FreeCAD, aside from generally being an excellent free and opensource CAD environment is ever developing and being extended. Over the last year or so a really interesting development has been the Rocket workbench. If you are new at the zoo, FreeCAD works with a workbench system where different workbenches contain lots of different tools grouped into themes. So for example if you want to convert a 3D part into a technical drawing there is a specific Techdraw workbench which, when you switch to it, has all the tools to lay out a technical drawing. Many workbenches are built in but you can also download and install extra workbenches of which the Rocket workbench is a good example. I’d love to see more rocketry people using FreeCAD and so this post is aiming to show why FreeCAD, as well as Openrocket, might be well worth learning!
Openrocket and FreeCAD have lots of active development happening and it just happens that an amazing contributor, Dave Carter, AKA DavesRocketShop, is contributing development to both these excellent opensource pieces of software. Further than that Dave realises how powerful interaction between Openrocket and FreeCAD might be and is working to make both these packages work together usefully.
As a starter example (but frankly enough of a reason for many rocketry types to learn some basics of both these packages) is the built in parts database. In Openrocket if you are designing a rocket from scratch you might chose to incorporate an off the shelf nosecone for example. Clicking the Nosecone icon in openrocket the component database will either launch automatically, or you can launch it from the regular nosecone dialogue window by clicking the “parts library” button in the upper right hand corner. Either way you’ll see a well maintained and curated list of commercially available nosecones from a range of manufacturers.
OK, Over to FreeCAD. Say we now can’t find that commercial part to buy in our local rocket shop we might think about having to draw it in CAD and perhaps 3D print it. Well, the exact same database is available in the Rocket Workbench in FreeCAD. Clicking the nosecone tool icon should launch a nosecone parameter dialogue in the combo view window on the left of the screen. Scrolling down you can click “Lookup” to launch the exact same database of components as you just launched in openrocket. You can scroll to the same nosecone and select it and it will appear as an object in the live preview and also as an object in the combo view. If you wanted to simply 3D print this you can select the object in the combo view window and then click “File-Export” to export the nosecone ready for printing. You can pretty much do this without learning any more about FreeCAD and Openrocket if you wanted too, but, if we learn a few more skills, we can do some other really simple yet useful rocketry tasks.
Another simple example perhaps of use is imagining we want to build an upscale version of a rocket with a scaled up nosecone. If we select a nosecone from the database in FreeCAD we can then jump over to the Draft Workbench. With the nosecone selected we can now click the “Scale” tool icon. As a tip to help you find tools, if you hover over any icon in FreeCAD it will say the name and a small description of the tool and I describe the tools with the names these rollover descriptions use. In the scale dialogue click the “enter point” button and in the next dialogue make sure that both the “Uniform Scaling” and the “Create Clone” buttons are selected. Then change any one of the X Y or Z axis scale amounts to the scale you require, so for example if you want to double the size of the nosecone change one value to “2”. The other values should change automatically and then when you click OK an upscaled (or downscaled) version of your nosecone will appear as an object.
Finally, for this example, if you know a little about using FreeCAD you can easily add geometry to parts you create on the rocket workbench. In the image I’ve simply brought a cloned nosecone part into the Part Design workbench and then added some features to make an attachment point for a recovery system. If you are interested in developing your FreeCAD skills my free to download tutorial book FreeCAD for Makers is available from the Raspberry Pi Press here.
This is only the tip of the iceberg in terms of what what FreeCAD and Openrocket are capable of. The Rocket workbench is amazing in terms of what it can automatically generate parts wise. Nosecones, transitions, tubes rings, rail buttons, rail guides and more; there is a really impressive fin can generator as well as some pretty high end fin flutter analysis tools. The real beauty is that you can simply transfer dimensions and data over from a design you have worked on in Openrocket. Having rebuilt it quickly in FreeCAD there are so many options available, as an example I can simply select a centring ring in the FreeCAD design and take that part to the Path workbench and create toolpaths to then cut the rings on my CNC router. I can export all manner of files for parts for laser cutting or other processes. It’s a really good tool to learn some skills on if you are a rocket fanatic!
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