How to diagnose low amplitude

[heifetz17]

I just finished this Waltham that was previously not running and I’m curious about the seemingly low amplitude.

I ran it for 24 hours after reassembling and wound it back up and tested it this morning. The first picture is in the horizontal position and the second is vertical.

I believe I have a fairly strong hold on adjusting the rate and beat error, but watchmaking is still new to me so I’m a bit lost on the amplitude. I know about possible end shake, possible weak mainspring, etc, just not sure where to start and what exactly to look for.

This is a Lorsa P72A movement.

 

[karlmansson]

Amplitude is probably the one thing that can have the most things affect it. Most common are probably dirty/poorly lubricated power train and set mainspring. Any wear or misalignment of gear meshes due to that wear will also reduce the efficiency of the transmission of power. Then there’s the adjustment of the escapement. Excessive locks will decrease amplitude, but if the watch hasn’t been tampered with before the locks and drop should be adjusted from factory. Beat error can also play a role if large. Worn pallet stones. Loose impulse jewel. Worn pallet fork horns. Magnetism. A high amplitude (within reason) is the result of few or small errors downstream, rather than a variable that can be controlled and adjusted on its own.

Best of luck!

Karl

 

[heifetz17]

Yesterday upon reassembly the amplitude was 190. I did see higher numbers such as 240 and 280. This morning after 24 hours it’s 226 (at horizontal). Would it be acceptable to run for another 24 hours and check again tomorrow or does this tell me for sure there’s an issue or wear somewhere?

 

[Skutt50]

Did you peg the jewel holes? Such variation can be many things but also as simple as dirty jewels with old oil that is slowely loosening up.....

You can let down the main spring and remove the pallet fork. Now give the crown half a wind and observe the escape wheel. It should spinn and then stop only to reverse right away. Even if it does not reverse it shold show a tendency to move backwards. If so the gear train is probably not the culprit.

Next test is to instal the balance and to give it gentle push. It should swing for some 20 seconds or more and slowely come to a halt. If not there is a problem with the balance pivots, the jewels or a hairspring that is not flat.

Next thing to check is the pallet fork. Once installed it should drop from one banking pin to the other with a gentle shake of the movement.

If all this works out there might be a more complex problem with a loose jewel or some other damaged part.

 

[karlmansson]

Yesterday upon reassembly the amplitude was 190. I did see higher numbers such as 240 and 280. This morning after 24 hours it’s 226 (at horizontal). Would it be acceptable to run for another 24 hours and check again tomorrow or does this tell me for sure there’s an issue or wear somewhere?

Amplitude should be consistent for a given position over at least an hour. It will vary between the horizontal and vertical positions due to friction. But for a given position it should not fluctuate. If it does you likely have gear train issues (bent teeth, dirt in pinions etc.).

An acceptable amplitude for a modern Swiss lever watch (1940s and later) is about 270-300 deg at full wind and above 200 after 24h running.

 

[gmorse]

Hi Heifetz17,

The timing machine calculates the amplitude from the lift angle, (that's all it's used for), and pocket watches probably won't have angles of 52º, (the default on many timers), but a lower figure. It may be worth discovering the actual amplitude in some other way, such as taking a video and replaying it in slow motion.

Regards,

Graham

 

[heifetz17]

Graham, my apologies I didn’t specify. This is a late model Waltham wristwatch, and I verified the lift angle at 52.

Karl, is that after 24 on the original wind, or re-wound?

Skutt, yes to your question, and thank you for the guidance! Great things for me to double check!

 

[karlmansson]

Graham, my apologies I didn’t specify. This is a late model Waltham wristwatch, and I verified the lift angle at 52.

Karl, is that after 24 on the original wind, or re-wound?

Skutt, yes to your question, and thank you for the guidance! Great things for me to double check!

The original wind. Not sure why it would be different after winding again? It normally takes a couple of hours of running for everything to “settle in” after lubrication but after that you should see no variation.

 

[everydaycats]

Amplitude should be consistent for a given position over at least an hour. It will vary between the horizontal and vertical positions due to friction. But for a given position it should not fluctuate. If it does you likely have gear train issues (bent teeth, dirt in pinions etc.).

An acceptable amplitude for a modern Swiss lever watch (1940s and later) is about 270-300 deg at full wind and above 200 after 24h running.

Fluctuation in different positions—if watched closely for a pattern—should be traceable to the gear via math if it is really that hard to pinpoint visually. Patterns can be your friend if you are really really inquisitive.
Regards