The "plastic stacking chair and back end of racing bike"
generator design works quite well and is easy
to make. The front tube of the bicycle is easily converted into an adjustable
length link to the chair, and extending the legs of the chair with tubing
from bike frames or old tent poles to bring it to a horizontal position
is also straightforward. However there is a disadvantage in that the seat
finishes up at about 30 inches from the ground which can make it difficult
to get on and off, particularly with the adjuster pole coming out horizontally
from the front of the seat.
Having found a fresh (but rusty) racing bike in a local
skip, and the base of some sort of antique hospital light stand which fitted
nicely onto an old stacking chair, I decided to investigate the feasiblility
of a lower level chair design.
It looks possible though the back legs of the chair had
to be extended slightly to get the adjuster
pole exactly horizontal. (One of our very earliest
designs several years ago featured a non horizontal adjusting pole; it
looked
good but was just too much hassle to adjust)
Fixing the adjuster pole to the centre of the crank turned
out to be quite difficult; in the end I finished
up doing a complicated join to two of the tubes
already coming out in unhelpful directions. There wasn't really another
way to do it. Welding straight onto the crank housing would have destroyed
the hardening and probably distorted it so it wouldn't have worked any
more. The crank position is now a couple of inches above the seat, but
I've seen other generators with this configuration so I think it's got
a chance of working. On the other hand it's already looking like a much
more complicated fabrication than the usual designs.
Having got the chair and bicycle rear end connected together, the next problem is what to do with the alternator. It's really got to go somewhere low down to stop the thing becoming top heavy and also to avoid building loads of extra superstructure on something that's already looking complicated. I decided the best (only?) place for it was below and just in front of the wheel, pivoting at the bottom and leaning towards the pedaller. Notice in the last picture the brake mounting plate had got in the way of the belt so it was cut off and refitted lower down. The wheel is a 26 inch one and a A78 (78 inch circumference) belt was used in the hope the alternator would fit between the wheel and the ground. The idea of having the alternator leaning in the direction of belt travel is to make the belt grip tighter the harder it pulls to avoid slipping. A base for the alternator mount was made out of some parts of an office chair. The fixing is obviously quite fragile and liable to put a lot of leverage on the joint where the bicycle seat used to be, so some braces made of leftover bicycle tubing were put on, allowing room for an alternator on one side. To give the thing more portability, the inner tube of the telescopic coupling was joined to the pedal unit with a socket and split pin.
The next stages of this generator are featured in the Druid Network Workshops - see 2004 Events, it also got used to run the PA in the Children's Tent at Kingston Green Fair as well as powering the Bass Amp at the Druid Network Camp's Seize The Day gig.
