This man made me take a break frim the video after half an huor and order one of his books. It is truly remarkable what he knows about the topic and he knows how to present it.
I'm endlessly amazed how Calum finds tech that I naively thought was recent. The high-altitude pre-combustion chamber was new to me. Great stuff as always.
Whoops note a mistake in my oration at about 42:00, I read off the slide that the Allied fuel was 86% iso-octane, this isnt true, what I mean to say is that the fuel was 86% parrafins, of which iso-octane forms a part. The fuel overall was about 50% iso-octane.
@CalumDouglas fact that you know how Honda's VTEC works but called it "their tech from the 80's" was my favorite part of the whole thing. Brilliant, 10/10 tomatoes, 2 thumbs up.
Where do you think the limits lie for these engines, if they had been “developed until the pinnacle” of the technology? We seemingly have neither commercial nor military reason to apply modern materials and electronic controls to piston engines focused on the performance profile of a dog fighter, so it seems unlikely that we will know for sure. But, given your insight, where do you think it would have gone? Right up to the edge of the speed of sound in level flight? More? How high do you think they could have operated? Or is it some other barrier you think they’d run into aside from speed and altitude?
RE: Alfa Romeo- a friend who worked at Alfa gave me a technical paper from the late 30's outlining their rudimentary EFI system they were developing for their auto racing engines. Given their success in the '30s (third only to Mercedes and AUDI relative to best race cars), I suspect they would be more advanced engines than what came out of FIAT for the aircraft motors. May need to find more auto tech papers to get a hint what they did for airplanes.
Good video. The pretty colours help to bring the book to life. I have not used it as a doorstop but it would make an excellent paperweight to hold down a map or set of plans, etcetera😁. Calum is possibly eccentric, to be putting in so much effort, to research and publicise this material but … in a good way. I came across Calum and his work via Christoph Berg’s Military Aviation History RU-vid channel. Calum always appears to observe ‘The First Rule of Instruction- Tell The Truth’, something that is all too rare in the world. He tells it straight, explicates and explains. Never boring, despite the fact that I sometimes have to read a section several times, have a cuppa and then read it again to gain a full appreciation, given that the finer details are outside my vocational and instructional expertise. Thank you for inviting Calum and sharing this video.
My father was made redundant as a flight engineer in Australia 1962 and returned to the Netherlands. (He was in the Dutch resistance during the war.) At Fokker he bucked the very hierarchical system that was in place. His brother for example was a solid achiever but he hardly moved up since the war. My father was tasked with rust prevention in the F27 fuel tank. Apparently his work was quite good. When presented to the technical board his boss claimed my father's work as his own. I think he objected, was told to know his place, and the chap bounced off the window when punched. It was the first floor. He then on being sacked returned to Australia and flew with another airline. I bring this up as anecdote simply bc absence of truth is not just the failing of politicians, lawyers and real estate agents, in the technical world, prejudice, jealousy, deceit are as equally rampant. And Calum brings this up with his tweet on Beatrice Shilling twitter.com/CalumDouglas1/status/1650227982739427332
Thanks Calum, finally got a chance to watch this and learnt even more! I have both your books and love them. Can't wait to get the expanded version of the first book, when you get it done.
1:16:20 I seem to remember reading (i think it was in 'Metals in the service of man') that from the German industrial viewpoint, full on WW2 started about 3 years too early for the stock piles of strategic metals nickel, chromium, manganese etc etc were not complete to economic war plans worked out in the mid 30's...
at the 5 minute mark, there is mention of the problem of coronal discharge at high altitudes when dealing with the high voltages of the ignition system. This surprises me, because I used to work with vacuum tube radios for military aircraft. These use somewhat high voltages for the tubes, and these were in a sealed container with a pressurized gas. No problems with discharge at high altitudes because the electronics were not exposed to the low pressures. Was this just considered not practical to do the same with the ignition system?
The ignition harness of these High altitude aircraft engines were sealed and pressurized probably to sea level pressure....if you look at pictures of these engines you can see the ignition harness is quite bulky and substantial.
