Building a concentric rotary switch from two simple circuit twelve positions rotary switches (English).
J. Pedro Bibiloni. Translation by Manolo Hdez-PeñaLopez Muñoz
The only aim of this tutorial is trying to build rotary concentric switches. We can use them on our NAV and COMM panels simulating the ones used in the real cockpits. We will use one knob to select integer frequencies and the other for the decimals. These rotary switches are designed to be used with the IOCARDS designed by Manuel Vélez <ahref="http: www.opencockpits.com"="">www.opencockpits.com .
1. TAKING ROTARY NO. 1 TO PIECES (OUTER KNOB FOR DECIMALS)
Lightly force the plastic hooks (be careful not to break them). Open it being cautious with the metallidc balls and spring inside the switch (the balls can be thrown really far away by the spring, far enough to loose them forever). Take apart these pieces for later. Also apart the metallic contact that closes the circuit; take into account the initial position for this piece.
2. ROTARY SWITCH NO. 1 AXLE REPLACEMENT
Cut the plastic axle leveled with the switch body.
Then put a mark in the centre of the axle and drill a 6 mm. hole (is better doing it by steps, 4 mm. first, then 5 mm. and so on).
Cut the aluminium pipe to the desired length (main body + fitting screw + knob) and glue it into the hole. You can sand down the parts to glue, they will make better contact if you do so.
3. CUTTING ROTARY SWITCH NO. 1 INNER SPRING
We have tu cut the spring into two pieces. The length of each part is more or less: (original spring - aluminium pipe - ball radius) / 2. It isn't an exact formula, so it's better not cutting so much the first time and adjust in several cuttings.
4. DRILLING THE BOTTOM BODY
Drill a 5 mm. hole just in the centre of the bottom body, as shown in the picture. This hole must to be centered with the 6 mm. pipe previously glued.
5. ROTARY SWITCH NO. 1 ASSEMBLY
We are ready now to assembly all the parts. Be careful with the small parts as balls and springs. Test the correct switch operation. If you think the strenght is not the correct one (consider that in the real airplanes, the strenght is enough to avoid the rotary encoders move with the plane vibration), cut the springs a little more.
6. ROTARY SWITCH NO. 2 AXLE (INNER KNOB FOR INTEGERS)
Cut the axle near the fitting screw. The lenght must let mounting both rotary switches without interferences. Drill a 4 mm. hole in the axle. Cut a 4 mm. aluminium pipe (lenght must be: 4 mm. hole depth + distance between switches + switch no. 1 length + knob housing). Glue this pipe into the hole. The 4 mm. pipe will run inside the 6 mm. so they must be well lined up. The joint in both cases must be good because those are the points where the forces are going to be applied, so use a powerful glue.
7. FINAL ASSEMBLY.
Cut 20 mm. of squared aluminium frame. Drill two 10 mm. lined up holes at opposite sides of this piece. Fix rotary switch no. 1 in the upper hole and switch no. 2 in the other (4mm. pipe must fit through the hole made in the bottom body piece of switch no.1). Fix all the screws and test the correct operation of both switches.
8. KNOBS INSTALLATION
If the switches are fitted in the corresponding panel, we can now proceed to install the knobs. The best are the ones with lateral screw (see picture). The only thing to do is drilling the upper side of the 22 mm. knob with a 5 mm. hole, fixing it to the 6 mm. aluminium pipe. For the small knob, we have to fix it to the 4 mm. pipe. It's convenient make this pipe bigger, adding a little piece of the 6 mm. one; this way installing the knob centered will be easier. And know we're ready for the final test.
9. WE ARE ARTISTS
But only if we now test that all works properly ;·)