In 1964 I was in school for my A&P license, and our powerplant instructor was a WWII veteran mechanic. The man knew his engines and propellers better than anybody else, and he taught us well. However, when he told us about the Sabre engine we just looked at each other and wondered if he was joking with us. Actually, the engine was very real, and very important in the history of British fighter aircraft.The success of the Sabre convinced the Brits that the sleeve valve would eventually replace all poppet valve engines, but of course the jet engine ended the contest by the end of the war.
A good attempt by Napier at the time, but technology was already moving on to jets. Great overview of Brit fighter big engine development and sleeve valves.
Well done, most videos on these high-powered WWII piston aircraft engines are full of errors, this video has what I believe to be one. There is no proof that the Sabre officially got to 3500hp. The last one, the VII, was type-rated at 3050hp for takeoff on ADI . Did they produce more than this? Probably, but this would have been more along the line of WEP, which I have never seen specified. I once believed the 3500hp figure, but after extensive searching, I have found no primary source to confirm this, so, for me, it is 3050hp One of the more interesting things about the sleeve valves used on the Sabre and Bristol engines was that the block had five ports but the sleeve only had four ports. This means that one port in the sleeve would alternatively pass cold inlet mixture followed by hot exhaust gases. This heat cycling is generally considered a bad idea, although I have never seen this issue explored in any detail. There is a great deal to cover in any complete story of the Sabre, unfortunately, much of the original Napier documentation has been lost. Many H pattern aircraft engine designs have been put forward, but the Sabre was the only one that made it to production. In the USA, both Continental and Pratt & Whitney worked on sleeve valve engines, P&W on the X1800 aka H2600 H24 for the army and the H3130 H24 for the Navy. These engines were considerably different to the Sabre and were closer to the layout of the Napier Dagger, albeit, with water cooling. Examples of these prototype engines still exist. The P&W effort came to an end after a change of management at P&W, P&W essentially bought their way out of the contract. Kimble D. McCutcheon's book "American Sleeve-Valve Aircraft Engines " has a wealth of information on the subject.
Thanks. I should perhaps have cited my sources for the 3,500hp claim (Oldmachinepress which I believe reputable, and some research papers with the same claim). There is even some sources claiming it achieved 4,000hp, but I did find counter-claims that there is no proof of that, so I reverted to the 3,500hp number. But I'm happy to concede if it was only 3,050hp, you may have researched that detail more extensively. I did consider including other H engines in the video but when I started digging deeper for research months ago I got very fascinated by the details of the the Sabre and so decided to focus on it. The Lycoming H-2470 may feature in a video soon though. I was in contact with Kimble some time ago but didn't realise he wrote the book about American sleeve valve engines. Thanks for the info.
Great stuff! One of the unanticipated downsides of sodium filled valves, widely used by Lycoming, is moving the heat from the head to the stem tends to promote deposit buildup on the stem. Valve sticking from lead/carbon deposits on the stem/guide is a chronic problem on Lycomings.
Well presented! I learned a lot, especially on sleeve vales. I believe another advantage of the larger piston count and hence smaller bores is that the faster completion of the flame front across the smaller cylinder reduces tendency of pre-ignition (knock). I recall that from school in 1980. Regards.
The Sabre was quite innovative in some respects. It was oversquare, and a high rpm design with comparatively small cylinders. Had they instead gone with the tried and tested poppet valves, perhaps they'd had it in service years earlier.
Very good. Thanks. In my ignorance, I thought that the cylinders in the H engines were actually placed like an H. I didn't know that it was an H lying on its side.
That was a fantastic video, I've been wanting a detailled breakdown of the Sabre for ages. The engine was dogged by technical issues due to its complexity at the start. Do you know what the issues were?
Mainly the sleeve's, which was sorted once Bristol agreed (not willingly) to assist Napier with this. Bristol has been making sleeve valves for some time by now and got all issues sorted out in peace time before the war. The issue I believe was out of roundness, meaning the sleeves wasn't perfectly circular on a very small scale, and the sleeves wore out prematurely. The other issue was the Coffman starter which damaged the sleeve drive componenets due to the sudden shock of the cartridge firing. And lastly (as far as I know) I carbon build-up also caused issues, sorted by some additive to the oil. All issues were sorted eventually making it more reliable that many would like to admit.
