Introduction: Bike Generator (mechanics)

Good morning.

This is about a bike generator (one more), that is an electrical power generator that takes movement from wheels and pedals of a bike (in fact, it converts the power of your legs into electrical power);

I already constructed the electrical part of the generator (you can see it in one of my previous Instructables), then I needed the mechanical part of the generator.

You can found several bike generators in Instructables' website (here are some examples: This, this, and this ).

I just was looking for a model that you can adapt on any bike with wheels of about 26", instead to have a "dedicated" and/or modified bike for this purpose.

Step 1: The Wheel's Support.

In order to support the bike leaving the rear wheel free to turn, I used a fork salvaged from another old bike (see draft); in this way you already have a shape that is suitable to fix the wheel without the need to dismount it from the bike used for the generator : just need to unscrew the two nuts of the rear wheel, put the same wheel on the fork (this fork will be installed upside-down, see picture) and re-tighten the nuts.

Now we just need a way to keep the fork vertical and stable...

Step 2: Boards Assembly Method.

The support is made of several wood board (I used scrap wood);

A way to keep together two boards perpendicularly, is to do 2 holes, like in the schema;

The first hole, the larger one, is about 20 to 30mm wide (around 1"); this empty space will receive the nut, and the larger diameter will give us enough space to insert a tool to tighten it. I usually keep the hole 1cm away (around 1/2") from the edge of the board, in order to leave enough wood for the bolt-and-nut to catch.

The second hole passes through the 2nd board, enters the first board in its thickness and pass through the 'larger' hole perpendicularly. I usually choose the diameter of this 2nd hole 1mm larger than the screw that I will use: in this case, 6mm screw and 7mm drill bit.

Step 3: The 3 Main Pieces.

For the main support, I use 3 boards (wood form scrapped furniture): 2 of them (lighter colour in the picture) were around 20cm (8") square, about 20mm thick; no need to be very precise, and no need to be really square.

the 3rd board was around 10 x 60cm, 18mm thick.

Step 4: The Cut-out Shape (detail)

This is the detail about board N°1;

the U-shaped cut-out has to be a little bit (let's say 1/10 inch) larger than the base board; in this way, during installation we could shift a little bit the board to compensate an eventual imprecision in the holes' position.

Step 5: The Perpendicular Holes (detail)

Here some details about the holes in the board N°2.

Maybe the picture isn't clear, but the two 7mm holes are parallel one to the other;

The distance between the two 7mm holes has to be the same distance between the screws.

Step 6: Assembly: Board N°1

- Put the two M6x65mm screws through the base board, inserting them from bottom: the heads of the screws will remain, at the end, hidden under the base board.

- put the board N°1 vertically on the base board, as in the picture (the U-shaped cut-out is downward); the screws have to get into the two 7mm holes: that's why is maybe useful to drill the hole a little bit larger than the screws, insertion will be easier even if the holes' position isn't very precise.

- fix screws and boards wit the 2 nuts, as in the picture. Tighten the nuts.

Step 7: Assembly: Board N°2

It works just as for the board N°1:

- put the two M6x65mm screws through the base board, inserting them from bottom.

- put the board N°1 vertically on the base board: the screws have to get into the two 7mm holes.

- fix screws and boards wit the 2 nuts; tighten the nuts.

Step 8: Improving the Fork's Fixing (details)

(... sorry for my English ...)

We can fix the upside-down fork to the vertical boards with some shaped metal bar; as the boards are perpendicular one to the other, the fork will be stable in all directions.

Step 9: Board N°3

I added another 6x60cm wood board, about 15mm thick, perpendicularly to the base board (see picture), in order to stabilize the support.

Please notice that I had to add two small pieces of wood under the board N°3 (one piece at both end, as in the picture), otherwise this board N°3 won't touch the ground and couldn't stabilize nothing at all.

Board N°4 is a shelf that will receive the generator: some details in next step.

Step 10: The Generator's Shelf

About the generator's shelf that you could perceive in previous step:

- this board ('N°4') is about 20x25 cm (8"x10"), about 18mm thick;

- the 'fixing holes' in the picture are about 6mm wide (once more, they are a little larger than the screws that will be used - I used four 5 x 40mm wood screws), and about 10cm spaced; of course number, position and type of screws are free, the important is that you can fix this shelf on the base board in a reliable way.

- the vertical bolt-and-nuts: they will receive the generator's shifting support (see next step); in the picture screws are M6x50 (roughly) screws. Please notice that around the nuts there are two 'bowls', dig with a 15mm drill tip, in order to keep nuts recessed UNDER the top surface of the wood board (as in the drawing).

Step 11: The Generator's Shifting Support

For this support, I used a 10x22cm (roughly) 18mm thick wood board;

At one side the generator was fixed (1st picture); at the opposite side I dig a 12cm long / 8mm wide slot (2nd picture);

Once the support board is installed as in 3rd picture, it could be shifted along some cm in order to adapt the generator's position to the bike's wheel; than you can easily fix it in the chosen position with 2 washers and 2 nuts.

Step 12: Generator's Wheel

For the generator wheel, a 68mm (roughly) round wood piece was cut with a bell saw;

Luckily, the central hole was just ideal for the generator's shaft; so, this wheel is kept on the shaft only by friction between metal and wood!

This wooden wheel will be placed in contact with the bike's wheel (see 3rd picture): they will turn together in opposite directions.

Step 13: Pedaling.

Now, all is ready;

Just pedal fast enough to get at least about 13Volt; in the picture, the voltmeter on the red box has a 40 V end-of scale, so in that moment we got about 20V generated.

The lamp was a 12V led bulb (indicating success!)

Step 14: Test in Real Conditions - Further Improvements

Recently, a second version of the bike generator was made: both a new mechanical support and a new electrical adapter; the only real difference was that the new adapter includes a charger for a Lead-acid 12V battery;

We used the generator in a local 'bike festival' (see picture): the adapter supplied a 5V led stripe (not very visible, in that sunny day...) connected on the USB outlet and a boom-box modified to be supplied at 12Vdc.

As the generator was intended for a pedagogical use, we didn't use any battery for the moment, in order to show that the power was coming ONLY from the bike (no pedaling, no music).


Finally, I would like to thanks:

- People at the "Atelier Solidaire" (sort of bike-oriented volunteers-based shared workshop) in Saint-Ouen-sur-Seine, France, for space & tools availability, for help in construction, especially the mechanical support (I still don't know who kindly realized the support ver.2.0) and for the possibility to participate to my first 'Bike Festival'.

- the Instructables' website for this (free!) space.

- and all the readers for their kind attention and interest.

*** Have a good day! ***