Prototype of a variable-area nozzle for use on EDF RC airplanes.

More info about the original build can be found here: https://imgur.com/a/Njsps6G.

Keep in mind this is a prototype meant for testing the basic design, and as such it lacks features such as mounting points and appropriate attachments for the servo rods (the ones present at the moment are probably too weak).

Before printing, please take some time to read my notes in the print settings section.

In addition to the STLs, I've uploaded the original Fusion 360 file for those wishing to modify the design. If you're one of them, a couple of useful tips can be found below.

Edit: following VV3sl3y's suggestion I uploaded a taller version of the inner ring. This one has a longer threaded section in order to enable greater expansion of the nozzle's flaps.

Print Settings

Printer Brand:

Prusa

Printer:

Rafts:

No

Supports:

Resolution:

0.15

Infill:

Notes:

Gaps between parts have been tailored to my printer accuracy: 0.15mm gap is used for clearance fit and 0.10mm gap for transition fit. Less accurate printers might require sanding or even editing the source file in order for the mechanism to work.

The design makes use of living hinges and snap fit joints. As such, non-brittle materials such as PETG are reccommended.

Supports are only needed for the upper outer ring. Everything else has been designed in order to print fine without them.

The two threaded parts are challenging because of the very steep overhang the thread itself causes. After two failed attempts I finally managed to print them with 10mm/s speed and 100% cooling settings for the outer perimeter.

Parts have already been oriented in the intended print direction.

Part count is as follows:

• 1x Lower outer ring
• 10x Flap
• 10x Rod
• 1x Inner ring
• 1x Upper outer ring

Fusion 360 file editing

If you wish to edit the source file please keep in mind:

• All main dimensions are defined in the first two sketches of the timeline. Additional parameters such as gaps and fillets radii are defined in the user parameters section
• The thread has custom pitch and starts, and as such is obtained by coil operations. Since I haven't been able to parametrize the coil's main dimensions, scaling the nozzle requires manual editing of these values
• Fusion 360 constraint resolutor isn't the most reliable. When scaling the nozzle proceed in small steps or the tree reconstruction will fail

Category: Hobby