The Brits produced 2 Major sleeve-valve engines during the War - the Sabre - by Napier, of course, and the Hercules - by Bristol. A RADIAL engine used in the Halifax and Beaufighter. Sleeve Valves have several advantages in engines - they are MUCH quieter, since they have NO valve noise (the Germans called the Beaufighter "Whispering Death" because it was much quieter than other twin-engine fighters) They can use lower octane fuel for the same compression ratio - or conversely - use much HIGHER Compression for the same octane fuel - giving them a MUCH higher power output for the same size engine and fuel quality. No Valve wear - They don't bang up and down, they just slide. They also have some DISadvantages - they are harder to machine - the sleeve has to be made to EXACT Tolerances, or it will jam - especially as engine temps go up and down. The block, sleeve and pistons all expand and contract at different rates. Because of this, they are prone to using a lot of oil.
Just for dumb curiosity, how many parts did it take to make one of these engines? It almost seems like a Rube-Goldberg of engines. Some intriguing concepts, though.
The very first 'powered flight' was In 1852: Henri Giffard used a steam powered airship. The first powered flight of a heavier that air craft was in 1848. It was a steam powered lightweight model aeroplane designed by John Stringfellow, that was when the first powered flight of a heavier than air craft was made. 1903 was the date of the first successful flight of a man carrying powered aircraft!
Sleeve valves have a major advantage in flow over poppet valves because when the sleeve valve port is open, there is nothing in the way to block flow, while a poppet valve, even when fully opened, has the head of the valve impeding the flow of air or exhaust gasses. On the other hand, sleeve valves tend to be difficult to seal perfectly. Even so, if only the Napier had multi-stage supercharger or a turbo supercharger, it would have been the king of the skies.
The biggest advantage actually comes from the ability to compress higher than a poppet valve engine given same petrol fuel. But a poppet valve engine can allow more boost....
Just increase lift until the head is out of the high velocity zone. Ideally, 4 poppet valves on a hemisphere. Diagonally opposed valves belong together because they don’t interfere.
@@ArneChristianRosenfeldt Unfortunately, high poppet valve lift leads to a substantial decrease in mechanical efficiency, high consumption issues, big and heavy engine design with reliability issues. The Merlins e.g. were literally eating up their high lift camshafts as the friction was so high. As an unwanted by-product your engine has insanely high valve spring forces which must be even higher if you work with boost. The highest RPM of your poppet valve engine is unfortunately mechanically limited in the event of the poppet valve not returning in time at its seat, which will happen at a certain RPM because your spring is simply not strong enough, but you cant go higher force as the camshafts are already wearing out real fast. You can build a desmodromik valve gear which can level this out, though. The sleeve valve engine has as much free breathing area as a 4 valve head but the sleeve is completely guided by mechanics, no springs in the system, so a sleeve valve has usually much higher RPM. So you cant just increase lift because it leads to an engineering dead end whereas the sleeve valve is absolutely superior in this regard. The sleeve valve has other flaws...
@@ThorstenKreutzenberger ah, the US V8 community seems to regard high lift as a silver bullet. I did not know that Merlin had breathing problems. So that is where the (low) 3000 RPM limit comes from. The rocker arms already extend over the whole bore! Maybe they should have added a small spring directly on said rocker arm. Not for bias, just to make it return to the top at RPM limit.
Quality control issue. You'd think I'd pickup an error like that rewatching a dozen or so times looking for errors, especially since I have it correct everywhere else.
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In 1964 I was in school for my A&P license, and our powerplant instructor was a WWII veteran mechanic. The man knew his engines and propellers better than anybody else, and he taught us well. However, when he told us about the Sabre engine we just looked at each other and wondered if he was joking with us. Actually, the engine was very real, and very important in the history of British fighter aircraft.The success of the Sabre convinced the Brits that the sleeve valve would eventually replace all poppet valve engines, but of course the jet engine ended the contest by the end of the war.
A good attempt by Napier at the time, but technology was already moving on to jets.
Great overview of Brit fighter big engine development and sleeve valves.
My father was a master machinist who made torpedo gears among other things. He would have loved this engine. Thanks for the excellent video.
