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Harvey rv12

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I am planning on installing a Ray Allen G303 stick grip with single axis trim switch, and a PTT switch. I have studied the wiring for the plane. I did not build it, but it is an ELSA std build, sn 120278. I think I should be able to wire the stick grip switch in parallel with the trim switch on the instrument panel, and no need for an intermediate relay. But I spoke with the folks at Ray Allen today, and the gent there told me I would need a relay board.
I just don't see it. What am I missing here ?. Has anyone here installed a stick trim switch on this type of plane ?
They also told me they just acquired a RV-12 and are studying it for a roll trim system.

Thanks in advance.
Tom O.
 
Tom, you'll be fine without the relay board (as you surmised). The relay board is necessary if there is a possibility that both trim switches will be operated simultaneously and with opposite inputs. So just don't do that! Or be prepared to replace a fuse.

--
Joe
 
Joe;
You are right, I hadn't considered that. It is possible to push trim down on the instrument panel, and trim up on the stick, and create a short....blown fuse.
I think I will pass on the relay, and either leave as is, or disable the switch on the instrument panel.
 
Joe said:
The relay board is necessary if there is a possibility that both trim switches will be operated simultaneously and with opposite inputs.
Click to expand...

This is only part of the reason The primary reason is that the tiny switches in the stick grips are not rated to the current that the servo motor requires.

Even if the only switch you would have is the one in the stick grip, Ray Allen still recommends using a relay deck to protect the switch.
 
The requirement for relays all depends on whether the RV-12 has the Dynon D-180 or SkyView.
No relays are required for the SkyView system because there is a logic board that monitors two input wires. Grounding one wire causes up trim and grounding the other wire causes down trim.
The D-180 system does not have a logic board to control trim direction. Instead, the Double Pole Double Throw (DPDT) panel-mounted trim switch controls the polarity of power going to the trim servo. Since the Ray Allen G303 switches are SPDT, I do not know how to wire them to the D-180 trim circuit without using 2 relays. Tapping into the PWM trim circuit will require disassembling Van's control board.
If your RV-12 has the D-180 system, it might be easier to buy everything from Ray Allen including their speed control. Then disconnect the trim servo wires from Van's control board and connect them to Ray Allen's system.
 
Quote from Ray Allen's G303 pdf:
The trim and PTT switches in the G3 series stick grip are all 15 amp, single pole, double throw (SPDT), Honeywell Microswitches. These high quality switches were specifically chosen for their superior tactile feedback.
Click to expand...
Another consideration is run-away trim. Extending trim switch control wires beyond the instrument panel increases the chance that a control wire could accidentally short to ground, especially where subject to motion like the control stick.
 
Per Ray Allen, the G303 will run the trim motor direct, no problem, no relay needed, and motor current runs through the switch. The switch is rated at 15a, and the motor draws about 150ma normal, and 600ma when stalled. It is protected on a 2a fuse. I don't think I will overload the switch by running the trim motor.
I will "unwire" the trim switch in the panel for safety, so I can't get simultaneous commands to the motor, and use just one trim switch.
As far as one of the conductors shorting to ground, this can be minimized by proper routing, securing, and sheathing of the wire. I don't think that is too great of risk.

Thanks for all the input.
I will report my progress as I get there.

Which raises the question, what would be the consequences of a runaway trim motor ?, I have flown the plane while considerably out of trim, and needed to add light back or forward pressure. But I have never experienced full trim in either direction while trying to achieve level flight or climb or descent.
Any thoughts ?
 
Mich48041 said:
Quote from Ray Allen's G303 pdf:
Another consideration is run-away trim. Extending trim switch control wires beyond the instrument panel increases the chance that a control wire could accidentally short to ground, especially where subject to motion like the control stick.
Click to expand...

Harvey rv12 said:
Per Ray Allen, the G303 will run the trim motor direct, no problem, no relay needed, and motor current runs through the switch. The switch is rated at 15a, and the motor draws about 150ma normal, and 600ma when stalled.
Click to expand...

Thanks
I wasn't aware they had a grip with higher amperage switches (we don't use them and all of the older models required relays).
 
rvbuilder2002 said:
Thanks
I wasn't aware they had a grip with higher amperage switches (we don't use them and all of the older models required relays).
Click to expand...
Looks like it. From the RAC installation instructions for the G301/G303:
The trim and PTT switches in the G3 series stick grip are all 15 amp, single pole, double throw (SPDT), Honeywell Microswitches.
Click to expand...
The G205/G207 switches are rated at 5A.
 
Since you have the SkyView, it will be relatively easy to connect the Ray Allen stick grip trim switch. No relays are needed. Either tap into or remove the wires from pins 18 & 19 of the AV-50001 Fuse and Switch Module and connect one wire to the N.O. terminal of each stick trim switch. Connect both of the stick trim switch common terminals to ground. Do NOT use the N.C. terminals. If the trim tab moves the wrong way, reverse the two wires. Do NOT connect 12 volts to the stick switches. And do NOT connect the stick switches to the trim motor.
 
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Joe;
What are your thoughts on a runaway trim scenario?, I'm guessing you could still fly, land and take off.
 
Joe;
What are your thoughts on a runaway trim scenario?, I'm guessing you could still fly, land and take off.
 
My guess is the same as yours, but it is only a guess. Scott is the person to ask. If nobody with experience replies, I suggest that you go flying and add trim a little at a time until the stick forces get close to your maximum comfort level. Then after landing, see how much further the trim will go before maxing out.
 
Consider the SkyView AP Panel module

Folks ... don?t overlook the SkyView AP Panel module. The module is easy to install and it has a built in relay deck. Other features include a two-step trim motor speed controller (user programmable) and the unit has built in runaway trim protection plus it expands the capabilities of the SkyView AP. Another feature is that the pilot trim input overrides the co-pilot trim input. In my case, I kept the panel mounted trim switch wired to the pilot input (as it normally would be) and wired the stick trim switches for both pilot and co-pilot to the co-pilot input on the AP Panel module ?. the logic being during critical phases of operation, hands will be on the throttle and the panel mounted trim switch is right there to make a quick override should a stick trim switch get snagged on a piece of clothing or inadvertently pressed by a passenger.

In my opinion, RV-12 builders considering stick mounted trim switches should give the Dynon AP Panel module serious consideration from both a safety and feature aspect.

Happy building,
 
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