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

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

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

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

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

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

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

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

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.
Attachment 237

$39.50 and available from Van's Aircraft .

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

Please do not contact Motion Systems. They want nothing to do with aircraft. Not unusal.

If there is a way we can help please let us know.

Good tip Randy on the Circuit Board.

Welcome aboard John.. Wondered how you and Chuck have been.

We also have rocker switches as well...

Ditto on not mentioning the word "aircraft" to Motion Systems -- they stopped supplying Van's Aircraft for that reason. I needed a specially configured actuator for my RV-3 and said it was for the "automatic trunk lift on my show car".

Motion Systems is the correct make and the website is listed in an earlier post. The model # of the unit in my Series 6 did not match anything that they have on their website. I thought I wrote the model number down when I had it out to clean it but I can't seem to find it. I'll keep looking. Craig

Bruce,

With the help of a mirror, a bright light and long arms I was able to read the part number of the motor on my trim actuator and the date 11-23-99. The name "Motion" was on the gear box. I called Motion Systems and described the unit. He said it was their actuator unit P/N 85615. I described to him the trim circuit in the Kitfox and what my problem was (failure of the trim switch due to arching of contacts). He stated the current in-rush when the contacts first close can initally exceed several amps causing arching and eventually weld the contacts together. The normal current flow in the 85615 model is less than 1 amp and varies with load.

I told him I wanted to add a series resistor to slow down the motor and relays to actuate the motor in lieu of the switch. I gave him the following current readings based on my tests in my Bird.

UP = 0.58 amp w/o resistor
DWN = 0.36 amp w/o resistor
UP = 0.54 amp with 8 ohm resistor
DWN = 0.32 amp with 8 ohm resistor

He stated that they were typical readings depending on load and that realays are the way to go for that application. I also asked about actuator luberication and he said that they use a perminate luberication that does not requird any periodic maintance.

I also called VAN's about their Flap Control Circuit board referenced by Randyl. They had no circuit drawings available, but felt that it could be used in the Kitfox trim sustem. I ordered one and will test it out combined with the 8 0hm ballast resistor.

BTW, the two DPDT switches I mentioned earlier and the one I ordered from Spruce A/C are all smaller than the hole available in the Kitfox center console. If the new circuit design with relays and the resistor works out, I just may use the same type make switch I had before. I should't be a problem any more due to the use of the relays.

I have developed a new circuit diagram for the use of the relays and speed resistor, and if the VAN's circuit board works out I will modify it accordinally and send in a copy.

John

John,

Great to hear from you. Chuck Tippett and I are still flying and doing great. Chuck has his commercial now and is also a Sport Pilot flight instructor. As you probably already read by now, I called Motion Systems
in an effort to help identify the trim actuator and ask about maintenance. They were very friendly and informative and did not hesitate in answering my questions. They did say that they no longer provide the actuators for aviation applications due to past libaility concerns.

If the circuit design I am working with on the Series 6 trim system does all I hope it will, I will provide you all the details. In that application I will probably use the same switch you provide. Good to hear your business is back on line. Let me know if I can help in any way, like showing prospective buyers what a Kitfox looks and feels like.

John

John, Excellent detective work on finding out about the actuator. Do us all a favor and keep photos and possibly a schematic of your work with the trim switching system that you come up with . Sounds like a mod that we all may be interested in retrofitting in to our airplanes. For those of you on the list who may be relatively new to the Kitfox aircraft. John King is one of the legends of the Kitfox line. He has built some beautiful Kitfoxes and has led some Kitfox expeditions to Alaska and Canada. So I would advise you all to listen up when John posts on this forum because he is a wealth of information for the rest of us. John , hope I didn't embarass you but I want this list to know that we are lucky to have you chime in from time to time. Bruce Lina N199CL

Bruce,

Just a little more information on that ballast resistor you mentioned. It is actually two seperate resistors encased in a ceramic housing with the resistor spade terminals sticking out of the bottom of the housing. One resistor is 2 ohms and the other is 6 ohms. By a combination of jumpers you can get a variation of resistances from less than 2 ohms to 8 ohms. I also found that the 8 ohm combination provided the slowest and best trim speed for my desires.

It is a very hefty resistor and can tolerate the current required to drive the actuator. It's size is 3 1/8" x 1 1/2" x 5/8" not including the spade terminals. It weights 3.0 ounces. It is sold through NAPA and manufactured by Echlin under P/N ICR24 and sells for $7.10 retail.

John
Warrenton, VA

I had the intermittent trim problem as well, and found it was gunk
on the commutator, and brushes. Cleaned it up, and has worked fine
since. I also bench ran the motor for a couple hours at full speed to
seat the brushes.

