Shortround6
Major General
It was used in the "Nasty" class torpedo boats too, but diesels have bit different power output than gas engines. At least until recently. The march of technology 
Build the perfect water cooled engine
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Readie
Chief Master Sergeant
It was used in the "Nasty" class torpedo boats too, but diesels have bit different power output than gas engines. At least until recently. The march of technology
Yes, indeed.I wonder what's next?
I saw the electric Lotus..the Tesla on a test and it went rather well to say the least.
Cheers
John
Shortround6
Major General
Are they 'American' books
This is one of those deals where you have to look at the bias of the author. Sleeve valves in theory had a lot few parts, didn't require periodic valve adjustment, reduced the number of 'hot spots' in cylinder/head that could caused detonation and allowed higher compression. They might have allowed smaller diameter radial engines or narrower flat engines.
It is also estimated that they took millions of pounds and almost 15 years of effort to get to a reliable standard. Was the cost and effort worth it?
Also consider the following sentence "Although the cost of manufacturing a sleeve valve-engine was almost twice that of the Merlin, it is worth noting that neither the Merlin nor the American engines ever rivaled the TBO of the sleeve-valve Bristol Hercules and Centaurus."
This sentence may be true as far as it goes but it does not go far enough. Which sleeve-valve engine(s) is he referring to? The 24 cylinder Sabre in which case I would expect a 24 cylinder engine to cost about double what 12 cylinder does. The 18 Cylinder Centaurus which has not only 50% more cylinders but on a cost per horsepower basis isn't that far behind the Merlin, with around 50% more cruising power available. While he may be right about the TBO that wasn't until the post war period in commercial use.
It would be nice to see some direct engine to engine comparisons in the same year for the same use, both for cost and for TBOs. I beleive P&W rated the R-1830 for about 2-3 times longer between overhauls for airline use vs military use even before WW II.
Quote is from "Major Piston Aero Engines of World War II" by Victor Bingham.
Lighthunmust
Banned
What is your opinion on a sleeve valved engine versus poppet valved engine in resistance to battle damage and ease of repair?
Lighthunmust
Banned
I have been within 6 inches of the Tesla. There was one parked at my Doctor's office a month ago. It is great looking and definitely displays the Lotus bloodline. If only it wasn't so expensive. I saw it reviewed on Top Gear awhile back. The real Top Gear, not that genetically deformed and mentally deficient American clone of Top Gear.
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wuzak
Captain
Interestingly, the air cooled air racers at Reno spray water onto the engine to keep their monsters cool. Liquid cooled racers spray water on their radiators - basically because in both instances they are operating beyond the cooling capacity of their installations.
wuzak
Captain
Yes and no.
It does depend on what service the engine will see. Bomber, fighter, reconnaissance, etc. A 3000lb, 3000hp engine is probably not the best for a fighter, where light weight is a virtue, but would be great in a B-29.
Propellor tip speed would be adressed in the propellor reduction gearing - turning the prop more slowly. Or replacing the prop with a smaller diameter alternative.
I don't think a contra prop is any more vulnerable than a single rotation prop, other than there are two mechanisms that can go wrong rather than one.
Contra props allow more power to be absorbed, and can be with smaller diameters than single rotation props. They also eliminate the torque effects - which cuases aircraft to turn and roll better in one direction than the other.
Macchi had some success with their go at contra-props, with the MC.72. Though, to be fair, that was essentially two separate engines. A similar thing could have been done with the V-3420, as they could be set up with opposite rotating crankshafts. The Sabre had both cranks rotating in the same direction, so it wouldn't have been as easy.
Rolls-Royce were probably the most successful at using contra-props - The Shackleton and late model Seafires had contra-props fitted to their Griffons.
Shortround6
Major General
I haven't realy read anything so these are guesses.
Liquid cooled Sabre vs Merlin or Hercules vs R-2600/R-2800?
The Sabre is going to have all the problems of the Merlin if hit in the cooling system or oil system. A hit in the block bad enough to screwup the sleeve valve mechanism is going to cause a massive coolant/oil leak so the plane is lost anyway.
