Been working on various ways to get the Bell (made years ago), to ring automatically.  Spent a lot of time experimenting with Air Operated Bell Ringers.  Ended up making dozens of various designs.  Couldn't get the fine "regular" ringing cycle that was needed (about once a second).  On a parallel path, work was progressing on an electronic solution.  This isn't a digitally simulated bell sound, but one in which a timed pulse activates a solenoid which strikes the bell. 

A Grade Crossing Bell Ringer Circuit kit was bought (see link) along with various solenoids, resisters and capacitors.  The original kit was modified to handle the additional power needed to activate the solenoid.  If you're not familiar with electronics, it's suggested you get someone to help if you want to go this route.  The kit comes as-is and up to the buyer to do any modifications.  When the right capacitor/resistor combination was found to get the correct timing and power for the solenoid, the circuit was soldered together and installed in the cab of the engine (hidden away).

Next thing was to figure out how to mount the solenoid to strike the bell and still look acceptable.  Actually, looks weren't too important in this case because the bell is under the smokebox and can barely be seen.  What ended up being used was a 5/16" rod suspended from the mounting hole at the top of the bell.  To hold the solenoid, 1/8" steel was bent and soldered onto the rod (see below). 

Here is the apparatus all hooked up. 

(Need to finish smoothing out the inside of the bell.  That's for another time)

Adjustments were made up/down and left/right to get the solenoid in the right place for a good sounding ring.  Once the right spot was found, the solenoid was hot-glued in place.  Wire was run from the solenoid, through the rod, under the smokebox, under the walkway and into the cab where the circuit board was mounted and powered by the battery in the tender.  From a side view, only a small portion of the solenoid can be seen.  If hiding the solenoid is preferred, moving it up or angled differently should also work.  Just need to fiddle around with it until you get what you want.

Ding...  Ding...  Ding...

The operation and sound of the ringer was great in the shop.  Once it was taken outside with all the ambient noise, I quickly realized it wasn't loud enough to be heard from any distance.  The capacitor/solenoid combination needs to be changed to provide the additional current to operate a more powerful solenoid.  Back to the drawing board.  Grrr.....    

Gave up on the solenoid idea.  Decided to go a different route with a pneumatic bell ringer.