Originally Posted by
TromboneAl
The FD is indeed a brute force mechanism, that's why I can't see how an electromagnet is any improvement over the delicate and sophisticated muscles in my fingers.
Concerning precision, I push that lever, and the FD moves to exactly the correct point for shifting. (1) It is a lot more precise than it needs to be, and (2) I don't see how precision affects shifting under load.
Concerning smoothness, (1) I can do it smoothly, and (2) smoothness doesn't matter.
I could understand an argument that the electronic FD provides more force, is that the case? Maybe more force is needed to move the FD under extreme load.
You don't have any control whatsoever over the movement of the derailleur when shifting from the big ring to the small one. All you do with the shifter on a manual system is release the tension on the spring by clicking the lever.
This is in contrast with the upshift where you use the lever to directly move the derailleur outward.
On the downshift, the derailleur snaps back, dragging the chain, with luck, with it. I suppose you could call the snap a smooth action, but even with the standard spring, it's not gentle.
However, that snap also is one of the reasons why a chain will go further than the inner ring and come off. It's like catapulting off the derailleur plate.
The solenoid has a defined movement, and it doesn't snap because it is not, I gather, spring loaded. That means the shift will be a lot smooth and will place the chain exactly where it's meant to be.
And yes, a mechanism such as used in an electronic FD does create considerable force. As an example, I have used electric secateur for pruning fruit trees (commercially).
When the trigger is pressed, the electric "motor" moves a defined amount then returns to its start position. With the leverage to the cutting blade, I can cut through limbs two inches or more in thickness without any effort from me other than positioning the unit. To cut the same limb with a manual pair of hand secateurs requires quite considerable hand strength.