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Thread: Double groove trim on PA-12 -front pulley location

  1. #1

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    Double groove trim on PA-12 -front pulley location

    We located the front idler pulley on the diagonal fuselage tube just like on a PA-18. At that location it is not in line with the front drive pulley. It looks like the PA-12 tube angles inward where the PA-18 tube is straight up and down.
    There is room to move the idler pully outward to align. Maybe some type of bracket.
    What is the best way to do this?
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  2. #2

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    I had that same problem with my 12 and had to move it outboard as much as I could but it still didn`t line up perfectly but it isn`t as bad as yours looks

  3. #3
    Darrel Starr's Avatar
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    Keep in mind that the idler pulley must be angled with respect to the crank pulley to avoid having the endless cable rub on itself.
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  4. #4

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    That's what I had to work on I have about 1/2 clearance between them. Mine looks almost exactly like yours
    Quote Originally Posted by Darrel Starr View Post
    Keep in mind that the idler pulley must be angled with respect to the crank pulley to avoid having the endless cable rub on itself.
    Click image for larger version. 

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  5. #5

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    I moved the pulley out until the cables rubbed then backed off a little. It only needed to move out about 1/4" or 3/8". looks like the cage can still weld direct to the fuselage tube without a bracket.
    Thanks for the help.
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    skywagon8a's Avatar
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    Notice that the cable is rubbing on the side of the groove on the inboard pulley. This could cause excessive wear on both the pulley and cable. Try moving the idler pulley some more. The idler axle does not want to be parallel to the crank axle. Not sure that I said this right. Look very closely at Darrel's picture.
    N1PA

  7. #7
    Darrel Starr's Avatar
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    Frogdad, looks like you installed Oilite bearing at the crank - that too is an important change. Good job.

  8. #8
    www.SkupTech.com mike mcs repair's Avatar
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    this is a job for a pulley positioning tool!!

    I forgot about that...

    just bend up some 1/16" welding rod around the pulleys


  9. #9

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    Mine has a bronze bushing on one side where can I get the oilite bushings for both sides? thanks

  10. #10
    Darrel Starr's Avatar
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    The Oilite bearing number is F520-15 and they are for sale at Aircraft Spruce under that number:
    http://www.aircraftspruce.com/catalo...lickkey=129209
    The Oilite Bearings are green in the following drawing. Missing from the drawing are two AN960C816 washers in the gaps between the bearings and the frame brackets on either side of the pulley.

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  11. #11

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    got em on the way thanks

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Darrel Starr View Post
    The Oilite bearing number is ....
    bah!!!
    unneeded over engineered optimization....

    hell, throw some 6" tapered roller bearing in there just because!!

  13. #13
    Darrel Starr's Avatar
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    Mike, what do you do when the holes in the pulley brackets wallow out?

  14. #14

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    Mine had worn a groove in the clevis in so the bushings will help me. I was going to turn one on the lathe but I can buy one easier

  15. #15
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Darrel Starr View Post
    Mike, what do you do when the holes in the pulley brackets wallow out?
    they don't...
    and you ALWAYS replace the pin/shaft at rebuild, just like all the rest of the CAD plated hardware that doesn't get reused.

  16. #16
    Darrel Starr's Avatar
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    Guess things in Anchorage are a world apart because the steel pulley brackets running against a steel shaft wear out fast in Minnesota. You are lucky to live in a non-wearout state.

  17. #17
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Darrel Starr View Post
    Guess things in Anchorage are a world apart because the steel pulley brackets running against a steel shaft wear out fast in Minnesota. You are lucky to live in a non-wearout state.
    not gonna get in a pissing match with an over-engineer on a 1930's design....

    so you magically fix that end of the steel on steel problem, and did ya fix the other end??

    I go by what wears out by inspection on disassembly, to judge what needs attention.. and THAT DOES NOT warrant consideration anymore

    I'm done......

  18. #18
    Darrel Starr's Avatar
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    Good!

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    I'm not sure what I can add to this conversation but I will second the oilite bushing. I installed new clevis pin and new stand off brackets for the main crank pulley. Mine were COMPLETELY wallowed out, in a real bad way. I initially installed the new clevis pin with lube on it. It was soo hard to turn with it being steel on steel. I took it all apart and installed the oilite bushing as in Darrel's diagram. My crank mechanism is now like butter. I think it's a must for all cubs. I haven't flown the plane yet but I do not anticipate and problems once airborne.

  20. #20
    Darrel Starr's Avatar
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    Thanks Kevin, Your experience mirrors mine and several other SCs here at KANE. Two owners had a round inspection ring installed in the fabric next to the crank pulley so they could CAREFULLY move the pulley keeping the endless cable from slipping out of sight so they could then make the modification. Worked well in both cases. These were "new" SCs built up with new Airframes Inc. fuselages (when Lee Bode was still making them) but the brackets started to wear within the first 100 hrs making the crank hard to turn.

  21. #21
    Gordon Misch's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    they don't...
    and you ALWAYS replace the pin/shaft at rebuild, just like all the rest of the CAD plated hardware that doesn't get reused.
    Dang, so only the shaft wears!? Suuuure. So how come I had plenty of bores to re-machine and re-fit in my machine shop? Oh, musta been all that Minnesota machinery that showed up in Alaska at that time. C'mon, Mike - you aren't the only experienced person around - - -
    Gordon

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    Wow yall sure get peevish over a bushing

  23. #23
    Steve Pierce's Avatar
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    Quote Originally Posted by Darrel Starr View Post
    Thanks Kevin, Your experience mirrors mine and several other SCs here at KANE. Two owners had a round inspection ring installed in the fabric next to the crank pulley so they could CAREFULLY move the pulley keeping the endless cable from slipping out of sight so they could then make the modification. Worked well in both cases. These were "new" SCs built up with new Airframes Inc. fuselages (when Lee Bode was still making them) but the brackets started to wear within the first 100 hrs making the crank hard to turn.
    The early Airframes fuselage I have seen wore prematurely. Have seen the same thing on Piper fuselage but took way, way more hours. I fix at rebuild and should last till the next one.
    Steve Pierce

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    Will Rogers

  24. #24
    Darrel Starr's Avatar
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    Steve, sounds right. My original Piper fuselage had wallowed out brackets too but with about 3600 hrs. - assuming the brackets were original.

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