The Holy Grail of WWII Aviation Engines - The Rolls Royce Crecy

[@josephkey9680]

Great work! What a beautiful piece of engineering! As a modern day engineer, I can only marvel at these guys who designed everything without CAD and in the middle of wartime. It shows you what the indomitable human spirit can achieve.

[@Dave5843-d9m]

Proper engineers can think in three dimensions. CAD just speeds up the development process.

[@michaelf.2449]

Don't feel bad buddy you're only one guy! People have a hard time believing the Egyptians built the pyramids, but everyone forgets what is capable when you have enough people working on something especially slaves.

[@ATEC101]

Yeah, the V2 rocked engineering. Good thing the US and Russia split up the spoils of 'Nazi' brainpower or we wouldn't have had the Cold War! 'Spirit' can go perform a solitary ritual in a corner.

[@davelowets]

@@Dave5843-d9m Exactly... CAD doesn't design the engine, humans do, and still have to.... 🍻

[@jakobquick6875]

I love u put a top fuel blown hemi in this video, great monster that could have been the mighty Crecy

[@JohnyG29]

Harry Ricardo was a bit of a genius to put it lightly.

[@Dave5843-d9m]

He certainly was but he also took a long while to realise that Merlin’s (and therefore Crecy) were served by inadequate oil pumps. They literally could not meet to oil demand at high revs that caused big end failures. He also used sleeve valves on the Crecy which were just not necessary. Loop scavenging is enough.

[@The_ZeroLine]

And I’m just slightly more brilliant! All my innovations are, of course, classified. But, like many engineering geniuses, I like to brag anonymously on KZbin about it.

[@geesehoward700]

@@Dave5843-d9msuch a shame he was the only person working on the merlin and all of its short comings fell on one person.

[@acrazedtanker1550]

Sleeve valve, two-stroke, V12?!? Why haven't I heard of this before, holy crap. Such a beautiful marvel of engineering.

[@rogertycholiz2218]

ACrazed Tanker ~ I always thought of Rolls Royce as OHC 4-stroke. Bristol & Napier produced thousands of sleeve-valves engines.

[@leneanderthalien]

@@rogertycholiz2218 Yes, but Bristol (Napier did use Bristol technolgy) was 4 strokes engines and they specific consumption (gram gas to hp/hour) was excellent (lover than a common 4 stroke), but two strokes have a bad specific consumption and nee more oil than Bristol sleeve valves who not need more oil as common US radial engines...

[@johnbrewer8954]

@@rogertycholiz2218 RR also made the Eagle which was a HH type very similar to the Sabre used in the Wyvern aircraft until it got a turbo-prop. At the same time they were also developing centrifugal and axial jets. Basically the same team went through the Merlin and Griffon onto the RB211 turbo fan which powered some of the early Jumbos and the same family of engines are still used today.

[@wilburfinnigan2142]

It was too complicated and expensive why it never went into production !!!

[@wilburfinnigan2142]

@@rogertycholiz2218 RR built various types of engines !!! DUUUUUHH!!!!!

[@intentionally_obscure]

This is incredible. This engine, the mad lad stuff being cooked up at the end of the piston-engine era, and your in depth video about it all. Top quality content. I thought I understood two-stroke engines fairly well but I was shown otherwise. Can't wait for the next one.

[@martinnicholls9056]

There was a famously pithy remark by Rolls Royce's Stanley Hooker. He wrote in favour of the two-stroke thus: In a four stroke "there is one stroke to deliver power and three to wear the engine out." I'm not sure if he was entirely correct, but an interesting observation by the man who designed and developed the famous two-stage, two speed supercharger for the Merlin 61 engine.

[@toomanyuserids]

One to power and three to cool them off and lubricate everything...

[@matchrocket1702]

I think it's safe to say that the sound of the Crecy alone would be enough to scare the crap out of any would-be enemy.

[@rogertycholiz2218]

Matchrocket ~ The sleeve-valve-2-strokes had a sound like no other.

[@coolhand1964]

The scream in a dive at full power would have made the Ju87 sound like a child's toy.

[@tonylam9548]

The name Crecy would have guarantee you make more enemies south of the UK. Not wise when you want the French cooperation in any large projects.

[@neilpuckett359]

Hats off to the machine shops and machinists who made it all possible.

[@boreas_rt1667]

Absolutely amazing content! I never knew just how incredibly complex and intricately designed it was, amazing that this was all done with 1940s technology. Have you heard of some of the Italian engine prototypes of ww2? They're pretty insane too

[@WalterWhiteFootballSharing]

I read Italian ww2 airpower engineering were all a work of art. Intricate artwork AWFUL for mass production. USSR and USA engineering 'genius' was war machine designs that lent themselves to mass production. 10,000 planes a month at one point. Even more tanks, shells, etc.

[@jimgoodwin6294]

My late mother worked for a company (still in existence) based in the cellar of a remote country house in England during the early war years. They created the tooling to manufacture the first turbine blades for Whittle.. No one knew of course what they were helping to make but had to sign the officials secrets act. They joked that after being given the contract to make "knives" they wondered if they would be making tooling for spoons and forks...... Creative genius of men & women in sheds........

[@ianmangham4570]

Whetstone

[@originalforgery]

Lullington. @@ianmangham4570

[@alt5494]

As a engineer the sheer complexity of sleeve valves/hours to develop the assembly for a modest valve control advantage verses exhaust ports & one-way valves. Is a proper mind bending exercise being able to delete major design features on the development path is a underrated skill. Great video Cheers

[@SheepInACart]

I mostly agree with your take away, the sleeve valve proved a bridge to far even in 4stroke time where simple ports where not an option (see Napier Sabre). However regarding your suggested alternative, 1 way valves in that context prove to be one of those issues that sound simple on the surface, but due to how rapid the changes of direction are intended to be, actually prove enormously difficult, failure prone and restrictive to airflow, and so rarely feature in any 2stroke design (even the V1's reed valved pulsejet capped out at 2,520 cycles per minute, and offered worse power to weight than contemporary 4 stroke motors... it was just more expendable). Instead in the world of high speed engines, cheap small designs use a timed reflection of exhaust gas, and more powerful/costly/larger engines use a "powervalve" which forms the same role as the sleeve here. As is often the case complexity of a motor isn't the number of parts, a v12 has few design challenges and little reduction in mean time before failure of an inline6, despite in many cases having just one shared part in main rotating assembly.

