Shortround6
Major General
I am taking a wild guess but manifold pressure would be measured at the manifold (after the supercharger and/or intercooler on the two stage Merlins) and before the intake port on the cylinder head.
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I was wondering what fundamental problems existed with the following engines, from a technical standpoint
While I know that the H-2600 and H-3730 were cancelled because of a desire to focus on radial engines, I'm curious if either had technical flaws that were difficult to work-out?
- I-1430
- O-1230
- X-1800/H-2600
- H-3130/3730
What was an "O" configuration for the O-1230?
Opposed, that is flat.What was an "O" configuration for the O-1230?
Why was it prone to failure under load?Lycoming's O-1230 may have been rated at 1,200 hp, but it was prone to failure under load and that caused aircraft manufacturers who were interested in using it, and the Army, to back away from the project.
What caused the general crappiness? As for the separate cylinder design, I thought that contributed to bulk more than anything else -- I didn't know it undermined performance. As for the number of valves, I'm curious as to how many the V-1710 had...I-1430: Separate cylinder design, 2 valves per cylinder, smallish capacity and general crappiness.
O-1230: Separate cylinder design, 2 valves per cylinder, smallish capacity and general crappiness.
Pratt & Whitney never made a liquid cooled engine? Regardless, that seems more like preference over functionality.X-1800/H-2600/H-3130/3730: Liquid cooled in an air-cooled company
What problems occur with sleeve valves? I do remember that the British used them in the Centaurus and I think it made a lot of smoke or something...sleeve valves.
Was he driving both the H-2600 and 3730? Or just one of the two designs?The man driving the project became ill, so went on the back-burner.
Why was it prone to failure under load?
What caused the general crappiness? As for the separate cylinder design, I thought that contributed to bulk more than anything else -- I didn't know it undermined performance. As for the number of valves, I'm curious as to how many the V-1710 had...
Pratt & Whitney never made a liquid cooled engine? Regardless, that seems more like preference over functionality.
What problems occur with sleeve valves? I do remember that the British used them in the Centaurus and I think it made a lot of smoke or something...
Was he driving both the H-2600 and 3730? Or just one of the two designs?
So they were trying to do too much with too little?For one thing it was trying to make about the same power as an Allison (or Merlin) from an engine about 3/4s the displacement, there is only so much higher rpm can do but........
And this all started because of the requirement for the higher coolant temperatures back with the hyper engine, and they figured that individual cylinders would be needed?Separate cylinders mean the crankshaft and crankcase are longer, yes it adds bulk, but it also adds weight and in causes problems with crankshaft flex and torsional vibration.
They DB-600's used 4.Allison and Merlin used 4 valves per cylinder, you want to know how many the DB 600s and Jumos used, google it.
So firstly: The devil was in the details? I'm guessing vibration had to do with the greater length of the engine?It was preference but remember that P& W made very good air cooled engines. Functionality would mean learning all the ins and outs of the vibration patterns of the liquid cooled engine layouts.
So basically you want the coldest fastest moving fluid to cool the hottest parts and the slowest and warmest to cool the coolest parts?P & W spent hundreds of engine test hours figuring (thousands of engineering hours?) out the vibration problems of the R-2800. Making good liquid cooled engines was not as easy as it seems, how much liquid moving how fast is needed to cool the different parts of the engine?
So there was a general disinterest in the matter?He was basically incharge of everything and so could direct the companies efforts. When he fell ill his replacement decided to stick with what P & W knew best, air cooled radials.
If the H-2600 had been developed, would the H-3730 have likely continued along over the R-4360?They estimated in 1940 that they might have the R-4360 ready in time for the war
So they were trying to do too much with too little?
And this all started because of the requirement for the higher coolant temperatures back with the hyper engine, and they figured that individual cylinders would be needed?
They DB-600's used 4.
So firstly: The devil was in the details? I'm guessing vibration had to do with the greater length of the engine?
Just to get back to the point: Did they ever design a liquid cooled engine prior to this point?
So basically you want the coldest fastest moving fluid to cool the hottest parts and the slowest and warmest to cool the coolest parts?
So there was a general disinterest in the matter?
If the H-2600 had been developed, would the H-3730 have likely continued along over the R-4360?
British used Perseus, Taurus and Hercules engines more than they used the Centaurus and it was far from beer and skittles for quite some time.
P&W was a radial engine company. Single separate cylinders were their stock in trade. Monoblock design was foreign to them and too devilishly full of details that had taken other companies years and iterations to learn.Maybe it was convenient to put 12 of the "hyper" cylinders together rather than build a monoblock design
P&W was a radial engine company. Single separate cylinders were their stock in trade. Monoblock design was foreign to them and too devilishly full of details that had taken other companies years and iterations to learn.
Cheers,
Wes
Because on the bench, it's performance looked good, but once it was installed in the Vultee and put through performance testing, the engine suffered from excessive detonation (until higher grade fuel was provided) as well as cracks in the crankcase and bearing failure.Why was it prone to failure under load?
The 1008 arrangement was also a V from what I recall.Basically.
The IV-1430 had already been enlarged over the original design based on the "hyper" cylinder, which was 1008ci, IIRC, for an opposed 12.
They really should have redrawn the contract as technology advanced to allow for monoblock construction -- actually, why didn't they?No. . . .Maybe it was convenient to put 12 of the "hyper" cylinders together rather than build a monoblock design (like the V-1710, Merlin and DB-60x). . . . Note that the IV-1430 had a single cylinder head per bank.
That's how I got the information, you said don't ask, use google. I used google.So you can use google?
Which they'd have to work out.Yes, partly. The radial engines had 7 or 9 cylinders on each crankshaft throw, while the V-12s had only 2, which meant different vibration characteristics.
But they would have a body of knowledge on radial engines, to some extent, anyway.Yes, but none that went into production.
I'll see what I can find onlineThe R-2060 was one, a liquid cooled radial.
Understood.You need to balance the coolant flow with the amount of heat that you can extract from the cylinders and reject through the radiator.
So the key is providing proper cooling for cruise power, but being able to cool the engine enough for WEP settings?Cooling systems in aircraft were, generally, designed around normal or cruise power, not maximum WEP.
I'm actually curious why the USN was so interested in developing the design at all. That surprised me more than anything else.It was outside Pratt & Whitney's core competency.
What I was curious about was basically, from an academic standpoint, is basically...Given that the R-4360 was essentially chosen over the H-2600, the question is moot. . . . The R-4360 was an easier development path for Pratt & Whitney, since the starting point was the R-2800 cylinder.
They really should have redrawn the contract as technology advanced to allow for monoblock construction.
What I was curious about was basically, from an academic standpoint, is basically...
- If the H-2600 was given the go-ahead: Would the R-2800 have likely been given the go-ahead or been cancelled?
- If the H-2600 was given the go-ahead: Would the H-3730 likely been given the go-ahead, essentially, by extension
According to most sources, Mead became interested in Sleeve valves at some point in 1937.
No, I get that. I just think the US Army should have re-written the contract when time came to go to 12-cylinders. I'm not sure how easy it was to deduce the effect of two cylinders in a test-rig versus twelve cylinders.Continental and to some extent, Lycoming were building what the Army told them to build. If the Army said "design separate cylinder engines" that is what they did. . . . If they had designed monoblock engines the Army would have said "that is not what we ordered, we are not paying for it".
I asked if the H-2600 had been given the go-ahead would the R-2800 have proceeded.If you cancel the R-2800 (which was earlier in timing than the H-2600) you give Wright market domination in the 1500 hp and market for several years (maybe 4 or 5).