As far as the radials go, the Hercules was used in the Bristol Beaufighter for anti-shipping and close support work. It powered the Stirling bomber, the Wellington, a few Lancaster's, and a lot of Halifax's in addition to a few less successful aircraft. I would think that if there was a real problem it would have been mentioned. Not every push rod radial exhibited the R-2800s ability to keep running with missing cylinders. As long as the sleeve valve radial engine wasn't below average in regards to most radial engines I don't think it matters much.
While a hit to the cylinder barrel might jam a sleeve valve (the drive may break allowing the other cylinders to keep running) that would not affect the piston on a poppet valve engine, a hit the dents the cylinder wall to bind/obstruct the piston is equally bad for either engine. The sleeve valve engine actually has less area to hit, It's cylinder heads are nothing but cooling fins and spark plugs. And the plugs a buried deep inside. No push rods, rocker arms, valves or valve springs to to get shot away stopping a cylinder from making power.
It perhaps wasn't the best engine for glider towing but I am not sure what engine was. The Merlin didn't seem to like target towing duty. A lot of planes used for target or glider towing (high power at slow aircraft speeds) suffered cooling problems because their cowls/radiators weren't designed for that duty.
As far as repair goes, not having worked on one I can't figure out why replacing a cylinder on a sleeve valve radial should be that much harder than replacing a cylinder on a push rod engine. What time you may loose fiddling with the sleeve valve and sleeve drive you gain by not having to deal with push rods, rocker arms and valve lash adjustment.
Here is a British magazine article from 1941 describing the Hercules.
1941 | 2827 | Flight Archive
While there maybe some war time propaganda in there along with some politically incorrect view points, the flight archives are a wonderful resource and a good insight as to what some of the thinking of the day was.
Edit, if you have trouble try a different browser, for some reason it doesn't work with google chrome but it works fine with firefox
wuzak
Captain
That also depends on the type of aircraft being used.
It would seem that the leading edge radiators were among the best for drag - Whirlwind, Mosquito, Tempest I. But there was some resistance, at least on the part of the British, to have leading edge radiators for single engined fighters. The Germans liked annular radiators, allowing them to fit radials and inlines to the same aircraft without changing their lines significantly. Though, it has to be said, they sacrifice the smaller profile possible with an in-line.
The belly scoop was also quite successful. The P-51 is the most famous exponent of that, but there were others - the rear engine in a Do335 was cooled by a belly radiator, the P-40 originally had a belly scoop, the XP-46 did (Curtiss didn't get it to work well, though), the Hurricane did, and the Typhoon/Tornado started out with a belly scoop.
Spits and Bf109s had theirs on the wings, of course.
I think the best option would have been to have the radiator group in the rear fuselage, behind the pilot, fed by ducts from the leading edge of the wing - like the engine intakes for a jet.
Lighthunmust
Banned
It opened just fine on my MacBook. Very interesting article. Thanks for the link, I Bookmarked it with all others you and others have posted.
Lighthunmust
Banned
delete
Lighthunmust
Banned
I think there was a 3000hp engine powered B-29 but it was called the B-50
I was thinking of fighters with the 5000hp monsters proposed when I posted the fuel issue. With the much lower horsepower engines already in use piston engine fighters were being pushed about as fast as mach allows.
I knew about the late model Seafires and Spits, but forgot about the long serving Shackleton. I understood the advantages they promise with torque cancelation and smaller diameter props. But I suspect that with a contrarotating gear box a very minor hit in combat that would be sloughed-off by a single prop gear box would result in frequent XF-11 type events. I recall they were removed from some late mark Spits because of problems. I don't thing the Seafire or Shackleton ever had their day in battle to determine vulnerability of contrarotating props.
wuzak
Captain
Yes, but that was decidely post war. B-29s could have done with 3000hp engines during the war, and the V-3420 was the only real possibility during that time frame.
None were built, but both Supermarine and Hawkers proposed aircraft to use the 3500hp Eagle22, which may have ended up more towards 4000hp.
A 5000hp monster would have been preferable for the B-36, but they got stuck with the (by then) 3500hp R-4360s. The R-77755 was intended for the B-36.
The Corsair was fitted with a 3000hp R-4360 to become the F2G, the length only changing by a little over one inch. The R-4360 was also fitted to the XF8B.
