Pratt and Whitney R-2800 - America's Indestructible WWII Aircraft Engine

war is a messy business a business frequently filled with harsh conditions and expensive equipment that lives depend on and that notion that lives depend on that equipment whether it be a radio a rifle or an engine makes the design of that equipment all the more important to those who use it perhaps that's why despite the double wasp not being the most powerful engine or having the biggest displacement or using the most advanced technology it was still loved by aircraft designers and pilots alike not because it was a temperamental tuned racing engine but because it was a reliable workhorse that wouldn't cut out on you when the carts were down like its namesake the wasp the pratt mini r 2800 proved to be a stubborn thing refusing to quit even when it had no business forging on the engine routinely absorbed harrowing amounts of battle damage with little complaint damage that would have surely stopped a liquid-cooled merlin dead in its tracks instead pilots would simply return from missions noting little more than a slight reduction in power to their crew chief only to later discover entire cylinder heads and barrels sitting in the bottom of the engine to sell this is the incredible story of the pratt whitney r 2800 double wasp an engine that may have been the perfect embodiment of the rugged allied war effort an unstoppable machine that refused to quit until its job was done [Music] in 1922 the u.s signed the washington naval treaty which required them to limit naval construction avoiding what would have been an inevitable arms race following the end of world war one the treaty not only limited future construction but also placed limits on standing tonnage to comply with these new restrictions the us navy decided to convert several of its battle cruisers to aircraft carriers the conversion left the navy with a sudden demand for a new generation of naval aircraft seeing the opportunity to open uncle sam's wallet a man named frederick renschler the current president of wright aeronautical corporation claimed he could provide the navy with an engine producing 400 horsepower while weighing less than 650 pounds a feet other engine manufacturers considered beyond their reach the navy encouraged wrenchler to build such an engine expressing a keen interest in placing orders should it be successful but wrenchler soon found a wrench in his gears after bringing his air-cooled radial design to the right aeronautical board of directors it turned out that they wanted nothing to do with it at the time the prevailing theory was that heavier liquid-cooled engines were the future of aviation and so unwilling to rock the boat they declined to support wrenchler's project unwilling to simply give up such a promising business opportunity wrenchler immediately left the company stealing its chief engineer george mead and founding the pratt whitney aircraft company not long after the first prototype engine was completed producing 420 horsepower at exactly 650 pounds while searching for a name for the lightweight but deadly quick engine rancher's wife suggested the name wasp and a legend was born shortly after trialling their wasp the brand new pratt whitney aircraft company found themselves with an order from the navy for 200 engines so if the board of directors at wright aeronautical wanted a liquid-cooled design why did wrenchler choose a radial engine over some of the more impressive liquid cool designs being developed at the time well even today there is an ongoing argument between liquid-cooled engine designs and their air-cooled radial brethren like the montagues and the capulets or the hatfields and the mccoys some liquid-cooled loyalists claim superiority while their air-cooled enemies scoff doubling down that their air-cooled radials are clearly superior the truth is like most dichotomies there's nothing really clear-cut about it to highlight this let's take a quick look at piston driven air speed records throughout history in 1939 an airspeed record was claimed by a messerschmitt bf-109r powered by a liquid-cooled inverted v12 engine proving that liquid-cooled engines dominate once and for all except after the war this record was claimed by a radial-powered grumman f-8f bearcat in 1969 which settled the debate except for when in the 1970s a gryphon 57 powered p-51 called the red baron reclaimed the record again and after that things were quiet until an f8f bearcat powered by a right r3350 dubbed at the rare bear stole the record again you see the thing is there are so many factors that convolute an aircraft's performance the debate between a liquid cooled or an air-cooled engine is essentially worthless so if it really doesn't matter between a liquid cooled or an air-cooled design why did wrencher go to the links that he did well we have to remember that the one thing that he was focused on the most was saving weight particularly he wanted to create an engine that weighed less than 650 pounds and when weight is your chief constraint a radial design is your best bet you see wrench learn knew that air-cooled designs tend to be shorter and more compact than liquid-cooled engines and their cooling systems are obviously much simpler the lack of need for ducting and radiators ultimately allows them to be lighter overall but not necessarily more powerful another advantage is that air-cooled radials tend to be much more resistant to failing after taking damage because the cooling system is ambient damage to an engine does not inhibit the cooling system as it does in a liquid cooled engine while a liquid-cooled merlin may begin losing coolant after absorbing a straight bullet soon overheating a radial engine is more than likely happy to keep chugging along now that isn't to say though that an air-cooled engine doesn't have its share of disadvantages early designs suffered from increased installed aerodynamic drag before naca began helping solve this issue in the 30s and also specific power tends to be lower overall because of the less efficient cooling system because the cylinder head temperatures tend to be higher than their liquid cooled counterparts air-cooled engines tend to suffer from detonation sooner than liquid-cooled designs and if you're wondering what detonation is it's when things explode in the engine outside the timeline we'd like them to [Music] so essentially with an air cooled design what you gain in weight reduction you lose in cooling efficiency the name of the game and radial design is maximizing the cooling fin surface area to offset the thermal buildup that isn't being as efficiently dealt with as it might be in a liquid cooled application essentially we're thermal limited the more we can cool the engine the more power we can make so why a radial