variable trim speed control

[scottmillhouse]

This is only for the RV-12 ULS and my question does not involve autopilot trim control but is for hand flying. My trim is too coarse for cruise speeds. I can hunt up and down and can rarely trim for hands off. What I want is full trim authority at slow speed and a finer control for at speed. I thought it could be set through the Dynon but I don't see the capability. Searches show the use of the Ray Allen spd-1 controller ( https://www.aircraftspruce.com/cata....php?msockid=28faea7d2c3e61a61444fafa2d12601f ) and installing a switch to allow full and slow speed. Anyone else have an easier or better solution?

 

[ryane67]

if you are OK with manual control, you could use / build a variable voltage output circuit / dimmer, these trim motors will run slower on less voltage and faster on more. Of course the difficulty becomes you have to manually change it for your current flight conditions to be effective.

 

[j4cbo]

This is only for the RV-12 ULS and my question does not involve autopilot trim control [...] What I want is full trim authority at slow speed and a finer control for at speed. I thought it could be set through the Dynon but I don't see the capability.

Those are different features but they're implemented the same way - by routing the trim control through the SV-AP-PANEL. If the trim is wired that way, two things are enabled: the Dynon autopilot logic can control the trim, and the Dynon system can adjust the trim speed according to airspeed. The setup info starts on page 18-7 of the SkyView installation manual.

 

[rtlongdon]

I built a trim wheel based on a rotary encoder. It works like a traditional trim wheel with regards to pilot operation.

 

[Jamesey]

If it’s a legacy model slow it down through the box where everything is plugged in under the panel lhs. Adjusting screw on this box. Read the earlier installation instructions. I adjusted mine to the slowest setting. Had no issues.

 

[scottmillhouse]

Those are different features but they're implemented the same way - by routing the trim control through the SV-AP-PANEL. If the trim is wired that way, two things are enabled: the Dynon autopilot logic can control the trim, and the Dynon system can adjust the trim speed according to airspeed. The setup info starts on page 18-7 of the SkyView installation manual.

I know that setup applies to typical Dynon bus wiring but I don't believe the 12 is wired that way. Everything is routed through a RV-12 specific control box rather than a network connection hub. With the typical installation as I wired in my 7 I could set a slower rate above 100 knots.

 

[Piper J3]

I converted to Ray Allen 2-speed trim controller back in 2017. Works beautifully. See....https://vansairforce.net/threads/modifications-that-you-have-made-to-your-rv-12-after-certification-e-lsa-only.64145/post-1202259
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[j4cbo]

I know that setup applies to typical Dynon bus wiring but I don't believe the 12 is wired that way. Everything is routed through a RV-12 specific control box rather than a network connection hub. With the typical installation as I wired in my 7 I could set a slower rate above 100 knots.

The 12 with Skyview is wired that way as well, if the Dynon autopilot panel was installed according to the plans - see the schematic (with connections to pins 3, 4, 7, and 8 on the autopilot panel) and KAI section 58. The pitch trim wires are removed from the switch module harness in step 4 of page 58-04 and new wires are added in step 3 of page 58-05 to take the trim switch signals directly to the Dynon autopilot panel. The trim control output from the autopilot panel then goes through the AV-50000A box to the fuselage harness.

Or do you have the older D-180 avionics? If so you might be out of luck

 

[scottmillhouse]

If it’s a legacy model slow it down through the box where everything is plugged in under the panel lhs. Adjusting screw on this box. Read the earlier installation instructions. I adjusted mine to the slowest setting. Had no issues.

According to the PAP from Vans: "Actuate “NOSE DOWN” side of trim switch and use a stopwatch to determine how long it takes the motor to run full travel. Run time for trim motor between 25 and 30 seconds. " How did slowest setting effect the specified time? Mine was right in the middle at 28 seconds.

 

[flightdoc101]

I found a simpler solution to this problem for the ULS model.

Get the trim close, then adjust the vernier throttle to fine adjust the nose pitch.

 

[rzbill]

I don't know RV-12 construction so this may not apply.
On my 7A I used the standard Ray Allen Servo and up/down rocker switch. However, to obtain easy slow trim movement at cruise speed, I installed a momentary push button and resistor in the 12v supply line to the rocker switch. A push button can have Normally Closed and/or Normally Open contacts. You want to use Normally Closed contacts for the 12v supply line. Solder a 50 Ohm resistor across those same contacts.
With that arrangement, the Ray Allen servo will run as designed (fast) by using the rocker switch by itself. If you want slow, push the momentary button (which breaks the straight 12v path and forces it though the resistor) and activate the rocker as needed. Trim motor will move slowly.
I have the switches mounted such that I can use my index finger on the button and thumb on the rocker.