The idea of using only tack welds is to avoid distortion of the housing with the heat of welding. I'm hoping that the silicon gasket goo will stand up to the temperatures involved - if not, I'll try gasket cement. The housing is almost complete, as is the rotor and shaft, and the bearing housing is being turned up out of aluminium at the moment and should be ready early next week. I built the combustion chamber a couple of months ago. It's made of mild steel - I anticipate doing a lot of cutting and trying.
Vibration is minimal - similar to an electric motor at the same speeds.
The disks have been randomly assembled on the shaft and the holes aligned, and the whole assembly has not been balanced. Based on my experience with the first turbine, I can expect a massive increase in speed when the nozzle is installed and I can throttle the slot down to the optimum. Narrowing the slot will increase the velocity of the airflow up to a certain point, and will increase the distance the air travels around the disks between the slot and the exhaust. From the breeze at the exhaust, it is obvious that not all the energy has been extracted from the airflow as it passes through the disks. I'm sure that the energy in the exhaust has a centrifugal component, and I don't expect that to change, but I do expect more energy to be extracted from the air as it passes through the disks, and thus reduce the breeze.