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Thread: Packard/merlin engines

  1. #61
    Boolit Master
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    I can see you have a great deal of first-hand knowledge that I don't, and yet positioning of weight away from the centre of mass of anything can't help but reduce its ability to turn. It is like the difference between a best grade British shotgun and an imported copy of very similar weight and similarly located point of balance. Suspend both of them by threads, force them out of the horizontal, and the former will return to horizontal faster and after fewer oscillations. It even works with mine and a very good Spanish double, although mine is nineteenth century, and only George Gibbs's third quality sidelock. The difference is in moment of inertia.

    Supercharging is about as old as internal combustion, and turbocharging has been used in aircraft since WW1. Undoubtedly turbo lag is what made it very useful for bombers, but unacceptable for fighters. Bell tried it with the Airacobra (incidentally an ingenious solution to the moment of inertia problem), and found themselves with an aircraft unsuitable for high altitude combat.

    There is an interesting benefit of the turbocharger. Being linked to the engine only by a column of compressed gases, generating that boost imposes very little stress, and the engine is stressed only by the increased power it produces. With the mechanical supercharger quite a bit of power must be taken from the engine to drive the thing. This produces a considerably higher increase in power, so your net profit is the difference between them. The stress imposed on the engine, however, is the sum of the two.

    Funny things certainly happened to the controls of the fastest piston-engine fighters in power dives, but I think that was at least partly due to flexure, and actually coming even close to sonic velocity couldn't happen. The problem of propeller tips approaching sonic velocity is much more pronounced, and a serious danger, with helicopter otors. For on one side the airspeed of the rotor blade is the difference between rotational velocity and the aircraft's airspeed, and on the other side it is the sum of the two, with each blade alternating rapidly between them.

    Perhaps the biggest snag with the Griffon-engined Spitfires (and the Spiteful, which was little if any more different that the late Spitfires) was fitting enough airscrew to use the power. Even slight increases in undercarriage height still required five blades. I don't think any Spitfire used contra-rotating propellers, although the naval Seafire did. They were used in the Martin-Baker MB5, though, and this was a very interesting aircraft. It incorporated many lessons which had been learned, offering much improved visibility and a speed of 460mph as a prototype. It had the P51's under-fuselage radiator, and was exceptionally easy to repair.

    Test-pilots' reports were extremely good, and it could have seen wartime service, but I don't think it was any mystery, as Martin-Baker's own website says, why it wasn't adopted by the RAF. They had done some extremely good design work, including a rear-engine monoplane in 1934, and Britain's first eight-gun fighter, but they had never brought an aircraft into production. I believe it was thought that jets were the coming thing, and meanwhile conversion to high production of a recently-established small company was a lot riskier than asking Supermarine to improve the Spitfire.

    http://www.martin-baker.com/about/mb1-mb5
    Last edited by Ballistics in Scotland; 03-06-2015 at 10:48 AM.

  2. #62
    Boolit Grand Master Artful's Avatar
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    That MB-5 is a good looking plane!







    http://www.mycity-military.com/imgs2...4963_2.jpg.jpg


    John Marlin reconstructed his own MB5
    http://johnmarlinsmb5replica.mysite.com/index_1.html
    A Sad Ending to the MB5

    Although the MB5 did little flying after this, the engineless airframe was used for training purposes by the Air Ministry Servicing Development Unit at RAF Wattisham, Suffolk, from 1948-49. The aircraft subsequently served as a ground target, the battered remains ending up at RAF Bircham Newton, Norfolk, in 1963. It was then burnt; an ignominious fate for an aircraft that represented the acme of piston-engined fighter development.
    http://johnmarlinsmb5replica.mysite.com/photo3.html
    Last edited by Artful; 03-06-2015 at 08:32 PM.
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  3. #63
    Boolit Grand Master Artful's Avatar
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    Quote Originally Posted by Ballistics in Scotland View Post
    Funny things certainly happened to the controls of the fastest piston-engine fighters in power dives, but I think that was at least partly due to flexure, and actually coming even close to sonic velocity couldn't happen. The problem of propeller tips approaching sonic velocity is much more pronounced, and a serious danger, with helicopter otors. For on one side the airspeed of the rotor blade is the difference between rotational velocity and the aircraft's airspeed, and on the other side it is the sum of the two, with each blade alternating rapidly between them.
    compressibility
    http://www.history.com/topics/world-...orst-nightmare