The XF-11 incident was due to a hydraulic failure in the pitch control mechanism, causing one of the propss to go into reverse pitch. This could happen to a single rotation prop as well.
In the case of the Griffon the dual rotation was achieved with 2 extra gears - a small pinion and the drive gear for the second prop shaft. Not much to go wrong there.
Readie
Chief Master Sergeant
You need Jeremy Clarkson with all his non PC gaffs to make TG. The Germans are a favourite subject....Now, why would that be as we are friends in the EU?
Not
Cheers
John
billswagger
Airman 1st Class
- 256
- Mar 12, 2009
Leading edge radiators were not the best for drag.
The intake usually disrupts the boundary layer going over the wing, which causes more drag than just the frontal area of the intake.
Similar to sticking your hand out of the window of a car, the air that doesn't fit in the intake creates a pressure gradient that increases the aerodynamic drag of the original frontal area. The drag is not just created by your hand, but also extends to the air trying to go around your hand.
This disruption can interfere with air going over the wing, which would simulate the same effect as having a thicker wing section.
The point of putting the radiator on the leading edge has its benefits despite the drag.
The Tempest was a heavy bird, and designing drag into the air frame may have been beneficial to help control over speeding.
Birds that flew low altitude missions that were more vulnerable to ground fire and flak would also be less vulnerable since their would be less ducting/plumbing for the radiator, and having it centered near or around the engine doesn't make it any more vulnerable.
This probably coincides with the XP-40 have a rear scoop originally, but then instead designing it into into the chin, due to the roll the aircraft.
The Mustang and the P-39/Aircobra both had aft pilot radiator intakes which both had the same Allison engines.
Their top speeds increased remarkably over the P-40 by that engineering move alone.
They probably had no quams about lend leasing the P-39 because of the learned hazards and limitations of the rear-engined plane, but the Mustang had too much potential to lend away, at least, not until newer and improved versions were made.
The P-51 was considered more vulnerable to ground fire which is no surprise given my explanation, but being primarily intended for long-range escort, why worry.
Shortround6
Major General
Ah, I see, the fact that the P-39 and P-51 had different airfoils, different fuselage contours (the Spitfire lost 6mph by fitting the bullet proof glass to the outside of the wind screen) had nothing to do with the different drag, it was all radiator placement?
The fact that the XP-40 picked up 43mph (from 299mph to 342mph)when the radiator was changed from the rear position to the front had nothing to do with change either?
Further changes were made to bring the guarantee speed up to 360mph ( new carb air intake , enlarged radiator fairing ,modified tailwheel housing, ejector exhausts). I don't know if the XP-40 prototype ever made the 360 but production planes were good for 357mph.
Once again, I ask for somebody to come up with proof that the P-40 was "supposed" to be a close support (ground attack) fighter.
The initial armament of a pair of synchronized .50s is a pretty pathetic ground attack armament and the prototypes ability to carry 3 20lb bombs under each wing is laughable compared to the P-26's ability to carry a 200lb bomb load the P-35's ability to carry 300lbs. (six 50lb bombs). It really reaches absurdity when no mention is made of ANY bomb load for the 300+ P-40s the USAAC accepted before the P-40C with it's external fuel rack which was, at times, modified to carry "A" bomb. The absurd part comes in when you consider that Curtiss was marketing the export Hawk 75 with a total bomb load of 850lbs, one 500lb under the fuselage, two 100lb bombs under the wing inboard of the 'standard' bomb beam or rack but still clear of the propeller for dive bombing attacks and six 25lb bombs on the standard bomb beam or racks. Alternative loads on the standard bomb beams with no other external loads were ten 30lb fragmentation bombs, or ten 25lb chemical bombs or six 50lb demolition bombs.
I will grant that the Hawk 75 with this loads was not equipped with ANY wing guns but if the P-40 was 'supposed' to be a close support fighter and the Hawk 75 was in existence before it (P-36?) then whoever speced the P-40 did a mighty lousy job.