[@andyharman3022]

The sleeve valve system is actually less complex than the typical camshaft/cam follower/valve spring/poppet valve system that is almost universal to engines today. They have the advantages of better breathing due to no valve stems getting in the way in the ports, no problems with high-speed dynamics due to valve spring coil surge, they are transparent to heat, allowing higher compression ratio with low octane fuel, and allow complete freedom in combustion chamber design because the valve heads no longer take up most of the available space in the cylinder head.

[@2down4up]

I went to a trade school that had a compound forced induction (turbo on top of the super charger) running Detroit 8V92 on an engine frame. Even with the turbo and exhaust extractor the sound that thing made was so unique and fantastic. The instructor I had would love to start it up, wait a few seconds for oil pressure, and then go full WOT and let it eat for a bit. Such an amazing engine. And incredibly smooth running as well. For a twelve liter diesel it sounded unreal. Even though I’ve seen that entire DeBoss garage video, your quick brief replaying of that amazing sound took me right back to school and to simpler times. Thank you for the trip down memory lane and for making a great video. You deserve far more subscribers then you have.

[@joeh8784]

During the '80s I drove buses equipped with Detroit 6V92 TA engines. Still remember the full throttle sound, scream, of them getting up to full highway speed. Even louder in the garage when they were run at full throttle during steam cleaning.

[@6528ken]

Drove a '77 Kenworth with a Detroit 8V92 for a few years hauling drywall in the Sacramento region. Ran like a top, very reliable, made good money running this truck, but it always used a lot of motor oil. A LOT of motor oil. Like 1 Gallon every 400 miles or so! And this was just accepted as normal with a solid, good Detroit two-cycle engine. This truck with it's 13 Speed could out accelerate most trucks with an 80K load on flat ground, but get in the hills ... well this "445 HP" Kenworth could not match a small cam Cummins 350 with the same load. Go Figure ...

[@2down4up]

@@6528ken 4 stroke torque vs 2 stroke HP.

[@joeh8784]

@@6528ken They made several versions of the Series 92 engines. One variant had a broader torque curve for just the situation you mentioned, hill climbing. Tradeoff was a bit less peak HP. There were also the TAA models, turbocharged with an aftercooler. Or at least TAA was the code used when they purchased the buses I drove. Came across something saying later on it was TAC. For the buses they only were TA, but the 6V92 TA buses took off much better than the smaller ones with just a 6V71. As for the oil usage, I recall we saw about 2 qts every 6-700 miles when they were newish.

[@anachronisticon]

Would you have an educated guess at what the RR Crecy could have produced with a turbocompounded exhaust system? I imagine the power to weight would be over 2?

[@keithglaysher9201]

Great content! The Crecy certainly lived up to the Rolls Royce doctrine of "show us something simple and we will soon design the simplicity out of it"!

[@pu1869]

oh yes they will, with vigor.

[@Biketunerfy]

That’s RR all over, but it also pushes development. The sleeve valve system would of been just amazing. I really wish they could develop some modern race engines out of this technology but there is a lot of parasitical loss with the sleeve valve system plus the parasitic loss of power from the blower (super charger). May be a turbo would be better since it has no parasitic loss of HP on the engine because of the exhaust gases velocity is so fast on sleeve valve system but then again 2 strokes don’t like the resonance been played with on the exhaust system so may be that’s why they went with a supercharger….

[@g8ymw]

@@Biketunerfy They might have been able to extract more power with expansion chamber exhausts as was done on 2-stroke racing bikes. Later aero engines would run at a near constant speed with variable pitch propellors so suited to expansion chambers

[@Biketunerfy]

@@g8ymw SORRY FOR THE LENGTH OF THIS REPLY BUT ITS NEEDED TO BE EXPLAINED IN SOME DETAIL: but that’s what I’m talking about, basically 2 strokes need a partial vacuum in the exhaust to help scavenge some of the exhaust gasses from the engine so they use what’s called a Venturi on the exhaust to help cause suction which is why 2 strokes with expansion chamber exhausts have more power and throttle response but they don’t like being messed with and you can upset the resonance and suction because of a turbo being fitted. There is a reason why turbos have never been fitted to 2 stroke my friend. If it had a poppet exhaust valve you would not need the expansion exhaust instead of just a hole on the top end. A power valve on a 2 stroke is like turbo in the sense that it opens up at about 6 or 7 grand on the rpm that cause more suction and there for more fuel and air being pulled in and they even feel like a turbo with the lag until you hit the power band and the power valves open up and off you go, great fun. You feel it more on the road bikes than the dirt bikes because of the longer gear ratios but I love 2 strokes. 2 stroke bike engines pull in the air fuel mixture through the reed valve in the crank case instead of the cylinder heads so there is only a set amount of volume of air that can be forced in using forced induction so a turbo is really useless on a 2 stroke because turbos shift huge volumes of air at relatively low pressures like 10 to 35 + PSI for effective boost but some turbos can shift over 400 to 500 cubic feet per Minuit easily on a big bore turbos which makes them way more efficient than a super charger and a lot more cheaper which is why we are seeing them more and more in IC engines these days because it makes them more efficient so they would not work in a 2 stroke bike engine but could on this engine above because if it’s design.

[@TarenGarond]

@@Biketunerfy "a turbo is really useless on a 2 stroke" What?! You know there is even several factory turbocharged two-stroke snowmobiles built these days?

