Piaggio P.XII

Discussion in 'Engines' started by krieghund, Jul 15, 2010.

  1. krieghund

    krieghund Member

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    #1 krieghund, Jul 15, 2010
    Last edited: Jul 15, 2010
    I thought it was time to spice up the engine section it's been in the doldrums

    So first off is the page out of Wilkerson's "Aircraft Engines of the World" is the Piaggio P.XII which of course powers Italy's Fortress the P.108.

    Enjoy!!
     

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  2. vikingBerserker

    vikingBerserker Well-Known Member

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    Man, that's a big honkin engine!
     
  3. davebender

    davebender Well-Known Member

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    A nice looking aircraft. However I have read that the radial engines were unreliable. Maybe they should have just used 4 x Jumo211 engines.
     
  4. Shortround6

    Shortround6 Well-Known Member

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    Not without some serious reduction gears.

    It is torque that turns propellers and there is no way that a 35 liter engine is going to compete with a 53 liter engine on that score.

    may Krieghund will show us what is on the next page.:D
     
  5. krieghund

    krieghund Member

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    No problem that book is the 1941 edition and it is in the states in a safe til I'm home on vacation
     
  6. davebender

    davebender Well-Known Member

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    Most German bomber aircraft were powered by Jumo211 engines. Did they use reduction gears?
     
  7. Shortround6

    Shortround6 Well-Known Member

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    Yes they did. But you are going to need a bigger set of gears.

    Piaggo P.XII turned 2100rpm for take-off at 1500hp using 0.62 gears for 1302 propeller rpm.

    A 1500hp Jumo 211 was turning 2700rpm for take off. Most Jumo reduction gears were in the .68 range so they were swing a smaller prop.

    To turn the Italian prop at the speeds the Italians were planning on using the Jumo would need 2 to 1 reduction gears. Not impossible but getting into the why bother category.
    Not enough Jumos to go around to begin with and now you need to design and test new reduction gears (even if they will fit in the same case) before the Italians get their own engine figured out?
     
  8. davebender

    davebender Well-Known Member

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    - There were plenty of Jumo211 engines available by 1941.
    - The Jumo211 was reliable.
    - The Jumo211 was fuel efficient.
    - The Jumo211 was relatively inexpensive to mass produce.
    - The Jumo211 was more powerful then the P&W R-1830 engine which powered most U.S. 4 engine bombers. Therefore it should have been plenty powerful for the new Italian heavy bomber.

    http://orbat.com/site/sturmvogel/images/ussbs/figvii-7.jpg
    [​IMG]
     
  9. Shortround6

    Shortround6 Well-Known Member

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    Used for Ju-88s, Ju-87s and He 111s. Got more than enough of them for the invasion of Russia?
    No argument.
    Do you have the cost figures?
    Jumos need radiators and coolant systems, many later model Jumos used intercoolers, the only single stage supercharged engines to do so in WW II. The Jumos fuel injection system is more expensive than the carburetor on the Italian engine. While the radial used more cylinders it's individual parts were usually smaller than a V-12s.

    If by most you mean the B-24s you are correct. However I would note that the the B-24 used turbo superchargers, which while they did nothing for take off power did allow for a much higher cruise and combat power at altitudes where both the Italian engine and the Jumo would be running out of breath.

    There is also the question of take off distance. The Americans might have been blessed with longer runways for getting heavy aircraft into the air. All those bulldozers and other construction equipment that the US forces never seemed to travel without.
    ALL aspects of an aircrafts performance have to be considered.
     
  10. Alexfly

    Alexfly Member

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    I do not agree with your statement regarding engines not being reliable. The problem was that they were not powerful enough for the new aircrafts. Italy designed and produced many aricrafts prior to WWII all powered by Fiat, Alfa Romeo, Macchi or Piaggio engines. The good ones were built expressly for record planes and after that boom everything stopped. Germany could not supply enough engines and for this reason airplanes that on paper had optimum performances like the MC200 had a limited production with DB engines.
     
  11. davebender

    davebender Well-Known Member

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    How can that be when American B-17s and B-24s were powered by 1,200 P&W R-1830 engines?


