Speedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0 Posted (6 years 11 months 1 week 2 days 14 hours ago) and read 3653 times:
I donno why, but I was on a piston engine kick tonight, and spent too much of my free time researching various WWII engines online. The questions began to mount.
Messerschmidt's ME-109 was particularly interesting. I was reminded of its inverted V12, and wondered if an inverted engine suffers power losses because its power stroke must work against gravity. My armchair engineer imagination tells me that working against gravity on a power stroke is no less costly to overall power than doing the same on a down stroke in a right-side-up engine, to say nothing of the tiny impact gravity might have on the powerful power stroke of an inverted 1500+ engine. After all, some WWII submarine diesels were inverted for some reason, and those things were slow revving and must have had very heavy pistons and rods. But perhaps some of the REAL engineers here can confirm my imagination.
Radial engines have always puzzled me with their seeming complexity. What is the advantage of having, say, 9 cylinders arranged in such away as to have essentially 9 separate banks, thus requiring and equal number of separate valve train and lubricating components? I suppose compact packaging is a major plus, and even necessary with engines over 12 cylinders. And i suppose it would also be impossible to air-cool a many-cylinder V engine.
But still, I'm curious about the inherent advantages and disadvantages of V and Radial designs. Are their any unique solutions to either that have been employed in little-known recip engineering experiments? Thanks for your replies.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 23 Reply 2, posted (6 years 11 months 1 week 2 days 10 hours ago) and read 3620 times:
Hi Speedracer, Buzz here. A V-banked engine can be air cooled, take a look at the Flying Heritage Collection's Fieseler-Storch. She's an inverted, air cooled V-8.
There's an interesting web site, Aircraft Engine Historical Society and an interesting book "Allied aircraft engines of WW2" that you might enjoy. It's got a lot of the background to aircraft engine engineering - solving the problems.
Buzz Fuselsausage: Line Mechanic by night, DC-3 Crew Chief by choice, taildragger pilot for fun
TripleDelta From Croatia, joined Jul 2004, 1053 posts, RR: 7 Reply 3, posted (6 years 11 months 1 week 2 days 9 hours ago) and read 3615 times:
AIRLINERS.NET CREW PHOTO SCREENER
As far as I have read in various publications, the inverted V came into being to improve forward visibility, both on the ground and in the air - since by this token, the bulk of the engine would be lower, not blocking the forward view. In the end, as far as the Bf.109 is concerned, the material I've read stated that there were no major practical differences in the end, but since the production lines were geared to inverted Vs, they continued to be produced.
The V engine in general was used since it gave more power per frontal area than a radial, but it's disadvantage was the added system of water (or otherwise) cooling, which was vulnerable to attack (indeed, the only way to bring down the Ilyushin Il-2 was to target its prominent oil cooler).
The valve train for a radial is wonderfully simple. The cam is typically a drum, rather than a shaft, and rotates concentric with the crankshaft forward of the cylinders. There is one track of intake lobes and one track of exhaust lobes. The number of lobes is not equal to the number of valves, but rather, the speed of rotation is matched by geartrain to open any given valve at the correct point in that cylinder's cycle. Timing is apparently done to the entire drum at one time.
From the cam, it is a simple pushrod and rocker arm to the valve stem just like any OHV engine.
Lubrication is often routed externally (most of the oil winds up on the outside anyway!) You can see external oil plumbing around the banks.
Firing order is simple too. For a single-row of nine it would be:
What's simple about that? It is just every other cylinder all the way around twice. That is why each row has an odd number of cylinders.
About the only thing that is somewhat complicated is the crankcase castings with their internal oil passages and so forth. But these are normally cast in halves and bolted together during engine build so even they are not as bad as they look at a glance. The accessory section appears to be rather complex but it is not much different from other engine layouts. Just gear trains.
One advantage is the ability to change out one cylinder at a time, on the wing. Another is cooling air flow is pretty clean.
Happiness is not seeing another trite Ste. Maarten photo all week long.
FLY2HMO From , joined Dec 1969, posts, RR: Reply 5, posted (6 years 11 months 1 week 1 day 18 hours ago) and read 3523 times:
This diagram makes a radial look simple.
The most intriguing engine by far I've ever seen is the one used in the B36, the Pratt & Whitney R-4360. It is a mix between a radial and an inline engine I guess you could say, with the cylinders in a corkscrew shape. There is one on display at the Pima air museum at TUS. It is "disected" , and you can press a button and everything starts moving. 28 cylinders, 4300 hp. A really impressive engineering masterpiece !!!
Dougloid From , joined Dec 1969, posts, RR: Reply 8, posted (6 years 11 months 1 week 1 day 1 hour ago) and read 3448 times:
Quoting 411A (Reply 6): The 4360 was a VERY smooth running engine...that used a LOT of oil.
What is a lot?
Remids me one time I was at the air show in K'zoo and Miss Budweiser was there. One of the crew was refilling the oil tank on number 3 with a 5 gallon tin (gluck*gluck*gluck*) so I asked him how much they used and he said "Well they prestage the stuff at every place we're supposed to be and I'm getting worried because we've only got 200 gallons here."
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 10, posted (6 years 11 months 1 week 1 day ago) and read 3434 times:
Do inverted Vee's (and inlines, like the Ranger?) suffer the same maladies as the lower cylinders on big radials, where you need to walk the prop before starting to prevent potential hydraulic lock from oil leaking past the rings and into the cylinder?
Something I've always been curious about,
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Dougloid From , joined Dec 1969, posts, RR: Reply 14, posted (6 years 11 months 1 week 22 hours ago) and read 3409 times:
Quoting KELPkid (Reply 10): Do inverted Vee's (and inlines, like the Ranger?) suffer the same maladies as the lower cylinders on big radials, where you need to walk the prop before starting to prevent potential hydraulic lock from oil leaking past the rings and into the cylinder?
Something I've always been curious about,
I'd be inclined to think that the prudent and cautious operator would walk the prop through a couple times for that very reason if it was sitting somehwere for more than four hours. I've worked on a couple Rangers and I liked them...
Musta kept the crews busy on the Bf109s.
Now.....the most outrageous piston engine of all time musta been the Napier Sabre.
this guy's got some good information about the Sabre and the Hawker Typhoon. Just my friggin' luck I was born forty years too late.