Great explanation and perfectly detailed explanation, thank you. I love big old piston engines and the prop theory too. I'm happy I subscribed 🙂
That's awesome, thanks.
Excellent presentation
Well done, most videos on these high-powered WWII piston aircraft engines are full of errors, this video has what I believe to be one. There is no proof that the Sabre officially got to 3500hp. The last one, the VII, was type-rated at 3050hp for takeoff on ADI . Did they produce more than this? Probably, but this would have been more along the line of WEP, which I have never seen specified. I once believed the 3500hp figure, but after extensive searching, I have found no primary source to confirm this, so, for me, it is 3050hp
One of the more interesting things about the sleeve valves used on the Sabre and Bristol engines was that the block had five ports but the sleeve only had four ports. This means that one port in the sleeve would alternatively pass cold inlet mixture followed by hot exhaust gases. This heat cycling is generally considered a bad idea, although I have never seen this issue explored in any detail.
There is a great deal to cover in any complete story of the Sabre, unfortunately, much of the original Napier documentation has been lost.
Many H pattern aircraft engine designs have been put forward, but the Sabre was the only one that made it to production.
In the USA, both Continental and Pratt & Whitney worked on sleeve valve engines, P&W on the X1800 aka H2600 H24 for the army and the H3130 H24 for the Navy. These engines were considerably different to the Sabre and were closer to the layout of the Napier Dagger, albeit, with water cooling. Examples of these prototype engines still exist. The P&W effort came to an end after a change of management at P&W, P&W essentially bought their way out of the contract. Kimble D. McCutcheon's book "American Sleeve-Valve Aircraft Engines " has a wealth of information on the subject.
Thanks. I should perhaps have cited my sources for the 3,500hp claim (Oldmachinepress which I believe reputable, and some research papers with the same claim). There is even some sources claiming it achieved 4,000hp, but I did find counter-claims that there is no proof of that, so I reverted to the 3,500hp number.
But I'm happy to concede if it was only 3,050hp, you may have researched that detail more extensively.
I did consider including other H engines in the video but when I started digging deeper for research months ago I got very fascinated by the details of the the Sabre and so decided to focus on it. The Lycoming H-2470 may feature in a video soon though.
I was in contact with Kimble some time ago but didn't realise he wrote the book about American sleeve valve engines.
Thanks for the info.
Great stuff! One of the unanticipated downsides of sodium filled valves, widely used by Lycoming, is moving the heat from the head to the stem tends to promote deposit buildup on the stem. Valve sticking from lead/carbon deposits on the stem/guide is a chronic problem on Lycomings.
Well presented! I learned a lot, especially on sleeve vales. I believe another advantage of the larger piston count and hence smaller bores is that the faster completion of the flame front across the smaller cylinder reduces tendency of pre-ignition (knock). I recall that from school in 1980.
Regards.
The Sabre was quite innovative in some respects. It was oversquare, and a high rpm design with comparatively small cylinders.
Had they instead gone with the tried and tested poppet valves, perhaps they'd had it in service years earlier.
Very good. Thanks. In my ignorance, I thought that the cylinders in the H engines were actually placed like an H. I didn't know that it was an H lying on its side.
Yeah they turned the Sabre on it's side but the Napier Rapier and Dagger engines that preceded the Sabre was upright like an "H".
@@LetsGoAviate I assumed it was like a P&W X-1800.
That was a fantastic video, I've been wanting a detailled breakdown of the Sabre for ages. The engine was dogged by technical issues due to its complexity at the start. Do you know what the issues were?
Mainly the sleeve's, which was sorted once Bristol agreed (not willingly) to assist Napier with this. Bristol has been making sleeve valves for some time by now and got all issues sorted out in peace time before the war. The issue I believe was out of roundness, meaning the sleeves wasn't perfectly circular on a very small scale, and the sleeves wore out prematurely.
The other issue was the Coffman starter which damaged the sleeve drive componenets due to the sudden shock of the cartridge firing.
And lastly (as far as I know) I carbon build-up also caused issues, sorted by some additive to the oil.
All issues were sorted eventually making it more reliable that many would like to admit.
The main issue was sleeve seizures, eventually solved when Bristol were involved and made the sleeves for Napier.
This video is mind blowing!! Fantastic job!
