The Rough Science hand-cranked generator showing the induction coils (each 1000 turns of thin enamalled wire), magnets (x4) and the homemade gear mechanism / crank (far right). Two magnets, one either side of the crank shaft will work well but if you have space then you can double up to 4 as I have done here to get more electricity. Two nuts in the micddle of the (studding / thread) shaft allow the magnets to be positioned properly - the magnetism holding them in place. The coils need to be positioned as close to the rotating magnets as possible.
The simple ball bearing mechanism used to reduce friction. The balls came from an old bicycle wheel while the axal is simply a piece of studding drilled at the ends to make an indentation for the ball to sit in. A sheet of metal with a small hole to locate the ball applies tension to the assembly. A drop of oil and the thing spins very nicely.
An earlier version of the simple gearing. A single turn of the handle rotates the magnets many times with this simple gearing. This means that the magnets can get up a good speed between the coils to induce as much voltage as possible. The grey gear is made from two coffee lids bolted together, while the white 'gear' is made from two water bottle caps fitted back-to-back (held in place with nuts). The ribbed edge of the caps gives a good grip to the rubber band. A slightly smaller tube-of-glue cap was eventually used in the final design (shown in black in the first picture above)
At a steady pace 8-10V at 200-300mA was possible, enough to light 4 or 5 small torch bulbs. These were wired to hard hats and used as mining lamps. With this gear we investigated a Colorado mine. I took a tape measure apart and used the internal steel spring to power the generator. Winding up the generator one way produced electricity but also wound-up the tape measure spring. On releasing, the energy stored in the spring powered the generator as it un-wound. Repeating this procedure gave us continious light without me having to spend all my time cranking the handle. Note: as this simple design has no moving electrical contacts it is safe to use in wet conditions (I tried it completely immersed in a bowl of water and it worked a treat!) and also where there may be explosive gases such as down in a poorly ventalated mine shaft.