[@billeudy8481]

I have to take a moment to thank you for making this complex topic much easier to grasp for a person like me who spent my formative years studying (primarily) English, business and finance. In spite of my poor background this presentation was informative and exceptionally interesting.

[@jamest.5001]

Those Detroit engines did make a sound, our work truck, had a 6-71 with no muffler, a 6" stack,. You could hear that thing across town!! And a awesome sound!!

[@Kenneth-p1b]

And screaming, at 2100rpm...

[@Kenneth-p1b]

I worked with Detroits as a fitter, marine engines in the ArmyWater Transport, 6/71 and 6/53 series ..came across a 6/53 with numbers suggesting land vehicle, probably M113 Armoured Personnel Carrier (APC)

[@ATomRileyA]

Really enjoying these series of videos, you do a great job of explaining how it all works. I always think its a shame that we never knew what happened to the test Crecy engines after the project was canceled, makes you wonder if they are still around in the back of a old warehouse one can hope :).

[@P_RO_]

Being British, there's actually some hope for that. Abandoned things there usually just get shoved to the side, then to the back, then off to the shop or shed of someone who was involved with it where it may get passed around to several other people before all track of it is lost. Anywhere else it would get stripped for anything useful then turned into scrap metal quickly.

[@keithglaysher9201]

There's probably an old boy in a shed wondering where to start with his strip-down of the big lump he bought off of eBay, lol.

[@TheAmazingCowpig]

I remember coming across the Crecy in some reading about WWII engines and was just astounded that such a thing existed. A two-stroke aero engine with sleeve valves really is kind of ludicrous to think about... much like its power output, I guess. A bit sad to think about all the odd tech paths we've missed out on due to the way and speed technology developed. Would've loved to see this strange monster of an engine amount to even something.

[@gutofuhr]

Great video about a very interesting topic. Just to add that the Rolls-Royce Heritage Trust (RRHT) published a book in 1994 about this engine, which can be bought in many bookseller sites. Most data about this engine can be found there.

[@Lord.Kiltridge]

I encountered a Kawasaki H2 Mach IV 750cc, two stroke, three cylinder motorcycle in the early '80s. That thing was a screamer.

[@whalesong999]

Yes, and it's predecessor the 500cc H1. I worked as a mechanic for a dealer just north of N.Y. city when our first H1 was uncrated, serviced, and test ridden. It let out quite a wail, both from the intake and the exhaust. Sound of a Ferrari came to mind. Later smaller triples were produced but their time was limited as pollution standards favored the four cycle engines. The Crecy would have been deafening I'd think.

[@Lord.Kiltridge]

@@whalesong999 Yes, I rode a friends RZ350 and knew a guy who rode a RD500. But the H2 was by far the most memorable.

[@mdlanor5414]

Yes it is

[@andrewfarrow4699]

I think the sprint Spitfire would have been deployed somewhat like an Me163. Crippling fuel consumption. Rapid ground to air intercept for point defense, without decent range or endurance for offense. But by 1942 or 1943 the allies didn't need point defense.

[@BrickNewton]

Wish I could hear one of these running, apparently so loud you hear it miles away, and sounded amazing

[@CanadairCL44]

I can't thank you enoigh for this presentation. Having worked on two Spitfire restorations myself, I have often wondered about the Rolls Royce Crecy aero engine and what happened to it. You have gained a subscriber!

[@aldenconsolver3428]

Much enjoyed your video on the Crecy engines. My experience with 2 stroke motorcycles clearly shows the advantage of a two-stroke aero engine. The two-stroke engine in street motorcycle applications provided nearly twice the horsepower per CC that four-stroke engines were in 1976. It would take another decade and the rise of electronic ignitions/4 and 5 valve heads/ much more sophisticated carburation (and later fuel injection) before the 4stroke motorcycles could catch up with the two strokes and at that in 1976 due to EPA rules the 2 stroke had ceased to be advanced. This was even without the turbo which aided the 2 strokes immensely by allowing the necessary fuel-air input not to have to be compressed in the crankcase.

[@40-forty-plus]

+1 for the exhaust note demonstration alone LOL. Epic!

[@peterbustin2683]

Great video about this amazing engine ! Wouldn't it be inspiring to get together a few retired engineers, like myself, and actually build one - in the true nature of James May, in the shed !

[@monsieurcommissaire1628]

I'll second that. The sound alone would be astonishing.

[@steveskouson9620]

Allen Millyard! He could most likely do it. Interesting guy, Mister Millyard. steve

[@peterbustin2683]

@@monsieurcommissaire1628 Wouldnt it just !!

[@timedmondson1307]

I am really loving these vids. Your info is always nicely fully backed up and can see you put soooo much time into your research and for that I would like to say thank you and please keep it coming

[@peceed]

Additional thrust from Crecy engine was not a net benefit: Excessive (many times more) air was needed to remove the combustion gases from the bulb-shaped combustion chamber, so it increased the supercharger load. Turbocharger and motorjet configurations were just playing around this inherent disadvantage. Btw. fuel injection doesn't leave unburnt fuel as in typical ww2 engine on rich mixture, Cracy had a lot of air in the fumes. 2 stroke engine is the only application where sleeve-valve engines can have real advantages over poppet valves. Sleeves allow to use full stroke for power generation, not losing effective displacements for ports. 2 stroke cycle allows to simplify engine timing for sleeves. It is very strange that the idea was not pushed earlier before the war.

[@drstrangelove4998]

Ricardo was a genius. I wasn’t aware of the Cressy. A brilliant documentary!

[@jimmcmahon217]

Excellent presentation! This somewhat answers the question I've always had..."Why didn't the Brits do more to support Whittle's program?" The answer being that it really didn't appear to hold as much promise in the short term as some of the advanced ICE projects being carried out at RR, Bristol and Napier.

