Advantages of sleeve valves for H-24 engines?

[Writer]

Cylinder block spacing was more defined by the crankshaft swing than the sparkplug spacing
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Sabre engine.
The Sabre spark plugs were not all that easy to change.

Yes but imagine adjusting the tappets of 24 cylinders outside in the middle of winter!

 

[Bretoal2]

Yes but imagine adjusting the tappets of 24 cylinders outside in the middle of winter!

That's why Rapier had automatic (hydraulic) tappets adujstment.

And just for the fun... Vulture : 24 x 4 = 96 tappets per engine !

 

[BarnOwlLover]

Very little attention seems to be given to the weight of the engines spoken about here. Given that the Rolls-Royce Griffon, in Mk VI form, gave well over 2,000 BHP, makes it a rival to the Napier Sabre. The Mk VII Sabre weighed 2540 pounds, the Griffon just 1790 pounds. I am an admirer of the Napier Sabre, (I read Setright's "The Power to Fly" at an early, impressionable age!), but it certainly would appear that the Griffon was the better choice....

And later Griffons were lighter still (though heavier than the VI), and had a two stage supercharger, hence better at altitude.

 

[don4331]

Y'all lost me:

On 100 octane (It's what I have numbers for in my '45 copy of Aircraft Engines of the World)
Griffon VI - 1,835hp take off; 1,850hp @ 2k'; 1,900 lbs. (basically Griffon IV with cropped impeller [9.75" for VI vs 10" for IV] 2 speed, single stage
Napier Sabre IIB - 2,400hp take off; 2,360 lbs. 2 speed, single

For 450lbs (~25%) weight, Sabre is providing 30% more power

Griffon 65 - 1,650hp take off; 2,035hp @7k'; 2,075lbs. 2 stage engine weighs 175lbs more, but the 2 impellers are more efficient.
On 150 octane
Griffon 65 - 2,300hp @6,750'; 2,075lbs.

For all its faults, Sabre's power/weight & outright power weren't one of them.

I was at the Aviation Museum in Ottawa on weekend, they had both Merlin and Sabre on display. Changing plugs on Sabre looks pretty easy (there's just a lot of them) compared to those on inside of V of Merlin/Griffon (underneath the flame trap and intake manifolds).

 

[Reluctant Poster]

Very little attention seems to be given to the weight of the engines spoken about here. Given that the Rolls-Royce Griffon, in Mk VI form, gave well over 2,000 BHP, makes it a rival to the Napier Sabre. The Mk VII Sabre weighed 2540 pounds, the Griffon just 1790 pounds. I am an admirer of the Napier Sabre, (I read Setright's "The Power to Fly" at an early, impressionable age!), but it certainly would appear that the Griffon was the better choice....

I read Setright's column in Car magazine for many years. If there's is two things I gleaned it's that he loved sleeve valves and despised Rolls Royce. He also claimed that the only use for seatbelts was to hold grocery bags and the smoking was good for you. He died of cancer although I'm not sure of what kind.
He was a lawyer, not an engineer although his father was an engineer.

 

[Bretoal2]

Yes, the Griffon was a most interesting engine. But it ran for the first time in June 1940, when the Sabre had made its first type-test mid-1938 !

 

[Snowygrouch]

Yes, the Griffon was a most interesting engine. But it ran for the first time in June 1940, when the Sabre had made its first type-test mid-1938 !

Yes the problem was the Sabre`s put through the initial Ministry test were all hand crafted prototypes, it took several attempts and essentially the engines were rebuilt and hand fettled until one managed to get through the test. So it "passed" but it would be years before it was actually ready for reliable mass production.

This 1938 "pass" was also not a 100 hour full type test approval for service, it was an "initial acceptance test". The proper type test 100 hour was not done until June 1940.

See Napier case history file (in my book, see refs for Chapter 2: "1930`s prelude to war" archive file ref No.70, on page 463.)

 

[z42]

Yes the problem was the Sabre`s put through the type test were all hand crafted prototypes, it took several attempts and essentially the engines were rebuilt and hand fettled until one managed to get through the test. So it "passed" but it would be years before it was actually ready for reliable mass production.

Per Wikipedia, the Typhoon entered service in September 1941, vs the first Griffon Spits in October 1942, so by that time the gap had narrowed to one year. And of course, the Sabre gave no end of trouble for the entire war and was retired from service relatively soon after the war, whereas the Griffon soldiered on until the 1980'ies in the Shackleton.

 

[wuzak]

Yes the problem was the Sabre`s put through the initial Ministry test were all hand crafted prototypes, it took several attempts and essentially the engines were rebuilt and hand fettled until one managed to get through the test. So it "passed" but it would be years before it was actually ready for reliable mass production.

This 1938 "pass" was also not a 100 hour full type test approval for service, it was an "initial acceptance test". The proper type test 100 hour was not done until June 1940.

See Napier case history file (in my book, see refs for Chapter 2: "1930`s prelude to war" archive file ref No.70, on page 463.)


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Was there some delay in the development of the Griffon during 1940 as priority was given to the Merlin?