What happens when a mainspring breaks?

This post demonstrates what could happen when a mainspring breaks.  The clock in question is a standard American time & strike clock movement.  When a mainspring breaks at the tip where the spring attaches to the mainspring barrel, that can be repaired. 

If the mainspring breaks in the middle (like our example) or where it attaches to the mainspring arbor, the spring needs to be replaced.

The image below shows the broken mainspring in the middle of the spring.  Note the remaining spring is still attached to the mainspring arbor.

This image shows damage to the 2nd wheel arbor.  Luckily only this arbor was damaged.  Pinions and/or trundles can also be damaged.  In our case here only the 2nd wheel arbor too the brunt of the breakage.

Usually the bend is primarily located right next to the lantern pinion.  The repair this the wheel was chucked into a lathe close to the pinion.  The arbor was gently tapped and checked until the arbor bent back to true position.  It should be noted that tapping the arbor should only be done to metal that is NOT hardened steel.  American T&S clocks do not have hardens arbors.  If in doubt, check first.

The next image shows the straightened arbor.

Finally the movement with all the wheels and levers reinstalled just before the top plate is placed.  The entire movement was ultrasonically cleaned before reassembly.

A job well done.