[@grahamharrity9937]

A lot of the time especially after the war it was the stupid labor party, a lot of expertise came over to America

[@wilburfinnigan2142]

The Brits brought the whittle engine to USA for research, development and PRODUCTION !!!!! Because the USA had more manufacturing capacity. GE did the development on the whittle and seen its limitations and developed their own axial floe design the J35 that went into production and it developed into the J47's !!! !

[@andersoncarroll6282]

That actually reminds me of another Rolls-Royce sprint aero engine, the Rolls-Royce R. Great video by the way.

[@sovereign126]

This is incredibly well researched. I have had a love for the crecy for many years being a mechanic and a bit of a history buff. I was not aware of the operating principles of the sleeve valve design, and this explained it beautifully. I hope those that didn't have as strong a background in engines found it as simple to understand. Personally I could visualise it moving. Also thank you for the 12v72 (I think) sound clip. Now that is always a pleasure. It ranks up there with the 8v92 & BRM v16 in how damn good it sounds.

[@SpanishJohn]

This is great and im pretty sure your channel will explode soon amongst history buffs like us. Please keep them coming and you got my sub. Cheers and good luck! Theres a typo in octane for the Ricardo quote.

[@tonym480]

The company Harry Ricardo founded immediately post WW1, Ricardo Consulting Engineering, is still in business on the original site near Shoreham airport in West Sussex in the south of England. On the issue of what the Crecy might have sounded like, could I suggest looking for a recording of the Napier Deltic Diesel engine. Developed from a Junkers aero engine as a possible power plant for Royal Navy MTB's it was famously used in the Deltic railway locomotives for British Rail. The sound is not unlike the Detroit Diesel in the clip, but even more so 😄

[@coolhand1964]

What a shame the Crecy never made its way into the Westland Whirlwind, replacing the highly troublesome Rolls Royce Peregrine engines that required much maintenance and lost large amounts of power at altitude. It may have become as popular as the Mosquito or the P-38 as a twin engine fighter. Well done on the video, covered everything in depth and left me with few questions regarding the engine. 👍

[@ronjon7942]

Nice work. Curious Droid's channel has an interesting perspective (just like FlightDojo) on the Crecy, along w the Napier Deltic and the Sabre. Kudos to FlightDojo on the research and presentation of the Crecy.

[@marcstlaurent3719]

Two stroke motorcycles are never super or turbo charged and few snowmobiles are , tuned exhaust will evacuate the cylinders which all two strokes have had for 50 years other than small utility engines , and I don’t know of a single two stroke that is throttled by fuel like a diesel. Btw that clip of a running two stroke was a GMC Detroit Diesel truck/industrial engine which does have a blower that fills the engine through ports but does not provide any boost and has four exhaust valves , maximum revs are 2300 but sound much higher hence the nickname “ screaming Jimmy “

[@flavortown3781]

There is a guy on KZbin called 2stroke stuffing check him out

[@MitzvosGolem1]

True Expansion chamber and power valves on Modern MX bikes.

[@marcstlaurent3719]

@@MitzvosGolem1 true that except the KX500 never had more or a better power curve than the power valveless CR500 but that's not the case for everything else that was sold to the public that I'm aware of

[@MitzvosGolem1]

@@marcstlaurent3719 I had both bikes 1987 kx500 violent fast . Cr was smoother .True

[@MitzvosGolem1]

@@marcstlaurent3719 my point was the chamber initially not kips valve.

[@samrodian919]

Just watched your first video and immediately subscribed! Wonderful information, I'd heard of the RR Crecy but didn't know it was a two stroke! Great vid! Thank you!

[@rtqii]

I remember watching an aircraft video from this channel a while back, and then I saw a post with a poll asking if people would be interested in aviation engines, and I responded to that and said I would subscribe for those type videos. I saw one pop up in my feed yesterday on the RR Merlin, one of my favorite engines, and just watched the two-parter on the Napier Sabre engine. New sub enjoying every minute of these historical engine videos.

[@robertwinsper7409]

Look at the history of the Napier Nomad. Using a piston engine as the gas generator in a compound engine was being looked at very seriously. In the case of the Nomad they tried re heating the exhaust gas that was driving the turbo compound recovery wheel. About 1000hp jumped onto the crankshaft. At this point they must have known it was basically all over for reciprocating engines. Someone must have said at some point "So if you chuck away all this uppity/downity, roundity, roundity stuff and replace it with a big blow lamp and run that through the recovery turbine you'd have a 1000hp engine just like that, what are we mucking about with here"? All the technology for the early jets and turboprops was there, it was only a matter of time.

[@michaelf.2449]

Yeah once they realized just how much simpler they could make this whole system once they figured out the mountain of a learning curve it makes dealing with Pistons, valves look ridiculous.

[@madbrowndog4887]

The Nomad was aimed at achieving the lowest possible specific fuel consumption for its power output. In that regard it succeeded, but of course its complexity made it impractical. But as a piece of engineering, WOW! You just have to wonder about the mad geniuses that dreamed it up.

[@ekim000]

The idea that Whittle's Power Jets received less money in total than was expended on sleeve valve development does my head in. Fantastic content, thank you!

[@stevenborham1584]

Another fan of the "Motor-jet" I see. I have always been obsessed with this type of engine, and have dreamt up many possible power plants that could have at least rivaled the early jet engine power, and who knows maybe very different developments could have seen 40,000 hp motor-jet configurations. Going by figures quoted in this video that would be a fairly whopping engine of some 200 L displacement, put another way nearly three corncob radials (R-4360's). Motorj-ets would have quickly breached the possibilities later discovered in Turbo-fan engines regards thermal and aerodynamic efficiency and high bypass ratios for subsonic flight. I still feel it hasn't found it's place yet.

[@andyharman3022]

By the end of the recip engine era of aircraft propulsion, the superchargers were as big as the engines themselves. In motor-jet systems, the recip engine would have just been getting in the way of power production. Whittle had it right that the path to high speed was the turbojet. Even turbojets have their limits. In the SR-71, by the time it is flying at Mach 3.2, the turbomachinery is just along for the ride, most of the thrust is coming from the ramjet mode.

