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Thread: Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

  1. #1

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    Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

    Hi, this is my first post on supercub.org and I'm looking forward to becoming a regular contributor I'm an ex Jodel D112, Pitts S-1S and Andreasson BA4B owner, driver and maintainer and have approximately 60 hours in PA-18 Super Cub.

    I've diagnosed a slipping stabiliser trim system to a worn front crank handle pulley, by noticing it slipping when even slight additional pressure is applied by fingertips to the trim cable. I added some friction tape to the pulley which immediately cured the problem and then ordered the replacement pulley from Univair.

    I've added external access to the back of the pulley crank by a new inspection hole and slackened off the trim tension as much as I dare, by adjusting the rear horizontal tension adjusting bolt to the end of its travel

    I've looked at the 4 existing threads on this topic which have been useful, but I still have 2 removal/replacement questions please:

    I can see the locking pin in the (fiber) pulley as in the attached photograph. The pin doesn't SEEM to be ended, but gently tapping with a hammer and drift from the less exposed pin end produced no movement. From looking at the photograph last night, MAYBE the easier "ramp" in the pulley groove is at the least exposed end and maybe I should tap from the other, more exposed pin end? Is it necessary to "help" the pin coming out by further grinding the pin ramp? Is there a better way to remove than tapping? In short, what is the best way to get the pin out of a fiber pulley

    I suspect I may need to reduce cable tension further as part of the pulley replacement and am trying to decide which of the very tricky options is easiest/most recommended:

    Completely take the adjusting nut off the horizontal rear tension adjuster and then swear lots in trying to get it back on again
    Take off the split pin and castellated nut from the tensioning pulley axle, take out the axle and pulley and then swear lots in trying to put them back in again
    Take off the split pin and castellated nut from the pivot arm of the horizontal rear tension adjuster and then swear lots in trying to get it back on again
    OR!!!! Is there an easier way?!!!!!

    Thank you!!

    Philly
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    cruiser's Avatar
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    Increase that gentle tapping to a moderate tapping. Revamp that whole pin area with bushings, google on the bottom of the home page for a drawing with dimensions. Clean the old grease off the pulleys and cable. Hardest part is drilling the new hole in the new pin allowing for the change due to the new bronze bushings. My machinist friend drilled it for me, Jim
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    Quote Originally Posted by cruiser View Post
    Increase that gentle tapping to a moderate tapping. Revamp that whole pin area with bushings, google on the bottom of the home page for a drawing with dimensions. Clean the old grease off the pulleys and cable. Hardest part is drilling the new hole in the new pin allowing for the change due to the new bronze bushings. My machinist friend drilled it for me, Jim
    Thanks for this Cruiser I'm not really sure what I'm looking for with google on the bottom of the home page for a drawing with dimensions?
    I've looked at the supercub.org home page and couldn't really see any drawing links?

    I'm thinking I'll put a block under the crank mounting plates to help with the moderate tapping

    I've also pretty much decided to cut a small access hole to get to the horizontal tension adjusting bolt nut and take that route to reduce the tension, covering it with a small grommet, but I'm still open to suggestions

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    cruiser's Avatar
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    Somewhere on the site is a drawing for supporting that pin in oilite bushings. Drill out the bracket and move the hole in the pin the thickness of the head of the bushing basically. Really smooths things up. I cannot find it, maybe someone will come to our rescue
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    Steve Pierce's Avatar
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    Quote Originally Posted by Philly5G View Post
    Thanks for this Cruiser I'm not really sure what I'm looking for with google on the bottom of the home page for a drawing with dimensions?
    I've looked at the supercub.org home page and couldn't really see any drawing links?

