This should put the current thread about lights and dynamos and
batteries in the shade.
Filaments, LEDs, halogens, batteries versus generators--bah!
Real men use tandems to charge batteries to power x-ray machines.
In 1899, the Strand magazine described how the new-fangled Rontgen
rays illuminated bullets in wounded soldiers and how British surgeons
in the Sudan used a tandem to run the x-ray department.
In 110 F heat, it took two men on a trainer to charge the x-ray
machine's battery.
(Let's not hear any more complaints about drag, hot weather, feeble
generators, or heavy batteries.)
The details may interest the electrically inclined:
"The pulley of a small dynamo," writes Major Battersby, "was connected
by means of a leather strap with the back wheel of a specially
constructed tandem bicycle. The required velocity for the dynamo was
then obtained. Having carefully adjusted the circuit with the storage
battery, and also with the voltmeter and ammeter, the warrant officer
took his position on the seat of the bicycle and commenced pedalling.
When 15 volts and 4 amperes were registered, the switch close to the
handle of the bicycle was opened and the charging of the battery
commenced; as the resistance became greater, a sensation of riding up
hill was experienced, and the services of an additional orderly
requisitioned for the front seat. This bicycle practice was generally
carried out in a shade temperature of 110 deg. F., so that everyone
was glad when (the switch having been turned off before pedalling
ceased, in order to avoid any discharge from the battery) the machine
was brought to a standstill."
Pictures of the field x-ray machine, suitable for taping to the wall
at your local x-ray shop:
http://i26.tinypic.com/mvogpf.jpg
Picture of the back half of the tandem, ready to charge the battery,
which would be hard to haul around even on a tandem:
http://i32.tinypic.com/ta22zb.jpg
The frame under the seat and forward of the crank shows that it is
indeed a tandem, but I don't see the front chain.
The PDF is over 50 mb (not searchable). If you're curious and want to
see bullets in old x-rays, the article starts at image 160 of 204:
http://ia310906.us.archive.org/1/items/StrandMagazine_102/StrandMagazine_102.pdf
Cheers,
Carl Fogel