[@iskandartaib]

There IS an excellent book on the Crecy, available from the Rolls Royce Heritage Trust- I have a copy of it. The company Ricardo founded is still at it, by the way, doing research on advanced engines - I listened to a talk some years ago given by one of their engineers, he talked about advances in car and truck engines, compared petrol vs. diesels, and mentioned that they were experimenting on an engine that convert between four and two stroke operation on the fly. Blown two strokes are actually pretty common.. these days they're mainly large diesels (trucks, trains, maybe ships). In the context of WW2 aero engines supercharging was always present in any case, so it wouldn't have been a big deal in terms of an engine that absolutely needed one to run. They ran into a LOT of problems getting the Crecy to run reliably - mainly cooling of the pistons - remember there was the sleeve valve to keep heat from flowing away from the piston. One thing they tried (among others) was pumping oil up the conrods and spraying it under the cylinder skirt. According to the book it was the most unreliable engine Rolls Royce had ever worked on, including the Vulture. The latter part of the book was more speculative, about using engines like the Crecy (scaled down) as "cores" for turbines, and also the fighter they (Rolls Royce!) were developing for the Crecy - it was to use Mustang wings (in abundant supply) with a fuselage where the engine was mounted behind the pilot, and the pilot sat right behind the propeller (kind of P-39 style except even more radical). It got to the mock-up stage before the war ended and cancelled everything. I think you can still order this book.

[@iskandartaib]

Incidentally the RRHT also has a book about fitting the Mustang with the Merlin. It was quite a bit more complicated that you'd think - lots of plumbing issues. Rolls Royce was tasked with this job, they came up with the Mustang X (I think two built) before the effort was moved to the US.

[@marshallgray645]

Amazing research, writing, and narrating. Enjoyed it immensely thank you

[@TamagoHead]

Great Vid! Two stokes are very interesting air pumps, but are very RPM depending due to pulse resonances that start from the intake.

[@donaldduff-mccracken448]

Your work is great and this is wonderful as I have always wanted to know more about the Crecy. This is my fave aero channel now!

[@gerardoppewal372]

A very impressive engine! A few remarks: 1. At 3:20 'octane' is misspelled. 2. At 12:28 the animation clearly shows that two-strokes will scavenge without supercharging, if you use the crankcase as inlet chamber, and the downward motion of the piston provides the pressure. Common in mopeds, lawnmowers, etc. I realize that Crecy, Deltic, Jumo 205 do not use the crankcase for scavenging.

[@Biketunerfy]

I really enjoyed that. Sat in front of tv with my dad and a few beers watching British ingenuity at its finest. The British have always been some of the best engine builders in the world they even build engines for motoring sports still today and build some of the best jet engines in the world so Rolls Royce still pumping out industry leading technological marvels. Id love to see some of this engine technology transferred to racing car engines that might kick off a new breed of racing engines.

[@rtqii]

In 1927, Harry Ricardo published a study on the concept of the sleeve valve engine. This was applied commercially by at least one automobile manufacturer. Ricardo was heavily involved in the development of the Napier Sabre engine (videos on this channel!) which also used sleeve valves. He was an engine genius who did not invent new engines really, he learned everything about every type of internal combustion engine, he played with hot-bulb two-stroke oil (diesel now, crude oil back then) engines, and he combined the best features that he saw in conventional engine technologies and design, into a new class of engines. The development of jet and turbojet engine technology completely changed the engine industry for many traditional piston engine companies in the aircraft industry. Wright, Pratt and Whitney, and others either went out of business, were bought up, or completely changed their business models.

[@Roddy_Zeh]

KZbin just recommended me this video...and I was not disappointed. 10/10. 👌🏻😌

[@abbottsplace8080]

Amazing video! I was very surprised years ago when I learned of the existence of the radial sleeve valve engines. I didn't know about these engines. Wow. It is a shame we didn't see them in service. Thanks for the video!

[@PositionLight]

A better 2-stroke reference might be the line of EMD 2-stroke diesel rail and marine engines. They use a positive pressure air box design with inlet ports and poppet exhaust and can support turbocharging using a turbine driven at low RPM and exhaust powered at high RPM.

[@rogertycholiz2218]

Jersey Mike ~ The GM EMD locomotive engines had a Rootes blower intake.These engines lasted thousands of hours before maintenance.

[@PositionLight]

@@rogertycholiz2218 The 567D and 645E engines both had a turbo option with the overrunning clutch.

[@joebonavita6935]

Wow. What a time to be alive. The design of old aero engines is absolutely amazing.

[@brianmcneese9425]

While I appreciate the content of this video, ( and I'm no fan of the Germans of WW2) the Germans did develop and mostly deploy a pretty successful a 2 stroke, diesel and turbocharged engine in the JU- 86. Mark Felton describes this in " Germany's U-2".

[@leneanderthalien]

Yes diesel 2 strokes, but not gasoline 2 strokes

[@monsieurcommissaire1628]

Love your videos. This one was awesome. It's really a loss to those of us with engines on the brain that the no recording exists of the Crecy running. Considering the staggering power it generated, what thrilling aircraft could've been made.

[@CaptHollister]

Just for clarification, your description of a two-stroke applies to typical two-stroke diesels and by extension the Crecy which was developed from one of these. It ignores the fact that spark-ignition two-strokes do not require a blower. They use the aspiration created by the rising piston to pull mixture into the sealed crankcase during compression. Following ignition, the descending piston pushes the mixture into the cylinder through transfer ports while also uncovering the exhaust port. The exhaust gasses are pushed out of the exhaust port by their own inertia, with an additional push provided by intake mixture coming up through the transfers and, in the case of high performance two-strokes, and additional pull from the pressure drop created by an expansion chamber in the exhaust pipe.

[@danhammond8406]

That is a 2 stroke where the crankcase is used as the air pump. The engine in this video does not use the crankcase that way. The engine oil and the fuel were separate.