I always believed that a major limitation was high speed balancing equipment. The compressors back in the 40's were large and low RPM. A modern compressor is balanced to run at 150k rpm.
Maybe low rpm. But further on in his oration , as he calls it , he mentions the German compressors reach 500 metres/sec at the tips. Which is as high as is reached at 120k rpm in tractorpulling where 600-700 metres/sec are reached with smaller turbo compressors. Holsett Hx82 with billet 5" wheels. But Those only have to last minutes instead hours.....
if you recall the bit about intake air volume vs mass and hitting the sonic limit. more speed wouldn't help because the air is so thin. you need a pre-compressor, effectively ram air before the compressor, in addition to turbo super charging. bear in mind all our automotive comparisons are at sea level and relatively stationary speeds.
Imagine a turbo charged aluminum and magnesium engine built like a 12v71 2 stroke Detroit diesel engine. Only larger with a variable supercharger/scavenger 12 cylinders , coming in at about 140-150 cid per cylinder. The super turbocharger system capable of boosting /scavenging at 6-8 bar absolute, at 50k feet with a rev range to 3600-3800 in an emergency situation. And a gear reduction possibly, and a lightweight forged crank and rods, both having all excess material removed and polished hollow journals 4340 steel, light weigt pistons, four oversized exhaust Valves per cylinder (imaginea scream Jimmy on take off 😮) a aero Detroit engine in a v12 and flat 12. 12v149 and 12H149. Just under 1800 cubic inches, also a 6 cylinder and 24 cylinder, 56 and 88 ci/cylinder version avalible for smaller and large applications. Like the Detroit 53 and 71 series engines. Also maybe a gas version could be developed. A two stroke gas engine with valves and supercharger and turbo! 😮
Callum you mention how the German engines were using a lot of valve overlap and so using a portion of the inlet air to cool the combustion chamber and exhaust valves.....is this compressed air a loss out of the exhaust or would have they been able to recoup some of that by using the heating of that air and subsequent energy and use that as thrust at the exhaust exit.
You would get a small amount back in theory as anything coming out the exhaust will force the aircraft forwards, but this would be fairly minimal especially as this would not occur during the main high pressure exhaust expulsion. So basically this air is "lost" out the exhaust, yes.
At 34:00 I hate giving away my secrets, but an opposing rotating blade section with a clutch engagement, would act like a flow control so it could be engine powered by hydraulic and cut in and out from powered to parasitic. But I assume he will get to this design shortly.
When you think about it when you go higher in altitude you're actually creating something similar to a vacuum tube oddly enough this is what used to be used in electronics during the second world war.
I've flown C172s at 12,500ft many times, with a DA at least a few thousand feet higher than that. And we did that regularly. Due to our high field elevation, to do performance maneuvers safely (minimum AGL in case of spin) we'd regularly get to 12k ft altitude during maneuvers, usually starting at ~9k ft. no big deal. I've flown a Cessna 150 at 14,500ft DA (11,500ft MSL) crossing the grand canyon and still had tons of climb performance left. to be fair that one had 150hp and some other mods.
@@alexander-lc4dr tons = lots in this context, tons is a mere word, not a unit of measure. I take it English is not your first language? Just like how fillet of fish is not the same as fillet on a machined part. They are spelled the same, pronounced vary differently though, and mean totally different things.
@@alexander-lc4dr "To say a 150 with 150 naturally aspirated horsepower has "tons" of climb performance over 10,000 feet agl isnt English, its rather unbelievable." then english isn't your native language, as this is a commonly used term in day-to-day conversation. "a video discussing non dimensional axes on compressor maps, instead of using "tons" you could have said "200 fpm"" not really, as I was flying the corridor for teh grand canyon with strict altitudes, and could only climb for a few moments before returning to altitude, so I don't know what it was getting exactly, but it was way more than a Cessna 172 at that altitude, at least 3-4x more. "tons" is an appropriate description, as the airplane was climbing far better than anyone would expect it to.
