9 - Position Flaps Lever


 

The 9-pos. flaps lever is located in the mechanics panel.

In the first version of my cockpit I used a slider potentiometer as a flaps lever. Even though it did the job quite well, I was never really satisfied with the way it moved. The sliding motion was just too smooth to feel right, and there were no detentes. Since the cockpit developed quickly towards a closer resemblance with the B737, I decided that I needed the Boing 9-position flap lever.

But 9-position switches are not easy to find, so build my own. That turned out to be easier said than done. I had to go through 2 versions to get it right, but now my cockpit has a flaps lever that is a joy to use.

Here is some information on construction details and photos to illustrate the building process:

 

Version 1.

Attached to the lever was a spring loaded steel ball that slid over a wave shaped surface and directly depressed the microswitches. It was supposed to produced audible and tactile detents for each flap position. Unfortunately, friction between the steel ball and the acrylic surfacees made the movement of the lever feel rather crude. Pulling to hard could easily result in skipping a flaps detente.

Also, when shifting the lever to a new flap position, I often had to wiggle it a bit so the microswitch would make contact - not the kind of reliablility you would expect from a multi-million-$, high-tech plane...

Anyway, after only a few weeks of use the lever got stuck for good (I never completely understood why). It was time to scrap the first model and go back to the drawing board...

Version 2.

This is what evolution is all about...

Now the lever has to be pulled out before it can be moved to a new detente. Detents are defined by an undulated profile. A small nylon wheel attached to the lever slides into each position when the lever is released. A large spring close to the axis gives nice tactile feedback during operation. The upper and lower housing of the main spring are greased to eliminate noise and reduce friction.

The microswitches are depressed by a spring loaded plunger. This design results in accurate switching as soon as the main spring returns the lever to the "down"-position. It also made the construction easier, because utmost precision in the placement of the plunger is not required - the spring compensates for minor differences in switch positions. And last but not least: the full force of the main spring is never applied to the microswitches, thus prolonging the service life of the assembly.

...the image reminds me of the long gone days when I used to assemble scale model aircraft...

These are all the pieces that form the flaps switch. I had them cut out of 3mm acrylic glass and joined them with super glue and superglued 3mm threaded rods for reinforcement (where necessary).

The upper and lower housing of the main spring. The lower part is attached to the lever. The upper part is fixed to the axis. The lever - when pulled - slides along it.

The prodtruding metal pin in the upper spring housing fits into the oblong opening in the metal lever. It acts as a guide, so the upper spring housing is always lined up with the lever. This helps to achive unobstructed and uniform longitudinal movement of the lever, no matter what detent position it is in.

 

The spring mounted plunger and spring housing. Gettin the spring lengh right is a bit of hit and miss. It should be long enough to produce the pressure necesary for actuating the micro switches. On the other hand, it has to be short enough not to block or hinder the movement of lever and plunger over the switches.

The micro switches, glued into place with super glue. To the left, note the wave shaped profile that defines the lever's up/down movement and the flap's positions.

The completed flaps lever assembly.

The front decal with the 9 flaps positions is made with the same technique used for the face plates of the panels throughout the cockpit.

As an added touch the handle of the lever has a built-in LED that illuminates for a second when a microswitch is pressed - visual feedback on flap movement.

The wires from the micro switches and LED are soldered to a 10-ribbon flat cable, which plugs into the mechanics panel connector board. There are 13 cables: 9 data leads, 2 ModRow leads (EPIC accepts up to 8 data leads per ModRow) and two cables for the LED.