is this a savage escapement?

[lanzhou]

Dear All,
I just found this one,pivot bent, heavy balance, large impulse jewel,overcoiled, is this a savage escapement?

 

[gmorse]

Hi Ianzhou, and welcome to the Forum,

It certainly looks like a Savage. Can you post any sharper pictures? The important part is the "cutout" in the roller next to the jewel.

Regards,

Graham

 

[lanzhou]

Thank you very much for your kind reply. I hope the following pics are sharper. I do see there is a very tiny cutout on the edge of roller by the jewel.

 

[gmorse]

Hi Ianzhou,

Your new pictures show that this isn't in fact a Savage, but a variant of an English lever. In a Savage, there's a square cutout in the roller table which takes the impulse from the pin in the lever; the two pins, (or in this case a jewel), on the roller are only there for unlocking. Your table just has a shallow passing crescent which indicates a normal lever action with the impulse being given by the jewel pin.

Sorry not to confirm your hopes!

Regards,

Graham

 

[Burkhard Rasch]

I´m not an expert in any respect,but as far as I understand the idea of Savage's two pin escapement was to separate the unlocking action from the impulse action in the roller (for whatever purpose I do not know) The cut out in the table is for the third pin on the fork to pass through IMO for a kind of safety action like the "knive" or dart in the modern anchor escapement . I have a Savage two pin lever escapement,but-sorry I´m not a watchmaker- I´m not able go "get out" the balance to show.I recall descriptions in the cathalogues of "Pieces of Time,UK" of an escapement with a "double width roller jewel" which should-as they stated-serve the same (obscure) purpose.I never realy understood the reason of that design,but it looks like You've got one of the later.I also don't know which name is connected with this principle.Anyway:a variation not too often seen,hope You get it running again!The real experts might correct me if I´m wrong.
Burkhard

 

[gmorse]

Hi Burkhard,

You're quite right about the separation of locking and impulse, but in the Savage the impulse is provided by the pin in the lever fork engaging with the square cutout in the roller table, and the jewel in the roller, (which in an English lever provides both locking and impulse), is just there to accomplish locking and unlocking. The cutout in the OP's roller table is crescent shaped, and provides the usual lever safety function in partnership with the pin on the lever, (or the safety dart in the case of a double roller).

One of the claimed advantages of the Savage was that impulse was given very close to the line of centres.

Regards,

Graham

 

[lanzhou]

Thank you for your kind help.

 

[Dr. Jon]

As others wrote, the essential feature of the Savage escapement is a slot in the roller that takes impulse from the pin on the lever. There was a jeweled version in which the slot is cut into a jewel mounted on the roller. This is the Hutton patent version.

The lever on this watch looks a lot like a Savage lever. The essential difference is that fork cut is angle to take impulse from the ruby pin. In a Savage the fork opens wider out towards its end and extends in a straight line on each side. I had to stare a picture to see this . I can't share this picture because I do not have the right to do so.

Also, as other noted, the advantage of this is that the impulse is very close to the line of centers. The advantage of this advantage in my view was vastly over rated. A paper by Dr George Feinstein discusses "escapement error". The paper points out the the any deviation from dead on center changes the rate but impulse gets very close to the end of the swing the effect is linear. This means that so long as the impulses are about equal on both sides the escapement induced rate changes offset each other on each side of the full cycle.

One problem with the Savage are that it has to be very well set up with much smaller tolerances than more popular variants like the single and double roller. There is some disagreement among enthusiasts as to whether the Savage has wear problems. I am on the side that believes the pins working on the lever wear out the horns of the lever. I suspect a lot of these wore out and were either junked or updated with more conventional levers making them even more rare.

This watch may have started out as a Savage and the watchmaker who converted it tried to retain some of that look.

 

[gmorse]

Hi Ianzhou,

This page has a good drawing of a Savage escapement.

Regards,

Graham

 

[Tom McIntyre]

I was going to post some pictures, but the link will do. Anyone is free to post pictures here from AWCo.org, which is my site, as long at they acknowledge the source.

 

[gmorse]

Hi Tom,

My apologies for not giving you the credit for your site.

Regards,

Graham

 

[lanzhou]

Thank you all for the kind and generous help.
It is a fusee half plate McGregor, maybe an early sample. I guess the grade is not low.
The first thing attracted me is the overcoiled hairspring. From my own knowledge, the English balance equipped with this cock and stud design usually used flat hairspring.
I easily restored the shape of balance rim to normal shape.