How To Make A Pedal-Powered Sound System

“Pedal power uses the most powerful muscles in the body: the quads, hamstrings, and calves. When pedalling in a circular motion at 60-80 revolutions per minute, with the use of toe clips, almost every muscle in the human legs can be used to make energy. Ninety-five percent of the exertion put into pedal power is converted into energy. The average rider at a continuous road speed of 12 miles per hour can produce a quarter horsepower, or enoughenergy to light two, one hundred-watt light bulbs.”

- The Pedal Power Project at the Campus Centre for Appropriate Technology (CCAT), Humboldt State University, from Grassroots Good News, Jan. 2004.

While the manifold benefits of the bicycle as a form of transport frequently cover the pages of CarBusters and other environmental publications, pedal power as an energy source is less discussed. In fact, the bicycle is perhaps the most efficient energy system yet developed by humanity.

“With the human population at six billion and growing, pedal power can be incorporated in the lives of families living in Third World countries to improve the quality of their lives while being friendly to the earth,” say members of the CCAT project (pronounced sea cat). “Pedal power is an appropriate technology for now and for the future.”

I would include the “First World” and any other “world” as well, as CCAT do themselves.

CCAT  uses pedalpower (along with solar and wind energy) to cover most of the energy requirements in their alternative energy demonstration house.

The “Human Energy Converter,” a fleet of stationary bikes connected to small 12-volt generators, is used to power laptops, TVs, washing machines, pottery wheels, drill presses, grinders, sanders, wood carvers, stone polishers,blenders, generators, etc. The same technology is also used to power the sound system at political rallies and parties.

(1) CCAT and The Human Energy Converter

So what the heck is the Human Energy Converter?

Otherwise known as the HEC, it’s “a series of exercise bikes individually hooked up to small 12-volt generators, connected by flywheels,” the CCAT website explains.

“They each put out about 50-100 watts, depending on who’s pedalling, and we connect them in series and in parallel to make a 24-volt charge. We have eight matching bikes mounted to a flat bed or just lined up on a lawn, and people line up to pedal the power for the event! It’s a great hit among all party-goers, usually affording agreat view of the stage as well as fun for kids and the kid within the adults.”

The electricity made by the bikes is run through a 4024 Trace inverter to make clean AC electricity good for sound systems. Excess electricity can be fed into the public energy grid or stored in batteries.

While they also sometimes wire in solar panels to the HEC set-up for extra power, this is not required, but as they say “it’s just nice to say we made more electricity than we used.”

For Each 12-Volt Power Generator You Will Need…

An exercise bike, preferably a front mounted flywheel with a channel to accommodate a fan belt. The most effective gearing is a 52-tooth chainring on the bike connected by the chain to the flywheel, which has a 16-tooth freewheel.

A flywheel of solid metal 15.5″ diameter.

A generator pulley 2.5″ diameter. The diameter can be increased to make it easier to spin.

A fan belt big enough to cover the flywheel and generator wheel.

Generator. 24-volt DC permanent magnetic generator, rated at 1800 rpm, with a potential of 1/3 horsepower output. The voltage output is directly proportional to the rpm. The generator can be rotated by this system at 900 rpm’s, leading to an output of 12 volts.

Wiring. 10 gauge copper solid copper wire, Resistance value of R = 1 ohm’s % 1,000 feet

Voltage regulator. 20 amp flat automotive fuse to be placed in line with the positive electric wire. This limits the amount of current when the battery is full to prevent damage.

Diode. A one way electricity valve placed on either the positive or negative wiring. Rated at 25 amps, and at least 35 volts.

Lead-Acid Battery. 12 volt marine/trolling battery, 55 lbs., 100 amp hour, 20 hour cycle, with cycles life 300 discharges.

Inverter. Changes 12 volt DC into 110 volt AC. Inverters must be able to handle potential peak electrical loads. To determine the loads, look at the watt requirement on the back of the appliances.

- Erickson, based on Ben Errickson, CCAT

(2) The Rinky Dink Pedal-Powered Sound System

My personal favourite system though has to be Rinky Dink, a familiar sight to many regulars at UK festivals, parties, and protests. I last saw them at on the fateful day of September 11, 2001, at the protest against DSEI, Europe’s biggest arms fair held in London’s Docklands. They never fail to give inspiration at these events and a general lift of spirits. Like CCAT it combines pedal power with a sprinkling of solar and wind energy, but adds potential movability into the mix.

It is made from a series of linked tractor units made from recycled bike frames. It is 17 feet long and 8 feet high. It can be ridden up to 30 miles a day as a mobile exhibition or converted into a stationary sound system/light show for bands, dj’s, radio broadcasts and live recordings. A purpose built permanent magnet generator (720 rpm output; 20W), originally designed to power the radio communications for the Flying Doctor Service in Tanzania, is mounted on the rear of a tandem. Two riders produce an average of 40 watts. The three phase electricity produced is transferred  hrough a cable as a spiral helix to a switch mode power supply, where it is regulated from AC to a constant 13.8v DC direct drive (or 24v battery charging) which is then fed to the amplifiers. When not needed immediately, this power,  long with 40 W solar energy can be stored in batteries for later use. Using two four-person stationary generators to produce an average 600 W of power, as well as wind generators and solar panels, Rinky Dink can power 100 v DC amps at 300 W and, using invertors, provide mains (240 v) power for any low powered stage equipment (e.g mixers, samplers) thereby providing a clean sustainable PA.

Pedal-powered sound systems demonstrate the direct use of pedal power, and are great for community participation and direct experience as different people take their turns to “dance” on the pedals. If you’ve got a Critical Mass in your town, why not try to make one? ! If you find these instructions a bit too hard to follow for your level of technical know-how, consult someone with electrical engineering knowledge before proceeding.

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One Comment

  1. Dave Wilcox
    Posted 12 April, 2012 at 13:10 | Permalink

    Top idea, been following grass roots in Leeds for a while. Looking at setting up a semi-permanent out door pedal powered rig. Would appreciate some advise on what’s needed. Have a few options on location, but adding a few complications to the mix could do with a an extra feed for charging, thinking solar or possibly a small wind turbine. Hence could do with some advise from someone who knows their stuff. Thanks, Dave

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