N1 & N2 indicators

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. That requires the motor to reach

Initial idea to put a stepper motor behind the main shaft proofed unpractical due to [more to follow]

 

B707 engine spool up