One critical point not mentioned was the metallurgical work to develop a steel for the sleeves that would expand and contract at the same rate as the aluminon cylinder yet were hard enough to keep bore wear to acceptable levels. Also, because of the design, and tight tolerances required new machining methods and machines had to be developed. All carried out under war time conditions. To the younguns out there. There were no CAD or CNC machines back in 1939 when these engines were starting to be manufactured. Over 57,000 were produced,

Worked on these when I was an apprentice with Bristol Siddeley in the early 1960's. Bristol freighters normally had Hercules 14 cylinders with carbs. The Centaurus had fuel injection. Those actuators we called knuckle joints. Knuckle jonts failed if oil was not drained from sleeve valve/cylinder head gap, causing hydraulic lock. Secret was the nitrided sleeves, a Bristol Aero Engines patent, using ammonia in ovens ( No 3 shop if I recall correctly). When the ovens were opened the ammonia was overpowering if you were close; but then we were still using open trichlorethylene degreasing baths and proper zinc chromate primer; and other 'nasties' everywhere. No 1 shop was still making these engines for the French, who collected them using a Noratlas from Filton Airfield. The Centaurus test beds were next to 'Shadow Patch' , opposite the Orpheus test beds - all gone now. Seems like yesterday, but a very different world then. Just glad to have lived during that dynamic period; except the disaster to the industry by political interference. Great contnet by the way - I enjoy your videos. Still flying at 80.

Boy ,that guy certainly wasn’t over excited about demonstrating it all…. Cool looking engine..

Keyboard time! All right people! STOP calling sleeve valves complex! This 18 cylinder engine has 18 sleeve drive pinions and 18 sleeve valves. Period. An equivalent P&W will have: 4 cam rings, 36 followers, 36 pushrods, 36 rockers, 36 rockerboxes, 36 rockershafts, 36 rocker covers, 36 valves, 36 valve seats, 36 valve springs (or 72), 36 valve spring retianers, 76 valve colletts. My math not too hot, anybody wanna count 'em up???????

I worked for Bristol Aero Engines and the Centaurus was still being manufactured in the 1960’s, RB, Nova Scotia.

I worked briefly at an aircraft engine manufacturer in the 1980s. One of the engineers there told me one advantage of sleeve valves (which were first developed by an American inventor before WWI) was that the interior surface of the combustion chamber was always in motion relative to the piston rings. On a conventional poppet valve engine there comes a time where the piston stops and reverses its motion. When that halt occurs, according to my engineer friend, the oil film tended to separate and you'd get a brief instant of metal on metal contact, before the piston ring started to drag a film of oil with it on its return journey. On a sleeve valve engine, the valve itself was still rotating when the piston was stationary and this breakdown of the oil film didn't occur. So at very high manifold pressures there was better sealing and less wear, or at least that was his view. But he also did say that the valve drive mechanism, and the many parts it took to run it, was a drawback of these engines.

The development between 1939 and 1945 was amazing. This is one of my favorite engines. There wasn't a Sabre lying around there somewhere too? My ex's father used to fly around in the back of a Lancaster with three Merlins idling and one Sabre hauling it round the sky. His role was monitoring the experimental engine, he ended his career running three parts of BAE. He said that the versions they were testing at the end of the war were running over 2,800hp and over 3,000 in emergency mode.

The owner has such a wonderful personality

The related Bristol Hercules engine was of fourteen cylinders. Whilst it was mechanically complex, the sleeve drives ran from a single gear set in the front of the engine with some shafts short for the front cylinder row and others long for the rear cylinder row. With the 18 cylinder Centaurus, there was less workspace between the individual cylinders of the front row for long driveshafts to pass and for relay gearsets to be spaced so in effect, the designers coupled two 9 cylinder radial engines back to back. It is the nature of the sleeve valve design to burn more oil than a traditional poppet valve engine. As well as the rings on the pistons, there were rings on the "junk" head which was in effect a fixed contrapiston that the sleeve moved upon. At TDC and the instant of mixture ignition, the ports in the sleeve were hidden in the channel between the outer cylinder and the head but during the exhaust-induction cycle, the sleeve ports exposed cylinder wall oil coatings. There was also a ring fitted into an internal groove in the lower end of the aluminium outer cylinder. Transfer of heat within the engine was an issue which may not have been entirely resolved. For later iterations of the Hercules engine and likely the Centaurus as well, the working surfaces of the heads were tin-plated to solve the problem of "pick-up" which was partial seizure of the heads to the upper sleeves. This would impose severe strains on the sleeve drives. Sleeve binding could be heard in the Hercules engine of the museum Beaufighter in Moorabbin Victoria at the end of one of its ground runs. I was told but have not verified that the matured Hercules engine design, properly maintained and conservatively operated in commercial service was capable of 3000hour TBOs. Of the Centaurus design I have no information. In war service and in air racing, engine longevity is less assured. For a worker of metals, the precision and surface finish of the cylinder sleeves and their surrounding cylinders is a delight to behold.

