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Author Topic: 3D Printed Prop Form  (Read 2623 times)
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lincoln
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« Reply #25 on: January 18, 2019, 06:05:39 PM »

If you have a 3D  printer, maybe this makes sense. If not, it seems to me the easiest way to make a prop block is to make a 3 sided partial box out of any old material and then plank it. One side is a triangle. All the important cuts are straight. I've done this. For a thin blade, I've made a fairly thin camber form, with the same outline as the blade, which I put between the blade and the block. Worked great.
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bobm123
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« Reply #26 on: January 18, 2019, 07:45:07 PM »

@uggy Good catch! I added the missing file.

By the way, the missing file has to do with a method for defining the shape of the prop blade as a function of the pitch. I found it in an article "The Larrabee way to a Better Propeller" from the October 1990 issue of AeroModeller. It was recommended to me by Don Srull, so I thought I'd give it a try. The code fits a smooth curve to the root, max chord and tip coordinates and uses that to trim the prop block. If nothing else, it makes for a pretty blade shape!

Enjoy!

Edit: Added a screenshot
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frash
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« Reply #27 on: January 18, 2019, 08:28:46 PM »

Good work folks.

Somewhere here on HPA there is a method by Hepcat (John Barker) that is similar, or perhaps identical, to the one that you have used for blade shape layout.

Some people will also want to move more of the blade's width ahead of the spar for flaring indoor props.

Fred Rash
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Uggy
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« Reply #28 on: January 19, 2019, 04:57:20 AM »

Quote from: bobm123
@uggy Good catch! I added the missing file.

Hi Bob,
I still can't see the missing file on Github..
?
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bobm123
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« Reply #29 on: January 19, 2019, 08:16:10 AM »

Try again now, I just did another "push" to the github server. If you are familiar with the git tool, you should be able do a "git pull" command now. Or you download the .zip from the project page (use the "Clone or Download" button on https://github.com/bobm123/PropForm).

In either case you should see something like this:

Directory of C:\Users\Robert\ptest\PropForm

01/19/2019  08:06 AM    <DIR>          .
01/19/2019  08:06 AM    <DIR>          ..
01/19/2019  08:06 AM             5,361 alt_extrude.scad
01/19/2019  08:06 AM             1,296 LarrabeePlanformSpline.scad
01/19/2019  08:06 AM             3,081 PropForm.scad
01/19/2019  08:06 AM             3,625 PropFormMkII.scad
01/19/2019  08:06 AM                86 README.md
               5 File(s)         13,449 bytes
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Uggy
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« Reply #30 on: January 19, 2019, 10:43:15 AM »

Hi Bob,
Thank's, got it now.   Smiley

Again, quite impressive what can be done with OpenSCAD knowledge  Smiley

Does xsection="curved"  is still supposed working in this version?
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BR549
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« Reply #31 on: January 19, 2019, 08:16:41 PM »

Bob

I downloaded the new files and I keep getting an error in the PropFormMkII.scad on line 100.
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bobm123
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« Reply #32 on: January 19, 2019, 08:29:52 PM »

@BR549, It looks like that line uses some features only available in later versions of OpenSCAD. I saw an error on the same line when I tried it with version  2015.03-3 (the official release version), but it worked with newer version (2018.01.06) I've been using. It doesn't seem to be supported in the official release yet, so I'll see if I can rewrite it to be more backward compatible.

Sorry about that!
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Uggy
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« Reply #33 on: January 20, 2019, 06:32:49 AM »

Hi Bob,

All seems to open fine now on my updated OpenSCAD version 2019.01.11.nightly.
Thank you
Will play with it a bit today Smiley

I don't think you should take of your time to rewrite for older version.
You may just add a comment at beginning of the code and into the Github readme..

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BR549
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« Reply #34 on: January 20, 2019, 08:45:00 AM »

Got it, didn't realize there were nightly builds. I was using the 2015 version. Everything's working great now.

Thanks all.
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bobm123
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« Reply #35 on: January 20, 2019, 09:20:12 AM »

Thanks for checking that out guys! I went ahead and made the change for comparability since it was easy enough to do and because that 2015 version is still the one listed on the OpenSCAD website. The current version is really a lot nicer though and I hope they do another release soon. For example, it lets you bring up a user interface panel with sliders an buttons that allow you to adjust parameters without changing code. Its like on the thingiverse web site, but faster since it runs locally.

I also added comments and rearranged some of the code so I hope it will be clearer. It took me way to long to remember how all of that was supposed to work. My own code and after just a few months >.<

Ok, now to fire up the printer and make a few prop forms and props to see how all this code and theory actually works!
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Uggy
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« Reply #36 on: January 20, 2019, 12:14:04 PM »

Here is the first test print.

Printed with 0.6mm walls /top /bottom and only 5% infill
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BR549
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« Reply #37 on: January 20, 2019, 03:45:41 PM »

New prop for my MiniSlick on the form.

https://scontent-dfw5-1.xx.fbcdn.net/v/t1.0-9/50528985_10156850190924847_2236965022414667776_o.jpg?_nc_cat=104&_nc_ht=scontent-dfw5-1.xx&oh=9835bfeff2139a45ab54ad1ffffe7706&oe=5CCD9906
3D Printed Prop Form
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BR549
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« Reply #38 on: January 20, 2019, 08:42:50 PM »

I've been making my props on a cylinder since I started in free flight last year. I have a couple questions.

