Darby Chassis[105k jpeg]
The drivetrain seems to be almost the same in all. A small ring
drives a 7 spd freewheel giving the user a choice of 6 gears. Then
the chain continues (from the largest cog) to yet another cog. This
is very versatile if you are working with < 26" wheels.
Darby Chassis[105k jpeg]
Darby 4 wheel commuter, duet [44k jpeg]
Aluminium space frame construction, it weighs under 100lbs complete with
child seat and doors. The swingarms have been updated since this picture
was taken to handle the lateral forces. Minibike shocks in the rear and
rubber damping (internal and invisible) in the front. The pedals are
adjustble and he has a hand crank mechanism that can be bolted in very
easily. It's a lot more nimble than it looks and it handles very well
at speed (I've had it up to 40 [downhill]). The front brakes are drum
hubs, similiar to the Atoms but I think they're different (they're not
the type you see on a lot of tandems with the drum threading on like
a freewheel), modified to use Magura hydraulic actuation. The rears
are cantilevers, hydraulic as well I think. The steering rod is in the
center so either rider can reach it and it has the front brake lever
on it and each rider has an independant rear brake. I don't know how
many gears it's got, I'd say at least twenty per side but maybe a lot
more.
Darby 4 wheel commuter, duet [44k jpeg]
Darby 'Genie' [89k jpeg]
Yeah, very labor intensive, but worth it. Very stiff frame and very
comfortable as well. Again, lots-o-gears, Bill likes gears.
Darby 'Genie' [89k jpeg]
Darby 'Sprite' [61k jpeg]
The drive system has a bunch of things going for it. It solves the
chain line problems, it does what idlers do but give you something for
your loss. It give you all the gears you could ever wish for, with two
eight speed freewheels you've got 48 gears available. And it solves the
problem of driving a 20" wheel without using a 60+ tooth chainring.
With the plastic wheels that this one has you're limited to a six speed
rear freewheel without getting real tricky, the plastic wheels are meant
to take a single cog and if you pop a freewheel on you wind up messing
with the offset and you can't just re-dish a plastic wheel. The plastic
wheels do have some things going for them. They're a bit more expensive
and a bit heavier than real cheap steel wheels (but just a bit) but they
last better, they never rust or go out of true, and they do give a pretty
good braking surface.
Darby 'Sprite' [61k jpeg]
http://www.ihpva.org/SourceGuide/Vehicles/Darby/ revised 9/25/95 bhw