On the matter of trim speed, a better solution is to use a Pulse
Width Modulator circuit. That said, the ballast resistor solution is
simple, and most likely will work fine (as per Bruce's system).
The difference is that a pulse width modulator will reduce speed
while maintaining motor torque. A resistor will reduce torque, and
increase motor heat.

I found replacing the factory supplied Rocker switch with a better
switch was all I need to solve trim sensitivity problems. Since the
better quality switch allows a simple tap to adjust trim. So I've
never needed to slow down the motor. The grey black switch has
such strong springs it's hard to just tap in a minor adjustment.

Jeff

Jeff,
Do you have a supplier and p/n for the better quality switch? And does it fit in the same hole as the Kitfox supplied switch?

in fact here's a model railroad (yes that's what I said), controller
pre-made which would probably work just great. It claims 12VDC
at 30 amps continuous which should work fine.

http://www.bakatronics.com/shop/item.aspx?itemid=581

Regards,
Jeff

Sorry I don't. The switch I bought from either mouser, or digikey
it's an industrial rocker switch. It was close, but slightly smaller, so I made
an adapter plate for it, which I riveted to the console top using the
existing switch hole.

I'll look through my box of junk next time at the airport and see if I can
find the box with a part number.

Somebody mentioned using relays, which would be a better choice. Then
you could use a REALLY light touch switch to control it.

Almost positive the switch is a Carling Contura. It is repackaged by
Bluesea systems as a marine rocker. It's rated at 20A, looking
online it looks and specs identically to what I have so I'm just
about positive it is the one I have.

http://bluesea.com/category/4/productline/overview/147

The Part number's would be 8222 (Gray) or 8290 (Black)

They can be bought from a lot of marine suppliers

Another manufacturer of nice switch is Apem

Jeff

Bruce,

I finally received the Flap Control Circuit Board from Van's that Randyl recommended. I am impressed with it's small size, packaging and workmanship. I have attached a couple of pictures that are not of good quality, but will give you an idea as to it's size. I like the terminal block provided. The developer and manufacturer of the circuit card is "Advanced Control Systems" in Canby , Ohio.

Van's does not provide a schematic of what is on the circuit board, only how to connect it up. Based on analyzing the circuit lands on the card and going to the internet for the relay module design, I was able to establish the internal circuits. With that done, I generated a schematic diagram required to function in the Kitfox trim system, incorporating the speed control we discussed earlier. I will soon generate a parts list of everything required and where to purchase everything.Attachment 242

Attachment 243

My next step is to fabricate a prototype for test purposes and ensure that it functions as expected in the aircraft. Once satisfied, I will construct the final packaged configuration and hopefully forget about future trim problems. I forgot to load in the schematic diagram with the others, so I will provide it in the very next response to follow.
--
John
Warrenton, VA

John, Thanks for the photos and schematic, as I mentioned in an earlier post your knowledge and expertise is a welcome addition to this forum. Let us know how your test setup works . If you are successful I suspect many of us will be using your system. Bruce

Bruce & All,

The attached schematic drawing of the Trim Control Circuit I sent in the previous message had an error on it, so I deleted it from the Forum. The error in the drawing was that the up/down switch was placed in the hot side of the line to the relays. It should be in the return side of the relays. The attached drawing to this message shows the correct up/down switch configuration. The previous drawing configuration would not work with the Van's Flap Control Circuit board.

I have also included the parts list for the Trim Control Circuit.
--
John
Warrenton, VA

John,
I too am new to this forum, and like you I have a Series 6 serial no. S60007-032 (still working on it) that may have been purchased about the same time as yours. From my assy manual I have the notation that the label on the trim motor is:
Motion Systems Corp.
Eatontown, NJ

9234C120-R8
73833-011
12vdc
08-12-99
I bench tested this unit and noted: 30.6 ohms
This is Skystar P/N 61012.101 Trim Actuator as shown on page 25 of chapt. IV figure IV-11

Good to make contact with you, been quite awhile since I came down to look at your Kitfox just before you covered it.

I later was able to establish that the actuator was manufactured by Motion Systems and I called them. The other numbers are for the motor itself.

BTW, your serial number of S60007-032 indicates your Series 6 kit was manufactured in July of 2000 and is the 32nd kit for that year. My serial number indicates mine was manufactured in April 2000 and was the 26th kit for that same year. I strongly recommend that you change the design of your electric trim system, especially since yours is still in the build stage.
The current design is bound to fail in the feature. Mine failed twice for the same reasons.
--
John King
Warrenton, VA

To All,

I finally installed and flight tested the electric trim control circuit I developed that contained the Flap Control Board designed by Vans for the RV's. The new design also includes the speed control circuitry discussed earlier by others on the Forum. All of the circuitry except the two switches is mounted behind the instrument panel for easy access. There is actually no room in the center console due to all of the fuel lines, rudder cables, venturi lines, etc. This does require an eight wire harness to connect the console switches to the control circuitry behind the instrument panel.

