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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).
Carburettor components including the accelerator pump, slow running unit, and Zenith float.

Identifier  ExFiles\Box 13\3\  03-page318
Date  1st May 1931
  
Hs{Lord Ernest Hives - Chair}/Lovl/AHS.5.31 contd.

-4-

The piston is a working fit in the cylinder and the fuel replenishment obtained past a little loose disc valve attached to the base of the piston. The accelerating fuel is discharged into the main fuel passage past a spring loaded ball valve at the base of the accelerator cylinder.

The accelerator pump when fully depressed mechanically holds open the ball valve and so provides an extra feed of fuel to the main jet which gives a richer mixture for full throttle work. In other words the mixture is proportioned for the minimum strength for throttled running and a rich mixture under full load conditions.

R.R. Slow Running Unit.

We think the slow running unit could be considerably simplified without affecting its performance.

The centre moveable brass sleeve forming the venturi and mixture passage could be deleted. We have found no need for this adjustment as the initial setting can be obtained by the quick thread of the outer sleeve and by loosening off and setting the operating lever in its desired normal position.

We have never made an adjustment by this centre bronze piece after the assembly of the parts.

Zenith Float.

The Zenith has a single cylindrical float and they get it quite light by employing a simple sheet brass pressing for the fulcrum arm instead of a casting.

Hs{Lord Ernest Hives - Chair}/Lov.{Mr Lovesey}
  
  


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