    Regarding Jumo211 engine cost......
    1941 prices. per Olaf Groehlers GdLk
    131,175 marks. Ju-87B with engine.
    100,300 marks. Ju-87B without engine.
    ------------------------------------------------------
    30,875. Cost for Jumo211 engine.
    $12,350. Assumes 2.5 marks per American dollars.

    For comparison purposes.
    $25,000. Packard built RR Merlin engine.
    $19,000. Allison V-1710 engine.
    $11,188. DB601 engine (27,970 marks).

    WWII Germany clearly knew how to mass produce liquid cooled V12 aircraft engines at low cost.
     
  12. Shortround6

    Shortround6 Well-Known Member

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    OK, I'll bite, just which models of the B-17 were powered by P&W R-1830s and how many were there?

    You are still ignoring the turbos which allowed for more power from smaller engines at high altitudes and we don't know the take off requirements that were specified for each bomber.

    people are still arguing over the exchange rate of the Euro to the Dollar or the Chinese Yuen to the Dollar and if they are artificially high or low and by how much. trying to compare prices based solely on exchange rate is highly suspect.
    May be they should have had a few spies in the US.
    Price for Allison's dropped from $18,500 in 1941 to $14,000 in 1942 to $12,000 in 1943 to $9,500 in 1944 and $9,304 in 1945.
    Contract prices, to be fairly compared, need the number of engines contracted for, delivery times, special circumstances (government supplied machines, parts or materials) and what percentage of spare parts (if any) are included in the contract price.
     
  13. davebender

    davebender Well-Known Member

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    Bomber Accuracy in 1938.
    HyperWar: The Battle of Britain--A German Perspective
    30 meter target size. Ju-87B dive bomber. 25% chance for success.
    50 meter target size. Ju-88 dive bomber. 50% chance for success.
    100 meter target size. Horizontal bomber at 13,500ft. 2% chance for success.
    100 meter target size. Horizontal bomber at low level. 20 to 25% chance for success.

    I ignored turbos because I intend to hit the target. You cannot accomplish that from high altitude using iron bombs. Not even after introduction of the gyro stabilized Lotfernrohr 7C bomb sight during January 1941.
     
  14. Shortround6

    Shortround6 Well-Known Member

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    And this post has sod all to do with Piaggio engines or Piaggio 4 engine bombers does it.

    Unless you think the Piaggio 108 was going to dive bomb? :rolleyes:
     
  15. davebender

    davebender Well-Known Member

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    No way. The P.108 was too large for that mission.

    The P.108A carried out a series of trials at altitudes between 1,500 and 4,500 meters. That's about where a WWII era level bomber should be operating if you want to hit anything.
     
  16. Civettone

    Civettone Active Member

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    Why would you keep the Italian prop if you are going to use a Jumo?

    Kris
     
  17. engguy

    engguy Member

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    Yeah cheap labor, POW's.
     
  18. Shortround6

    Shortround6 Well-Known Member

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    The Italian prop may be bigger in diameter. Propellers have to be not only matched to the engine but to the speed range and operating altitude of the aircraft.

    High speed aircraft can use smaller diameter propellers than larger, slower moving aircraft. Large, heavy aircraft need their propellers to move a large quantity of air, but they need the propeller stream to be matched in velocity to the speed of the aircraft.

    While US fighters with 2000-2300hp P&W engines used propellers of around 13 feet in diameter, the Lockheed Constellation used 3 bladed propellers of over 16ft for it's 2000hp R-3350s and the B-29 used 16'7" 4 bladed props for it's 2200hp R-3350 engines.
    The larger, heavier airplanes may need bigger propellers for better take-off and climb performance even if they hurt top speed by a percentage point or two.

    While the Germans could certainly have built a propeller of their own and not used an Italian manufactured propeller the propeller would have to be a close match in performance to the original. as I said before, this might require using a different gear ratio on the Jumo engine.
     
  19. fastmongrel

    fastmongrel Well-Known Member

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    Unfortunately thats also the height where your going to die if your flying a big bomber over enemy territory. The age old accuracy versus acceptable losses.
     
  20. Civettone

    Civettone Active Member

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    I understand what you are saying Shortround but I don't think it matters much in this case. The Jumo 211 was used on German bombers which were similar enough to the P.108.


    Kris
     
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