Physics for gearheads..or why gear ratios matter

this idea was first mass produced and used in street legal cars in 1958 (to the best of my knowledge)

very short wiki article here
Variomatic - Wikipedia, the free encyclopedia

the biggest drawback on the DAF version as it was offered in their 600 model was that it was partially controlled by engine vacuum
then meant that as the car reached its top speed and you let of the gas, engine vacuum changed, which shifted the transmission and caused the car to keep accelerating passed its "pedal to the metal top speed"

(or, as explained by a wiki on the 600)
"The DAF Variomatic employs engine speed, via centrifugal weights, to shift the transmission and is enhanced by an engine manifold vacuum. It was the only car ever produced which went faster by the simple expedient of gently and gradually releasing the accelerator once top speed had been reached. This increased manifold vacuum which helped the variable pulleys shift to an even higher ratio so even though the engine RPM stays the same, the transmission increases the car's speed, in the case of the DAF 600, from 60 miles per hour (97 km/h) to nearly 70 mph (110 km/h) given enough time and level road"

and, a link to an article on it in popular mechanics, December of 1959, p.140-142

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