I posted about this mod over in my Watchmaking Journey thread, but figured I'd make a post here for more visibility. The clone 3120 movement found in reps of the 15400 is great except for the fact that it doesn't have an instant date change at midnight like the gen 3120 movement does. I recently got the chance to work on a modded clone 3120 movement which had an instant date change mod installed. Here's a pic that compares the modded (red) and unmodded (blue) 3120 movements:
The mod itself consists of three parts: the date gear, the spring, and a part that looks like the number 6.
The mechanical interaction between the three parts is very clever and enables an instantaneous date flip at midnight:
Here's what it looks like when the dial and hands are in place.
I'm not sure which modder in China came up with this design, or if it's a copy of the gen design. But I thought it was cool and worth sharing.
The mod itself consists of three parts: the date gear, the spring, and a part that looks like the number 6.
The mechanical interaction between the three parts is very clever and enables an instantaneous date flip at midnight:
Here's what it looks like when the dial and hands are in place.
I'm not sure which modder in China came up with this design, or if it's a copy of the gen design. But I thought it was cool and worth sharing.