Expert: Martin Meyer - 3/1/2009

Question
On a Big Ben #5 Chime Alarm: I see there are four gears between the Time mainspring and the escapement wheel. Am I correct to assume that the gear under the spring is the #1 wheel and the #4 is the one that drives the escapement?
Please let me know whichever way is correct.     Thanks

Answer
Hi Glenn,

I wish I had a Big Ben in my shop right now, but unfortunately I don't. So I will have to answer rather generically, and your clock may have a slightly different design from what I describe. Also, I would warn that clock terminology is far from standardized, and you will find many different names for some parts.

The large gear which is on the same arbor (shaft) as the mainspring is often called the Great wheel and is, in the American system, numbered as #1. The most common gear train will have a Second wheel (gear), a third wheel, a fourth wheel, and finally the escape wheel, which interacts with the verge (anchor). In some clocks, there is no fourth wheel. The escapement is driven by the mainspring, with the gear train reducing the force as it passes it on to, finally, the escape wheel.

It is essential to understand that there is a second gear train which engages with the Time train. This is the Motion Work, and its gears can sometimes be mistaken for Time train gears. Its gears consist of the hour wheel, the minute wheel and the center wheel. The motion work synchronizes the hour and minute hand, often includes the clutch which allows the hands to be turned to set the time, and often transfers the power from the time train to make the hands move. The power takeoff is most often the second wheel in the time train to the hour wheel in the motion work.  http://www.clockmasteronline.com