Years ago reading up on it I got a bit familiar about how one of these worked. I commented to my A & P mechanic dad about how neat this scheme was. He got a horrified look on his face and said, "You don't know what your are saying."

I was just watching this on Patreon when the KZfaq version popped up. The sleeve valve engine was noted for using some what more oil than a typical valve engine. The British are brilliant mechanical engineers. Notice 3 intake valves, to get more fuel air charge into the cylinder. A brilliant design.

Charles Y Knight developed the sleeve valve engine design in 1905, his engine design was first used in automobiles and nicknamed "silent knight" because without the typical valvetrain used at the time you could barely hear it running at idle.

That cutaway engine was fantastic. It's an easy way to understand the operation of a very complex engine.

Sleeve valves are amazing! they were set to take over before the turbine was created. the one downside of the sleeve valve was the one benefit to a turbine. how many moving parts and things can go wrong. There was never any subsequent generations and revisions like piston engines. these were only made for something like a decade if memory serves, and going to these mechanical and manufacturing lengths just didn't make sense in a turbine world, where shaft horsepower came easy

He was so enthusiastic to share his knowledge with us.

Cool! My dad restored a 1927 Willys-Knight 4 door car with sliding sleeve valves. Was a very quiet smooth running engine.

Crazy British engineering! 3000 HP!

In the early 1970's, these used to fly over our house in the Bristol Freighters from Rochford-Southend Airport, carrying cars to Le Touquet in France. They made a very characteristic sound. When I was learning to fly at Rochford, the Airport manager came in to the Aero club and asked if we could help move the Blackburn Beverley military transport, which had been on display for some years but its location was needed for a new service facility. The airport did not have a big enough tug to move it, so we decided to start the engines. It had a hand cranked mini-turbine APU, which started just fine and we left it running for a couple of hours to charge the batteries. We then proceeded to try and start the Centaurus engines. We manually propped them standing on the front end loader of a tractor and both were free. We did get one started but as we were about to try and start the second, the airport manager came rushing over to ask us to shut down. We had filled the whole airport with oil smoke and he had had to shut the main runway down. Eventually we borrowed 2 US Army 6 x 6 recovery trucks and towed it to its new location with those.

Brian's my kind of guy, I as well have had the same hat for 25 years.

Hawker Sea Fury rocks. I worked on Bristol Freighters in Canada back in the day. Nice cut-a-way engine.

I remember the Bristol Freighter from childhood. They used to be a regular sight over the skies of Wellington New Zealand as they flew between the North and South Islands up until the mid 1970s.

Thank Brian from me for creating this cut-away. Outstanding explanation!

During my time as a student of mechanical engineering i was fascinated with this type of engine. I was really obsessed to figure out how it worked. Took me three years to combine the mathematics of the sleeve valve in excel with a 3D program (Rhino3d). But in the end i had/have a working procedure where you can enter ALL relevant specs of the engine in excel and paste it into the 3D program and this "prints" the desired sleeve and cylinder geometry for further processing. If anyone has use or interest, write a comment. Sleeve Valves are really good for economics as this type of "valve" scavenges the cylinder with much less friction and the breathing of the engine is very much improved. Due to the lack of multiple red hot exhaust valves, the compression ratio can be higher for a given octane number of fuel compared to poppet valves before knocking occurs. It can even have higher RPM as there are no springs in the valvetrain. It has far fewer parts, builds more compact and needs less machining time to produce. It is a winner, right? Well almost, the weakness of this engine was supercharging. Due to distortion issues from high temperatures at the sleeves exhaust ports, the amount of pressure is limited and you cant thicken the sleeve up too much before you run into heat transfer problems. A poppet valve engine does cope much better with supercharging and the heat side effects; but it is always less efficient. The joke is, we are driving engines in our cars and even tractors and lorries which are derivatives of air race engines having excessive supercharging and power output but what we really want now is economics instead. But I can understand the car industry, investing in combustion engines is probably a lost cause and enough money goes down the drain with electric cars right now. Thanks for this channel I watch it as a most reliable source of information on aviation related topics and it certainly delivers outstanding content like this one.

