Omega bumper automatic

[hewybaby]

I've always been fascinated by early Omega automatics -- the bumper or hammer automatics.

There were two sizes: 28.10 mm and 30.10 mm, and the movements lifespan extended through Omega's beginning to use calibre numbers in 1949 so there were initially sized-based designations, later calibre numbers.

This table shows how these movements were related and how they differed. I included photos of some of the movements I own, which range from pristine to far from it. Perhaps someone could use this as a reference . . .

Old Designation	30.10 mm subseconds	Calibre Number		Seconds	Date	Springs	Regulation	Chronometer
30.10 RA PC		330		subseconds	none	exposed	standard	no
30.10 RA PC AM JUB		331 see photo below		subseconds	none	exposed	standard	yes "Jubilee"
		332see photo below		subseconds	none	covered	standard	no
		333		subseconds	none	covered	"rg" fine regulation	Yes

Example of 331/30.10 RA PC JUB "Centenary"




Example of calibre 332, courtesy of Father John Shinall "jmrolls"

Old Designation	28.10 mm subseconds	Calibre Number		Seconds	Date	Springs	Regulation	Chronometer
28.10 RA PC		340 see photo below		subseconds	none	exposed	standard	no
28.10 RA PC BULL		341 see photo below		subseconds	none	exposed	standard	Yes
		342		subseconds	none	covered	standard	yes
		343 see photo below		subseconds	none	covered	"rg" fine regulation	Yes
		344 see photo below		subseconds	none	covered	swans neck regulation	Yes

28.10 RA PC (later calibre 340)




Calibre 341, courtesy of SteveG




Calibre 343




Calibre 344

Old Designation	28.10 mm center seconds, no date	Calibre Number		Seconds	Date	Springs	Regulation	Chronometer
28.10 RA SC PC AM		350		center seconds	none	exposed	standard	no
		351 see photo below		center seconds	none	covered		Yes
		352 see photo below		center seconds	none	covered	"rg" fine regulation	Yes
		354 see photo below		center seconds	none	covered	swans neck regulation	Yes

Calibre 351






Calibre 352

Old Designation	28.10 mm center seconds with date	Calibre Number		Seconds	Date	Springs	Regulation	Chronometer
		353 see photo below		center seconds	none	covered	standard	no
		355		center seconds	none	covered	swans neck regulation	Yes

Calibre 353

[jmsrolls]

Thanks Sam!

Here's my cal. 332:





Fr. John+

[hewybaby]

May I edit the post to include your movement photo?

[Houston]

Hey Sam

Many thanks for this splendid resource.

As you know I'm not a movement person. Indeed, not by a long shot I'd say so I have a beginner's question

You mentioned bumper or hammer automatics which led me to look for a hammer-shaped part in the movement. Well I can't see it. Presumably, it's a metaphorical hammer?


Thanks pal and be well now


ZIN
Not usually shaken nor stirred ;D ;D ;D

[jmsrolls]

hewybaby said:

May I edit the post to include your movement photo?

Sure, Sam, be my guest.

Fr. John+

[timefinder]

WOW Great information! Thanks!

[hewybaby]

cafezinfandel said:

Hey Sam

Many thanks for this splendid resource.

As you know I'm not a movement person. Indeed, not by a long shot I'd say so I have a beginner's question

You mentioned bumper or hammer automatics which led me to look for a hammer-shaped part in the movement. Well I can't see it. Presumably, it's a metaphorical hammer?


Thanks pal and be well now


ZIN
Not usually shaken nor stirred ;D ;D ;D

The 28.10 RA PC (which is later known as a calibre 340) in this photo



Modern movements have a rotor which rotates, winding the watch. These movements have a "hammer" or "bumper" which bounces or "bumps" from side to side against the springs, providing the winding. Later versions of these movements have the springs covered.

In this photo, the silver colored arm extending upward from the center jewel attaches the massive bumper, which rotates from side to side to bounce against the springs in the bottom of the photo. The range of motion is about 120 degrees.

The gentle bump of these movements as they wind the watch that you can sometimes feel while wearing them is part of their charm.

[fergie]

Great post Sam. I too am like Mr HoustZin and don't really know much about the movement or inner workings of a watch. I realised a while ago why these were called bumpers (and all by myself, ain't I good ;D) and would love to see one of these in action.

[Houston]

Sam

It's been a great education. Many Pal for taking the time and trouble to put that together.


Keep well my friend


ZIN
Not usually shaken nor stirred ;D ;D ;D

[timefinder]

Dis postt shuld go in da BoSkoE schul of educashion tread! ;D

Seriously, great information. Thanks again!

[hewybaby]

Added two photos to the post