    http://en.wikipedia.org/wiki/High-speed_flight

    Transonic flow patterns on an airfoil showing the formation of shock waves at different Mach numbers (M) in high-speed flight.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

  4. #64
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    Quote Originally Posted by castalott View Post
    the p38 was so clean it could hit the sound barrier in a dive...The latest models had dive brakes for just such an emergency as the controls locked up in a fast dive. That's what I've read anyway....
    Airflow on parts of the airframe of several WW II planes could achieve compressibility in a dive. The planes themselves didn't. The difference is moot because if the shockwaves masked control surfaces, control was lost.

    dale in Louisiana

  5. #65
    Boolit Grand Master Artful's Avatar
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    I was told at air/space museum some probably did reach/exceed the speed of sound while diving away from enemy plane on their tail - and very likely they broke apart at that point, lots of pilots warned about diving away from enemy aircraft too fast. It was compressibility that locked the controls and I guess G forces that kept guys from being able to bail out. Also sad that when the big bombers started spinning the forces pinned the crew inside the aircraft so they couldn't get out.
    Last edited by Artful; 03-06-2015 at 08:31 PM.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

  6. #66
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    That is an excellent explanation of compressibility, for which much thanks, and also for those pictures of the replica MB5. One of them shows engine accessibility which could hardly be bettered, and the Rolls-Royce magazine link tells us the frame members could all be replaced individually. Despite the benefits of monocoque construction, that must be considered an improvement.

    The magazine, which is no doubt the authoritative version, contradicts what I had believed, by saying it was continuing design work by Martin which delayed completion of the aircraft. I had heard elsewhere that it could have been ready much sooner if the Ministry had wished. Of course it is hard to say which came first, the chicken or the egg.

    What I find most interesting is the grooved strip of presumably thicker metal in the cowling, behind the exhaust stubs, which didn't exist in Merlin Spitfires or the P51. It might just have been because the exhaust is set a little more deeply to reduce drag, or is hotter than most. But it may also have been designed to best direct the small amount of forward thrust which was obtained.

    I suppose I have an ambivalent attitude to anyone being able to spend what an MB5 replica must have cost. But I suppose he could have invested it in derivatives. Andrew Carnegie said that anybody who dies rich dies disgraced, and the creator of something like this is a patron of the arts, employing good people on what they most want to do. I have this image, possibly perverse, of Leonardo da Vinci the engineer cursing the need to earn a living painting that woman with the silly smirk.

  7. #67
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    Many Griffon Spits used counter-rotating props. I have seen several of them.



    https://www.youtube.com/watch?v=VZ8BUNJYtOo

    "Bell tried it with the Airacobra (incidentally an ingenious solution to the moment of inertia problem), and
    found themselves with an aircraft unsuitable for high altitude combat."

    Not sure exactly what you mean. Sounds like you are saying that the P-39 had a turbocharger, which it did not,
    other than an early prototype. The production P-39s used Allison engines with single speed-single stage superchargers and
    that is why they were no good at altitude, like all Allisons other than the Lockheed P-38 which had external turbochargers.
    The Army told GM not to develop a two speed, two stage, intercooled version of the Allison before the war,
    and by the time they understood the mistake, it was easier to put the Merlin into production by Packard
    rather than develop the Allison 2 spd,2 stg system.
    Last edited by MtGun44; 03-07-2015 at 12:59 AM.
    If it was easy, anybody could do it.

