Here's something fun to play with! I'm working hard to understand both the nozzle design and OpenSCAD, so i only have a very simple version modeled.(attached below) plug in your parameters and you will have a simple conical De Laval nozzle negative. By casting something around it (plaster, cement, etc) and then melting out the core, you can have your own rocket nozzle. I hope to make this into a printable nozzle that you could attach to things. obviously not for combustion, but attaching it to an air compressor hose could be fun, or a balloon. Should stand up well to steam, too, as long as it's bellow the melting temp of the plastic (please, please be careful with hot steam). of course, if the code is terrible please help make it better. So far the best page i've found for just general, rule-of-thumb dimensions is here: http://www.braeunig.us/space/propuls.htm Anyone with experience with openscad who wants to try a parametric bell nozzle, Please do! That page has all the parameters about half way down. https://reprap.org/forum/read.php?88,319401,319401#msg-319401 Tue, 16 Jun 2026 21:09:49 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?88,319401,330150#msg-330150 https://reprap.org/forum/read.php?88,319401,330150#msg-330150 [attachment 29351 _DSC4444.JPG]]]> Buback Let's design something! (I've got an idea ...) Tue, 25 Mar 2014 23:51:58 -0400 https://reprap.org/forum/read.php?88,319401,323486#msg-323486 https://reprap.org/forum/read.php?88,319401,323486#msg-323486 my Github, if you want to check it out and contribute.

[attachment 28443 bezier2.png]
It is pretty good, but there are a couple places that need refinement. I kinda just guessed on the second point for the bezier curve. it's been way too long since i've been out of school :S

The p1 tangent, where the bell meets the throat, also doesn't look tangent at certain angles.

the combustion chamber is just a very rough outline.]]> Buback Let's design something! (I've got an idea ...) Wed, 12 Mar 2014 01:16:34 -0400 https://reprap.org/forum/read.php?88,319401,323473#msg-323473 https://reprap.org/forum/read.php?88,319401,323473#msg-323473
I'm assuming there's nothing wrong with this in regards to ITAR. All the information i pulled for the nozzle is from Wikipedia or elsewhere openly on the web.]]> Buback Let's design something! (I've got an idea ...) Tue, 11 Mar 2014 23:36:57 -0400 https://reprap.org/forum/read.php?88,319401,323341#msg-323341 https://reprap.org/forum/read.php?88,319401,323341#msg-323341
Thanks to Bezier curve scad by donb on thingiverse!
This is much, much better! I need to clean up the code, so i won't post it yet, but this really looks like a rocket nozzle.]]> Buback Let's design something! (I've got an idea ...) Tue, 11 Mar 2014 16:52:35 -0400 https://reprap.org/forum/read.php?88,319401,323243#msg-323243 https://reprap.org/forum/read.php?88,319401,323243#msg-323243 the1st is the point where the divergent nozzle is tangent to the throat radius;
the 3rd is tangent to the exit radius;
and the 2nd point is where those two tangents intersect.

I would like to be able to define the angles of the two tangents as variables.

Still learning how to program this in openscad, though.]]> Buback Let's design something! (I've got an idea ...) Tue, 11 Mar 2014 13:46:31 -0400 https://reprap.org/forum/read.php?88,319401,322684#msg-322684 https://reprap.org/forum/read.php?88,319401,322684#msg-322684
The nitty gritty of rocket nozzles is complex. it is rocket science, after all. I suppose as it gets more complex, the inputs should be more in line with the variables for the formulas rocket scientists use. That's all very complex, though, and beyond my abilities, so I think this version will be the "Hobbyist Nozzle".

EDIT:
Your code if fine, but i need to integrate it better into mine. I need to figure out the starting angle of the parabola at different sharpnesses. ~60 deg works for .36, and ~80 deg works for .16.
[attachment 28362 bell.png]

EDIT 2:
I attached a cleaned up, modulized version.]]> Buback Let's design something! (I've got an idea ...) Mon, 10 Mar 2014 11:27:48 -0400 https://reprap.org/forum/read.php?88,319401,321622#msg-321622 https://reprap.org/forum/read.php?88,319401,321622#msg-321622 [attachment 28200 parabolic_bell.PNG]]]> MattMoses Let's design something! (I've got an idea ...) Sat, 08 Mar 2014 02:54:28 -0500 https://reprap.org/forum/read.php?88,319401,321393#msg-321393 https://reprap.org/forum/read.php?88,319401,321393#msg-321393
I'm still not having any luck with the parabola for a bell nozzle. I tried a 2d plotting module, but that wasn't great.]]> Buback Let's design something! (I've got an idea ...) Fri, 07 Mar 2014 15:02:39 -0500 https://reprap.org/forum/read.php?88,319401,319923#msg-319923 https://reprap.org/forum/read.php?88,319401,319923#msg-319923
The "hull" command makes the nozzle cylindrical. I don't know how much force there is at the throat, but if there's a lot, then this makes that part thicker. it could also be used for mounting holes.
Commenting out the hull command makes it much lighter, though.]]> Buback Let's design something! (I've got an idea ...) Wed, 05 Mar 2014 00:59:28 -0500 https://reprap.org/forum/read.php?88,319401,319722#msg-319722 https://reprap.org/forum/read.php?88,319401,319722#msg-319722
I'm even having trouble getting the conic nozzle to be tangent to the throat exit radius. Openscad makes it hard, at least for me.

From what i understand, water rockets wouldn't benifit, since it's an incompressible flow situation. I've read it would even hurt performance, probably from the surface tension slowing the flow. However, I'm wondering if it would work in a vacuum.]]> Buback Let's design something! (I've got an idea ...) Tue, 04 Mar 2014 15:09:03 -0500 https://reprap.org/forum/read.php?88,319401,319688#msg-319688 https://reprap.org/forum/read.php?88,319401,319688#msg-319688 this to make water rockets. Although the nozzle shape probably doesn't affect the performance of a water rocket that much...

You could also make ceramic nozzles if you have access to a clay printer like this one or this one.

It would be fun to put in embedded cooling channels. Making a model of an A4/V-2 rocket engine would be really fun too. :)]]> MattMoses Let's design something! (I've got an idea ...) Tue, 04 Mar 2014 14:09:42 -0500 https://reprap.org/forum/read.php?88,319401,319401#msg-319401 https://reprap.org/forum/read.php?88,319401,319401#msg-319401
I'm working hard to understand both the nozzle design and OpenSCAD, so i only have a very simple version modeled.(attached below)

plug in your parameters and you will have a simple conical De Laval nozzle negative. By casting something around it (plaster, cement, etc) and then melting out the core, you can have your own rocket nozzle.

I hope to make this into a printable nozzle that you could attach to things. obviously not for combustion, but attaching it to an air compressor hose could be fun, or a balloon. Should stand up well to steam, too, as long as it's bellow the melting temp of the plastic (please, please be careful with hot steam).

of course, if the code is terrible please help make it better.

So far the best page i've found for just general, rule-of-thumb dimensions is here:
http://www.braeunig.us/space/propuls.htm

Anyone with experience with openscad who wants to try a parametric bell nozzle, Please do! That page has all the parameters about half way down.]]> Buback Let's design something! (I've got an idea ...) Tue, 04 Mar 2014 00:50:54 -0500