I first heard of this type engine in an automobile. Good to see technology that ended up in use, however short the term. Thanks to Brian for keeping something unusual and marvelous in public eye. And to Blancolirio’s star reporter.

Some 20 years ago I did see a sleeve valve engine at the Beaulieu motor museum in Brockenhurst, UK. There's a lot of other items there as well, but I don't know what has happened since I was there. If you go there, also take a look at the Eling Tide Mill a few km north of it. A museum mill driven by tidal water, it has been a mill there since medieval times. Both are worth a visit if you haven't been there.

I am a HUGE engine guy.....known of sleeve valves for decades...this is one of.. if not thee...premier videos of concept. What will never be known by half of this marvelous contents viewers... the engineering involved...the precision of machining nessasary...... the beauty....the Bennifit of valve diameter clearence..heat dissapation...performance.....over a standard P $ W... cam traditional valve engine. As usual.. Juan put it out of the park..again. magnificent content sir. One more thing..next time I am osh...see Juan going the other way on opposing tram...risking expulsion from the greatest aviation show in the WORLD... I am jumping from my tram.....asking for forgiveness easier than permission.. regret not meeting him in 2021..bit he was going the other way.!

Looks like a great show there. The moving cutaway engine was very interesting. If you have time on your next lay over in London, if you haven't been try the Science museum. They have a static sleeve valve engine with cutaways and probably over 50 different engines from across the ages. Also an intact V1 and V2 rocket and a whole section dedicated to space travel with a full size Apollo Command module and Lunar Module. But be warned, you will need a whole day just to scratch the surface! You can take the Piccadilly line on the underground all the way from LHR👍 You can find it here: EXHIBITION ROAD SOUTH KENSINGTON LONDON SW7 2DD

Wow, I thought I knew a lot about airplane engines but I never knew anything like this existed. That’s incredible engineering right there.

Brilliant video. Believed to be 34 variants manufactured and they powered the British Airspeed Ambassador passenger airliner. There’s some great footage of those on You Tube and l’ll always remember the experiences of Arthur’s Whitlock who was an Ambassador pilot for BKS in starting those engines on cold grey mornings which he recounts in the amazing book ‘Behind the Cockpit Door’. The arrival of the Rolls Royce Dart turboprop was a huge leap forward for civilian transport, supporting the production of c445 Vickers Viscounts against the c22 Ambassadors. Thank you Juan.

I have wondered how a sleeve valve works since I heard about it in a movie when I was a child in the 50’s. I had forgotten about this till you put Imm this video. Thanks so much for answering this for me.

Saw you there live. To bad about the smoke. Awesome engine.

Wow!! Amazing engine! Thanks for sharing it, I had no idea these were once a thing.

That is so cool! I've seen the illustrations of the sleeve valve system, but seeing it in real time is much more informative. Thank you!

Another awesome, rare, technical aviation video! Thanks for your effort!

Fascinating example of old school ingenuity! Thanks for showing! 👍

I used to work on 'tiny little' P&W 1830's on DC-3's and thought that was a fairly complex engine - all things considered - but holy cow that's a lot of 'monkey-motion' to produce 3000hp! No wonder they were prone to break!

In all my 50 years of building and designing race engines for snowmobiles, motorcycles and cars I've never seen anything quite like that!! I thought the cam plate and valve actuation system for P&W radials was strange and complex, this takes the cake!! LOL I wonder what RPM it turns before reduction? I would guess not too many. Very interesting!!! Thanks Juan!!! 8) --gary

Great video Juan! I've never seen a cutaway of one of those, and the explanation of the engineering was great.

