugar, from the floor to the table, and take 10 seconds to do so, you have worked at a rate of 1 watt. Assuming table is 1metre, and standard bag of sugar.

My new ebike came with a hub dynamo for the lighting. I think that this is a good idea .. if the battery packed up, i would still be legal after dark.

Edited April 2, 20179 yr by Danidl

 

stick the motor on a rack and take off the disc rotor and replace it with a sprocket and a chain or belt.

 

now if yo got a 12v charger @2a then it would take about 10hrs to charge up a 500w batt.

.. if you were using a 12v and 2a your power would be 24w. and it would take about 25 hrs . Nice video

..... Would that be like the brexit thread debate?

 

Almost certainly! We've had a few of these recharge-while-cycling threads in here and have often been "informed" that technical advances will make it possible before long.

 

I call it subservient physics.

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