Sunday, May 27, 2012

Valves By Request

I had a request for additional details on some of the valves I use.   I polished up my drawing and loaded it on the website,   It includes a little bit of useful details about o-ring material as well as McMaster-Carr part numbers.

Open Source Hardware is all the rage these days.  I'm not sure that OSH will be quite the revolution that OSS was - replicating hardware from a "source" has a higher barrier to entry than replicating executable software from source.  It also takes more time and effort to develop new hardware - I wonder about the sustainability of OSH because in the end, people have to be compensated for their time somehow.

In any case, part of the point of this post is that I do requests!  So if people have things they want to see, drop me a line or post a comment.

Saturday, May 5, 2012

Plastic Rockets

Sort of.   I ordered two of my latest chamber designs in plastic from    The cost is very inexpensive and even though i can really fire them, they do help to visualize the design.   Its also useful for fitting up the chamber to other components like the test stand.

The picture above is the 50 lbf scaled up design that I did on request.   The material is Shapeways' Frosted Ultra Detail and it came out very well.   The regen passages are very crisp and well defined.   The only drawback is that they are still full of powder.  I actually mailed this part over to the individual who asked about the feasibility of scaling up the thrust.  

As you can see in the picture below, the 50 lbf version is comparable in size to my original chamber, which is only 12 lbf.   The original chamber was fairly conservative in size, and so the results of testing and additional analysis indicate that the chamber volume can be  quite a bit smaller for a given thrust level.   The other plastic model is version two of the 12lbf motor - notice the size difference.   This part was printed in Shapeways' Transparent Detail material and the results were not quite as good.   I'll be using Frosted Ultra Detail in the future.