[@ricardodavidson3813]

Very clear and informative, congratulations!

[@dufus7396]

If Rolls Royce ,Bristol and Napier had got together..what monsters the could have created

[@bravo0105]

The scenario of 2-cycles bridging the gap between 4-cycles and turbojets for high performance is effectively what occurred for RC airplanes prior to the availability of small turbojets (very high-end uncommon models) and especially brushless motors coupled with lithium batteries. RC “jets” used to be ducted fans driven by specialized high-rpm 2-cycle glow engines; engines required frequent rebuild/replacement and the demand for these ceased with the mainstreaming of electric brushless motors. Model wing loading was high to where loss of thrust was typically catastrophic. The fastest RC airplanes were minimalist airframes with a high-rpm 2-cycle glow engine running a small-diameter high-pitch propeller. These have also been displaced by brushless electrics.

[@fortboy66]

Imagine this engine in a Martin Baker MB5 aeroplane , a real combination of beauty and the beast!

[@gmanbuilder9843]

The complexity and efficiency of late-war reciprocating engines will always occupy my mind, as a modern day mechanic and engineer I can only marvel at the wonders achieved by these men with no CAD, no computers, and no modern machining architecture. 200 HP PER LITER???? I thought I was happy with my god damn chevy 350 that makes 1.2 HP per liter..... The Crecy is absolute engineering marvel that I'd never even heard of before viewing this video, but that goes for the Merlin, Griffon, Allison, DB-610, R-3350, and many more that slip my mind. Gosh, I know I'm not alone in wondering what could have been achieved had the jet turbine never took off. Literally.

[@JonathanAtAchean]

This is a beautifully well researched video essay about an engine at the very back end of development of big piston prime aeromotive power. Well deserving of my full praise. I had, for years, thought I was possibly the only person on the planet still interested in this. I'm really struck by your quote of from Ricardo about the quality of fuels, which leads me to this suggestion: What about a video about the concomitant development of engines and fuels? There seems to be a gap between the development of the early inline engines, Puma, RR Falcon and Eagle, better developed engines like the Liberty, later engines like the Napier Lion, RR Kestrel and Buzzard, the specialised mixing of fuels for the RR type R engines and the development of those later big aero engines used so widely in WW2, using standardised fuel mixes. What do you think?

[@arkhsm]

The Germans may have heard it leaving the airport though !!

[@kennethm.pricejr.8921]

It seems there is no end to the different types of combustion piston engines that have been developed since 1857 (when Drake's Well hit oil).

[@guard13007]

Oh gosh, please do cover early jet power! :D (I happen to have a book that might be useful for some of that. No idea if it's common info or not though.)

[@henryfleischer404]

What's the book?

[@jwholmes2]

I’ve had the paperback version of Crecy book for years. An amazing engine story and One of my favorites! 👍🏾

[@Technoid_Mutant]

I liked this a lot. There was an Italian monstrosity in the 40's Caprione something. It was a piston-powered ducted-fan engine. The fuselage resembled a nose-breathing jet like the MIg15 or North American F86 sabre, but is just a standard aircraft engine driving the rotors. As such it was a failure, but it did fly and give fair numbers. An afterburner such as you describe was envisioned. Dig it man, an afterburning piston engine. Turbo is sicker from an engineering standpoint but to make afterburning, a wasteful expenditure of fuel a feature, they had to rid themselves of the wasteful aspects. It seems a success. The note of the engine throughout the operating envelope you provide is very smooth and rational. This wasn't a drag-race motor, might have powered a 45 ton mining dump=truck quite well. My only concern for universal adoption is PW versus gas turbine, and how susceptible the engine is to foreign object ingestion. That last is where axial-flow turbines start to totter.

[@philgiglio7922]

At 14 minutes... sounds more like a racing engine rather than the drone we expect from aero engines of the day

[@dougcox4310]

9:30 know this is pre-computers, even the hand drawing of the engine is impressive

[@Matt_The_Hugenot]

The Air Ministry were adamantly opposed to fuel injection in four stroke engines yet both Bristol and RR had access to the technology as the Crecy shows and it worked. At the end of the war the government was too scared to show its hand and deploy jet powered Meteors so basically the RAF was forced to fly with its metaphorical bootlaces tied together in the form of carburetted four strokes.

[@briancavanagh7048]

Your diagrams of the mid engined Mustang with the 4 different variations was actually built as real mock by Rolls Royce during the war. There are photos of the mockup about. The mid engine layout was done to provide enough room for all the ducting and the supercharger. So the cockpit was moved forward and the prop shaft ran between the legs of the pilot. Not unlike the Bell P39 Airacobra but for totally different reasons.

[@leneanderthalien]

the reasons was always to allow tricycle landing gear who improve a lot the ground controll and forward visibility (taildragger landing gear was source of a huge level of accidents) and allow a canon firing trough the propeller shaft (was made sinze the 1938 Morane 406 and he's Hispano HS404 20mm canon, but was limited in ammo capacity (60shots drum magazine on Morane 406 and Dewoine D520)

[@suabroboro]

Great job buddy. Been watching your videos on aero engines. Keep'em coming.

[@specforged5651]

I’m not the person to go around calling people wrong because your content is awesome and brings a lot of great knowledge. However, just to be clear, a 2 stroke does not “need” forced induction (meaning a turbo or supercharger) to run. In this case, yes because the air/fuel mixture does not run through the crankcase therefore becoming “pressurized” by the downstroke of the piston the driven from there through the intake port. As in every small 2 stroke on earth in motorcycles, snowmobiles, weed eaters, etc etc. However, when these types of engines are turbocharged like our snowmobiles boy are they fun! We’re talking two completely different engine architectures I know, but that is the funny thing about 2 strokes. Many people think they they need forced induction while plenty think forced induction simply will not work on 2 strokes. Well I’m here to tell you it works well and it is so much fun! Thanks for the videos, they are like porn for us gearheads and with them being aviation specific that makes them ever better to us aviation fanatics. Not here to call you wrong by any means, but there seems to be confusion on this forced induction/two stroke subject anyways. I just had to explain this to someone yesterday telling me turbos do it work on 2 strokes because it all goes out the exhaust.

