Wednesday, 27 June 2012

Weekend test, vehicle progress

I tested the new catalyst pack on Saturday and although thrust still isn't what I want it to be (10Kg) it is a definite improvement over the last pack.

Roughness is defiantly an issue but I am not so concerned with it as getting higher flow rates through my pack. I applied about half as much compression as the last pack but it seems like that was still too much. 

I decided to start testing on a plastic sheets after I heard about a incident where peroxide leaked into cracks between two concrete slabs. Apparently pressure built up underneath and caused an explosion which killed a person. This meant that I needed to test on an incline so the sheets didn't catch on fire....

Engine with injector removed and pack removed from engine:

Both the distribution plate moving and the bits of teflon tape are of concern. I have probably gotten a bit slack with cleaning the old tape off fittings. The plate rotated because it was only pressed in place and not held up against anything. Its difficult to get the top of the pack to line up with the injector, especially when you are assembling a new pack as it shrinks so much. In future I will take it out and add spacers to the bottom. I think the roughness/oscillations are mostly due to the head space.

The pack fared very well and was not at all stuck together. The combination of the stainless mesh and the top and bottom distribution plates gave the pack good strength and seems to work well.

I used about half as much compression in this pack as the last one but I think that was still too much. I really need to add a pressure gauge to the press so I can quantify exactly how much force I am applying. That might be a task for the weekend. I am hopping that with less compression I can get an even higher flow rate.

If not then I think that I will need to go to a larger diameter pack for more flow rate. I really like the 20mm size pack because I can get 60mm square pure silver mesh easily from which I can get 9 discs. The original vehicle design called for a 30Kg vehicle with 10Kg of fuel. With the new tank/design I should be able to get the weight down to about 12Kg without optimising its structure. There is a lot of room for weight saving if necessary as things like the base plates and solenoids could easily be drilled/milled to save weight. I could also make my own aluminium fittings instead of using the heavy stainless ones if it came to it.  If I can get more thrust out of the engine then that will mean more flight time but if not I would rather just use what I have and get something flying. 

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