  8. #68
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    Quote Originally Posted by MtGun44 View Post
    Many Griffon Spits used counter-rotating props. I have seen several of them.



    https://www.youtube.com/watch?v=VZ8BUNJYtOo

    "Bell tried it with the Airacobra (incidentally an ingenious solution to the moment of inertia problem), and
    found themselves with an aircraft unsuitable for high altitude combat."

    Not sure exactly what you mean. Sounds like you are saying that the P-39 had a turbocharger, which it did not,
    other than an early prototype. The production P-39s used Allison engines with single speed-single stage superchargers and
    that is why they were no good at altitude, like all Allisons other than the Lockheed P-38 which had external turbochargers.
    The Army told GM not to develop a two speed, two stage, intercooled version of the Allison before the war,
    and by the time they understood the mistake, it was easier to put the Merlin into production by Packard
    rather than develop the Allison 2 spd,2 stg system.
    The reason for the mid-engine design was not for inertia. It was because they installed a 37 mm cannon thru the driveshaft and was fired through the center of the propeller. The driveshaft had a gearbox that dropped it down and ran between the pilot's legs. It also did not have a top canopy, rather had a door to get in and out of. I'm told that it was virtual suicide to try to bail from one as the pilot would end up getting hit by the elevator. Not many of them were used by the U.S. Most were sent to Russia as part of the lend-lease program. Many never made it to Russia, as many of the supply ships were sunk on the northern route. Many of the planes sent to Russia were flown from Alaska and the Aleutians to Siberia and then to where they were to be used. There were many ladies who flew the missions to get the planes where they were going. The first time I saw an Aircobra, I couldn't figure out why there were exhaust burns on the middle of the fuselage. My feeling is that had a decent engine like the Merlin or Packard had been installed in the aircobra, it would have been a much better plane as per the 51 when they figured out to put in the Merlin. Until the Merlin was installed, the 51 was mediocre at best. Enter the Merlin, and it made the Mustang. There was only one thing the Mustang couldn't do that the 47 could. With the big radial and all that frontal area, they could come up behind, back off, and keep from over-running their target. Most people don't realize that the very last model of the 47 was actually a little faster than the 51. Not much, but a little. There was one fighter group that was offered the 51, but they turned it down and stayed with the 47. Interesting some of the little things most don't hear about. Sometimes fact is stranger than fiction.
    As a side note, Supercorsair race number 57 is being repaired and put back in flying condition in northern California.

  9. #69
    Boolit Master
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    Quote Originally Posted by MtGun44 View Post
    Many Griffon Spits used counter-rotating props. I have seen several of them.



    https://www.youtube.com/watch?v=VZ8BUNJYtOo

    "Bell tried it with the Airacobra (incidentally an ingenious solution to the moment of inertia problem), and
    found themselves with an aircraft unsuitable for high altitude combat."

    Not sure exactly what you mean. Sounds like you are saying that the P-39 had a turbocharger, which it did not,
    other than an early prototype. The production P-39s used Allison engines with single speed-single stage superchargers and
    that is why they were no good at altitude, like all Allisons other than the Lockheed P-38 which had external turbochargers.
    The Army told GM not to develop a two speed, two stage, intercooled version of the Allison before the war,
    and by the time they understood the mistake, it was easier to put the Merlin into production by Packard
    rather than develop the Allison 2 spd,2 stg system.
    Not that many. My understanding was that only a prototype MkXIV Spitfire was tested with a contra-rotating propeller. I could well be wrong, and it is possible that some MkXIXs were so fitted, since it proved worthwhile with the Seafire, but not many, and most likely not in wartime service. Those pictures are available online, and show a MkXIX at the Chino Air Show, which has been modified by the fitting of an Avro Shackleton engine and propeller unit. So far as I know all contra-rotating Seafires, and certainly the Shackleton, were post-war.

    http://www.richard-seaman.com/Aircra...o2004/Sampler/

    I am aware that the Airacobra was designed and had the rear engine to accommodate that cannon, and that if the engine position produced improved manoeuvrability (other things being equal, which they weren't), it would be incidental. It was designed for the turbocharger, and the protype so equipped had dubious performance at altitude. I believe the single-stage mechanical supercharger was substituted to reach something like the intended speed, but in so doing made the altitude performance more than dubious. The British also found its speed didn't come up to specification.

