Airbus A320 FCU Push Pull mechanism

Design to recreate the Push Pull functionality needed for the ALT, Heading, Speed and Vertical Speed controls on the Airbus FCU. 

Design objective was to create a realistic feel, with a smooth, solid and weighty action. Push and Pull movement is +/-2.5mm, with no plastic on plastic contact. There are simpler and smaller alternatives available, but for a little extra cost and size, this design feels much more substantial and less “toy” like. Weight comes from use of 125mm brass shaft linking knob to fixed encoder at back of chassis.

Chassis, Centre support, Push-Pull disc, Encoder Actuator and Encoder slide are designed to be printed in PLA, 100% infill for strength.  PETG could be used, which is stronger, but parts tend to be less accurate and may need some clean-up in areas like the slide groove.  Light Pipe front support should be printed in clear PLA or PETG, 25% infill or higher. Knob printed in matte grey PLA. Marker line in white PLA or PETG, both 100% infill.

Light pipe has holes for 3 x 3mm warm white LEDs to help illuminate ring around knob on front panel. 

Fits into 3 layer FCU front panel. Top 3mm layer with 22mm circular aperture, Middle and Bottom 3mm layers with  26mm circular aperture. Will also work fine with single, or double layer panel. Designed to be glued, or a press fit into front panel, with support for chassis at rear. 2 x 3mm threaded holes are provided for this.

Light pipe and Centre Support are both bonded to Chassis with CA glue. Switches are bonded onto Chassis pads, positioned to touch, but not bind with push-pull disc. Encoder actuator is bonded onto encoder shaft. Push Pull Disc and Encoder Slide are clamped onto 6mm brass shaft with 3mm grub screw.

STL is included for 2mm washers, but ideally these are purchased PTFE washers to minimize any friction or roughness when rotating encoder.

Optional Top Cover is included. Will help keep mechanism clean, but is not structual or essential to operation.

Needed Parts, all available from AliExpress and Amazon as of June 2023:

4 x 8mmx8mm non-self locking push switches with black key caps:

Non-self-locking Switch | Self-locking Switch | Switch Caps | Key Switch - 10pcs - Aliexpress

3 x 3mm Warm White LEDs:

100pcs 3mm Led Light Emitting Diode Flat Top Warm White Red Blue Green Uv Orange Yellow Pink Color Bulb Lamp 2v 3v Indicator Diy - Diodes - AliExpress

26mm * 2mm PTFE washers:

Flat Washer Sealing Gasket | Pressure Washer Gasket | Ptfe Washer Gasket - 6 8 10 11 12 - Aliexpress

Precision Encoder: Design could easily accommodate different encoders

1pcs Japan 09 Precise Rotary Encoder with the press of a switch 20 positioning 10 Pulse Axial Length 25 mm| | - AliExpress

18mm * 2mm Steel Pin:

D2 (2mm x 18mm) Dowel Pins (M6) - Stainless Steel (A1) (Pack of 20) : Amazon.co.uk: DIY & Tools

6mm Brass Shaft: Cut to 125mm length

Glarks 2Pcs 6mm x 356mm Brass Straight Solid Round Rod Lathe Bar Stock for DIY RC Model Car, RC Helicopter Airplane, Model Ship (6mmx356) : Amazon.co.uk: Business, Industry & Science