Why Try our Trim Relay Boards/Hubs?

We’ve come a long way since I built my first RV in 1989, an RV-4.  Back then, it was a real hassle wiring my stick grip (a surplus USAF F-4 grip), trying to figure out how to get the wires through the stick and where to put the relays and how to route all of the wires for all of the functions available on the grip.  How in the world would you ever figure out which component failed if you had to troubleshoot this mess?  There wasn’t a lot of guidance or experience out there that you could tap into for ideas like there is today.

Around that time I started following Bob Nuckolls’ posts and reading his The AeroElectric Connection.  He certainly has brought a wealth of experience and information to the homebuilding scene, in my opinion.  Among other things, he introduced me to D-sub connectors and their various uses.  Today, D-sub connectors are ubiquitous on amateur-built aircraft.  In those days, D-subs were of the solder-cup variety and a real pain, but with the introduction of machined pins, which can be easily crimped to a wire and then inserted into the connector, the D-sub became an even more useful tool for making wiring harnesses.

In my latest build, an RV-6, I used D-subs throughout and found them to be especially effective in segmenting the wiring harness and to have disconnect points, especially at critical junctions such as the wing root.

So this brings me back to the stick grip.  I recently installed a new Infinity stick grip to the left stick on the RV-6.  I realized that what I really needed was a wiring hub somewhere in the system that would serve to centralize all of the various functions typically found in a grip.  This hub should be able to direct all of the inputs from the grip, process them, and then output the functions to the various components, all in one convenient unit.  So I set out to design a PCB where I could mount the relays needed for control of the trim servos, bring in the 12 volt power and grounds, and also provide a gateway for the signals from the various buttons on the grip.

The resulting trim relay boards and hub worked so well that I decided to make them available to other homebuilders and at a fraction of the cost of other relay boards out there.  This site is the result of that effort.

One of the huge advantages of the hub concept is what it brings to the maintenance troubleshooting process.  If you have a problem with a trim motor, for example, how would you troubleshoot it?  Besides the servo, it could also be the 4-way switch on the grip, it could be a relay, or it could be a broken wire.  Well, with the hub, you can remove the D-sub connectors at the hub and connect jumper wires for troubleshooting.  You can make these jumpers with machined pins or sockets crimped on the end of a short piece of AWG 22 wire.  Insert the jumpers onto the pins or sockets in the D-sub connectors and with an ohmmeter or voltmeter you can quickly figure out which component has malfunctioned.

Every trim relay board & hub that we manufacture is thoroughly tested with a test box and simulated load so that we can prove every circuit and relay.  For testing the flap/speedbrake relays, we use an actual flap actuator, weighted down, to simulate the normal operating loads on the circuit.

The finished product is an efficient and aesthetically pleasing design, tailored to the needs of the experimental homebuilder, and extremely small and lightweight.  I think you’re going to like it if you try it.

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