Rolls-Royce 20/25 - oil pump



oil pump


The oil pump main components.

The original tolerances are shown below with the final figures for this pump shown in parenthesis: -

gear backlash = 0.003" (0.013")

radial gear clearance = 0.002" (0.005")

gear end float = 0.002" (0.002")

drive shaft radial clearance = 0.0005" (0.0005")

Contrary to what is stated in Haynes & Grigsby the General Arrangement drawings show that there is no paper gasket used on the bronze bodied pump.

relief valve


The oil pressure relief valve in pieces.  The spacers fit over the pin in the threaded cap - a maximum of 5 spacers may be used.  The correct running oil pressure is18psi at 50mph with a hot engine.

dynamo brakes


The two brake assemblies for the dynamo drive pinion.  The shaped fibre shoes should be a tight sliding fit in their cases.  The movement range of the shoe is restricted by the cross-pin in the slot of each shoe.



Aperture for the brake assembly showing the drum on the back of the pinion.

brake fitted


Two gaskets are used on the casing; one above and one below the flange.  New shoes and springs were fitted.  The previous shoes had swollen to the point where they would no longer move in the casings.



The lower brake fitted and bolted down.