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Thread: os 55 ax


  1. #1

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    os 55 ax

    Have an OS 55ax, mounted on a profile.

    Always had issues with it cutting off after 2-3 mins of flying. It was run in as per instructions, fuel composition : 20 % Klotz, 10 % nitro, 70 % methyl alcohol.
    The issue was some what sorted out using the "F" plug. The engine would perform flawlessly for 10-15 flights, and the problem would re occur. Changing the plug would sort out the issue temporarily.
    The engine during flight cracked the connecting rod, though it was never run lean. The rod was changed, and the engine would run perfectly on the ground, but cut off in the air within a few minutes. The tank, and tubes are fine, no leak. The engine was run on the richer side.

    An on board glow was installed, and the engine performed perfectly, no more deadsticks !

    Was wondering if the Plugs are of poor quality or is it an engine issue. Have read on forums of several flyers having an issue with this engine. Is there another glow plug one can use ?

    I have an Irvine .53, later generation ( after OS took it over ) , that performs flawlessly , with a K&B plug !

    Would appreciate your inputs, if there are setting recommendations, which would obviate the need for an on board glow.

    Thanks

  2. #2

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    RE: os 55 ax

    I have two .55's and they both run very nicely. Can I ask what prop you are using? I'm wondering if you're putting on too light or too heavy a load. Your comment about breaking a connecting rod was curious. There shouldn't be any reason to have to run a OS "F" plug to cure a problem here.

    Has the engine evern been in a crash? I'm curious about any bent parts or dirt in the fuel line, scoring of the crankshaft or piston skirt, etc.

    Bob
    Club Saito #61 Cub Brotherhood #107
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  3. #3

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    RE: os 55 ax

    i found out that the muffler hose was not making a tight seal i would fly arond for 3-4 minutes and the engine would die when to a smaller tighter hose did the trick and o yea its a os -55

  4. #4
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    RE: os 55 ax

    If your engine was not reliable, and then would run reliably when you added on-board ignition, it is likely that you've been getting some kind of contamination or your carburetor was never well-set up. When an engine quits running after a few minutes, it usually means a lean condition. Engine vibration can agitate air into the fuel which will make the engine run lean. This will cause the engine to gradually overheat and quit. Profile models are more prone to this because there is little airframe to absorb the engine's vibrations. You also may need to examine your fuel. If the ingredients are contaminated, then the contaminants can cause the glow plug to fail very quickly. This problem can be masked by an on-board glow plug battery until the plug is just too damaged to continue to work.

    Breaking a connecting rod usually means that the engine is very heavily loaded. It should be allowed to run in excess of 11,000 RPM at full throttle on the ground. We like to prop it so that it's turning in the mid-12,000's. This is a very nice RPM range that allows the engine to develop good power and have good throttle handling. An 11 x 7 propeller or a 10 x 8 prop are good ones. For 3D flight, an APC 12.25 x 3.75 prop has been very successful.
    Bill Baxter, Manager Hobby Services/Futaba Service/North America
    3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
    Service Phone: 217 398-0007
    Email: hobbyservices@hobbico.com


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