A Recipe For Pedal Power

Bicycle generators can be made for next to nothing and used to power just about anything you want, not just sound systems.

The Ingredients

  • An old bike. An excersise bike will do but will mean you are less mobile.
  • A fan belt or something similiar.
  • An alternator or dynamo—dynamos are better than car alternators but harder to find.
  • A car battery. Find out if it has a built-in transformer or rectifier. If not, you will have to get one separately.
  • Lugs for connecting the cables between the alternator and the battery.
  • And of course, to make the par ty happen you will need a sound system, lots of music, happy and willing pedallers, a street and people that want to party.

You should be able to pick up most of the parts cheaply or for free in a car scrapyard.

Car batteries are not ideal but are the easiest to find. Lead-acid batteries, made for industrial electronic systems such as fire alarms, are best, as they are built to sustain long periods of noise.

Method

How to turn rotational energy into pedal power:

1. Connect the alternator to the bike. This can be done in a number of ways, either welded on, or bolted on through a hole in the bike. It must have leverage to be able to swing into and away from the fly wheel and the fan belt must be able to turn when pedalled from the bike.

2. Connect the fan belt to the wheel (fly wheel) of the bike, and onto the smaller wheel of the alternator. It is important that the smaller wheel of the alternator is lined up with the fly wheel—otherwise the belt will come unattached.

3. Connect a battery to the alternator. It is important to have a battery in between the alternator and the load, be it a sound system, toaster or whatever, as this soaks up extra voltage and provides steady voltage for the equipment. Check whether the battery has a diode output. A diode allows electricity to flow one way and not the other—most vehicle alternators and dynamos should already have them fitted.

4. Using a permanent magnet alternator or dynamo as a generator means that, to wire it up, the positive and negative terminals of the battery and alternator have to be connected.

To prevent loss of energy between the battery and generator, keep the cable lengths as short and thick as possible.

Connecting while using a nonpermanent magnet (such as an ordinary car battery or dynamo) can be a bit more complicated. From the alternator look for the main output terminal, usually labelled B+ or D+. This is the output (12 V) which connects to the positive terminal on the car battery. The negative terminal connects to the case of the alternator.

It may be necessary to give the field coil inside the alternator a gentle helping hand to get the magnetism going before pedalling. This need only be for a short time and a switch can be connected to the front of the bike that can easily be disconnected and reconnected.

In order to find the correct terminal for the field coil (can be difficult to find), touch the wire from the positive terminal onto each of the spade terminals. The field coil terminal becomes apparent when the alternator is much harder to turn when pedalling. This only needs to be done at the beginning of pedalling.

Once you have connected everything up, it is time to start pedalling and partying.

Mixing

In theory you should be capable of producing about 12 volts DC, or 720 watts. However it’s unlikely that you will actually produce that much, as some energy is lost in the equipment. It should, however, be enough to power a car stereo that can handle impedances as low as two ohms. This, connected with a fourohm base speaker with a pair of satellite midrange speakers, means you can be a mobile sound unit. The whole rig can feasibly fit on a bike trailer and run on the energy you generate from the bike.

In order to power loads that require more energy, you can increase the number of bike generators connected to the same battery or increase the number of batteries. Car batteries are self-regulating, so you cannot overcharge them. This is an outline of how to create a basic bike-powered system. There are several refinements that can be made. For example, if you are using a car alternator, having gears makes it easier to pedal. But that’s another story…

With thanks to Richie@greenloops and Chog@kreaktivnii. If you are concerned about playing with electrical gadgetry, please ask someone to help you.

Download the scheme

One Comment

  1. kevinbalu
    Posted 15 February, 2013 at 08:02 | Permalink

    how to work

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