The motor barrel is an old American system used in the highest grade railroad watches like the Illinois Bunn Special and the Hamilton 950. The motor barrel allows the mainspring barrel to ride between jewels when the watch is running. The purpose of this arrangement was that if the spring breaks, destructive recoil forces would not be applied to the gear train.

The Illinois Bunn Special and Hamilton 950 are two great examples of high-grade pocket watches that use a motor barrel in their movements

movement showing barrel arbor
Ratchet wheel in place
Complete mainspring assembled, showing top jewel and 3 small screws that hold the jewel in place. The 3 small screws have always been a problem with this barrel, the threads are very fine and they can easily be stripped.

The system is comprised of many parts compared to a traditional barrel.

All parts of a motor barrel shown

Traditional barrel and its parts

Motor barrel in a standard size mans movement
A beautiful Hamilton 950 showing their motor barrel

Mark Sirianni Watch Repair
25 Fraley Street
Kane, Pa. 16735
814-558-4818 (cell)

CHARLEY PHOTO OF THE WEEK: Here’s Charley taking a pre-bed nap after a long day of being a good girl. Her weekend plans include getting a bone, taking naps and watching 60 Minutes.