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dan
PostPosted: Wed May 23, 2012 8:07 pm 
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Lee is correct, control can be maintained at either extreme. I do have the trim cable, in the center of the verneer knob there is a lock button just like a throttle verneer. You can push this bottom in and work the trim from full aft,to full forward, in a split second. The plane remains very controllable at both extremes. I don't have to look at the knob to know where the trim is, my left fore finger gauges the take off trim no viewing needed. Dan


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SHIPCHIEF
PostPosted: Fri May 25, 2012 12:54 pm 
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While reading N883FF logs and other papers, I found an entry that states the trim motor is a Volvo windshield wiper motor.
Was this a common application in "the day"? this plane was built from 1970 to 1985.
I also have trim position indicator that consists of 3 lights. The wiring diagram is in the aircraft manual. The lights are mounted on the lower left sub-panel near the headphone jacks. I'm thinking they use the microswitches that control the limits of trim?


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Fraser MacPhee
PostPosted: Fri May 25, 2012 1:47 pm 
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N926WM has a little copper U-bracket with a positive wire connected to it that acts as a basic limit switch (well, more like an indicator) for both up and down lighting up on the panel. It's a twelve count full throw on the jack screw. Bin dare since first flight at N633PM in 1971. Its so simple, that if it ever craps out, I'll put a trunk monkey in the back with an LED flashlight, two soup cans and a string to tell me trim position.


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Rich Brazell
PostPosted: Fri May 25, 2012 6:14 pm 
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I like the idea of the Trunk Monkey !


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dan
PostPosted: Fri May 25, 2012 7:06 pm 
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Trunk Monkey, that's too complicated for me, but your system sounds simple Fraser, and I like simple.....Dan


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Rich Brazell
PostPosted: Fri May 25, 2012 9:59 pm 
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Trunk monkey is the Son Fraser never had.


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SHIPCHIEF
PostPosted: Fri Jul 06, 2012 10:10 am 
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Well, I don't have a trunk monkey, but I do have a tire iron.
Marilyn had a trim failure while on her third lesson, the roll pin broke at the motor end of the driveshaft.
They didn't get good indication on position, as the micro switches started acting up, so they drove it to full up and held it
hoping an indicator light would come on. ??? They had an interesting flight back to the home drome.
So I fixed that and got to know this system better.
The micro switches are for indication only on N883FF, they are not limit switches.
So I cleaned and fiddled with it until I realized that it's old and needs a refurb.
I got a NOS 1979 Mercruiser trim indicator and B-63115A13 sender from epay for $39. It arrived UPS last night (along with a Firgelli PQ12-100-p actuator, but that's for the aileron trim thread)
I've bench tested it and I'm making the hardware now.


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SHIPCHIEF
PostPosted: Sat Jul 07, 2012 9:12 pm 
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Stuart G asked me to elaborate on my trim indicator experiment, so you guys are in for it now!!
Here is a pic of back of the hardware.
I see the printing on the paperwork isn't very legible. The "b" lead on the sender is the ground. (black wire)
The "c" lead goes to the S terminal on the meter.
12V goes to the "I" terminal on the meter. The Meter ground is either stud on the case that holds the mounting bracket.
The part number is confusing; this is a sender made for use on single or dual pilot station vessels.
Any sender for Mercruiser alpha II and Bravo outdrives will work, in fact, many brands use the 10 to 167 Ohm (down to up) sender. This is one of many that could work.
This link has general instructions on trim indicators and a chart showing the sender resistance standards for different manufacturers:
http://www.volkhart.net/Boot/PDF/Trimm.pdf


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Last edited by SHIPCHIEF on Sat Jul 07, 2012 9:47 pm, edited 1 time in total.
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SHIPCHIEF
PostPosted: Sat Jul 07, 2012 9:25 pm 
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Here is a pick of the other side:
Faria is a maker of replacement gauges, which are priced very reasonably, Google "Mercruiser trim gauge" and you can see many styles.
I like the ones with meter movement similar to the one I have, with down and up deflection to remove doubt when reading the meter.
Knowing that the sender is a 10 Ohm to 167 Ohm pot with 1/4 turn, a generic pot of 500 to 1K Ohm could be used and the geometry of the arms made accordingly.


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Last edited by SHIPCHIEF on Sat Jul 07, 2012 9:54 pm, edited 2 times in total.
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SHIPCHIEF
PostPosted: Sat Jul 07, 2012 9:31 pm 
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A 1/2" box end wrench fits the 6 point sender shaft, but a little loose, so I made this to translate the trim shaft motion. (hand saw and file...CNC Billet it's not)
It's shaped to hold down a clear plastic gasket that keeps the wires in the grooves.
The arrow on the "wrench" is pointed to the reference mark on the sender shaft. Naturally I made one with the arm pointed straight out from the reference point. At full deflection, the arm covered a mounting hole. Bummer.


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SHIPCHIEF
PostPosted: Sat Jul 07, 2012 9:37 pm 
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Powered up and tested:


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stug
PostPosted: Tue Mar 12, 2013 4:56 pm 
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I have just been looking at the trim mechanism using the traxis drive shaft.
It seems to be a good solution. I am curious to know what others think is needed to reach an adequate safety standard for securing the universal joints to the drive shafts. Each universal appears to be of plastic and is secured onto the shaft with a pin which is threaded on one end and is approximately 3/32" diameter. The universal itself is made of metal and has a similar size shaft which is kept in place with a cir clip at each end.
These things take a pounding when in model race cars but is this setup adequate as is in an aviation setting or does it need more?
I would anticipate using loctite on the threads and was planning to test one of the plastic universals to determine it's maximum torque capability but possibly the greatest risk is from vibration loosening the circlips.

Any thoughts?


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Stug
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Hagle347
PostPosted: Fri May 17, 2013 4:30 pm 
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Hey Lee, a bunch of corrupt photos in this thread as well...

Terry


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Ryan Allen
PostPosted: Mon Dec 12, 2016 8:17 pm 
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Just to follow up on this old but outstanding thread......when installing this motor, make sure you have the Grainger gear motor oriented in the proper position. The shaft is off center on the gear motor housing, and upon installation, the shaft should be closest to the top skin (see Bill's photo on page one of this thread). If you install the gear motor in a different orientation, the Traxxis trim shaft (in black in Bill's photo) will hit the (tubular) horizontal tail spar when the control stick is in full up (back/aft) position. I just realized this the hard way!


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