The army had already decided several years before that it didn't want to use water cooled engines for ground attack aircraft.
billswagger
Airman 1st Class
- 256
- Mar 12, 2009
Well, of course not all of the increase in speed was due to the radiator placement, however the P-39, and early P-51As did use the exact same power plant as did the P-40. Part of having a better drag profile would be eliminating the chin radiator.
Its also been discussed the limitations of the chin radiator because of its effects on the boundary layer over the wing, something the engineers had payed particular attention to while designing the P-51.
I see what you're saying.
Rather than run too far off topic, i was simply taking notice that placement of the radiator intake would effect overall performance, and that leading edge vents would not present the best drag profile.
Whether its intended to be a ground attack/support fighter or not, having the radiator on the chin or near the engine would not make it more vulnerable, something that i'm sure was a consideration for war-time engineers.
Its also represented by the placement of the radiator on the P-40-XP to the first production model P-40B. Though that change was first implemented on the P-40(would've been A) and was said to have lowered performance. Obviously, there was more that went into the B that also accounted for its increase in speed from the XP model.
Bill
Were the planes with leading-edge radiators slow birds?
In other words, Camm decided it would've been good to have draggier plane, rather than a 'clean' one?
Agreed; how many fighter planes were designed with 'resistance to flak/ground fire' on the top of the proposal/request?
Not 'roll' - 'role' perhaps? What was P-40's role?
Already addressed by SR6.
P-39 went to LL like any piece of US hardware, so no point to state 'hazards limitations of a rear-engined plane'. USAAC gave green light to P-63, a plane with same layout anyway.
Mustang went to LL as soon as production ramped up (1st batches were purchased by UK?); USAAC took a while to reckon the potential.
Any sources that can support the claim that P-51 was primarily intended for long-range escort?
I was under impression that the engine layout (opposed vs. V) allows greater revs? I know that boxer is wider (was driving the Alfa 33 long time ago
); placing it lower would've meant that it's in line with wings, hopefully (sketch attached). Ditto for twin-engined usual installation.The big problem with a lot of these engine was keeping them cool enough to stay running. At 15lb of boost an 4 stroke engine is moving about the same amount of fuel and air as an EQUAL sized 2 stroke per minute with no super charger. Supercharging a 2 stroke means that much more heat being generated in the cylinder every minute. There may be some advantages but I wouldn't expect a big jump in performance.
You also need a supercharger that could keep up with it
Well put - thanks
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Shortround6
Major General
I was under impression that the engine layout (opposed vs. V) allows greater revs? I know that boxer is wider (was driving the Alfa 33 long time ago
The cylinders and crankshaft really don't care which they are pointed as far as ability to turn rpms go. Some flat engines had other features that allowed for high rpm.
The USAAC was big on opposed engines during the 30's, both hyper engines started out flat engines. As far a single engine fighters go, if you can figure out how to get the pilot down to two feet high and still see out the front of the plane the idea may have some merit. Laying the pilot on his back and putting a big bend in his neck never worked that well for very long, neither having him lie on his stomach and bend the neck backwards.
The USAAC lost interest as the 1930s went on a wing sections got thinner making it harder to bury the engine in the wing. The flat engines never wound up be quite as flat as promised anyhow. Little things like intake manifolds, starters, fuel and oil pumps and superchargers kept sticking out either above or below the rest of the engine
The Lycoming 0-1230 measured 44.1 in wide (it had overhead camshaft so a sleeve valve engine would be narrower) with a 133bore and a 120mm stroke vs the Allison and Merlin 152mm stroke. It was rated at 1200hp at 3400rpm so it did rev higher but it's piston speed 2,692fps. perhaps a later version could have revved higher.
But as far as "flatness" goes it was 37.9 inches high. Granted over a good part of it's length it wasn't that high but the USAAC realized that flat engines weren't going to fit into smaller aircraft and if you got a big airplane it was usually big enough that normal engines could be buryed in the wing. (B-36)
There was a french air cooled flat-12 Potez of about 500hp pre war that went nowhere and a flat 12 Franklin aircooled of 300hp pre war that also went nowhere. The Franklin was pretty much a standard light plane air-cooled flat engine stretched out to 12 cylinders, it was 24in high. and that would have been running the cowling right over the carburetor mouths.