    I'm thinking I'll put a block under the crank mounting plates to help with the moderate tapping

    I've also pretty much decided to cut a small access hole to get to the horizontal tension adjusting bolt nut and take that route to reduce the tension, covering it with a small grommet, but I'm still open to suggestions
    The block will help the pin come out. Here are a couple of threads including the one Jim is talking about dealing with the word trim shaft holes.

    http://www.supercub.org/forum/showth...ulley-location

    http://www.supercub.org/forum/showth...ve-trim-handle
    Steve Pierce

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    cruiser's Avatar
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    Thanks Steve, I could not find it
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    I think this is the thread with the Oilite bearings drawings guys? supercub.org/forum/showthread.php?49851-Trim-handle I had to drop the start of the URL, as the forum wouldn't let me post the URL otherwise?

    Looks like a really neat solution and I'm going to do this mod too
    Last edited by Philly5G; 06-22-2018 at 08:41 AM.
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    www.SkupTech.com mike mcs repair's Avatar
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    Never seen a fiber pulley for that use, usually aluminum. Save your self grief and just order double grove -18 pulleys and convert it to that style. You can make clamp in pulley mounts for the additional pulley


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    Steve Pierce's Avatar
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    Yet another trim handle thread. Here is the URL you posted. Gotta be here a while to post URLs. Spammers are a pita and that is why.
    supercub.org/forum/showthread.php?49851-Trim-handle
    Steve Pierce

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    Steve Pierce's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Never seen a fiber pulley for that use, usually aluminum. Save your self grief and just order double grove -18 pulleys and convert it to that style. You can make clamp in pulley mounts for the additional pulley


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    I have worked on a few original PA12s and J3s with the phenolic pulleys so I guess Piper originally used them.
    Steve Pierce

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    Quote Originally Posted by Steve Pierce View Post
    I have worked on a few original PA12s and J3s with the phenolic pulleys so I guess Piper originally used them.
    It could well be the original pulley Steve This is a very original PA12!! When you worked with these fiber pulleys, did the locking pin just tap out, as with the aluminium pulleys?

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    Quote Originally Posted by cruiser View Post
    Increase that gentle tapping to a moderate tapping. Revamp that whole pin area with bushings, google on the bottom of the home page for a drawing with dimensions. Clean the old grease off the pulleys and cable. Hardest part is drilling the new hole in the new pin allowing for the change due to the new bronze bushings. My machinist friend drilled it for me, Jim
    Moderate tapping worked like a charm Cruiser!!!! THANK YOU!!!

    Philly
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    Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

    Quote Originally Posted by Philly5G View Post
    I think this is the thread with the Oilite bearings drawings guys? supercub.org/forum/showthread.php?49851-Trim-handle I had to drop the start of the URL, as the forum wouldn't let me post the URL otherwise?

    Looks like a really neat solution and I'm going to do this mod too
    As I mentioned earlier in this thread, I’m going with the mod that Darrel Starr drew and posted, thanks Darrel!! All the components have now arrived and went together beautifully and I’ll be drilling out the holes for the Oilite bearings next week, but they certainly do a great job already and the new Clevis pin spins BEAUTIFULLY in them and the whole assembly looks FANTASTIC!!

    I’m planning on fitting the bearings with the flange on the inside of the steel brackets, so the tension of the brackets holds them in.

    Roll on next week and the fitting!!!





    Sent from my iPad using SuperCub.Org mobile appIMG_4447.JPGIMG_4448.JPGIMG_4449.JPG
    Last edited by Philly5G; 02-01-2019 at 08:13 PM.
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    Quote Originally Posted by cruiser View Post
    Increase that gentle tapping to a moderate tapping. Revamp that whole pin area with bushings, google on the bottom of the home page for a drawing with dimensions. Clean the old grease off the pulleys and cable. Hardest part is drilling the new hole in the new pin allowing for the change due to the new bronze bushings. My machinist friend drilled it for me, Jim
    Thanks again Cruiser, I’ve followed your advice 100%
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Philly5G View Post
    As I mentioned earlier in this thread, Iím going with the mod that Darrel Starr drew and posted, thanks Darrel!! All the components have now arrived and went together beautifully and Iíll be drilling out the holes for the Oilite bearings next week, but they certainly do a great job already and the new Clevis pin spins BEAUTIFULLY in them and the whole assembly looks FANTASTIC!!