That word you were looking for on the sleeve movement is reciprocate! Great video. Very informative. Thanks.

Love this ! My every-time go to at the Smithsonian Air & Space museum - Udvar-Hazy annex, is the propulsion parade tucked under the stairs on the base floor. I remember working F-16 test at Edwards, and one of the engineers sharing a truism of "better aerodynamics come from better pushies".

Your engine knowledge is the best I have seen

Thanks for sharing Juan! Great work on announcing the STOL Drags!!

Have been a gear head since about as long as I have a memory Juan, that means sometime about the age of 2½yrs. old, or maybe 3yrs. old, and for the life of me, I have never been able to understand the function of the Sleeve Valve, or rotary Sleeve engine design Juan ! Thank you SO MUCH for sharing that cut-away engine with us all ! A little after the fact, but please thank the owner/builder of the full scale ( actual ) engine for me ! And thank you Juan, for taking the time to bring it to the rest of us gear heads !

Grew up in Christchurch New Zealand watching Bristol Freighters come and go. On take off the tail came up real quick, and then they trundled off over the horizon. Good times.

Well done Juan - lucid and cogent communication is what separates man from the animals. That Brian just wouldn't shut up though! Cheers - Roger from England.

Complex! Thanks, Brian and Juan.

Caught your announcing and commentary on the livestream today - great job!

Nice to see how this engine works!

Just fabulous, Juan. Ellsworth Getchell, (also a TWA pilot), bought a Sea Fury and restored it. I went to Germany with him, to pick up a LOT of parts from the Luftwaffe. They used the plane for target tow. I was always fascinated by how this engine worked. It is more complicated than I imagined. Thanks for sharing!

Fascinating,i have always known of sleeve valve engines,but wondered how the sleeve was moved, this cutaway explains all, just a small rotating peg! amazing! I well remember the Silver City Bristol freighters that flew the cross chanell UK to France route and living in North London one would occasionaly be seen and heard heading toward Northolt in the 50's -60's much to the delight of us young spotters. Before i retired i worked for a light aviation company company (in the UK) who were an engine rebuild specialist, in the general office was an A65/0-200? that a couple of the engineers had fully sectioned,by full that included all of the accesories as well, carb, starter motor, filter,fuel pump etc! it was mounted on a mobile engine mount, I think after the company was taken over it got donated to a local Technical College.

I've done two overwater flights in a Bristol Freighter, aka, 40,000 rivets flying in formation, 1968.

...The Bristol Freighter and 'Super Freighter' series used 'Hercules' engines. 14 cylinder. The Hercules and Centaurus engines used the same sleeve valve cylinder design.

I knew it had to be special and you did not disappoint!

Incredible!! Amazing to think what engineers of the day could design using a slide rule and no computers. All those gears. Looks like a giant watch.

Quite a study. Can hardly imagine that thing turning a million mph. Have a nice time - thanks for sharing.

The Centaurus is really an 18 cylinder and bigger capacity version of the earlier 14 cylinder Hercules sleeve valve engine which was extensively used through out the war in many planes including the Halifax and the Wellington.. Over 57,000 of them were made. To the best of my knowledge only the Hercules was ever fitted to the Bristol Freighter.

I've heard comments that the sleeve valve engines (certainly the Bristol Hercules used on the Beaufighter) were relatively quiet. Years ago I met a mechanic who'd serviced Hawker Tempest aircraft during WW2. These were fitted with the Napier Sabre V sleeve valve engine. He said that if it backfired on start-up then there was a very good chance of snapping the sleeve valve actuators or parts thereof.

Brian was a real Chatty Charlie! It's amazing Juan could get a word in. A lot of work and an amazing project for a guy that apparently didn't even want to be there! 🤣

Now I know how a sleeve valve engine works! Thanks mate!

Thank God for the turbine, couldn't imagine dealing all that. Great video

Great video and a fascinating design. I would love to see footage of the cutaway R-4360 too.

You come up with the neatest stuff!

that is super interesting ! never seen how it actually worked. Amazing !

Wow!! Thank you so much for sharing!! This was extremely interesting and educational!! Entertaining too.

