Leg Power replaces electricity (May, 1945)

I don’t buy it. Hair dryers use a LOT of electricity. Plus, unless they have some sort of flywheel or intermediate battery, wouldn’t the power fluctuate if his speed alters?

Leg Power replaces electricity in this Parisian beauty salon, where Madame has her hair dried despite the lack of coal-generated current. An ingenious beautician hires unemployed 6-day bicycle racers to peddle away on a bike, the back wheel of which is attached to a small generator! The current runs 6 driers.

  1. Casandro says: July 7, 200810:22 pm

    If they don’t have a heater it might just work. A well trained human can output about a kilowatt, a normal person maybe about 500 watts.

  2. Mike Brown says: July 8, 20087:59 am

    You’d be amazed at how hard it is to power even a low-power device by pedaling a bicycle. About 20 years ago we ran a 10 Watt amateur radio transmitter off an alternator on the back wheel of a bike, much as shown in the article. (The ARRL Field Day competition offered extra points for “natural power” that year) An athletic Boy Scout of about 16 provided the motive power. It was striking how much he slowed down when we hit the Morse Code key.

  3. Charlie says: July 8, 20088:49 am

    Mike Brown: It would be awesome if he got to be able to read the messages just from the amount of resistance he felt in the bike. Kind of like those British telegraph operators in Bletchley Park during WWII. They got to be so good at listening to German radio transmissions that they could instantly tell who was operating the Morse code set just by their keying style.

  4. Myles says: July 8, 20089:12 am

    I remember hearing about a 100% energy efficient home on the radio. To stay off the power grid the owner had to make certain sacrifices. He couldn’t make toast, for example, because he couldn’t generate that kind of power. So I also say BS for even running one hair dryer off a bike generator.

  5. jayessell says: July 8, 20089:18 am

    Myles, I’d shenanigate even if it were cold air hair drying.
    With the efficiency losses from the generator and motors, he’d be better
    off pedaling a large blower with ducts to each chair.

  6. Richard C says: July 8, 20089:58 am

    Casandro, are those figures for peak output or sustained output? And do they account for generator losses?

    This guy http://www.los-gatos.ca… claims 425 watts peak when he was 25 years old, but only 150 watts continuous for 30 minutes at age 25. And he seems to be an enthusiastic proponent of pedal power, so I’d be skeptical of claims that were significantly higher.

  7. Casandro says: July 8, 200810:04 am

    Richard, I am not sure. I think the difference between peak and sustained should be bigger. Then there’s the question what sustained means? Does it means for a whole minute, an hour or a whole day?

  8. Myles says: July 8, 200812:29 pm

    I had a bike with a light powered by a generator that ran off the tire as a kid. I thought it was the coolest gadget. But when I engaged the generator it made pedaling the bike a real chore. At least twice as hard. The light was probably about 10 watts and pulsed brighter and dimmer as I pedalled. So if the bicyclist above can run 6 hair dryers at probably 1000 watts each, he can come over and power my home.

  9. bird says: July 8, 20089:14 pm

    The type of generator, how the mechanical energy is transferred to the electrical, how it is geared to produce current, quality of the wire and construction, and many other factors have to be weighed. Electricity is always best when it has the least resistance.

  10. Reed says: July 8, 20089:28 pm

    I’d agree with those calling bs. My recollection is that a world class athlete (i.e. Olympic sprinter or Tour de France champion) can produce the kind of numbers Casandro mentioned. Note that the pedal generator guy may be including more losses than the dynos that athletes use, so the numbers may not be directly comparable.

    This article http://www.cio.com/arti… suggests that if you are Lance Armstrong, you can average 400 watts over tour stage… but I’m guessing the guy in the picture isn’t Lance, and even so 400 is pretty pathetic for a hair dryer.

    If he was just running a fan to move air from some other heat source, that would be plausible.

  11. K!P says: July 9, 20081:56 am

    i still use a genarator that pushes against the bike tire, and it makes biking no where NEAR twice as hard, 5% maybe. In hub build types are even better.

  12. Adrian says: July 9, 20087:33 am

    Dynamos on cycle tyres are a drag whatever the percentage. Playing card in the spokes, now THAT made you go faster!

  13. Essjay says: July 9, 20087:01 pm

    Reed has the numbers.

    A strong amateur cyclist can produce 400 watts for a short time. A Tour de France champ can produce 400 watts consistently, a few hours a day, for a couple of weeks.

    A typical hand held hair dryer is 1000 to 1500 watts.

  14. docca says: July 11, 20087:02 pm

    “A strong amateur cyclist can produce 400 watts for a short time. A Tour de France champ can produce 400 watts consistently, a few hours a day, for a couple of weeks.”

    … before falling dead of exhaustion.

    (but the lady would have her hair dried!)

  15. Arglebarglefarglegleep says: August 20, 20103:54 pm

    Here’s a calculator for figuring bicycle energy. You’ll note its around *64 watts* for 10mph & *637 watts* for 30 mph


    We’re talking 2kW for a modern hair dryer.

    He might have been able to run a radio or table lamp for the ladies.

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