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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

3D printed parts allowed

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anachronist
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3D printed parts allowed

Post by anachronist » Sun May 07, 2017 2:40 pm

Clarification question on rules (particularly class D, which the current record, by my own physics-based simulations, is right near the theoretical limit for a 2L bottle, so it won't get beaten by much if at all):

Are 3-D printed parts allowable? There are several nuances to this question. Consider these four scenarios:
  1. I design my own part, and create it in virtual space in my computer, and then send the file to my own 3-D printer.
  2. I use a friend's 3-D printer to print the virtual part I created myself.
  3. I create the part myself and then send the saved file to one of the many available commercial 3-D printing services for them to print and send me back my part.
  4. I download a design I find online and 3-D print it myself on my own 3-D printer.
My own take on this, is that I must be the person who creates and builds the part in a virtual 3-D space. The final step of printing out a part has nothing to do with my skill in creating it (you just load the file into the printer and push a button), so it doesn't matter who prints it for me. Therefore I'd consider scenarios 1, 2, and 3 to be allowable.

On the other hand, if I print someone else's model of a part, I'm not actually doing any creative work, I didn't design the part, and I didn't create it in a virtual 3D space, someone else did. So even if I used my own printer, I would say scenario 4 isn't allowable.

Does that seem reasonable?



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Re: 3D printed parts allowed

Post by WRA2 » Sun May 07, 2017 11:04 pm

Hi,

3d printed parts would be legal to use in the competitions.

You are correct that options 1 - 3 would be acceptable. For #4 it would depend on a few things. A "downloaded" 3d model that you did not design may or may not be acceptable. A 3d model you purchase would not but a "free" model may. I would recommend if you are in that situation to ask before you build and we will handle it on a case by case basis until we can gather the membership and add a specific section detailing what will be allowed with 3d printing.


Lisa Walker,
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anachronist
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Re: 3D printed parts allowed

Post by anachronist » Tue May 09, 2017 12:09 pm

WRA2 wrote:3d printed parts would be legal to use in the competitions.

You are correct that options 1 - 3 would be acceptable. For #4 it would depend on a few things.
Thanks for confirming. Personally I don't see the fun in #4. :)

There's another scenario I didn't think of earlier.

5. I see a pre-made 3D printable model online that isn't intended for rocketry, but designed for some other purpose. I download it and print it for using in a model rocket.

I assume that's allowable under paragraph I.4 of the class D rules ("manufactured items that are not designed for rocketry ... are allowed").

I'm not yet the situation where I see a pre-made model online that I want to print (aside from bottle cap threads). But if I find myself in that situation, I'll ask here. Thanks!



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Re: 3D printed parts allowed

Post by WRA2 » Tue May 09, 2017 10:09 pm

#5 would be allowed. It would be the same thing as purchasing a gardenia hose quick connect from the hardware store.

Good Luck with your build.


Lisa Walker,
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:WRA2:The Water Rocket Achievement World Record Association :WRA2:

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