Good episode
The Brits produced 2 Major sleeve-valve engines during the War - the Sabre - by Napier, of course, and the Hercules - by Bristol. A RADIAL engine used in the Halifax and Beaufighter.
Sleeve Valves have several advantages in engines - they are MUCH quieter, since they have NO valve noise (the Germans called the Beaufighter "Whispering Death" because it was much quieter than other twin-engine fighters)
They can use lower octane fuel for the same compression ratio - or conversely - use much HIGHER Compression for the same octane fuel - giving them a MUCH higher power output for the same size engine and fuel quality.
No Valve wear - They don't bang up and down, they just slide.
They also have some DISadvantages - they are harder to machine - the sleeve has to be made to EXACT Tolerances, or it will jam - especially as engine temps go up and down. The block, sleeve and pistons all expand and contract at different rates. Because of this, they are prone to using a lot of oil.
Just for dumb curiosity, how many parts did it take to make one of these engines? It almost seems like a Rube-Goldberg of engines. Some intriguing concepts, though.
The very first 'powered flight' was In 1852: Henri Giffard used a steam powered airship. The first powered flight of a heavier that air craft was in 1848. It was a steam powered lightweight model aeroplane designed by John Stringfellow, that was when the first powered flight of a heavier than air craft was made. 1903 was the date of the first successful flight of a man carrying powered aircraft!
The photo of a plane carrying a person should clear up that confusion 🙂
Sleeve valves have a major advantage in flow over poppet valves because when the sleeve valve port is open, there is nothing in the way to block flow, while a poppet valve, even when fully opened, has the head of the valve impeding the flow of air or exhaust gasses.
On the other hand, sleeve valves tend to be difficult to seal perfectly.
Even so, if only the Napier had multi-stage supercharger or a turbo supercharger, it would have been the king of the skies.
The biggest advantage actually comes from the ability to compress higher than a poppet valve engine given same petrol fuel.
But a poppet valve engine can allow more boost....
Super complex!!! I wouldn't use it
Just increase lift until the head is out of the high velocity zone. Ideally, 4 poppet valves on a hemisphere. Diagonally opposed valves belong together because they don’t interfere.
@@ArneChristianRosenfeldt Unfortunately, high poppet valve lift leads to a substantial decrease in mechanical efficiency, high consumption issues, big and heavy engine design with reliability issues. The Merlins e.g. were literally eating up their high lift camshafts as the friction was so high. As an unwanted by-product your engine has insanely high valve spring forces which must be even higher if you work with boost.
The highest RPM of your poppet valve engine is unfortunately mechanically limited in the event of the poppet valve not returning in time at its seat, which will happen at a certain RPM because your spring is simply not strong enough, but you cant go higher force as the camshafts are already wearing out real fast. You can build a desmodromik valve gear which can level this out, though.
The sleeve valve engine has as much free breathing area as a 4 valve head but the sleeve is completely guided by mechanics, no springs in the system, so a sleeve valve has usually much higher RPM.
So you cant just increase lift because it leads to an engineering dead end whereas the sleeve valve is absolutely superior in this regard. The sleeve valve has other flaws...
@@ThorstenKreutzenberger ah, the US V8 community seems to regard high lift as a silver bullet. I did not know that Merlin had breathing problems. So that is where the (low) 3000 RPM limit comes from. The rocker arms already extend over the whole bore! Maybe they should have added a small spring directly on said rocker arm. Not for bias, just to make it return to the top at RPM limit.
How do the bore centers or bore pitch of the Sabre compare with the Allison V1710, the Merlin and the Griffon?
My memory says valves on the Merlin were sodium filled.
Confirm or deny
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Saber was in service before the PW 2800?
R-2800 went into production in 1940.
Did you confuse square inches and cubic inches?
Quality control issue. You'd think I'd pickup an error like that rewatching a dozen or so times looking for errors, especially since I have it correct everywhere else.
Torque x rpm means diesel engines have insanely high horsepower. Which is not the case. But then again it's not explaining anything.
What on earth are you talking about ??
@@AC-op4dg you have the mental grace of a lobotomised hippo.
It's correct. Horsepower = Torque x RPM / 5252
@@LetsGoAviate you only said torque x revs.
I'm not a big fan of the BOXER engine.. It's old tech. and Subaru needs to come up with something better!