The
model was demonstrated by turning the red handle, right (very fast and
hard!) As input speed increased, drive was taken up by a differential,
the free pulley on one side of which was progressively braked by a cord.
Input speed was measured by a layshaft (lower right ) which via a slip clutch placed a bias on a torsionally sprung rod. The cord was wound on this rod. As the rod twisted, the cord pulled tight, braking the differential pulley, and drive passed to the transmission proper (left).
The transmission itself consisted of two layshafts, each carrying a
differential. On both, the 'free' end of the differential carried
a pinion, braked by a pawl. The pawls were actuated via bowden cable
by a horizontally-turning crank on top. The crank was moved by a
centrifugal governor on the output shaft. As output speed increased,
the first, then the second layshaft differential was locked. The output from
each layshaft was via a ratchet wheel to allow the drive to be overridden
(at a higher speed) by the next. When both layshaft differentials were
unlocked, drive defaulted to a bypass, lowest ratio. Reverse gear was
selected by sliding an idler pinion (lower left of picture) into mesh.
Builder's comment: An impressively complicated-looking model, but better designs by far of Meccano automatic transmissions can be found.