From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Bell mouth 3D printed
Date: Thu, 19 Sep 2019 21:58:19 +0800
References: <list-12972172@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-12972172@logan.com>
Message-Id: <8789DB5F-9782-4891-A920-B003AB8D83DA@gmail.com>

Thanks  Finn
You have inspired me.
I=E2=80=99d like to venture into the world of NC routing or 3D printing =
one day.
Cheers

Steve Izett=20

> On 19 Sep 2019, at 9:15 pm, Finn Lassen finn.lassen@verizon.net =
<flyrotary@lancaironline.net> wrote:
>=20
> My first experience with 3D printing.
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> I had bought a new Ender-3 and a 1Kg spool of ABS for less than $200.
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> Article and pictures here:
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> https://drive.google.com/open?id=3D1LbQcJIGnjsfNWfL5qiwz5ev7ze9IWAzm
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> I copied the "best" picture from the RET_Bellmouth_Sept.pdf article, =
pasted it into Paint and saved as Bellmouth.bmp.
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> Imported that into Fusion360 as canvas. Calibrated it so throat was =
19.972mm (1.18")
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> Made a spline matching the left curve up to the top.
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> Added a tangent arc (radius).
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> Added a 2mm rectangle that extended the throat about 1" with an 1.25" =
ID. (The bell mouth will slide 1" down on the 1.25" OD pipe.)
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> Added a "looks good" spline from part of the arc down to the throat. =
(I believe that in our case, where most of the air comes from behind the =
bell mouth, air should have a smooth path along the outside of the pipe =
and radius of bellmouth.)
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> Revolved the whole thing to get the solid bell mouth.
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> [The result is actually a bit smaller overall diameter than the =
recommended 2.13 * 30 + 2 * (0.08 * 2.13 * 30) =3D 74mm]
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> Exported to a .stl file.
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> Downloaded and installed Ultimaker Cura 4.2.1.
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> Opened the .stl file with Cura and "sliced" it. 20% infill. This =
changes the solid inside to a criss-cross pattern. Looking at it being =
printed it appeared?? to produce about 3/32" thick walls by default.
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> Saved result to .gcode file.
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> Printed with the Ender-3. Took 3 hours and 15 mins.
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> Nozzle temp default for ABS is 240*C. Spool says 230-260*C. Seeing how =
some of the strands didn't stick and pulled across the mouth, I think =
I'll use a higher nozzle temp on the next print.
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> I printed it with mouth down. Unfortunately that resulted in a radius =
quite different from the design model. I'll try to smooth the lip on my =
first attempt with epoxy or JB Weld and sandpaper. If I print it throat =
down, it'll probably need support along the outside that'll have to be =
cut after printing.
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> Will ABS be strong enough? I think so. The airflow should keep temps =
well below 85*C.
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> Finn
>=20
>=20
> --
> Homepage:  http://www.flyrotary.com/
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