Test system assembled - OK!
Last week at the lab, I was able to assemble the full preliminary test system, with the cement nozzle now in place within the aluminium tube, next to a paraffin grain, and the tube entry closed by the aluminium part machined earlier.
The plan is now to fit a steel tube (length to be determined) in the hole of the machined part, where we will then release the compressed air from the lab compressor. At around 2 bars, that should not create much mass flow with the combustion, yet it should still create a nice flame.
I'm however currently going through a research phase as to the thrust which will be theorically generated, in order to determine how well the test system should be fastened to an external mass.
The other step that was achieved was a test of the spark gap igniter (which will provide the ignition of our rocket engine) coupled to rigid copper rods which were sheathed in plastic and passed through 2 drilled holes in an aluminium plate. Up to now all our spark gap tests were made using a "third hand" to hold the wires at the correct distance from each other, and each combustion lead to more plastic being burned. This copper rod solution is easily replaceable, and very convenient to generate the ignition in the enclosed space of our pre-combustion chamber.
You can see the test in this video.
And this is the view of the test system with the copper wire passed through the top plate - they still have to be shortened and maintained in place now:
I'm still not very confortable with the clamp collar maintaining the top part during the compressed air test, one solution could be to add two breeze blocks at the rear when this first test is made. Any feedback or suggestion would be welcome!