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# Human Powered Bike Powered Generator? Answered

HI,
I am an artist and I am creating a bike powered led sculpture for kids at a museum. I need some help making the connections correctly and finding the correct electric motor and volts not to over load the LED light bulbs as well as how to figure out the easiest gear ratio for kids to turn,

There will be five 60 Watt  /120 Volt LED bulbs connected to deep cycle car battery (used as a voltage regulator) that will be connected to a stationary bike pedaled by visitors to display the human energy potential.

I want to figure out what type of electric motor I will need for those lights and how to make the gear ratio for the bike easy enough to turn for kids...

Any knowledge on these calculations will help.

Thank you !
Jessie

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From Wikipedia

"A trained cyclist can produce about 400 watts of mechanical power
for an hour or more, but adults of good average fitness average between
50 and 150 watts for an hour of vigorous exercise. A healthy well-fed
laborer over the course of an 8-hour work shift can sustain an average
The yield of electric power is decreased by the inefficiency of the
human-powered generator, since all real generators will incur some
losses during the energy conversion process."

It's mostly about for how long. higher outputs in bursts is not unreasonable but over a long time not going to happen for us normal people. Watched the Olympics pursuit cycling last night and over 4 minutes they were averaging around 53 Km/hour in the shorter 3 lap races this only increased to 65 Km/hr despite it looking a lot faster.

According to this website, yes, 200W is the output of an experienced/pro cyclist.

But, if you reduce aerodynamic drag to zero (the generator won't be moving), power outputs required to "race" drop by an order of magnitude.

http://www.cyclingpowerlab.com/CyclingPowerOutput....

Years ago, the Science Museum in London had a similar installation for kids to that proposed - a pedalled generator lit a bulb, started a radio, even a small TV, depending how hard the child pedalled. Typically, it was only when the accompanying dads got on the bike that all the devices ran at once.

It is unlikely that the science mus. Drove thr lights etc directly from the generstor

The 200 watts is the total human out put and not dependent on drag - that would only effect how fast you can go for that power.

Bang goes the theory

1. You can see how many generators they needed

2. You can also see they they had to do this is relays because they quickly tire.

Ah, my mistake.

(I even watched that programme first time around - I should have remembered it.)

Passenger aircraft cooling systems are tested by placing a 60W to 75W incandescent light bulb in each seat...

To get a reasonable output from a 120 volt generator your going to need to run it at around 3000 RPM - also true if you use a car alternator at lower voltages.

You usually sit the wheel on a roller so you can work out the gear ratio required.

Unless you increase the number of poles of the machine, then you can go slower but need more toque.

How big are the kids?

To drive 300 watts of lights you would almost need need a pro bike rider.

Kids single speed bikes start at 1:1 ratios and go up to about 1:4 with tires starting at 6 inches and up.

An average adult human can output about 350 watts cycling - that is trying hard so easy cycling say 200 watts.

5 X 60=350 watts is going to be VERY hard work to keep illuminated at full brightness.

I would go for 12 volt 1 watt LED lights and say a 12 volt DC motor that can provide a suitable current. each 1 watt LED will draw about 83 milli Amps. easily attainable.

Your LED lights will need a current limiting circuit in series so the kids can't go mad and blow the LEDs out.

That should be 5 x 60=300 watts.