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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Trial report on an Isotta car fitted with a Wilson Gearbox and vacuum servo actuation.

Identifier  ExFiles\Box 136\4\  scan0076
Date  23th February 1934
  
X2067

To Eg.
Wcr.
P.
Hs.{Lord Ernest Hives - Chair}
By.{R.W. Bailey - Chief Engineer}
Pe.
Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}

HDY.{William Hardy}1/HP.23.2.34.

Wilson Gearbox with Servo Actuation.

Da.{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} and I have recently tried an Isotta fitted with a Wilson gearbox, a separate engine clutch and a vacuum servo for assisting the pedal operation of the wilson box.

The original purpose of the trial was the demonstration of the Don-Flex clutch by the makers of the clutch who are not interested in the wilson box except to show how their clutch can be used to improve the wilson transmission.

The first 2" movement of the clutch pedal released the clutch without any servo assistance, after which the servo came into operation to help in compressing the gearbox brake spring.

The control of the servo functioned very well giving a light actuation and introducing no objectionable features that we noticed, excepting that Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} complained that the return of the pedal was too slow for quick changing.

There was, of course, the usual loss of servo power when the throttle was opened sufficiently to destroy the vacuum, which in my opinion is a drawback as it means that it is not possible to change down, with servo assistance, without releasing the accelerator.

The total pedal travel was considerable and my impression was that in this respect no advantage had been taken of the servo actuation to reduce the travel.

Silent idling was obtained by providing a catch which retained the clutch pedal in the free position when the gear selector was placed at neutral.

On moving the selector lever to a gear and depressing the pedal slightly the catch was released and the clutch could then be engaged.

The noise made by the car was such that the silence of the box could not be safely judged.

HDY{William Hardy}
  
  


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