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Thread: Trim Assembly Overhaul Time

  1. #1
    JDWilliams's Avatar
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    Trim Assembly Overhaul Time

    Looks like itís time to rebuild the entire jack screw assembly on my PA12-150. Any recommendations on who to send it to for the work?

    (I would have searched the topic before asking but the search function is locked up on me for some reason.)

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
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    depends on if you have ORIGINAL -12 trim system (one groove pullies) or updated dual groove -18 style pullies & cable....

  3. #3
    Colorguns's Avatar
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    I replaced both pullies front and gear original style and that fixed my trim issues. Groove was worn out to the bottom of both.

    Doug
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  4. #4
    TurboBeaver's Avatar
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    98% of the time a single cable trim is slipping , its the pulleys . One or both has its V grooves worn down to the bottom .......... They are now U grooved and will slip constantly. Getting lubrication onto the trim pulleys will certainly spoil your system as well. As Doug suggests; two new pulleys and a clean cable with proper tension does wonders for any "single groove system. Steve Pierces cleaver mod to the "idler tightner" of adding an extra pulley into the original tightner sheath, allows it to pull on BOTH sides of the wire equally, instead of just pulling one side over till its touching itself, so something in the order of doubling the effectiveness of the tensioner.
    The double wire trim system is THE final answer no doubt , and should be done at recover. However a cleaned up single wire, riding high in new V grove pulleys that is correctly tensioned can work for years if properly maintained. Dont forget if the rear thru bushing on your stabilizer has corrosion in it binding the system up, a double pulley will slip as well???
    MMS Mike has converted some over from single/ double with the fabric on
    the plane, and knows all the tricks of the trade. However I would imagine if a mechanic has never done one before; you could easily double the labor bill; over a mechanic that already knows how its done........

    I ferryed a Cub a few years back that was less than 10 hours out of an expensive inspection by a big shop in Maryland. Here is what I found wrong with it the moment I pushed it out.
    Primer would not pull in fuel and leaked when full extended.
    Brake diaphragms both soft so almost no brakes even though fluid was full.
    Tailwheel totally out of adjustment and basically NON functional.
    Tach slipping constantly, Airspeed reading 140 on initial climb out.
    T&B laying over on a dogbox. Ampmeter snaping from charging 30 to discharging 30 constantly just like a wiper blade. Oil preasure below the yellow arc? Carb heat didnt work at all,
    Up to altitude and leveled off, tryed to trim it out......... No luck. Had to hold forward against the tail for next 3 hours. Airspeed reading 60/65 , gps reading 105. '1hr out' both guages showed only 1/4 tanks...... 2hrs out it showed totally nothing? It was quite an interesting flight to say the least.
    Landing it for the 1st time in a 10kt direct crosswind with no brakes and tailwheel basically unhooked, because the connector springs were compleately wrong for that airplane. Was a refreshing reminder of the tap dance and double shuffle of the rudder pedals to their extreame limits.
    Other than that stuff, it flew like a dream!
    2 weeks later into a " real inspection"
    Everything had been repaired or replaced. Both pullys on the trim were totally worn out, had to be replaced.
    The shop in Maryland had entered two pages of total BS in the books and had done really nothing except charge the customer $3k for an oil change and alot of fancy looking BS in a log book.....................
    Good luck with your new double trim system, they work exactly like the single pulley does when they are both set up correctly, but twice as good as a single pulley that is slipping!!! Lol.
    E


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  5. #5
    cubdriver2's Avatar
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    Cheap trick that works, rub some of this on the cable



    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  6. #6
    skywagon8a's Avatar
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    Quote Originally Posted by TurboBeaver View Post
    I ferryed a Cub a few years back that was less than 10 hours out of an expensive inspection by a big shop in Maryland. Here is what I found wrong with it the moment I pushed it out............................................... ...................."
    The shop in Maryland had entered two pages of total BS in the books and had done really nothing except charge the customer $3k for an oil change and alot of fancy looking BS in a log book.....................
    Good luck with your new double trim system, they work exactly like the single pulley does when they are both set up correctly, but twice as good as a single pulley that is slipping!!! Lol.
    E
    That reminds me of a Taylorcraft 15 that I flew home after a rebuild and annual for a new owner. I hope that the owner of "your" Cub reported that annual to the FAA. We did on ours, the FAA was grateful as they had been after that IA for years. The IA lost his ticket. The aviation industry is dangerous enough without having this type of maintenance.

    Edit: ps, That IA was an airline mechanic who did annuals out of the trunk of his car for some side cash.
    pps: Just remembered his last name. Crook. How very appropriate.
    Last edited by skywagon8a; 11-09-2019 at 06:29 PM.
    N1PA
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  7. #7
    JDWilliams's Avatar
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    Thanks for the great info. Decided to replace with the Dakota Cub assembly. Itís dual pulley already with the PA18 setup.


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