Tubes

Lenox Laser makes some really nifty orifice fittings. I recently ordered some of the 1/4" tube fittings because I wanted some orifices for my igniter that are smaller than the 0.014" available as flare jets.

The 1/8" tubes got me thinking about another project and so I was looking at buying some of the smaller orifice fittings and modifying them for my own use. The problem was they really only have up to 3" lengths without added cost. And even at $30 they seemed a bit pricey to buy and carve up. A search of the web found no easy source for the blanks they make so I tried my hand at making one myself.

I first tried to make a mandrel using a 1/8" ball end mill. That didn't work particularly well. I had a ball bearing spinning tool for the lathe left over from another project, so I tried it.

It worked very well. The tube in the picture below is my very first attempt with the technique. I was anticipating having to spot weld the end but it is water tight to 60 psi which should be good enough for what I have in mind.

Additional Testing

I modified the nozzle to a slightly larger throat area and added a diverging section. This test configuration had a 0.014" propane orifice, a 0.027" N2O orifice, and a throat of 0.201". It was running slightly lean at a chamber pressure of 110 psi. I plan to mount it to the thrust stand and get some performance data next.

Nitrous Propane Rocket Igniter

Second video, slightly smaller orifice size, chamber pressure of 110 psi.

More Igniter Testing

I am testing various nitrous oxide orifice sizes. This one generated about 135 psi of chamber pressure. And the video is in focus this time.

Loooooooong Time

I've built a new igniter. Same basic design but a bit bigger and uses a 14mm plug, the Champion L78V. I've also included a port for measuring the pressure inside the igniter combustion chamber.

Here are a couple of videos of it in action.