[@scrumpydrinker]

D B by definition all two strokes are “forced induction” as in the rotation cycle of the engine the induction process takes at around 120 to 240 degrees when the pistons are round about BDC, so there is little volume change and therefore pressure differential to draw the air into the cylinders. In the simple three port two stroke as fitted to my old BSA bantam this was achieved by the downward stroke of the piston and having the crank case air tight so you didn’t loose any pressure going past the main bearings…. They could be a bugger to start if the crankcase seals were shot. So, no, the simple two strokes didn’t have a separate blower or turbo as the pressurisation was done by the descending piston. On two stroke diesels, all of which are uniflow designs, the air going in one end of the cylinder and the exhaust gases out the other a mechanical blower is always needed. Typically these are specified to have about 40 percent more volume output than the cylinders need so there is a decent scavenging process. Turbochargers aren’t suitable as they have to have a reasonable exhaust flow through them before the begin to work and at low speed there just isn’t the gas flow.

[@specforged5651]

@@scrumpydrinker You know exactly what I meant by “forced induction.” Please don’t try to show how smart you are by bending what other people say just to fit your narrative, it’s annoying. Then you just reiterated about everything else I said to being with. However, turbos work amazingly well on two strokes. Especially where density altitude is becomes more of an issue on something like a snowmobile where we ride sometimes as high as 12,000 feet around here.

[@bobbysenterprises3220]

The hardest part of flying through a flak barrage or not making the ineffective small jerky evasive maneuvers is finding a plane big enough to carry the balls it takes.

[@kiwihame]

Brilliant overview of one of my favourite engines. You covered everything superbly. The sound clip was most appreciated. The Cressy mustve sounded nuts. They should have called it "The Kracken" because it was truly a Monster!

[@teebosaurusyou]

As a mechanical engineer designing automation I can't believe the artistic skills of those that drew the illustrations of all this technology.

[@MarsFKA]

Most interesting. Thank you. The Napier Nomad was a similar project to extract the maximum efficiency from a piston engine. I have read that it was considered the ultimate in piston engine design, efficiency, complexity and cost. I have seen the Nomad displayed in the National Air and Space Museum's Udvar Hazy Center, but I don't know of any Crecys that are on public display.

[@MarsFKA]

@@jackgee3200 "Contemporary developments" being the jet engine. A quantum leap upward from enormously complex piston engines and their multitudes of operation-critical moving parts. The last-generation aircraft piston engines had reached the very pinnacle of their development and could go no further. Piston engines are still the most efficient internal combustion motors, but there is only so much that can be done with parts that go up and down.

[@Red-Magic]

Damn, that Detroit, and presumably the Crecy, would've sounded awesome. Would be nice to hear it in a plane...

[@kevatut23]

Just love your videos. Where else can an aeronautical design engineer, with a forty plus year avocation of building high performance motorcycles and cars, get to nirvana with merely a click. Thanks so much for the quality work.

[@Simon_Nonymous]

Well worth watching. There's good reasons GP race bikes are still two stroke; I've had a couple of two stroke bikes myself, so to see that mated with sleeve valves alternatives to OHC type poppet valves...

[@griffspeed]

I think you'll find that they stopped using 2 strokes way back in 2002 mate...

[@rogertycholiz2218]

Simon ~ Two-stroke bikes were banned in 2002 due to stiff pollution laws.

[@Simon_Nonymous]

@@rogertycholiz2218 banned in which country(s)?

[@mrspandel5737]

@@Simon_Nonymous MotoGP have banned two stroke engines since the 2002 season, although I believe the lower classes banned them a bit later. You can still buy them for other applications though. But I must admit the modern MotoGP powerplants with their F1 like high rpm do sound quite similar to a two-stroke.

[@Simon_Nonymous]

@@mrspandel5737 well I never knew that - I stoppped watching bike racing a long time ago, thank you for correcting my mistake 🙂

[@randomname4726]

You have the production quality of a multi million sub count. Great work.

[@EmyrDerfel]

13:50 hey, it's the Tape Boss™ guy!

[@stevenhoman2253]

A truly remarkable engine by any measure and a testament to the genius of Sir H. Ricardo.

[@danielcgomez]

VERY interesting video! THanks for this ...and yes, would be very interested heading down the rabbit holes of the other related content that you touched on. Thanks again!

[@MARGATEorcMAULER]

I would love to hear that engine fitted with expansion chamber's!!! A 12 cylinder 2-stroke no way

[@robertdavis100]

Battle of Crécy, (August 26, 1346), battle that resulted in victory for the English in the first decade of the Hundred Years' War against the French. The battle at Crécy shocked European leaders because a small but disciplined English force fighting on foot had overwhelmed the finest cavalry in Europe.

[@billbright1755]

The Germans were hitting on the concept of a sprint interception type platform as well. They took the approach of liquid two component rocket fuel to be mixed in combustion chamber exhaust exit. Fuel consumption was deleted from consideration in as much to get maximum scramble to high altitude in rapid rate of climb. The craft took off on jettisoning landing wheels and relied on a deployment of a spring skid ski to land. The idea was to get to bomber stream hit an attack aircraft and dead stick the craft anywhere offering a suitable landing field. Extremely risky but boy could that thing climb. Pretty much vertical to thirty thousand feet.

