Why sleeve valves on the RR Eagle?

[Admiral Beez]

The Rolls Royce Eagle engine first range in 1944. This engine had sleeve valves. Why? Surely by 1943-44 the world has shown that sodium or otherwise cooled poppet valves were superior.

 

[EwenS]

The Rolls Royce Eagle engine first range in 1944. This engine had sleeve valves. Why? Surely by 1943-44 the world has shown that sodium or otherwise cooled poppet valves were superior.

We're they superior though? Just because the rest of the world was doing something different doesn't automatically make it "superior" or the sleeve valve somehow "inferior".

The manufacturing problems with Napier's Sabre had been overcome by then, thanks to Bristol. Bristol itself was churning out thousands of sleeve valve Hercules engines with Centaurus coming along.

RR had used sleeve valves on the Boreas / Exe (air cooled 24 cylinder 'X' layout 22.1ltr) until its cancellation in 1939 to concentrate on Merlin production. The only problems encountered in its successful development to that point was excessive oil consumption. Otherwise the set up was considered reliable.

RR continued studying the sleeve valve engine during the war.

The V-12 Crecy engine was tested in 1941. It used a reciprocating sleeve valve rather than a rotating one as designed by Roy Fedden and used by Bristol & Napier. Not sure of the technicalities of this or whether the same system was used in the Exe & Pennine.

Rolls-Royce Crecy - Wikipedia

en.wikipedia.org

Around June 1943 development started on the Pennine engine. Basically an enlarged Exe (45.8ltr), development was completed in Sept 1944, with a test engine being run in Dec.

Rolls-Royce Exe (Boreas) and Pennine Aircraft Engines

From the late 1930s to the mid-1940s, Rolls-Royce developed two air-cooled X-24 aircraft engines: the 1,200 hp (895 kW) Exe and the 2,800 hp (2,088 kW) Pennine. Neither engine entered production.

oldmachinepress.com

RR Eagle (liquid cooled 24 cylinder 'H' engine of 46 litres, 2 crankshafts) was more of a successor to the liquid cooled Vulture using a different cylinder layout.

So RR had been working with sleeve valves for some considerable time by the time Eagle development began. One source claimed RR found sleeve valves to be more reliable in operation and had a longer time between overhauls, hence the preference for them in these high powered last generation piston engines. With none of these RR engines finding their way into mass production and service, it's impossible to say if those claims would have been borne out in service. But for RR to stick with sleeve valves for so long, they must have held some perceived advantage over poppett valves in the eyes of the engineers.

 

[hobbes154]

Also possibly making the engine less wide - I think Calum Douglas mentioned this in his book with regard to the Sabre.

Given what was said in that book about sleeve valves limiting boost, I do wonder if/how RR got the claimed +18 psi on the Eagle and +22 psi (Wiki only says 18) on the Crecy.

 

[HP52]

Also possibly making the engine less wide - I think Calum Douglas mentioned this in his book with regard to the Sabre.

Given what was said in that book about sleeve valves limiting boost, I do wonder if/how RR got the claimed +18 psi on the Eagle and +22 psi (Wiki only says 18) on the Crecy.

A friend loaned me an American technical text

Also possibly making the engine less wide - I think Calum Douglas mentioned this in his book with regard to the Sabre.

Given what was said in that book about sleeve valves limiting boost, I do wonder if/how RR got the claimed +18 psi on the Eagle and +22 psi (Wiki only says 18) on the Crecy.

I have a friend with an American publication which dealt in part with the RR Vulture. Their drawings show an X form engine with 6 Master conrods.
In effect the engine was a (sort of) radial of 4 banks . The engine must have been the size of an English Mini Minor
HP52 Hampdemon