Today I finished the combustion chamber. The unit was chucked in the Harrison to skim the welds. I gripped it on the inner surface of the inner tube. This provided the maximum contact area, given that the unit wouldn't sit flush due to the flange weld bead.
This also meant that I had to spend some time truing the unit in the chuck, using a DTI. Once this was done it was a relatively simple operation to skim the weld bead. Due to the less than ideal chuck grip, I took very small cuts to minimise the cutting forces on the unit.
Once the bead was reasonably flush, I blended the weld into the flange using incrementally increasing grades of emery paper. Here is the chamber in the chuck of the Harrison during the skimming operation:-
On completion of the first face I reversed the unit in the chuck and skimmed the second bead. I had a major moment of anxiety at this point. Despite taking care to take small cuts, the tool dug in - I'm not sure why, I can only assume I misfed it. The chamber shifted in the chuck and one of the jaws damaged the flange face. My heart was in my mouth as I carefully removed the unit from the chuck. Fortunately the damage looked much worse than it was. I was easily able to blend it out using emery. After a few minutes it was barely noticeable. Returning the chamber to the chuck (and after changing my underpants) I finished skimming and blending the bead - using even smaller cuts than before!
I have to say that I am very pleased with the blended welds. I think they will be more than capable of withstanding the tensile forces exerted on the chamber. Here is one of the flanges after blending:-
I decided to give the outer surface of the cooling jacket a coat of heat resistant black paint. As mentioned previously, most rocket chamber heat transfer is by convection, but it will do no harm for this hot component to be as good a radiator as possible. I'll post some pictures of the painted chamber shortly. Until then here is the completed unit masked up awaiting paint:-
In the next few posts I'll be going into the engine design rationale, and start introducing a few equations. I bet you can't wait.