    Iím planning on fitting the bearings with the flange on the inside of the steel brackets, so the tension of the brackets holds them in.

    Roll on next week and the fitting!!!





    Sent from my iPad using SuperCub.Org mobile appIMG_4447.JPGIMG_4448.JPGIMG_4449.JPG
    Will your cable safety wires be long enough to keep cable in pulley and not rub if you bend ears out to fit the bushings?


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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Will your cable safety wires be long enough to keep cable in pulley and not rub if you bend ears out to fit the bushings?


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    And you will need a washer on head. Now is that pin going to be long enough since you are adding stuf to it??


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    cruiser's Avatar
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    Quote Originally Posted by Philly5G View Post
    As I mentioned earlier in this thread, I’m going with the mod that Darrel Starr drew and posted, thanks Darrel!! All the components have now arrived and went together beautifully and I’ll be drilling out the holes for the Oilite bearings next week, but they certainly do a great job already and the new Clevis pin spins BEAUTIFULLY in them and the whole assembly looks FANTASTIC!!

    I’m planning on fitting the bearings with the flange on the inside of the steel brackets, so the tension of the brackets holds them in.

    Roll on next week and the fitting!!!





    Sent from my iPad using SuperCub.Org mobile appIMG_4447.JPGIMG_4448.JPGIMG_4449.JPG
    If you reverse both of those bushings on the pin and shorten the height to the width of the bracket you will not need a washer on the outside and you will make up some of the room that Mike inquires about, Jim
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    Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

    Quote Originally Posted by mike mcs repair View Post
    Will your cable safety wires be long enough to keep cable in pulley and not rub if you bend ears out to fit the bushings?


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    The additional width required over the measured gap between the mounting brackets with the flanges inside is just .043Ē and thereís barely any deflection on test fit.

    Which safety wires do you mean?


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    Last edited by Philly5G; 02-02-2019 at 04:24 AM.

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    Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

    Quote Originally Posted by mike mcs repair View Post
    And you will need a washer on head. Now is that pin going to be long enough since you are adding stuf to it??


    Sent from my iPhone using SuperCub.Org mobile app
    Good spot!! Iíve ordered 1 1/2 and 1 3/4 inch pins, the one in the pic is 1 1/2 and Iíll be testing for length in situ before deciding which one and drilling the pulley pin hole

    Do you mean a washer between the clevis pin head and the bearing?


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    Last edited by Philly5G; 02-02-2019 at 04:26 AM.
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    Quote Originally Posted by cruiser View Post
    If you reverse both of those bushings on the pin and shorten the height to the width of the bracket you will not need a washer on the outside and you will make up some of the room that Mike inquires about, Jim
    If I do this and this was one of my original questions to Darrel, the pulley will be dragging against the sides of the mounting brackets if the head end bearing shifts out from its friction fit and certainly on the non head end. The current fibre pulley shows witness marks on the non head end of rubbing


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    Newbie (but aircraft experienced) PA-12 Crank Handle Trim Pulley replacement questions

    All the hardware installed and working beautifully, with ZERO slip even when the trim cable is held and the handle tried to turn at the same amount of friction I use to recognise when the trim limit is reached!!! Really really happy with the form and function of this and the winding action is now beautifully smooth and uniform Fingers crossed the air test proves both in action!!

    IMG_4553.JPGIMG_4554.JPGIMG_4556.JPGIMG_4558.JPG

    The next question is that the trim indicator line is WAY up at the rear of the trim handle cutout (the position of the spring can be seen in the top of pic 3 above) and really has to be pulled down to fit in the stock trim indicator groove in the stock cover plate. I wonder if itís caught up somewhere, or is it always high?

    If itís supposed to be high, Iím considering making a new plate, extending the hole upwards and cutting the groove in line with the indicator wire. As always, all steers on this appreciated


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    Last edited by Philly5G; 02-09-2019 at 07:08 PM.

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