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  1. #1
    nitroairplane's Avatar
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    Converted cox .049 reedies-Killer crank really necessary?

    Hello, I have converted about 5 cox engines to run on diesel 2 pee wees and 3 bees, two of the bees had simple aluminium disks in the head so they were fixed compression one of the bees and both the pee wees had davis heads.
    I know pee wees do not need a HD shaft but in recent months I had thought the .049s did but then my memory was telling me that my first converted .049 didn't have a HD shaft so I decided to go out and test one so cut the Aluminium disk and went out to see if the engine would take it and as I thought it did.
    I know others have broken cranks in them but is there anyone else out there running them with stock cranks as diesel?
    BTW here is a video
    [youtube]http://www.youtube.com/watch?v=bnPZFsUz_uQ[/youtube]
    All replies appreciated.
    Thanks
    Indra
    A NOSE HEAVY PLANE FLIES BADLY A TAIL HEAVY PLANE FLIES ONCE!!!!
    http://www.youtube.com/user/nitroairplane?feature=mheehttp:

  2. #2

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Nitroplane glad yours is ok (so far hope it stays that way) but there is a history of the stock shafts braking even in glow use Davis has made these for decades
    and sure he would not have bothered if no need martin

    Note its a safe bet that many wound up in glow use since many more glows out there than diesel conversions

  3. #3

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Dear Friend;
    How Do You modify the COX 'engines,What thickness Do You use

  4. #4
    nitroairplane's Avatar
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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Buy a 6 pack
    Of your favourite canned beverage.
    Drink one.
     Then cut up the can, you want to make the disc out of the thickest part at the bottom of the can.
    Cut it to the inner diameter of the threaded portion of the cylinder then drop it in.
    Screw on the glowhead and give it a try!
    A NOSE HEAVY PLANE FLIES BADLY A TAIL HEAVY PLANE FLIES ONCE!!!!
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  5. #5

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Your running your engine very, very under compressed.
    Bob Davis, Owner - Davis Diesel Development

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Your running your engine very,very over compressed. Put a tack on it and it will be seen that your Rpm is very, very low. RPM should be at east 15,000 on a 6 X3
    Bob Davis, Owner - Davis Diesel Development

  7. #7
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    RE: Converted cox .049 reedies-Killer crank really necessary?

    I don't think that all of the crankshafts break. But enough did and that caused people to make better crankshafts for the engines. it is possible that maybe people were overcompressing the engines and or running too large of a prop or too small of a prop. So it is really hard to say for sure.
    So it depends on the luck of the draw so to speak. Now in looking at the heavy duty crank, I can see where it may be best to put one on the engine as the stock crank could let go on you.

    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
    AMA # 928076

  8. #8

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    We knew the crank was not strong enough back in 1975 so we made one for the read valve diesel convertinon kit.
    Bob Davis, Owner - Davis Diesel Development

  9. #9
    nitroairplane's Avatar
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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Wait what, sorry been away fro a while but do you mean I am running it over compressed or under compressed?
    If you are referring to the black stuff on the tank that is not burnt oil, it is what's left of the paint that someone put on the tank.
    It sounds like it's running slow?
    That's because it is, it is running a 7x4 APC prop and rich.
    Since the video was taken I have played with head shims and eventually settled with how it was in the video originally , one above and one below the disk so far I have put around 30 minutes of run time on it and checked inside and all looks good so far.
    By no means am I telling people not to buy Davis is Cox HD cranks as they are great and good for high rpm glow engines too, I am sure a smaller prop and the crank would break but what I wanted to see is if I could get it diesel, not run a small prop.
    May have to fly it soon
    A NOSE HEAVY PLANE FLIES BADLY A TAIL HEAVY PLANE FLIES ONCE!!!!
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  10. #10

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    RE: Converted cox .049 reedies-Killer crank really necessary?

    Its running over compressed and rich as you know that why when it runs out of fuel it dies rather then speed up first. Put a tack on it and you will be able to set it right, as for breaking cranks; at the power you are putting out that is not likely.
    Bob Davis, Owner - Davis Diesel Development


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