The joy of learning machining and building rocket parts in a hackerspace

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How do you transform a 6x50x1cm rectangular aluminium bar into a round piece of metal with a 2mm high and 5mm wide shoulder and an inner hole 21mm wide? That's when machining comes into play. And that's when being a member of one of the largest hackerspaces in Europe gets even more amazing.

First, why the machining in the first place? In order to create a very basic combustion chamber, where we will be able to melt and mold the paraffin wax into the desired grain, and then test our ignition system and general combustion principle. This is the basic view of the expected result:

The steel pipe is only there for molding purposes, it will be removed afterwards. The machined component will be screwed into the steel tube.

So that was the idea. As for finished components, I had with me the 5cm wide aluminium tube, the 21mm wide steel tube, and a rectangular aluminium bar. And no idea as to how to use the tools available at the lab to machine the expected piece.

Fortunately, one the members of the core team, Ellyan (whose real first name happens to be Damien, too - there's definitely a connection) was kind enough to take me through the whole process, show me how to use the various tools, and actually do himself a large part of the machining. In details:

  • we first used a band saw to cut quickly from the aluminium bar a 6x6x1cm square.
  • we then used a drill press to create a 21mm hole in the center (the output of our combustion chamber, and the retainer for the molding steel tube)
  • then we switched to the (manual) lathe to create a plastic centering piece, to help maintain the machined part in place around the centering bolt on the milling machine
  • the last step was the (manual) milling machine, where the piece was slowly rotated to turn it from a square into a 5cm wide disc, and create the shoulder.

And here are pictures of the result (note that the aluminium tube will be much sawed to a much lower heighth for the molding and first tests):

I am deeply thankful to Ellyan for taking the time to show and teach me these various tools, I now have tons of ideas poping into my mind regarding their potential use. Learning by working on a project that one is passionnate about is just as much fun as anything I could spend my personnal time on - and it feels much more fullfilling!

Comments

ryan.pulkrabek's picture

This is great, Damien! Utilizing these types of machines is a big asset, especially for what we aim to accomplish. It's also a great skill to understand how the products we use everyday are manufactured.

The experience you got is going to be needed for the injector plate. Let's put a plan in place to get this done. I'll work on the first round of design, and you can let me know if it can be machined with the resources from the Hackerspace you belong to.

Damien's picture

In order to keep a minimum alive my few FreeCAD skills, I have created the CAD file of what I have machined so far - the paraffin grain is an exception, I still have to melt and mold it into place. I wanted to post it to Github, but without success, it asks me to debug through the shell... not my area.

There is such a satisfaction to create parts in a CAD software from scratch that I now understand all these zealots of Catia and other big CAD tools ;o)

ryan.pulkrabek's picture

Let's discuss the issues with GitHub during the next meeting.

Thanks for this post. What a great invention! It gave me an idea of recreational activity for our family this summer. Want to entertain the children with affordable science this summer? Sure, we all do. Why not make a water rocket to launch in the yard? It would be a lot of fun for sure.