Jumo 222 firing order question

Discussion in 'Engines' started by Piper106, Jan 19, 2010.

  1. Piper106

    Piper106 Member

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    Can anyone post or give a link that would have information on the crankshaft arrangement (angle between throws) and the cylinder firing order for the Jumo 222 engine??

    Did more than one cylinder fire at the same time??

    I am having a hard time figuring a firing order that does doesn't have two adjacent cylinders firing at one point in the sequence. Also trying to figure how the engineers could get the ideal 30 degrees of crankshaft rotation between firing impulses for this arrangement (6 banks x 4 row) of cylinders.

    Piper106
     
  2. jerryw

    jerryw Member

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    There was a very detailed article on the 222 published in VOL 6 No 3 of "Torque Meter", the journal of the AEHS. It was based on a report on the engine by the US AirForce done just after WW2.

    Back issues of "Torque Meter" are available from the AEHS via the website AEHS Home
     
  3. Piper106

    Piper106 Member

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    #3 Piper106, Jan 30, 2010
    Last edited: Jan 30, 2010
    Picked up V.6, N.3 of the "Torque Meter". I would recommend this excellent article to anyone interested in the Jumo 222.

    To answer my questions in my first post;
    When the crankshaft is described it is noted; "...throws #1 and #4 were 150 degrees from throws #2 and #3."
    A photo shows crank throws #1 and #4 are 'down' and throws #2 and #3 are both 'up'.

    Continuing;
    The six cylinder banks are numbered 1 to 6 counterclockwise (when viewed from the accessory end) with bank 1 being at 3 o'clock. The cylinders in each bank are numbered 1 to 4 , with the #1 cylinder at the propeller end of the engine.

    The firing order is given in the article as;
    " Two cylinders fired simultaneously" 2B1 (bank 2 cylinder 1) 5B2 (bank 5 cylinder 2), 1B1 4B2, 6B4 3B3, 2B3 5B4, 1B2 4B1, 6B2 3B1, 2B4 5B3, 1B4 4B3, 6B1 3B2, 2B2 5B1, 1B3 4B4, and 6B3 3B4.

    But... either the crank shaft description is wrong, or the notation 'two cylinder fired simultaneously' is wrong.

    A crankshaft with the end throws 150 degs from the center throws would not have 2B1 5B2 then 1B1 4B2, etc. firing at the same time. To have 2B1 5B2 firing simultaneously would imply a 'flat' crank with all throws 180 degees apart. A crank with the end throws at 150 degrees would fire one cylinder every 30 degrees of crankshaft rotation with a firing order of 2B1, 5B2, 1B1, 4B2, etc.

    Not having the original Wright Field report on the Jumo 222 I cannot be certain whether this 'error' was in the original report or came about during transcription into in the Torque Meter article.

    There is a photo reproduced in the article that shows an end view of the crankshaft and it appears that it is a 'flat' crank (180 deg throws), but due to the angle at which the photo was taken, it is less than 100% conclusive as to the crank arrangement.

    My opinion is that is that it is a 180 degree flat crank, and two cylinders fire simultaneously every 60 degrees of crankshaft rotaton, but if anyone can clarify this apparent error, that information would be apprectiated.

    Piper106
     
  4. jerryw

    jerryw Member

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    Piper,

    You are quite right re the shape of the crankshaft. In the next issue of "Torque Meter" (Vol 6 No 4) which I still have, a Mr Taylor points out in a letter to the editor that for paired firing, the crankshaft must have its throws at 180 deg.

    The author admits the error and publishes another pic showing a flat crank.

    Cheers, J.
     
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