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Alterations for a second synchromesh gearbox for the J.3 car.


Identifier  ExFiles\Box 123\3\  scan0151
Date  12th March 1934
  
ABRX X.4704

To BY. {R.W. Bailey - Chief Engineer} from HDY. {William Hardy}
HDY. {William Hardy} 1/HP.12.3.34.

c.c. Hs. {Lord Ernest Hives - Chair} Da. {Bernard Day - Chassis Design} WHO.

Gearbox for J.3.
----------------

The Experimental Department are about to build another gearbox of the J.3. synchromesh 2nd speed type which will be for the J.3. car, and as there have been a number of alterations since the first box was made we are giving below a list of the features we should like the box to have which are different from those on the first box.

Gears.
------

As on N. Sch.3788 except for constant mesh gears which are to have the same tooth particulars as for the 20/25. This alteration was instructed in our Hdy. {William Hardy} 2/HP.7.3.34.
The outside diameter of the 1st speed pinion is to be reduced to give 15/1000" clearance between the pinion teeth and the sleeve.

Synchromesh clutches and locking cam angles.
---------------------

The top and 3rd speed clutches to be as on N. Sch.3809 i.e. as originally designed with 10° angle and standard type oil grooves.
The 2nd speed clutch to be as on N. Sch.3997 except for the modification asked for in Hdy. {William Hardy} 1/HP.2.3.34.
The locking cam angles for top, 3rd and 2nd are to be increased and we will send a drawing of these.

Sliders.
--------

To have the interlock modification shown by N.Sch.3946.
  
  
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).


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