[@jamest.5001]

I have had the idea of a non symmetrical opposed piston engine, with the main goal to create peak cylinder compression with the piston down the bore nearly 1/3 down, with the ignition with the crank near 20° with a longer than usual stroke, basically. The stroke above the peak compression line, would allow more fuel/air to be pulled in, but maybe a similar outcome could be achieved with direct injection, and excessive compression, allowing the ignition with the piston further past the TDC although the excessive compression maybe nearly kill any benefits, but firing with more crank angle should make tons more power, and the tuning could make it very efficient Maybe the piston would be in a bore beside the main bore, only smaller, and use a similar to sleeve valves to make use of them, squeezing the pressure in as the piston goes down, and ignition when the valve closes, it's a bit complex to figure it all in my head even a cad and 3D printed model would make discovering if it's possible at all!

[@aldionsylkaj9654]

Fuck yes! I'm so happy you covered this engine. I'll re-watch it at home at first chance.

[@richardgreen7811]

The technology of this engine would be advanced even today. Four valves per cylinder, two stage supercharger, overhead camshafts. It's so great to listen to at idle, but cruising RPM's just sound like it's loafing. Also ... and You can argue all you want, but that whistling sound you hear as a P51 does a low pass is "not" the supercharger. It's the inboard gun ports that whistle. On most modern P51's, they plug the outer two barrel ports, but leave the inner barrel ports open. Very distinctive, but it's on several other planes as well.

[@EstorilEm]

Great content - must be noted that this was a stop-gap interceptor engine, whose power was simply unsustainable. It was not comparable to jet engines in that sense, nor common (performance) piston engines. The complexity and maintenance resources involved with the design made it almost useless to the war effort. It was a proof of design concept at best, for the most efficient and powerful piston aero engines of the day…. however exponentially more powerful and promising turbojet engines were evolving, and this became a waste of time.

[@arkhsm]

If the jet had not come along so quickly, this engine in an airframe that could handle it, would have been great to intercept the V1 flying bomb !!

[@EstorilEm]

@@arkhsm The allies had decent aircraft for intercepting the V1, but yeah - that’s essentially the concept that this engine was envisioned for. Just a quick zoom-climb interceptor with short endurance that could out-perform pretty much anything flying. I’m not trying to take anything away from it; it’s mechanically fascinating, but totally unrealistic if you take a step back and look at the big picture lol.

[@Biketunerfy]

@@EstorilEm I disagree, the big picture was in the middle of WW2 when Britain was swatting Nazi flies out its skies they needed to be more technologically advanced with their power plants for air dominance fighter aircraft and if the jet engine had fell through in Germany and in Britain then the British had a nice fall back engine to develop further, in Germany the jet engines didn’t last that long because the metals in the engine were spat out of the back of the engine because let’s face metallurgy was no where near sufficient enough to make turbine blades that didn’t melt and minerals were in short supply but frank whittle and his team had later developed ceramic turbine blades to use in hottest parts of the engine if I recall reading it correctly which means the British engine didn’t have cooling problems where the German engine did which led to very short flight hours. Anyway just saying that the British had a nice Easter egg to fall back in if the jet didn’t work out for both the British and Germans. I’m glad it didn’t because we would not of had the jet powered planes and world wide travel and trade because up until the transatlantic jet age it took more than a month if we ordered something in Britain and vice verser to reach us via shipping. Shipping is still used but mainly food and minerals although cars and other trade is shipped as long as it’s not so much dependent on time.

[@cncshrops]

Excellent and fascinating stuff. It's a constant wonder how the engineers of the period were able to do so much in such a short time.

[@glennpowell3444]

Fantastic content to someone like me.The Crecy 2 stroke made huge sense .Also you talked about carberation which is a whole topic in itself.So many ways to achieve an end result.Do you simply lift a needle with the same mass air flow or do you lift the needle/s and have an adjustable mass air flow and at what ratio do you achieve that?Weber seemed to achieve that in the auto industry but then you need to adjust mixture and needle opening times off the same cable linkage.A topic that few care about now because the carb.is a thing of the past largely.

[@paulduncan8032]

My apologies if you are already aware of this but have you heard of the Napier Nomad? Another two stroke but diesel, and essentially a form of "motor jet" with, at higher speeds, the reciprocating part of the engine acting as a gas generator for a multi stage axial supercharger. Needless to say it was killed off by the gas turbine (and development problems) but at least one of the prototype engines still exists at the Scottish National Aviation museum at East Fortune airfield near Edinburgh (Scotland, obviously). It is an awesome, in the original sense of that word, piece of engineering albeit, sadly, a dead end.

[@thamesmud]

How about doing the Napier Nomad. That was the true pinnacle of piston aero engines, though it was a turbo compound with insane boost pressure and remarkable specific fuel consumption. Typical Napier project, highly complicated and beautifully made. Cheap fuel killed it in the end as pure gas turbines could match the power but at the expense of much higher fuel consumption.

[@higgydufrane]

OMC (Outboard Marine Corporation) made Evinrude and Johnson brand V-8 two-stroke Outboards. They sounded amazing.

[@TheEulerID]

With all the exhaust providing 25% of the thrust, then it is pretty well a jet assisted piston engine in its own right. A sort of mix of piston engine and pulse jet and would be astonishingly noisy. Imagine dozens of those in the air at the same time. It would be like the apocalypse.

[@danmcdonald9117]

Just realised I have watched this 3 times now. Great!

[@johnserrano9689]

Excellent job. Very clean and concisely done 👍🇺🇸 But I will only truely believe said claims only after you provide me with a Crecy 2 engine, for uh "testing" procedures 😎

[@nidalshehahadeh7485]

Some of the information that I came across about technical development during World War II was the Pickering politics between competitions in which some use leverage to crippled the other Developers , that event is always kept out of the story as whose politics won the argument .

[@malakiblunt]

that detroit diesil had so ,much valve noise - were as sleve valves are notable for being very quite - so the crecy would of been all exhaust (note the bristol Beaufighter was called whispering death because its sleve valve radials (4 stroke ) were so quite

[@apexmcboob5161]

Great video! I'm curious how the BSFC compared with the 4 strokes of the day. Especially once the un-burnt or partially burnt fuel in the exhaust was ignited and use for additional thrust.

[@williammoore7928]

Keep the engine series up I love it