C900 Single Pusher Chronograph – JJ02 Movement the Story
History behind the JJ02 Christopher Ward Movement
Back in 2009 The guys behind Christopher Ward London saw a prototype of a chronograph based on the well known as Unitas 6497 calibre. Johannes Jahnke, who in the past had developed the King Albert single pusher chronograph for Lang & Heyne (£60k), quickly understood that the development had similarities with the work he had accomplished when still in Dresden and felt that there was a potential to realize a high quality chronograph offering the owner a unique opportunity to both see and understand the functions and working order of a stop watch.
Johannes also realized that the construction had room for improvement as the sample didn’t have a sliding gear and also that the functions and aesthetics needed to be addressed. He then took the initiative to contact Mr. Jean Fillon of James Aubert Ltd. in Le Brassus and found an 84 year old man lonely in his workshop and not willing to leave his passion of creating and manufacturing parts for chronograph movements.
Mr. Fillon quickly recognized the abilities of Johannes and a relationship developed that made Johannes refer to him as “Opi” or grandpa. Johannes then reconstructed the chronograph module on his CAD after making hand drawings and notes in order to have the necessary platform for the re-engineering process. And we come to the JJ02 well sort of…
Below are some technical details and information on the base movement and the adjustments to come to the JJ02, along with photos and explanations.
Size, description and function of base movement ETA Unitas 6497
Size: 16 ½” or 36.6 mm
Description: Pocket watch caliber Unitas (today ETA) 6497 as well as chronograph mechanism with especially bought in componentry which was then entirely assembled by hand in our workshops.
The following were areas reworked:
- main plate
- winding mechanism
- center wheel
- second wheel
- adjustment system (swan neck)
Column wheel: - Functioning as cam and door gate, see also explanation below. 1 x push = column wheel rotates 20 degrees
- clutch: separates/engages chrono function; sliding gear separates/engages minute counter
- brake: fixes stopped time
- reset function
Cycles (3): cycles follow each other endlessly (no continuation of stopped time)
- start (clutch engages chrono, brake released, reset off
- stop (clutch separates chrono, brake on, reset off
- reset (clutch off, brake off, reset on
1. Chrono started, clutch engaged:
A - Intermediate wheel (turns continuously with second) is connected to centre wheel
B – Clutch lever falls into space between columns
C – Sliding gear lever falls between columns
D – Minute counter intermediate wheel moves to the centre and engages the minute counter
2. Column wheel had turned 20° in clockwise direction. Chrono stopped, clutch separated / brake engaged:
A – Space between intermediate and centre wheel
B - Clutch is separated
C - Brake lever falls into space between columns
D - Brake lever holds centre wheel in position
3. Column wheel had turned again 20° in clockwise direction. Chrono reset function, clutch separated / brake separated / reset lever engaged:
A - Reset lever falls into space between colums
B - Reset lever pushes chrono wheels back to zero position
C - Brake lever does not touch centre wheel
Display on dial
Centre chrono second
Left eye: Continuous second
Right eye: Minute counter (30 minutes)
Sliding Gear n.
The above article and all Photographs have been provided by Christopher Ward London.