Hi Juan! And to thing that it`s what? 40 or 50`s engenering?? Man. No computers, no printers, just pure mechanics. Outstanding. Happy landings from Portugal

Brownie, at my age it's not often I see a new thing. Thanks for what you do.

Wow I bet that thing sounds incredible!

Excellent Juan. Much appreciated. I’m sure this has been said before but if they reduced the diameter of the can plate and fitted a roller/ball bearing to the actuator it may have helped but who am I to even dare to say. Once again. Thanks for your work. 👌

These Centaurus engines have always fascinated me for their complexity, especially the gear train for the sleeve drives.

that'amazing have read about these engines but seeing it answers questions reading can't . these people of the greatest generation thought up these things with slide rules (for younger people google slide rule you"ll be amazed ) , paper , pencils and skill . Thanks for this !!!

That is amazing the way it works. It looks like a two-stroke engine system or two-stroke engine or they don’t use valves either except on the two-stroke engine like a motorcycle per se those don’t rotate like these do on this engine. Very interesting.

Lol! that guy was Mr. Personality.

Nothing sounds like a Bristol Hercules with augmented exhaust ,thanx Juan.🙂

From a Bristol Frightner with throttles / mixture levers like garden spades. I’ve never regretted refusing the invitation to convert onto one….especially after watching this video !!

Bevels like an old Ducati motorcycle! I remember the noise when Safe Air in NZ operated Bristol Freighters until 1986. A beautiful noise! Like an old Ducati...

That is soooooo cool. The Napier Sabre engine in the Tempest and Typhoon had the same setup IIRC. They ran at pretty high RPM's.

Thanks Juan. Great stuff.

The Centaurus is one of my favorite engines.

They have one of those at the Aerospace Museum in Sacramento. It's a nice museum with a lot of interesting items and aircraft on display.

Very cool and unique!

Always wondered how those engines worked. They sound great.

Juan your Call and Stol Drag carried the Day. I have been coming to Reno since the early 70’s, little has changed which is good and bad. I believe there needs to be more done to freshen it up like Stol Drags. It would be nice to see more aviation products/manufactures and static displays.

Wow. What an impressive engine.

Amazing engineering!

My wife's grandfather was with the RAF. He was a powerplant mechanic and he explained to me how the Napier engine worked on the Hawker Typhoon. Same principle. I had to look it up. He later worked on the Goblin on the vampire. After the RAF he moved with his family to Montréal Canada. He then worked for Trans Canada airlines on Vanguard's, Viscount's and Canadair Northstar. It's a DC-4 but with 4 Merlin engines.

The old dirt riders should remember the rotary disc valves 2 strokes from 50 odd years ago. A much simpler system than this aero motor.

I watched a Sea Fury at a UK airshow in 2014. Great sound.

RCV engines out of the UK designed rotating cylinder vavle engines for the radio control hobby.

I saw one of these today! It was sitting in the back of an F350 right were it was in the video.An hour before I also seen Juan.He walked past me on a mission to the pit area.Soon after he was on the show broadcasting system talking away so I guess that was the mission!

Having worked with the Royal Navy's historic flight back in the late 80's, I can tell you that a Centaurus engine at full throttle sounds so much better than the Wright duplex cyclone/P&W R2800 in the Hellcat/Bearcat. It's like comparing the sound of a Ferrari V8 with a Hemi.

There is a beautiful revolving cutaway sleeve valve engine on display at the air museum at the McClellan Airpark (ex AFB) in Sacramento, Ca.

What a crazy design!

This reminds me of the Mazda 13B engines with both third porting and variable porting. but they do still have the rotary component still doing the job of moving the intake and exaust. But they do have on theintake ports on the sides of the rotary chambers which rotate to vary the size to match conditions in the engine, rather than a fixed size which original engines had w/o the porting. An extra port could switch on and off as well.

They have one of these at the Sacramento air museum, its a marvel to watch in slow motion. Its a cutaway also

What an engineering feat to design and build these engines

I loved the 3350 because that’s what I worked on EC121K

Missing the Aiir Races again this year. Wish I was up there. Hope smoke from the Mosquito fire isn’t affecting you too much. Have fun for me

Very interesting. I had nary a clue about sleeve valves before.

I have to wonder how reliable this was. Looks amazing.

Love the Sea Fury!