N1 and N2 indicator are basically exactly the same in terms of construction. The major problem here is the vernier dial and the speed at which it is rotating during engine acceleration. Here is an engine spool up table. It shows that the engine can spool up above 50% at 10% within ~0,2 seconds. After building 3 prototypes I have finally come up with a good solution of putting a larger NEMA stepper motor behind the main shaft, keeping the original gearing for the vernier. Watch the video – speed and precision!