    I think it is a bit of a myth, though, that it was outclassed as an air to air fighter. It never had a chance of being the high altitude interceptor of bombers which was originally intended. But it was well liked and successful with the Russians. A myth possibly engendered by that enormous gun was that the Russians used it as a tank-buster. They didn't. I believe they were supplied only with HE shells, not armour-piercing, and that probably meant with an air-pressure sensitive fuse which would explode on contacting thin aluminium or even canvas. Their Airacobras were most valuable against Stukas and larger bombers, but weren't hopelessly outclassed by German fighters.
    Last edited by Ballistics in Scotland; 03-07-2015 at 09:12 AM.

  10. #70
    Boolit Grand Master Artful's Avatar
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    the 37mm AP rounds were only good to penetrate 1" of armor so by the time the Airacobra came around most of the tanks were protected with more than an Inch of armor - would have been pointless to shoot at them.




    http://lend-lease.airforce.ru/englis.../sheppard/p39/
    Discovery

    This amazing Bell P39 was located at the bottom of Lake Mart-Yavr within the Russian Arctic Circle in the summer of 2004. As with other recoveries over the years, it was discovered by a fisherman who saw the silt covered outline through the crystal clear water.

    The P39 sat on the bottom of a shallow lake at a depth of 5m, covered and buried up to the top of the propeller spinner in fine silt. Covered in silt, no markings were initially visible but after a little brushing, a red star appeared together with a yellow serial on the fin and rudder. With the serial now known, a search through the archives showed the pilot had disappeared on a transfer flight in November 1944.

    Taking advantage of the good weather, the recovery team used air bags, tripod frames and a truck winch to bring the P39 to the shore. It caused concern that when the P39 emerged both the cockpit doors were still closed. Usually, if it was a water landing, one or both would have been jettisoned allowing for a quick exit. If the lake had been frozen, the team would still have expected one door to be open following any force landing.

    The reason soon became apparent; for some unknown reason, the pilot had not exited the P39 and his remains were located in the cockpit. Missing for 60 years, the pilot was buried on 6 October 2004 with full military honours at the Glory Valley Memorial, near the Litza Valley, NW of Murmansk.

    The P39 was remarkably complete, only missing the starboard inboard leading edge. As is always the case with magnesium-based components, the wheel hubs and engine cam covers to the engine had dissolved over the years and disappeared.

    An interesting discovery was that the wing 0.5in machine guns had been removed. This in itself was not unusual, but in the area for the ammunition trays the team discovered six cans of American stew and spare lengths of ammunition. The 11 1/2 oz food cans contained cooked pork, lard, and onions with spices and had been packaged by Beerfoot Farms Company, Southboro. Massachusetts. USA. Not all lend-lease supplies were hardware!

    The main fuselage weaponry was in place including the Colt-Browning M4 37mm cannon that fired through the spinner with 30 rounds of ammunition. The two 0.5inch heavy machine guns were located over the cannon and fired through the propeller and each had 200 rounds of ammunition as well.

    The most amazing discovery was in the document case on the starboard door. The team located the maintenance record book for this P39. Although a few pages had perished, the majority was still legible. Nearly all of the Russian information that follows concerning flight hours/dates, servicing and pilots’ names come from this unique document.

    The P39 was easily disassembled before being transported to Moscow where it received its export licence. It was then transported to Jim Pearce’s facility in West Sussex where it is currently being cleaned up and inspected. This amazing and historic P39 is currently for sale.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

  11. #71
    Boolit Grand Master Artful's Avatar
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    Uploaded on Jun 7, 2011
    Built in Buffalo, NY, this P39 crashed some 60 years ago in a lake in Russia. This was shot in 2009 as she's being loaded onto a lorry in the UK to be taken to a museum that happens to be in the same building she was original built in.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

  12. #72
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    Those are spectacular pictures, and a fascinating restoration project. The RAF Museum at Hendon has part of aa Halifax recovered from a Norwegian lake, but it is in much worse condition, and is being kept pretty much as found.