While I understand your defence of your commonly used aircraft, the engines in them are extensions of prewar designs and are indeed older than the VW beetle engine. A C172 is the most pedestrian of all the cessnas and my aircraft mechanic and aero sparkie Father refers to them as "VW Combi's with wings, with a lesser climb rate". Callum is talking about engines that put out 55 to 65 HP per litre above 20,000 feet. The lycoming and Continetals average 30 hp per litre on the ground and closer to 20 hp per litre at even 10,000 feet. The expression "tons" when used in common slang, infers the same as "Heaps" or "Bucket loads" etc, which no high wing cessna is close to. Expressions like "by the skin of its teeth" or "squeaked through" would probably be more appropriate. NOTE: C-172 listed as 700 feet per minute at sea level and 100 feet per minute at 13000 feet per minute. A Spitfire Mark V is listed as 2900 feet per minute at 13000 feet!
@@philkennedy8683 "A C172 is the most pedestrian of all the cessnas and my aircraft mechanic and aero sparkie Father refers to them as "VW Combi's with wings, with a lesser climb rate". " the fact you have no idea what a C150 or C140 is........clearly I'm not talking to an aviation expert. No VW engine is going to power a C172, I also own a VW powered airplane, and that engine with modifications only puts out 1/2 the HP of a C172 engine. " C-172 listed as 700 feet per minute at sea level and 100 feet per minute at 13000 feet per minute. A Spitfire Mark V is listed as 2900 feet per minute at 13000 feet!" this comparison has no relevance and proves nothing. wow. You clearly are talking out of your ass.
@@SoloRenegade I grew up around the airfield my Father worked at. I own a hangar and even have a 1946 Cessna 140 sititng there. A C172 engine, of 360 cubic inchs makes a measley 180 hp when in perfect condition and in perfect conditions. The 0-360 is fundimentally the same design as the prewar 0-145 and still only squeezes out 30 hp per litre. As a comparison the currently popular Rotax 912/915 series engines make 2000 TBO's with 100 hp per litre outputs. Calum's video is about performance engines for performance aircraft but you decide to get offended by him refering to your beloved Cessna's as asthmatic, without stopping to think that this man who is a highly qualified engineer and engine designer might know what he is talking about. By all means enjoy your cessna 140/150/172 or any other aircraft but please don't compare them to performance engines or aircraft
Hi Calum, I think there is a mistake at 46:20. The nickel content of exhaust-valves IMHO has no influence in knocking, but in valve erosion/burning. Am I wrong?
Yes you are wrong. Having a valve with low Nickel does not "instantly" make the engine knock, but when this valve inevitably does start eroding, (which can happen fairly fast, only a few hours is needed) several things happen, the valve head scales, these sharp edges glow and cause pre-ignition hotspots, the valve head also begins overheating because it starts not seating correctly and so the thermal transfer goes down, so the temperatures in the exhaust side of the chamber all go up. A mixture of detonation and pre-ignition then begins depending on the various circumstances/power levels used etc. You can read all the original reports yourself if you read my book, which quotes from them all and these translated reports on this issue begin on page 271.
@@CalumDouglas Ah, I've just seen the explanation in your other IMechE-video. Got your book some days ago, but will need several weeks to get through 🙂
@CalumDouglas How about the oil from Romania. During the presentation and after in the QA section you kept saying germans used synthetic gas from coal, but all through the war they had access to the oil fields of Romania which was their ally until August 1944. You can`t tell me that those oil reserves were insignificant as the repeteated allied bombings of Ploiesti prove otherwise.
The allied bombing drove the production numbers up greatly. The Germans were able to evaluate what was being done by the Romanians before the bombing and finally rebuild better. It's best not to look at those bombings as an allied victory.
The oil from Romania was judged to be of a type unsuitable for making aviation gasoline, I`m sure they used it but it probably almost all ended up as fuel for Jeeps, Trucks and the Navy.
