we get an old bike in the workshop, and this four speed retrodirect from
around 1925 is special enough to be shown here. This post-war quality bike
has two forward gears and two in reverse! Not that the reverse gears result
in driving backwards, as the crossed chain restored drive in the preferred
direction. The front changer follows the trend in providing upshift if
you pedal forward, and in allowing downshifts if you pedal back and doubles
the gears provided by the two freewheels!
The frame is,
as with more french bikes from this era, constructed in lugless gaswelded
construction, and the finish was nickel plated, as you can see on chainwheel
which was protected by lubricant.
Here you can
see how the driveline works. Pedal forward and the chain rotates the smallest
freewheel in the normal manner. The chain then runs over the idler and
back over the larger freewheel towards the chainwheel up front. As the
large freewheel spins slower than the smaller one, the freewheelpawls will
do their thing.
and the situation is reversed and the crossed chain will drive the largest
freewheel. The small freewheel will spin backwards
On this picture
you can see the curved chainstay, necessary to clear the crossed chain
must have inspired later designs
There is also
a front changer: this is the control lever
And here are
the mechanics. The arm rotates around the bracketshell and is provided
with two conical protrusions which lift the chain from one chaiwheel and
direct it to the next one. To change up you rotate the arm up while pedalling
forward, to change down you reverse the procedure while pedalling backwards.
bracketaxle is easily removed if you unscrew the lockring. The hole in
the RH side of the housing corresponds with an oiler in the bracketshell.
The flange on the left is part of the frontchanger.
of this 75 year old cup and conebearing still look a lot better than many
current offering new!
The same can
be said for the headset (not shown)
Yes, it is
an early cassettehub with outboard bearing on the RH side. The cogs slide
on the hexagonal hub-end and are secured with a lock-ring. Only here the
freewheels form part of the cogs, necessary because two independent freewheels
are needed for the different speeds
have their own logo. The prestavalves gave me another surprise, as I hadn't
seen valves with a lefthanded thread before!