This is what my recumbent bike, Jo, schemetically looks like.
It is a classical short base recumbent bike configuration, meaning that
it has a classic steering mechanism and the front wheel between the seat
and the pedals.
Long base bikes are quite rare, the french Roulant is one of few classic examples, Biggest problem with long base bikes is making the frame stiff enough, so it will not bent when putting some pressure on the pedals.
There are some bikes which use another configuration than the classical
ones. The Flevobike is the most reknown exception on this. It uses a hinge
joint in the middle of the bike to make steering possible.
Problems with non-classical configurations are that special material
is needed to construct it (the joint), and that the steering behaviour
can be so much different from a normal bike, that considerable training
time is needed to learn to drive it.
Nontheless it can be worthwhile, especially when building bikes on three
or four wheels, to consider other means of steering. A good example of
a bike with a three-wheeler steering mechanism (though not flawless) is
the Jouta.
But remember that notorious problems (ith keeping the bike in sharp curves
upright and the wheels straight) loom up when using three or four wheels
on a bike.
Jo does not have any suspension. This is mainly because I did
not have the knowledge or material to make it. But I would warmly advise
it to anybody who is going to work on building a bike.
Small bumps, especially at high speed, can make a ride quite uncomfortable.
(Besides of that, in the Netherlands, in contrast to for instance England,
the government has constructed seperate roads for bicycles, some of which
are in poor condition. Suspension can help you remaining seated on that
kind of pavement.)
Everything, when building a bike, starts with the frame.
Very trivial, but still, the most important thing, when designing a bike,
is that you, the future rider, fit on it. So take a book on ergonomics,
look up where your most important joints are, take a measuring tape and
start measuring yourself.
Critical points of your body are the knee- and hip-joint. Also very important
is the distance from your back to the end of your feet. You can easily
measure this when sitting, legs stretched out forward, against a wal. The
distance between your sadle and the pedals in the farthest position should
be some 10 cm (4") less than this. This is from preventing your knees
to 'lock up' (bent through downward)
Also important are the handle bars, which should be in a position so that
you can reach and move them easily.
When in doubt, collect some chairs, wooden blocks and sticks and make yourself
a mock up. Besides proof that everything fits comfortably, it is
also fun to do and might give you some inspiration for revolutionairy ideas.
After some measuring, drawing, trying and drawing my own stature (which was quite a revelation) on the design of the bike, I wound up with a design which I could easilly construct from existing material. Below here you can see the concept.
In the frame I used two old bicycle frames. One coming from a usual
28" bike, which you can see in red above,
and one coming from a 20" child bike, which you can see in blue.
To make the construction complete, I used extra tubing, which you can see
in green above here. I used rolled and welded
tubes which are usually used for constructing motor-carts. A cheaper alternative
would be the use of gas-tubing, which is drawn. But this type of tubes
might be brittle and are, in relation to the other thin walled tubes, quite
heavy in relation to their stiffness.
The blue frontpart of Jo, which was made of the childbike part, has been
replaced already. Reason was that it was mounted upside down, causing the
ball bearing holders to come loose, despite the extra fastening. It has
now been replaced by the pedal axis part of the frame of a normal bike,
which has the more modern industrial ball bearings.
The front lights are mounted on the tubes sticking out of this bearing
house. They are also left long to work as a thrust weapon to actively move
pedestrians out of the way (when needed of course).
On the frame in the middle there is also mounted a tube with bearings for
holding the steer. This holder should be parallel to the holder of the
front fork (a mistake I made).
Biggest challange is to get the produced power from the front to the
rear.
Jo uses 3 normal conventional chains (about 250 links) to connect the pedals
to the rear wheel.
3 small derailleur sprockets are used to guide the chain and bent it somewhat
in position. I tried to let the upper part of the chain run into a straight
line as much as possible, because it is this one that is pulled on most.
The chain runs mostly free. Only the front part is covered, because else
my trousers get dirty. A good possibility to neatly cover the chain is
to let it run through a hose.