@@CalumDouglas Thanks for the reply! 🙂 I really had no idea that crude was of different qualities. Considering that Japanese had facilities distilling oil from pine seed I would imagine proper oil would be better at getting gas.
24:46 a 2-stage turbocharger? :0 What would be the point of a two-stage turbocharger if a turbocharger can already vary its RPM infinitely (while below critical altitude)? Was it done in order to use an intercooler?
Because a single stage compressor (irrespective of whats driving it) of the period is limited to about 3.5:1 pressure ratio, which means the critical altitude (rated altitude) will always have a pretty moderate level. A two stage compressor will get you about 6:1 pressure ratio but will also consume several hundred horsepower to drive it, hence the attraction of using exhaust gas energy to do it.
@@CalumDouglas Hey Calum, may I ask another question. At 44:38 you say that Daimler-Benz used the variable inlet guide vanes on their compressors. But why would this be necessary if they had variable speed superchargers? Did the swirl throttle "add" efficiency in addition to the variable speed supercharger? Or was the swirl throttle only useful at low altitudes where the hydraulically-geared supercharger was limited by some minimum RPM due to maximum slip?
@@dogeness because the variable speed coupling is limited to about 33% slip otherwise the oil gets too hot. If you have BOTH IGV and variable speed couplings, you can extend your compressor by enlarging it so its a lot bigger in capacity than you would normally be able to stand at sea level without undue throttling losses on take-off, and then apply maximum slip AND very high pre-swirl on take off. Thus when you get to rated altitude with both of those set to zero, you will have a higher rated altitude AND manageable throttling losses at take off. There are also other factors at work but that's the very basic summary.
The valve overlap combined with the turbo pushing large amounts of fuel/air straight out the exhaust must have had a terrible effect on fuel consumption. Did the Germans mention this?
if you recall the valve overlap graph, direct injection let them fuel cut as soon as the overlap occurred, it was air blowing through the cylinder to cool it, not fuel. not something you could do with a carb. which was not a problem for the allies anyway because they had far more strategic resources like nickel.
@@throwback19841remember they used direct injection so they could just delay the injection of fuel until the exhaust valve closed though there was a limit as Callum pointed out. Still had to get the fuel to evaporate to keep it from collecting in the cylinder walls and getting into the oil. Contrast that process to a diesel where the fuel is only injected at the ideal time BTDC to initiate combustion around the fuel droplets that are produced by the injector. No need to evaporate the fuel!
I can think of a few answers why not, like availability, but were German aircraft ever raced in post-war air races? I ask after seeing the fuels section but in context of being able to finally install proper high temperature alloy valves, adjusting the timing and using racing fuel it would seem German aircraft and now that I think about it, late-war British aircraft would be competitive.
I cant answer this definitively, but I would very much suspect not. There have been a few Spitfires "at" the races but they were not race-prepared, but just warplanes that flew the circuit. Which is sometimes quite a different thing entirely. I think the main issue is a serious lack of parts (remember lots of Allied engines like the Merlin were made long after the war ended for civil use so you have lots of "new old stock" parts kicking about even today, and things like the civil Merlin had substantial development effort put into them post war to really iron out all the bugs. German engines never had any of that, and they would need very significant work to put them in a position to do that, given their rarity the risks are I think judged far too high to race. Ignoring all practicalities, I think something like a highly tuned FW190 or maybe some of the things Heinkel had on the drawing board would be contenders.
@@CalumDouglas To complete the alternate history, the idea of racing against fully tuned Zeroes or their descendants comes to mind. Once again the defeated ran out of swords and swordsmen, it's no wonder there were so few airworthy examples after the war. Great work Callum, thank you.
@@CalumDouglas Calum, your homepage doesn't really have a mention of your second book. I didn't realize it was out until I did a search based on your mentioning it in the video. I'm going to see if my son has an ASME membership, and then order a copy. Thanks for some really interesting material. Good luck!
@20:30 its sad that German and British engineers didnt agree on a standard of compressor maps..... I guess the real technicans would have loved to but war was standing in the way...😉
