Another update, now in 2012

Well, it's been a couple months since the last update. HOWEVER, I now have renewed my subscription to my local hackerspace, acquired the block of brass (for free), have very nearly acquired the coil-on-plug (for free, just have to pick it up), and have some favors I can call on for my local machinist. I also bought a decent CAD program, Alibre Design Personal, which makes certain things a lot easier (like putting threads in my drawing and making a 2D diagram).

And now, I think the valves need 12V and 24V, so that's three power supplies I need (5V for Arduino... could be from laptop, though I may want to be better isolated, 12V for one valve, and 24V for the other, and 12V for the coil-on-plug)

Still need:
*the right taps for my spark plug and my orifices (if I don't just drill them) or my existing adapters
*correct gender for the propane tank adapter
*orifices (again, if I don't drill them)
*propane tank (may have one lying around)

Semi-optional:
*filters
*usb opto-isolator (or, just run it from a cheap PC or semi-broken laptop).
*digital pressure and temperature probes

I've also been thinking about making the throat and nozzle replaceable, perhaps allowing me to 3d-print different nozzles (in steel) for testing different shapes in subscale.

Also been thinking of using two, three, or four servos to do some experiments with vectored thrust, ala V2 and Redstone, etc on a subscale. I've got 2 servos already.

I have to make sure I can safe the system by just turning the power off on everything. I'll have everything hooked up to a power strip I can just switch off or unplug everything if something goes bad. Also, I want a big, red "fire" button. ;)

Fire durations will necessarily be very short, one the order of a few seconds, starting with just two seconds.

I just got a nice digital SLR (not video-capable, though), so better pictures will be up shortly.

EDIT: Most of the stuff I got: