Bulgari Caliber BVL 138: Spacer Jewels Innovation

patrick_y · 2022-04-12T06:31:19Z

Explore the Bulgari Caliber BVL 138's unique 'spacer jewels' in Version 1 and their removal in V2. A deep dive into ultra-thin movement architecture and design evolution.

patrick_y

WPS member · Bulgari forum

36 replies19041 views2 photos

Patrick_y, a keen observer and respected member of the WatchProSite community, delves into the intriguing evolution of the Bulgari Caliber BVL 138. His initial post highlights a highly unusual architectural detail: the presence of 'spacer jewels' in Version 1 of the movement, a feature that sparked a fascinating discussion among collectors about its purpose, cost implications, and subsequent removal in Version 2. This exploration not only uncovers a rarely discussed aspect of watchmaking but also showcases the collective expertise of the WatchProSite forum.

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WOW. OUR MEMBERS ARE SUPER EAGLE EYED! I never ceased to be impressed by the readers on WatchProSite! Very impressed.

The Version 1 Caliber BVL 138 has 36 jewels. The Version 2 BVL 138 caliber only has 31 jewels. A funny detail about the V1 caliber is that many of the jewels aren't traditional pinion jewels. Meaning they don't hold a gear or a pinion in them. Many of them are actually "spacer" jewels, meaning that they're there so that way space can be maintained between the plates (since the watch is so thin)! You'll notice many of these jewels don't have a little hole in the middle where the pinion for a gear would go into. This is considered to be fairly unusual. It's also considered to be an elegant technical solution and an expensive solution, as jewels are more expensive than metal spacers, metal spacers can also just be CNC'd in the plate, whereas jewels would likely need to be pressed into the plate by a human. I haven't studied the V2 extensively, but it appears most of those spacer jewels have been removed. Possibly to cut costs, or to improve the overall movement, or both.

Version 1. Notice the jewels on the top left quadrant, many of them don’t have holes with metal pinions in them. Many of the ones without holes in them are ”spacer jewels" that are there to maintain space between the narrow plates. This is HIGHLY UNUSUAL architecture and not commonly seen nor discussed.

Version 2, notice many of the spacer jewels have been removed compared to the Version 1 movement. Almost all the jewels present in V2 have metal pinions in them. The rotor also looks a little bigger to me. So it seems like there are multiple changes between V1 and V2.

I will get in contact with our man on the inside at Bulgari and get some more details hopefully. Again, super impressed with the WatchProSite community for noticing this super minute detail. And Tim Mosso is definitely a greatly detailed fella! Without him mentioning it, I might not have noticed for months! Thank you WPS members and Tim Mosso!

Photo credit to Bulgari's website, both of these pics come from Bulgari's website.

Key Points from the Discussion

The Version 2 of the Bulgari BVL 138 caliber appears to be an upgrade in performance and reliability, incorporating developments from the BVL 318 ultra-thin automatic chronograph movement, despite some aesthetic changes that might be less appealing to certain collectors.
The redesigned automatic system in BVL 138 V2 features improved winding efficiency by approximately 40%, utilizing a micro-rotor with contiguous balls for shock resistance and a single 2-way inverter, similar to the BVL 318 caliber.
A key question for Bulgari is how jewels are counted, specifically if spacer jewels are included in the official jewel count, as historically, non-functional jewels were sometimes added to inflate numbers before stricter regulations.
Enthusiasts find it frustrating when watch companies modify movements without changing the name or designation, as it creates confusion and makes it difficult to distinguish between different iterations of a caliber.
Revisions to watch calibers are typically implemented to address real-world deficiencies, improve reliability, ease of assembly, regulation, and servicing, rather than primarily for increased accuracy.
The Version 2 of the BVL 138 shows a decrease in finishing details compared to Version 1, including the removal of gold-filled engravings, changes in anglage, Côtes de Genève, chamfered screw slots, and a different balance wheel, suggesting potential cost-cutting measures.
The larger platinum rotor and redesigned gears in the BVL 138 V2 suggest an adjustment to the automatic winding system, possibly to address previous difficulties in winding to full power, and may indicate a slight increase in platinum content.

The Discussion

JakubM

Apr 12, 2022

More changes...

The gold filled engravings are also gone, the new big plate design evokes Panerai rather than the svelte previous version, looks like automatic winding system was adjusted as we previously discussed difficulty to wind to full power, the rotor is certainly bigger and related gears were redesigned.

patrick_y

Apr 12, 2022

Agreed! You've got a keen eye!

I wanted to introduce some members to spacer jewels, as not everyone is familiar with spacer jewels in watchmaking as they're somewhat uncommon to be seen with the naked eye. But you took it to the next level! You mentioned many more of the changes!

Apr 12, 2022

Fixing the rotor issue?

Mine wouldn’t wind at all and I know a few others with similar issues fyi. Guessing these revisions are to fix it?

patrick_y

Apr 12, 2022

Definitely a possibility!

The BVL 138 does have some winding issues. So I wouldn't be surprised if they modified it to make it work a bit better. The new rotor does look larger, which would imply it should work better.

JakubM

Apr 12, 2022

Mine usually lasted for 30h after I worn it for couple of days.

SA at BG boutique said that it is normal and it likely cannot be fully wound from wearing it alone, I thought he was joking, I eventually ended up selling the watch (not for this reason, bought winder).

patrick_y

Apr 12, 2022

I see!

It takes 2170 turns in the CW direction, if I recall correctly, to satisfy this watch! Edit: Clockwise, not Counter-clockwise.

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