Today I decided to make a test rig for the eddy current tachometer, I need to get the scaling right before I start the bike up again.
Since the compressor has 14 blades I need a trigger wheel with a teeth number dividable with 14 to be able to find the right scaling factor, first I milled a 42 tooth trigger wheel but I couldn´t get enough rpm in the lathe for the tachometer to start registering rpm. Luckily I had a pile of old gocart sprockets so I took an 84-tooth sprocket and modified it for better trigger signal. That did the trick!
I measured 1710rpm on the sprocket with the highest gearing in the lathe, that equals 1710x6=10.260rpm on the compressor wheel. The bike tachometer read 31.400rpm (+-100rpm) which is just about three times too much. Now I just need to check the Auber manual to figure out how to reprogram it correctly.
I am extremely glad that I seem to have finally solved the tachometer problem, making a reliable tacho has been a constant issue since I built my first gas turbine 14 years ago....
Cheers!
/Anders