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Thread: Intermittent Electric Trim Actuator

  1. #1
    canelson's Avatar
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    Default Intermittent Electric Trim Actuator

    I have a Series 6 with Series 7 firewall forward Kitfox that has been flying for 2 years. I have been having trouble with the trim system where it intermittently stops working. I verified the switch is ok. A friend who is an RV builder found the following link that describes an issue with the electric flap actuator used on some RVs. It explains how grease from the actuator gear box gets into the motor housing and screws up the brush/commutator electrical connection. I took my actuator out and it is the same make as that shown in the RV document. I took it apart and found that grease was indeed in the motor housing and the commutator and brushes were coated with guck which I suspect is my problem. I have reassembled after cleaning and it works fine on the bench. Time will tell if I still have the intermittent problem but I don't think I will.

    Here is the link to the RV document:
    http://vansaircraft.com/pdf/flap_motor.pdf

    _______________
    Craig Nelson
    Eden Prairie, MN

  2. #2
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    Default Re: Intermittent Electric Trim Actuator

    Craig, I have a Series 5 with a rocker type switch for trim motor control. I have had a few times when trim ops becomes intermittent and have found that taking the switch apart and cleaning the contacts solves the problem. I have made it part of my condition inspection now. Bruce Lina N199CL

  3. #3
    canelson's Avatar
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    Default Re: Intermittent Electric Trim Actuator

    Thanks for the comment Bruce. I have the same rocker switch and realize that it has been the source of problems in some cases. I hooked up a temporary light harness that would light up if the switch was correctly outputing to the actuator, which it was. This lead me to look at the actuator itself.

    You have a good point on doing some PM on the switch to keep it functioning correctly especially with its failure history. Craig

  4. #4

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    Default Re: Intermittent Electric Trim Actuator

    canelson:

    I am a new subscriber to this forum and your thread caught my attention. I have a Series 6 that was completed in early 2002 and now has over 600 hours on the Hobbs. During that period I have replaced the trim rocker switch twice. The contacts detorate over a short period due to the continual actuation in cruise. I know that this problem be could be reduced if I had slowed the actuator speed with a series restistor. I have read where this has been done before. If anyone on the forum has done this successfully, I would like to know what restinance value they found most effective.

    I would also like to know the make and model of the actuator provided for the Series 6 without having to remove it. It sounds loud while operated with the engine not running. I'm trying to find out what is the normal running current, and if it requires periodic lubercation.

    John
    Warrenton, VA

  5. #5
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    Default Re: Intermittent Electric Trim Actuator

    Hi John, I suspect John King has joined us from what I can gather from your post. Welcome John haven't heard from you in awhile. Your expertise with all things Kitfox will be appreciated here. Now on to your question, I met an auto electrics guy at Sun n Fun years ago when I was building my Series 5 and he designed a 2 speed system for our trim setup and was kind enough to send me a wiring diagram. I incorporated the system into my airplane and have been very happy with its operation. I have a DPDT(double pole double throw) toggle switch mounted in the center console next to the trim rocker switch for Fast/SLow trim. I keep it in the fast position for pattern work and switch to slow for cruise operations. I find that my setup slows the trim down by about half. Full throw full up to full down in fast mode is about 7 or 8 seconds , and in slow about 13 or 14 seconds. Attached you will find all the information you need to install this setup. I used option "C" or the max retard option for mine. John, I would like to purchase another rocker switch to have in standby should mine ever crap out. Do you remember where you purchased yours and what the part number was for an exact duplicate of what we have? Thanks Bruce Lina N199CL
    Attached Images Attached Images

  6. #6

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    Default Re: Intermittent Electric Trim Actuator

    Airlina

    You got the name right. Thanks for the information on the trim speed control system. That ballast resistor has a resistance range of 1.2 to 5.0 ohms. I am still trying to find out what the make and model number is of the actuator arm in the Series 6.

    John

  7. #7
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    Default Re: Intermittent Electric Trim Actuator

    John, I would like to have a backup rocker switch in my parts inventory, do you recall where you got your replacement switches and if so what the part number for the switch was. Also I will see if I can find out about the actuator for you. Thanks Bruce

  8. #8

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    Default Re: Intermittent Electric Trim Actuator

    Bruce,

    I actually ordered two types of DPDT switches from Granger on the Internet: <http://www.granger.com>
    One was a Rocker for $21.89 and the other was a Toggle for $18.94 The Rocker is slightly smaller in length and width than the one provided by SkyStar. The Toggle uses a 1/2" mounting hole. They are both made by Hubbell Wiring Device-Kellems.

    Rocker = Granger #3JC10 and Toggle = Granger #3HZ95

    They are both rated at 15 amp inductive. I am not that impressed with with either of them, especially based on cost, and I think 15 amps is not suited for our application over the long haul. I just ordered a DPDT Rocker switch from Spruce A/C that is rated for 20 amps and at a cost of only $8.40. The Spruce P/N is 14-225. I will give that one a try. Note: all of the switches are spade terminal type, not terminal lugs.

    I am seriously thinking of designing a relay operating trim system in an effort to reduce the current flow through the switch contacts. My failure modes have been pitted switch contacts. The switch will only activate the relay coils. That combined with the speed control you suggested ought to be the most reliable speed selected electric trim system. Finding the proper 12 VDC relays will be the biggest problem. I would mount the relays and ballast resistor in a small metal box with a terminal board attached somewhere behing the instrument panel with easy access.
    Anyway, that's my current thinking.
    --
    John
    Warrenton, VA
    N993JK

  9. #9
    Administrator RandyL's Avatar
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    Default Re: Intermittent Electric Trim Actuator

    Good idea John, a relay sounds like a smart move and one that should extend rocker switch life given the constant use the trim actuator gets in a Kitfox (for trim rather than flaps as in an RV). Here is the relay board commonly used in RVs, seems like this would be perfect for our application.
    cat-med_flap-board.jpg

    $39.50 and available from Van's Aircraft .
    Randy Lervold
    TeamKitfox.com Admin Emeritus
    Day job: www.dynonavionics.com

  10. #10
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    Default Re: Intermittent Electric Trim Actuator

    John, here is a place to start for the trim actuator www.motionsystem.com. I suspect that ours is a model 85615/85616 however I am not positive about this. We will need someone who is still building to see if they can find a model number on their actuator as mine is buried in a completed airplane. Bruce Lina N199CL

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