Fogg' Patent

[RonD.]

Hi folks,

I recently picked up an old Waltham key wind that says "Fogg's Patent" on the movement. I was wondering what that might refer to.

Bye-the-way, the watch is an 1857 model.

Thanks,
Ron

[RonD.]

Hi folks,

I recently picked up an old Waltham key wind that says "Fogg's Patent" on the movement. I was wondering what that might refer to.

Bye-the-way, the watch is an 1857 model.

Thanks,
Ron

[doug sinclair]

Ron,

That would likely refer to the Fogg patented safety pinion on the centre wheel arbor. When a fully wound mainspring in a watch with a going barrel breaks, all of its energy is released against the barrel wall. And when that happens, teeth can break out of mainspring barrels and centre wheel pinions. A watch equipped with this feature will have a threaded centre wheel arbor where the pinion sits, and the pinion is likewise threaded, and screwed onto the arbor. When the barrel is driving the watch, the tendency is for the pinion to remain in place on its threaded arbor. When the mainspring breaks, the reverse backlash when the mainspring hits the barrel wall unscrews the pinion, and no harm is done. The pinion can easily be screwed back on.

[RonD.]

Thanks Doug,

I had seen something in the internet regarding a Fogg's floating hairspring (similar to the one on my Hamilton). It didn't look the same so I was curious.

That is a good feature. I have a Waltham Broadway that didn't have the safety pinion and when the mainspring broke, it broke a tooth on the center wheel and also bent a tooth on the mainspring barrel.

Ron

[Jon Hanson]

I believe what you are speaking about are the pivoted stud or vibrating hairspring stud AWCo. 16 and 20s 3/4 plate gilt movements that come in 15,20, and 21J.