Instructables
Picture of simple rowing bicycle
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.



 
 
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Step 1: Materials

Picture of Materials
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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.

Tools:

1-Chain tool
2-Crank wrench
3-Crank extractor

Step 2: Bearing

Picture of bearing
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Fix the cartridge bearing to the stem clamp. If the housing of your bottom bracket bearing is not strong enough it may be dangerous, the bearings are under the threads and the clamp of the stem is holding the housing at the middle. Do it on your own risk.

My housing is made of a very hard resin, I think it is OK. I cut the frame of the bicycle to take it out because I don't have the special tool needed to dismount it.

Step 3: Cranks

Picture of cranks
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Fix the cranks to the bracket. To dismount the cranks from a bicycle you need a crank extractor and a crank key. It's very easy, explained here:

http://www.instructables.com/id/How-to-remove-bicycle-cranks/

Step 4: Handles

Picture of handles
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Cut the plastic of pedals and polish to give a cylindrical shape.
Cut two pieces of metal tube and pressfit the pedals inside.
I made a hole in the tube and inseted a small nail for more safety.
m a r i a n o (author) 7 months ago

Some remarks:

If you don't want to use coaster brakes, or if you want to use hub or
dérailleur gears, it may be more convenient to arrange the handles in a
direction that is not parallel to the rotation axis of the crank. That's
what they do in hand bikes: http://en.wikipedia.org/wiki/File:Handcycle.jpg


I preferred coaster brakes because I don't want to have lots of cables
going out of my rotating handle. I also mounted automatic two speed hubs
for the same reason. Two brands are now making these old hubs again:
sram "automatix" and Sturmey Archer S2 or duomatic. I published an easy
way to change a hub here: http://www.instructables.com/id/Easy-wheel-lacing/


You may not like the idea of fixing the bearing with the clamp of the
stem, for instance because it is not very safe or because you want to
use a traditional bicycle bearing. In that case, you may just cut the
frame of a bicycle leaving only a tube and the bottom bracket, then fix
(solder, screw, clamp...) the tube to the stem.

It is more
efficient to synchronize the hand and feet movement, such that you push
with one foot while pulling with your arms. This can be done with a
relation of 2/3 between the gears ratio of the rear and front
transmissions. I mounted a gear ratio of 2 (46/23) in the rear wheel and
of 3 (48/16) in the front wheel. If you want to use chainrings of the
same size you should mount sprockets of 16 in the front wheel and of 24
in the rear. For same sprockets in the front and rear wheel you may use
chainrings of (front-rear) 36-24, 39-26, 42-28, 45-30, 48-32, 51-34,
54-36. Other posible ratios are: rear wheel: 36/18, 38/19, 42/21; front
wheel: 42/14.

rimar200012 months ago
Very creative design!
m a r i a n o (author)  rimar200012 months ago
¡Gracias Rimar!