Advantages of sleeve valves for H-24 engines?

[Writer]

Cylinder block spacing was more defined by the crankshaft swing than the sparkplug spacing
View attachment 731017
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 !

 

[Deleted member 68059]

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.)


View attachment 734710View attachment 734709

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

 

[J.A.W.]

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.

The Sabre cannot have "given no end of trouble", since only ~5,000 were built, and well over 4,000 planes flew with them, so there weren't
that many spare engines to keep on hand. The Tempest F.6 flew with Sabre power for years postwar operating in harsh primitive conditions,
from RAF airbases in hot dusty Africa/Middle East zones, & the RAF were flying its Tempest TT5s hard in realistic gunnery training exercises
for their 'jet-jockeys' right up 'til the mid 1950s - when Meteors were deemed available to take over the role.

 

[J.A.W.]

Here's a period write up which notes the improvements made to the Napier Sabre when 'fully productionised' by 1944,
including dynamic crankshaft balancing , steel shell-backed plain bearings and ignition timing mapping servo:

Napier Sabre Ii Icnition Servo Unit Distributor

MARCH 23RD, 1044 FLIGHT 3°9 1^1 Napier Bv F. C. SHEFFIELD Sabre II Twenty-four Cylinder, Sleeve-valve, Liquid-cooled Twin-crankshaft Engine Now in

docslib.org

 

[Deleted member 68059]

The Sabre cannot have "given no end of trouble", since only ~5,000 were built, and well over 4,000 planes flew with them, so there weren't
that many spare engines to keep on hand. The Tempest F.6 flew with Sabre power for years postwar operating in harsh primitive conditions,
from RAF airbases in hot dusty Africa/Middle East zones, & the RAF were flying its Tempest TT5s hard in realistic gunnery training exercises
for their 'jet-jockeys' right up 'til the mid 1950s - when Meteors were deemed available to take over the role.

That is quite a novel approach to inferring engine reliability.

It is worth noting, that an aircraft which crashes and the airframe of which is destroyed or even just written off does not require a new engine for that airframe,
and that an aircraft which is lost over enemy terratory does not require a new engine for that airframe.

The RAF knew perfectly well what the Sabre was like and were inspecting them constantly and rebuilding them at tiny service intervals
once the sleeves started playing up to make sure they DIDNT blow all engines up. For a very long time whilst Merlin`s were
doing 200>400 hours between major overhauls, Sabre`s were being taken apart at 50/70 hours or less. None of that
requires a replacement engine for that airframe either, but is still a catastrophically bad position.

A slightly more solid viewpoint on what it was actually like is to be found if you read the Air Ministry files,
part of the reason for there not being so much effort put into rebuilding them at tiny intervals was
that there WERE no spare engines.

Even in 1943, the Air Ministry description of the Sabre was "from bad to worse" (see 4th page down)

"never likely to become a reliable engine" (see 5th page down)

"it was on balance a miserable failure" (see 6th page down)

- By the final 12months of the war it was just about there in terms of being reliable to a practical degree, but
that was far too late.

Please note I think its a fascinating engine, and it would be a good thing to get one running again now,
but - at the point in time back then, it was an immensely troublesome, difficult unreliable engine
for most of the war, these are simply recorded facts.

Note: This is hours between FAILURES IN FLIGHT, not T.B.O.

"Average engine life is 67 hours"

 

[Geoffrey Sinclair]

Sabre, just over 5,000 built to end 1945, production continued through 1946, about another 200 built, plus there was a conversion program of II, IIA, IIB and IIC into VA

3,215 Typhoon plus 942 Tempest V and VI comes to 4,157. However the engine situation was so bad in 1943 several hundred Typhoons in storage were reduced to spares as they had little chance of ever receiving an engine. In 1945 even some Tempests were being reported as "slaved to purgatory storage", no engine fitted. Typhoons are over represented when it comes to numbers turned into Maintenance Airframes. So deduct about 10% from the aircraft figure.

The Tiffy was Pissy?

The Typhoon had a design flaw like the early Bf109F causing structural failure near the tail, in both cases the fix was simple once the problem had been understood. The main Typhoon problem was the engine performance and availability. Typhoon cumulative production was 227 by end June, 448 by...

ww2aircraft.net

The Tempest V finished production in August 1945, the 142 Tempest VI (July 1945 to June 1947) used the Sabre V, about 130 V and VA had been built by end 1945.

 

[wuzak]

View attachment 759093

Is the Tornado mentioned in the first page the Centaurus Tornado?

 

[Deleted member 68059]

Is the Tornado mentioned in the first page the Centaurus Tornado?

Not sure I`d have to go and check and I cant remember which file that was in now.

 

[Simon Thomas]

Have you got similar documentation dated after Spring 1943, which is the point in time when Napier's had received the Bristol Taurus sleeves and had the centreless grinders in operation making the sleeves? All the pages above appear to be prior that that.

I don't think anyone can claim the Sabre was any good prior to that point. The Squadron ORBs show they managed to get sufficient reliability for standing patrols, but I would put that down to the herculean effort of mechanics to keep them running.

I was surprised they stayed in production until 1946. Whoever labelled it a "miserable failure" must not have had much clout when it came to purchase orders.

 

[Deleted member 68059]

Have you got similar documentation dated after Spring 1943, which is the point in time when Napier's had received the Bristol Taurus sleeves and had the centreless grinders in operation making the sleeves? All the pages above appear to be prior that that.

I don't think anyone can claim the Sabre was any good prior to that point. The Squadron ORBs show they managed to get sufficient reliability for standing patrols, but I would put that down to the herculean effort of mechanics to keep them running.

I was surprised they stayed in production until 1946. Whoever labelled it a "miserable failure" must not have had much clout when it came to purchase orders.

Well see para 158, he was in overall control over the entire program at the Air Ministy. But you cant just "cancel" orders for an engine you dont like half way through a war when you have a major aircraft program underway which relies on it being delivered.

 

[Simon Thomas]

1946 is well after the war. A huge amount of orders were cancelled in 1945. If the Sabre was a "miserable failure" in 1945, surely it would have been cancelled as well.

 

[Deleted member 68059]

1946 is well after the war. A huge amount of orders were cancelled in 1945. If the Sabre was a "miserable failure" in 1945, surely it would have been cancelled as well.

Its a retrospective Air Ministry file, which was a review file the Ministry made of all major departments and projects to ensure learning was there for the future, recorded right afterwards when the events were all fresh in their minds, those particular pages were written about two years after the war. He is saying that the Sabre project as a whole, given the initial hopes and promise had been a failure. It is difficult to argue with that looking at the rest of the conclusions from wartime papers, many of which I posted above.

Nobody has to like it, but that is what was written.

 

[z42]

1946 is well after the war. A huge amount of orders were cancelled in 1945. If the Sabre was a "miserable failure" in 1945, surely it would have been cancelled as well.

One interpretation would be that despite the Sabre being considered a miserable failure, the Tempest was the fastest low-medium level fighter they had, so they needed a bunch of extra engines so that they could, no doubt through heroic effort by the maintenance workers, keep the Tempests flying for just a few more years until they were replaced by jets.