Saturday, 9 June 2012

Catalyst Pack Dissection

Today I dissected the catalyst pack and made some interesting observations.

The first thing I noticed is that all the layers of mesh seemed to be fused together. I could peel the top 10 or so layers off individually (with considerable effort) but after that they were all stuck together.

Eventually I managed to break the pack up where the anti-chanelling rings were by levering them.

There is a "tunnel" through the bottom 1/3rd of the pack but this doesn't exit the pack. The pack also seems to get progressively more degraded the farther down which I suppose is expected. Its really off the the tunnel doesn't exit the pack, but this could just be because it hadn't been used enough. The mechanism for the tunnelling seems to be bits of silver breaking off and impacting farther down.

The fact that all the layers are fused would explain why I can't get the flow rate I need through the pack, as the pressure drop would have increased significantly.

For the next catalyst pack I will use interspaced stainless mesh which should stop the fusing problem. I thought that the function of the stainless mesh was only to give the pack rigidity and that because my pack was so small I cold do without it but its other function is to stop the silver layers sticking togethere. I will also have a proper retaining ring at the bottom which should stop the bottom layers extruding through the bottom ring. Sets of 5 silver intersapced with stainless mesh seems to be the standard so thats what I am going to use. I have read about engines using 80 mesh so I am going to use the 70 mesh which is better value (more area for less weight) than the 40 mesh. The downside is that it is not as strong but hopefully the stainless mesh should take care of the strength.

I am still aiming for a limited test flight on the 26th of next month. Once I have the engine sorted I will continue with the vehicle but I don't think it will take long to finnish off the first prototype. I think we will probably have to make a second as I am not expecting everything to fit first time. I suppose the first vehicle will really be more of a mock up and we will probably figure out how to save a bunch of weight from it. Also I still don't have a final design for plumbing but it will be allot easier to plumb everything once I have something to work with. I was actually thinking of using stainless hard lines which would be lighter and more compact. Also the teflon-stainless lines don't have the best bending radius. Once exams are over I am hoping Buren and Scott will be able to put in more hours which should also speed up construction.

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