Hi Nicola, I can give it a try.
The CPS sensors are looking at small bars on the flywheel. Given they are required to count them in rotation, also the speed of the crank, even in cranking it takes very little difference to fool the computer. The slight torsional "backlash" that is created in cranking pulses from the piston acceleration of the crank on power is followed by compression on another piston. This dance creates the torsional moment and we hear this with gear lash in the gearbox. In the case of the CPS sensors they can't deal with too much backlash without creating confusion with the computer. To solve this they had to remove the 30 degree freeplay dog hub that had been used in the standard system.
You are right in that inertia plays a role. In Newton's first law of motion the propeller, once we start it to rotate, wants to continue to spin. The torsional moment is created from the compression fighting the spin of the prop on starting as it tries to slow it down so we have a possibility of damage to the gears if we can't absorb it. The damping is done in the case of the iS engine by a dog and ramp just like the standard 912/914 reacting to absorbing the moment in springs and releasing it. (once enough speed is attained it is negligible and no damping is needed once the pulses are very fast after starting) just after high idle the noise of this damping will disappear when the pulses are very fast.
The flywheel bars then appear to the CPS sensors to dance, that is move very slightly on initial cranking. This movement creates issues technically with picking up the right ignition side to fire. The solution was to damp some of the absorbing features by removing the 30 degree dog and replace it with zero degree. The overload clutch is still there and the dog and ramp system still there to deal with the torsional moment and smooth it all out.
I hope that sort of explains it. A careful look at the parts in the HMM and the relationship to the CPS sensors and the flywheel might bring it more into focus for you.
Cheers