because it's simple and light if we can keep it cool with world war ii on the horizon design firms were thirsty to build engines that would power the next generation of fighter aircraft pratt whitney were no exception and in 1936 they drafted plans for their largest engine yet the r-2180 soon after expecting horsepower needs that exceeded their initial plan the design was scrapped in favor of a larger 2600 cubic inch model work began and after developing the r2600 for nearly a year wrencher discovered that wright aeronautical had also begun work on a 2600 cubic inch radial so the design size was increased a second time to the final 2 804 cubic inches because you know size matters the early 2800 a and b models other than being larger than anything the company had produced thus far were not groundbreaking in their design but were only notable in that they exceeded 100 horsepower per cylinder a limit thought to be insurmountable in the 1930s due to inherent cooling limitations of air-cooled engines their method of achieving this proved to be simple incremental improvements to known issues a theme the company would become known for throughout the war specifically pratt whitney improved their casting machining design and materials to create an engine with deeper more closely pitched cooling fins coupled with improved baffling the resulting increase in cooling fin surface area allowed more power to be generated simply because the engine could dissipate more heat in terms of layout the r2800 featured 18 cylinders arranged in two rows of nine total displacement was 2804 cubic inches or 46 liters for you fancy folks meaning each one of its cylinders displaced more than an entire subaru outback engine concerning the internal design the cylinders had a five and three-quarter inch bore and a six-inch stroke while the combustion chambers were a smooth hemispherical design a term chevy would later dub the hemi inside each cylinder were two huge puppet valves controlled by push rods that actuated a roller bearing supporting rockers each valve was filled with liquid sodium which provided much needed cooling for the extremely hot exhaust valves under load to improve cooling further the pistons themselves were aluminum forgings sporting an assortment of fins inside the skirt the r2800 like nearly all its contemporaries used a forced induction system specifically it used a single stage unit that could either be of the single or two-speed variety although two-stage intercooled supercharging units were also built especially for the navy which had no plans of implementing turbochargers like the air force soon after the a and b models were developed the race for more horsepower led pratt whitney to discover that their current design was limited to 2000 horsepower due to various strength limitations of the components to fix this issue they just redesigned the whole engine no big deal the resulting c-series engine had only the five and three-quarter inch bore and the six-inch stroke in common with its predecessors featuring a strengthened crankcase rods nose case reduction gearing system and a larger prop shaft the c-series was now a fortress of an engine to solve the cooling issue which would undoubtedly be exacerbated by increasing the power the company completely redesigned the cylinders vastly increasing the total cooling fin surface area even the crankshaft was redesigned along with the carburetor and supercharger the results an engine now capable of producing 2 800 horsepower at 2800 rpm with water injection now some of you may be forgiven for being hung up on that last bit water injection how does squirting water into the engine help it well water injection is sort of a hack really a method for cooling the combustion chambers of engines so they produce more power by spraying water or water methanol mix into the incoming fuel air mixture you can achieve greater compression ratios and eliminate the pesky problem of engine knocking which is again when things are exploding when they're not supposed to doing this effectively increases the octane rating of the fuel meaning we can push more boost into the engine which means more power also of particular importance to our heat limited air cooled engine water injection can also delay overheating as it's temporarily cooling the engine while it runs at an increased power setting so in some respects it really is that simple you just stick a super soaker in the intake and away you go to horsepower heaven with all of this in mind to say that the r 2800 was a successful engine would be an obvious understatement using the same formula for success as rolls-royce did with their merlin engine pragmini took an otherwise unremarkable engine and focused on making incremental improvements over drastic aspirational design changes on paper the fact that the engine only features two valves per cylinder is a stark limitation to its overall potential but despite this its performance outshined this limitation with brute capacity furthermore the ingeniousness pratt would be displayed when revising this engine throughout the war is evidenced by the respectable boost it could tolerate despite its inherent volumetric inefficiency again this engine was not the greatest in any single category but it did have a winning combination of competitive performance rugged construction durability and reliability because of this potent cocktail of desirable features it's easy to see where the double wasp became such a sought after engine a brutal power plant powering countless famous aircraft such as the mighty p-47 which i should add essentially became an aircraft engineered entirely around the r2800 and its massive turbocharger effectively creating a two-stage turbo supercharged beast that routinely forgot it was at 30 000 feet and let's not forget the f4u corsair the f6f hellcat the f7f tiger cat the f8f bearcat the b-26 marauder the a-26 invader the p-61 black widow the curtis c-46 commando the lockheed ventura among other fighters and bombers i'd say the r-2800 was popular and what about when the war ended production was surely ended right well like a fighter that refuses to retire the r2800 just refused to quit going on to propel many 1950s airliners there was just something about the double wasp you could depend on it and maybe when it's your butt on the line somewhere over enemy territory cold and alone that's the only thing that matters hey guys thanks for watching if you enjoyed this video please shoot us a like and subscribe to see more future content and as always thanks for tuning in to flight dojo see you next time

Channel: Flight Dojo

Views: 808,999

Keywords: wwii aviation, aircraft engines, wwii aircraft engine, pratt & whitney, R-2800

Id: cG9DG6EQOQs

Length: 13min 31sec (811 seconds)

Published: Mon May 23 2022