I made the above block with the PropFormMkII.scad file and set to a flat camber. Is it a negative block, where I would attach the spar to the top (exposed) side of the blade? Or is it a minimal volume block with the unneeded volume removed?
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Uggy
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« Reply #39 on: January 21, 2019, 04:21:02 AM »

Hi BR549,

Current version is not a negative block. (But Bob mentioned the possibility to create one too). So the spar will be put "under". (Bob also mentioned the possibility to add a cut into the form, so the spar can be put under the blade.
So it sounds to me the prop is possibly on the wrong direction on your picture? You may possibly want to flip it so the "flaring" part to be moved on the left side of the spar... ?


Your print sounds better than mine.. Did you applied something on the block to make it smoother ?
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BR549
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« Reply #40 on: January 21, 2019, 06:52:30 AM »

OK, I suspected I was looking at it wrong. Thanks.

I printed PLA at .16 layer, 1 mm walls, .8 mm top and bottom layers, and 20% grid infill. Then ran some 220 grit over the top for a couple swipes.

I think the biggest thing to smooth it was I upped the "sections" to 40 in the scad file.
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Uggy
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« Reply #41 on: February 20, 2019, 09:41:57 AM »

Hi,

I printed a test block for F1L. 13.8 / 25.6 / 2" / 8%
To make a smoother surface, I tried to use some kind of adhesive foam.
Also, I wanted to test forming the blade, with the spar already glued first (acetone mix).
I know using acetone after forming the blade is not recommended due to a possible shrink.
But an INAV article suggesting gluing the spar first, then let everything dry (in oven in the article) and wanted to try that way.
Of course in our case, I did not put PLA block in oven.. but instead let it "air dry" 8 days.
For the groove needed for the spar, I simply glued the sticky foam roll on both "sides" letting 1 or 2 mm for the groove for the spar.

I used an old F1L prop blade to perform the tests...

In summary, I'm quite happy for now with this process... even if I will possibly try few others too.
Here is few pictures of the test result... Just wanted to share.. and discuss if you have some ideas.

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Re: 3D Printed Prop Form
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dslusarc
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« Reply #42 on: February 20, 2019, 06:14:12 PM »

I downloaded the scad files and 2019.01 RC2 version of SCAD and it works and makes a nice Larabee prop and such but there is no customizer panel/screen to the right as seen in the screen shots. I have to manually change the factors in the code. Do I have to activate that? Sorry for having to ask but I am stumped.

Don
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Uggy
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« Reply #43 on: February 21, 2019, 05:25:24 AM »

Hi Don, yes, this needs to be activated first in OpenSCAD prefs:

In [Edit] menu, select [Preferences] then open tab [Features], tick [Customizer], then close the window when tick is shown.
In View menu, you shall now have an option [Hide customizer], than you shall untick

https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/WIP#Activation_of_Customizer_functions
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dslusarc
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« Reply #44 on: February 21, 2019, 08:22:15 AM »

Thanks! How hard would it be to add a feature to split the model? The reason I ask is my 3D printer can only print 8" high, but if there was an option to split the block in two pieces I can print two 5" high sections and glue them together to make a 10" block.

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Uggy
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« Reply #45 on: February 21, 2019, 09:49:27 AM »

Hi Don,
I don't know how hard it would be into OpenSCAD itself. (But would be a great additional option indeed)

An alternative way would be to import the STL into another 3D software (like tinkercad), and there, split the part in 2 before giving back to the printing slicing software.
This is quite easy (like 2 minutes once you know the process)

Quick test in screenshot with tinkercad
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dslusarc
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« Reply #46 on: February 21, 2019, 10:27:31 AM »

Thanks! Just the info I needed. Can you point me in the direction of what I need to learn to make a different prop  blade outline? I have some shapes I like over the years of flying and would like to make that outline if possible. The outline could be approximated with lines and arc segments or coordinates from the centerline where the spar is. I can draw the outline in Autocad, any way to use that in openscad?
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dslusarc
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« Reply #47 on: February 21, 2019, 08:57:11 PM »

I was able to make a block with the customizer and it is printing now on my printer. How do I get more decimal precision on the variables in customizer? The radius arc for example only goes by 1" increments. The prop form I use most is a 5" diameter can but can not enter 2.5", only 2 or 3". Same for prop diameter, it only goes in 1" increments. How do get one more decimal place on those two variable. I do not see in the script where decimal precision is defined.

Don  
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dslusarc
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« Reply #48 on: February 23, 2019, 11:55:20 AM »

I wanted to make a LPP form for my dad for is flaring LPP blades. I decided to model in ACAD by drawing cross sections in a few radius locations and "lofting" to each cross section. I made a 6% thick arc airfoil at each section. Here is how it looks. I have it printing now. Going to try printing flat first then print one on its tip to see hot it affects surface finish. 
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dslusarc
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« Reply #49 on: February 24, 2019, 10:34:18 PM »

Printed two LPP prop blocks, one for me and one for my dad :-)
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