Comments:
The escape wheel benefits from having cap jewels because it spins quickly and it's close to the balance so any reduction in friction will improve timekeeping consistency and minimize wear. Cap jewels reduce the friction on the pivots in the horizontal positions especially and also help keep an abundant quantity of light oil exactly where you want it and somewhat protected from contamination. All good things.
The escape wheel does not benefit from mass at all (unlike the balance), so it's generally made as light as possible which means that shock protection is not a priority for its pivots. What looks like shock protection is just a similar spring system to hold the cap jewel in place. It's cheaper to manufacture and easier and quicker to service than alternatives, like polished steel caps held on with screws, etc. The jewel bearing underneath the cap jewel is completely fixed however unlike shock jewels which can shift to keep the pivots from breaking during an impact.
1. Yes, normal friction fit jewels. Either olive or flat.
2. Just different approaches. Steel cap with screw is much more expensive if done well (black polished, shaped to match bridge, beveled, etc.). Patek 215 uses a fixed cap with "vents" for cleaning solution to get in and out (cheaper and not one of Patek's "higher craft" moments).
Question about escape wheel jewel mounting variations
Good afternoon!
I have a questions about the mounting of the escape wheel jewel, in general.
First, I've noticed that some movements have this jewel mounted in shock absorber. How important/significant is this? Is staff breakage a common problem on this component?
Second, some movements have this jewel mounted in a polished steel plate. Does the steel plate serve a similar function as a chaton, in order to facilitate easy replacement of the jewel?
Thank you!
Brandon
they just look like shock absorbers
The escape wheel benefits from having cap jewels because it spins quickly and it's close to the balance so any reduction in friction will improve timekeeping consistency and minimize wear. Cap jewels reduce the friction on the pivots in the horizontal positions especially and also help keep an abundant quantity of light oil exactly where you want it and somewhat protected from contamination. All good things.
The escape wheel does not benefit from mass at all (unlike the balance), so it's generally made as light as possible which means that shock protection is not a priority for its pivots. What looks like shock protection is just a similar spring system to hold the cap jewel in place. It's cheaper to manufacture and easier and quicker to service than alternatives, like polished steel caps held on with screws, etc. The jewel bearing underneath the cap jewel is completely fixed however unlike shock jewels which can shift to keep the pivots from breaking during an impact.
Never knew that!
Thanks John, that's very interesting! Your answer has inspired two follow-up questions:
1. When no bushing or steel cap plate is used, is it just a normal friction fit jewel like any other?
2. Is one style or another considered to be a best practice, or is it fairly inconsequential/stylistic?
Thanks again; there's always so much to learn about even the tiniest details!
Cheers,
Brandon
more
1. Yes, normal friction fit jewels. Either olive or flat.
2. Just different approaches. Steel cap with screw is much more expensive if done well (black polished, shaped to match bridge, beveled, etc.). Patek 215 uses a fixed cap with "vents" for cleaning solution to get in and out (cheaper and not one of Patek's "higher craft" moments).