I have attached two pictures of the switches mounted on the center console. The fast/slow switch is mounted to the left of the trim indicator. The new trim up/down rocker switch, which I obtained from John McBean of Kitfox Aircraft next to the flap handle, has a plastic insert because the switch dimensions are smaller than the existing mounting hole. John McBean also provided that. I prefer this switch because it requires a softer touch to operate. I have yet to install the labels for the switches. The slower speed position and the softer touch rocker switch is real nice for making slight trim settings in cruise.

You may notice the access door I made in the side of the center console for easy inspection of the console interior and access to the trim switches. It is a lot easier than having to remove the side covers of the center console.

Sorry to bump this 13 year old thread but thought I would post because its still an issue. I have a Series 6 and had this intermittent trim problem at around 90 hours flight time. This thread mentions two causes of the intermittent trim problem: 1) gunk in trim motor's commutator and brushes and 2) arcing in the switch.


First a warning. Although others seem to have successfully taken the trim motor apart, cleaned it, and put it back together, it's not for the faint of heart. As careful as I was during disassembly, four washers fell out leaving me scratching my head as to the proper order and I didn't want to guess. Other problem is that getting the brushes back properly is very difficult. My suggestion is to do what I did and just order another trim motor assembly from John McBean.


In my case, the problem turned out to be arcing in the switch (see photos). I was initially fooled into thinking the switch was fine because when I removed the connector to the trim motor and measured the voltages there I got +12V with down trim activated and -12V with up trim activated. The issue though was that because of the worn contacts, the resistance was too high. Replaced the switch, and all worked fine.


Since this problem has not been reported since 2008, my guess is that only the Skystar kits that had the old arc-prone trim switch. The new rocker switch from John McBean is different.

Attached are photos of the affected Skystar switch, the messed up contacts, the delicate brush assembly of the trim motor, and the washer assortment that fell out when I opened the motor up :)
Attachment 28280Attachment 28281Attachment 28282Attachment 28283

Thanks Dan for the update on this issue. Hope your info will save others down time and some money also.

Quote:

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Originally Posted by DesertFox4

Thanks Dan for the update on this issue. Hope your info will save others down time and some money also.

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No problem. Wanted to add that if people are willing to tolerate a momentary contact toggle switch rather than the more convenient rocker switch, you can get a mil spec switch with the same wiring. The Aircraft Spruce part number is MS35059-27

dan

Giving this another bump and another update for those with the Skystar grey colored trim switch. I went flying two days ago and the electric trim only worked one way. No biggie, drop the flaps to 1/2 and the plane was trimmed nicely. Landed and back at the hanger things worked again. I had bought a new switch and bezel from Kitfox a few months back and swapped the old for the new. Afterwards I disassembled the old switch and found a bunch of debris in the housing and a bit of arcing. My advice to anybody running the old type, gray colored switch is to swap in a new switch of your choice.

Attachment 29507

Quote:

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Originally Posted by airlina

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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Update on this for anyone looking for the company making this actuator, it appears it has changed names: https://www.actuator.com/products/

Turns out the rod end they supplied is not the best quality and is very sticky so I was looking for a replacement on aircraftspruce but neither HM nor Aurora has a part as compact as what is supplied. The closest match is the GMM-4M-470 AURORA BEARING but its likely I will just have to use the sticky ball end unless I want to replace the whole actuator.

Is there some form of slippage or clutch to allow the motor to continue to spin when the actuator hits either limit? Reason I ask is I don't use the trim indicator. I just turn around and when the horizontal stops moving I release the button.

The ball screw just freewheels at each end of the range of motion, there is no clutch. When the actuator hits the end of its range of motion it simply stops extending/retracting while the motor keeps spinning at the same RPM.

Quote:

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Originally Posted by canelson

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

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Congratulations on disassembling your actuator and getting it back together, I ended up having to buy another. Just a warning, my problem turned out to be the rocker switch despite the fact that it appeared to be OK when checking with a voltmeter. The voltmeter read +12V with the actuator disconnected but the when the actuator was connected, the voltage was zero - this is because the bad rocker switch had very high resistance. I ended up replacing my rocker with a good old mil spec toggle switch and it has been working fine ever since.

I also have a series 6 with 7 FWF that has been flying for two years :)

Quote:

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Originally Posted by Birddog

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

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Hi John,

I also have a series 6 and my rocker switch failed after 90 hours of operation. I simply replaced it with the much more robust MIL spec switch from aircraft spruce. I now have 400 hours and have had no troubles since I put in the MIL spec switch. Its a SPDT momentary contact toggle switch, wired the same way as the rocker switch. The order number from aircraft spruce is MS35059-27.