    That cannon looks more like 20mm. in the picture, and I know some (I think a minority) of those sent to the Soviet Union were so armed. I wonder if the wreck showed firm evidence that the wing machine-guns had been present, and removed? For some were supplied that way, and later the Russians, perhaps placing more trust in guns which didn't have to be synchronized for a specific distance, sometimes removed the wing guns. The food and ammunition suggest that aircraft might have been dispersed on small fields without ground transport, which would probably have made a lot of sense in that sort of war. Dying with his service records in order but his stew uneaten makes him seem pretty much like the rest of us.

    The tanks that mattered, by that time, had a lot more than an inch of armour where they were exposed to direct fire land weapons, most notably anti-tank guns and those of other tanks. But weight is an important constraint, and they are seldom anywhere near as heavily armoured on the horizontal surfaces. The Germans made out pretty well against armour with 20 and 37mm guns on specialized anti-armour Stukas.

  13. #73
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    How about the "wooden wonder". Two melins are better than one.
    Click image for larger version. 

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    when you ignore the fine print you get experience

  14. #74
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    "It makes me furious when I see the Mosquito. I turn green and yellow with envy. The British, who can afford aluminium better than we can, knock together a beautiful wooden aircraft that every piano factory over there is building, and they give it a speed which they have now increased yet again. What do you make of that? There is nothing the British do not have. They have the geniuses and we have the nincompoops. After the war is over I'm going to buy a British radio set - then at least I'll own something that has always worked."

    Hermann Goering

  15. #75
    Boolit Master

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    Love it.
    Just one of those designs that went very well.
    633 Squadren, good movie.
    Dad was armored corps he loved the Centurian with the melin engines, "mexican overdrive"
    Met a guy that served on PT boats "merlins were nice, Napiers were wild"
    Last edited by leebuilder; 03-07-2015 at 05:06 PM.
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    when you ignore the fine print you get experience

  16. #76
    Boolit Master GabbyM's Avatar
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    37mm cannon on the P39 didn't run through the drive shaft. It's barrel ran through the upper bearing in a gear box that dropped down to receive the drive shaft. Which ran right under the pilots seat. Plane also had 50 caliber synchronized guns above the cannon in the nose plus wing mounted .30 calibers. 50's, 30's and 37mm cannon. Awesome firepower the Russians loved for taking down German bombers. To this day Russia flies a 37mm gun on it's newest fighters.

    Allison engines ran much better than the Rolls Royce engines. Merlin's were simply larger displacement and were developed further. We and the Canadians already had RR Merlin's in production before the US entered WWII.

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  17. #77
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    37mm on top would take out most tank's engines. Saw several P39s in Russian aviation museums, plus a B25.
    If it was easy, anybody could do it.

  18. #78
    Boolit Grand Master Artful's Avatar
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    Airacorbra cannon the M4 used 37x145mmR
    same as used on USN PT boat (deck gun)
    the projectile weighs 1.34 lb (608 g) at prescribed muzzle velocity of 2,000 ft/s (610 m/s).


    Stuka Cannon was the BK37 and used much more powerful 37x263B mm

    Muzzle velocity: 1,170 to 780 m/s (3,836 to 2,557 ft/s)
    Projectile weight: (Tungsten hard core) APCR 380 g, HE 640 g, AT 685 g
    Last edited by Artful; 03-07-2015 at 06:04 PM.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
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  19. #79
    Boolit Grand Master Artful's Avatar
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    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

  20. #80
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    Last edited by Artful; 03-08-2015 at 10:31 AM.
    je suis charlie

    It is better to live one day as a LION than a dozen days as a Sheep.

    Thomas Jefferson Quotations:
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
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GC Gas Check