Printed EDF casings

There are those that wish to print the actual fans. My own view is that a fan built up from a printed filament is an inappropriate application for the material. There is no way it will ever equal the properties of an injection moulded item.
However printing the EDF casings and motor mounts can be effective. It has the advantage it can be made with features to suite the application rather than the "one size fits all" of a commercial injected moulded one.

I found I had a spare Emax 2205 quad motor with a 4 blade 3x3.5 prop so for no specific application I decided to print an "EDF" casing for it.

A 3" prop is 77 mm diameter.
Of course this motor is very small by normal EDF standards but coupled to a prop rather than a fan it is rather more efficient at converting the limited Watts into thrust.

Printing your own duct means you can arrange the exhaust nozzle to what ever area you want. In this case it is 85% of the FSA (Fan Swept Area) which for this prop and motor combination does generate about 6% more static thrust. You might think that is insignificant but there is no penalty in doing it. A bit more thrust for free!
The external surface is covered in 2m Depron planks. A time consuming process as each has to be shaped in two planes and there are 27 of them.

This set me thinking could the outer surface be printed as well and preferably at the same time as the duct.



Virtually identical internally it is printed in 3 parts. The inlet, motor mount and exhaust. The inlet and exhaust fit exactly over and provide additional support and stiffness to the motor mount.

The motor mount with the motor and prop attached is carefully glued into the inlet to make sure all the prop tips have equal clearance. The exhaust duct fit is not so critical.
For interest the all printed duct is just 3.4 g heavier 26.3 g instead of 22.9 g. The motor, prop & leads adds 35.0 g.

Now to find a use for one or other of them. Perhaps as a thrust pod on a simple glider type airframe?

The varicose veins are a result of the "gyroid" infill pattern with a thin (0.3 mm) single wall.
Gyroid works well on circular or irregular shapes. The conventional 'cross' patterns do not give the same stiffness and support for the same infill weight.

The three parts of the 'all printed' duct
Exhaust Tube. 1hr 6 min

0.3 mm wall, 1 wall, 0.2 layer, 1 bottom layer, 0 top layer. 3% Gyroid infill.

Motor Mount. 50 minutes

0.3 mm Wall, 2 wall,. 0.2 bottom layer, 0.15 layer, 1 bottom layer, 2 top layers, 3% triangle infill.
The double wall is important to give sufficient compressive strength for the bolt holes.

Inlet Bell. 2hrs 26 min

0.3 mm wall, 1 wall, 0.2 bottom layer, 0.2 layer, 1 bottom layer, 2 top layers, 3 % gyroid infill.

All done in PLA, 0.4 nozzle, 50 mm/sec print speed, 34 mm/sec outer wall speed, 190 C nozzle, 40 C bed, no support required.
Using my masking tape covered bed no 'brim' bed adhesion required.
It works for me!

Ooops!
I forgot the tail cone that is glued on after the motor is installed to improve the nozzle performance

This uses the CURA spiralize (vase print) feature to give single wall structure.
0.3 mm wall, 1 wall, 0.2 bottom layer. 0.15 layer and the "spiralize the outer contour" box is ticked.

Whilst waiting for glue to dry on the HE 162 repairs I wondered if using the same techniques I could make a smaller lighter EDF casing,
Not intended to be a stream line pod type but closer to a conventional EDF casing with extra material only where it was needed for rigidity.
3 parts.

The motor mount is exactly the same as are the bell mouth dimensions.

The exhaust area is set at the FSA.

But terminates in such a way a thin vase printed tail pipe can be added that could incorporate a reducing nozzle if required.
The body of the casing is expanded around the location of the motor mount to provide adequate stiffness to keep the prop in the centre of the duct.
It weighs 18.1 g. The streamlined 'pod' version weighs 26.3 g representing a saving of over 30%.

There is just one problem. The printer has developed a printing fault. It does this.

And it does it only on the inner wall & at the same place on any hollow print. Of even more concern is it seems to getting worse.
I have a suspicion the print head is not tracking consistently. Hopefully it will be as simple as new tooth belts.

There are no pictures on Simons post just the ( you dont have access to this page ) on my computer

I can't see them either so here they are in order

It is considered that the airflow in the duct aft of an EDF is in a spiral. It follows that 'correcting' vanes to straighten the airflow would increase the thrust available.
Certainly in full size multi stage axial compressors stators are used to control the airflow between the rotating blades.

The question is just how much does the airflow "spiral" from an EDF so I thought it would be interesting to determine how much spiral.
These short ribbons were added to the motor support what in this case are only 25 mm behind the fan, actually a fairly coarse pitch 4 blade prop, so they should detect any spiral airflow.

In this view from behind the prop is rotating clockwise. The ribbons do show a slight degree of spiral but it is pretty small and thus there would be a fair chance that any extra vanes to correct it would restrict the airflow more than any likely benefit in thrust.
It is of course possible that a true multi blade EDF has a rather coarser pitch than any prop which might impart a bigger degree of spiral.