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Centrifugal fan

by jinhwanlazy Feb 2, 2015
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Hello ! I need some help on compiling.
I get an error in line 48. The comma between the two terms is the problem.
function spiral(start_r, end_r, start_angle, fn) =
(start_r+(end_r-start_r)i/fn)sin(start_angle+(360-start_angle)i/fn), <--- this comma

If I remove it OpenSCAD throws variable errors like crazy at me.
"Compiling design (CSG Tree generation)...
ECHO: "relativity.scad 2014.2.14"
WARNING: Ignoring unknown variable 'i'.
WARNING: Ignoring unknown variable 'i'.
WARNING: Ignoring unknown variable 'i'.
WARNING: Ignoring unknown variable 'i'.
WARNING: Ignoring unknown function 'for'.
WARNING: Ignoring unknown variable 'i'.

Also the case does not compile when uncommented at the bottom.

I want to modify this so it fits a 40mm fan because I have a ton of them laying around. Okay, there are two fans next to me :)

Thanks !

The function is generating a list of list of 2 points, that forms spiral shape on x-y plane. The comma should be there!

I don't know why the function makes an error. Have you installed this library?
I mentioned it on first line of the script.

You should be able to modify it by changing only variables and blade shapes.

The Openscad General Library of Relativity
by 16807

Sorry to ask again but it still does not compile. There was no problem with path varibales. I put the scad library in the fan's subfolder folder but still get the comma-syntax error. Have tried the current and an older version of openscad with no success.

This is the error
Parser error in line 1183: syntax error

ERROR: Compilation failed!

Openscad version was the problem. Try latest development snapshot. I get same syntax error with version 2014.03. Mine was 2015.01.23

Latest build works. Thanks !

Yep have this installed. The openscad is a fresh install. I think I'll need to add the path to Windows environment. Thanks

Looks like you made a backward impeller (reactive); did you try to make a forward one (active)?

Actually I didn't even know what I was making. :) After some research on wikipedia, now I know that there is 3 types of blades. forward, backward, and straight. I did the job this morning, intended to upload it after I print and test it. but If you want, I will update files now. check it out.

I have also changed the title

I don't have a decent motor for such application, but it would be nice to make some comparative tests between the 3 kinds of impeller...
BTW, reactive centrifugal impellers usually have much less blades (~10), and are OK to be used without volute, in kitchen exhaust hoods, for example...

Thanks for your advice! I'm happy with less blades backward version. It works far better than forward one when a narrow duct attached to it. Also whistle noises are gone, which was annoyed me with my first version.

Good! I'm planning to build such backward centrifugal fan, without volute, and aspirate through the hotend, instead of blowing towards it...