Airfield Models - How To

Make a Computer Radio Setup Rig

March 01, 2016



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Airfield Models (http://www.airfieldmodels.com/)How to Make a Computer Radio Test Rig

Recently I had a discussion with a good friend of mine who is currently flying a 33% scale Sukhoi using Futaba's newest nine-channel transmitter.  The model is very large and would be unwieldy to set up in the living room as we do with our smaller models.

He mentioned that a small rig with all the flight controls would be a really nice thing to have.

Since I owe Mike more favors than I can count (actually I only owe 37 now), I decided to build him something.  He handed me a bag of servos and I got started.

The mock-up shown below is my first attempt at this.  Mike gives me a hard time about building models with short tail-moments so as a joke I made the tail moment on the rig fairly long.

Of course I did not realize this would be a problem until I started plugging servos into the receiver and needed to use several extensions.  Learn from my mistake and build yours so all the leads can reach the receiver.

Construction took a couple of afternoons.  It is constructed primarily of foam-board using Weldbond as an adhesive.

 
 

Highly Modified Hanger 9 Sukhoi SU-31

Mike's Hangar 9 Sukhoi SU-31.  This model has been extensively modified by Mike's father.

Materials

  • Foam board Birch plywood could be substituted for a nicer appearance.
  • Thin scrap plywood (servo mounts and control horns)
  • 1/32" music wire or paper clips (pushrods)
  • Wood dowel
  • Tape (hinges)
  • White Glue (solvent glues will melt the foam board)
  • Old radio equipment that you wouldn't trust in a flying model
 
 

Building the Rig

I  considered building an F-14 complete with swing wings, Navy gray camo and decals, but after cutting all the servo mounts I snapped out of it and decided to keep it simple.  I did lacquer all the wood pieces.  It also wouldn't hurt to put a protective coat of some type of paint on it so it could be cleaned.  Foam board is paper faced and thus can not be cleaned with damp rag.

The completed rig.

A nicer way to make it would be from 1/8" birch plywood.  Separate servo mounts wouldn't be needed and it could be given a clear polyurethane finish.  Maybe it would even look nice displayed in your home somewhere.  I have not built mine yet, but that is probably what I will do.

The rig is held to the base with a rubber band that also holds the receiver and battery pack in place.  A small dowel cut in half and glued to the top of the fuselage prevents the rubber band from crushing the foam board.

 
 
The stand for rig is assembled in an egg-crate fashion. The stand is simply two pieces of foam board assembled in an egg-crate fashion.  Two pieces of 1/8" ply are glued to either side.  These pieces provide a cradle for the receiver on one side and a battery on the other.  A small dowel allows it all to be held together with a single rubber band.
Servo mounts are made from scrap aircraft plywood. Servo trays are made from 1/16" plywood scraps.
Pushrods are made from small wire are kinked to allow adjustment.

Pushrods are bent from 1/32" music wire with a Z-bend on each end.  A small kink in the wire allows some adjustment to get the surfaces close to neutral.

Servo, pushrod and plywood horn from thin plywood. Control horns are made from scraps of 1/32" plywood and glued into each control surface.
Bevel control surfaces to allow movement.  Make hinges from tape. Control surfaces are beveled 45 to allow movement and hinged using Mylar tape.
 
 

Before turning the rig over to my friend I spent a couple hours playing with it using my Futaba 8UHP heli radio.  It does not have as many features for aircraft as the 8UAP, but there are enough mixes to have fun playing with it.  I set up an aileron/flap (flaperon) mix, elevator/aileron/flap mix, butterfly (crow) and ailervators (elevators mixed to ailerons) in a single model memory.  Now I want to build an R/C model that does the same thing.

The primary benefit of the rig is to help get mixes set up properly.  However, it will not be very helpful in setting up mix percentages.  The servos may also have to be reversed from what you use on the rig.  But getting the mixes set up so they work properly is 90% of the problem solved.

The percentages should be set up on the actual aircraft using the recommended control throws and some educated guessing.  The mixes get zeroed in during test flights.

If you decide to build something like this for club PR (mall shows, etc.) then you might want to consider making a simple 4-channel version instead of or in addition to a rig like this one.  When a potential beginner sees a computer radio the word "expensive" comes to mind.

Taking the idea a step farther, it wouldn't be difficult to put a gimble near the rig's center of gravity and hook up pushrods from the control surfaces to the base.  In that way, moving the sticks could make the rig rotate about its axis and demonstrate the effect of the control surfaces on flight attitude.

 
 

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Copyright 2003 Paul K. Johnson