This bicycle is really easy to build and to ride. It is also cheap if you recycle two old bicycles to build it. Furthermore, it is quite effective and great training for most of the muscles of your body.


Step 1: Materials


1- One bicycle (better with coaster brake).
2- Cranks (better short cranks for a child's bicycle).
3- Bottom bracket cartridge bearing,  the sealed type, not the old system.
4- Pedals.
5- Two bicycle chains.
6- Some plastic tube to guide the chain.
7- Metal tube, about 25 mm inner diameter.

You may take items 2-4 from an old bicycle. I bought a long stem because the one in the bicycle was a bit too short for me. I also bought special  tube for chains because it is very cheap, but you may use any plastic tube of suitable diameter.


1-Chain tool
2-Crank wrench
3-Crank extractor
<p>Some remarks:</p><p>If you don't want to use coaster brakes, or if you want to use hub or <br>d&eacute;railleur gears, it may be more convenient to arrange the handles in a <br>direction that is not parallel to the rotation axis of the crank. That's <br> what they do in hand bikes: <a href="http://en.wikipedia.org/wiki/File:Handcycle.jpg" rel="nofollow">http://en.wikipedia.org/wiki/File:Handcycle.jpg</a><br> <br> <br> I preferred coaster brakes because I don't want to have lots of cables <br>going out of my rotating handle. I also mounted automatic two speed hubs <br> for the same reason. Two brands are now making these old hubs again: <br>sram &quot;automatix&quot; and Sturmey Archer S2 or duomatic. I published an easy <br>way to change a hub here: <a href="https://www.instructables.com/id/Easy-wheel-lacing/" rel="nofollow">https://www.instructables.com/id/Easy-wheel-lacing/</a><br> <br> <br> You may not like the idea of fixing the bearing with the clamp of the <br>stem, for instance because it is not very safe or because you want to <br>use a traditional bicycle bearing. In that case, you may just cut the <br>frame of a bicycle leaving only a tube and the bottom bracket, then fix <br>(solder, screw, clamp...) the tube to the stem.<br> <br> It is more <br>efficient to synchronize the hand and feet movement, such that you push <br>with one foot while pulling with your arms. This can be done with a <br>relation of 2/3 between the gears ratio of the rear and front <br>transmissions. I mounted a gear ratio of 2 (46/23) in the rear wheel and <br> of 3 (48/16) in the front wheel. If you want to use chainrings of the <br>same size you should mount sprockets of 16 in the front wheel and of 24 <br>in the rear. For same sprockets in the front and rear wheel you may use <br>chainrings of (front-rear) 36-24, 39-26, 42-28, 45-30, 48-32, 51-34, <br>54-36. Other posible ratios are: rear wheel: 36/18, 38/19, 42/21; front <br>wheel: 42/14.</p>
Very creative design!
&iexcl;Gracias Rimar!

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