I get the impression that its just a ETA 7750 with the chronograph complication taken out. Whats confusing is that there is a chronograph version of Valgranges - the Valgranges A07.171.
So what is it?
* A completely new movement with the automatic winding / timekeeping design based on the 7750?
* Just an enlarged 7750 with the chronograph features taken out (and put back in as needed).
JohnF posted this on 20 May 2006 on the old forum (before we had this big crash...:-|):
Chronos, a watch magazine in Germany, tested the Chopard Mille Miglia...
Chopard Mille Miglia Gran Turismo XL, COSC-certified with a 46-hour reserve, adjusted to five! positions, with the following results in the magazine Chronos 1/2006: Face up 0 seconds, face down -1 s., crown up +4 s., crown down +4s, crown left +2s, crown right +5 s. with middle amplitude flat of 294° and vertical of 260°. Total timing difference of 6 sec. with middle deviation of +2 sec.
Their review said that the Valgranges is a massive work with extremely stable timing results.
The Valgranges (A07.111) has a diameter of 16.5 lines, 7.9mm height, 24 jewels, Nivarox hairspring "Etastable", 28'800 bpm, etachron regulation, single main spring and one-sided automatic system (i.e. the rotor only winds when it moves clockwise). The caliber is based on the 7750, but the 7750 is only 13.25 lines, so this is
considerably larger (16.5 lines is 37.22 mm).
Chronos liked the caliber so much (it can use many parts of the 7750 for repairs but not all) that they felt it will probably be one of the most dependable calibers that ETA has ever manufactured, and with the COSC certification and the kind of results that at least Chopard was able to achieve, one with excellent accuracy.
Advantages 7750 vs Valganges:
The increase to 46 hour power reserve means several things.
First, you have more power to play with when adding complications; second and more interesting the power curve of the spring will also have a longer linear portion, which invariably increases accuracy.
There's room on the movement for the watchmaker to get down and funky with. Add a swan-neck regulator on a 7750 can be done, but it's tight, and on the A07 you've simply got more real estate to work with. Adding customized work is simply easier with a larger movement.
ETA is doing its horological homework and knows that watchmakers are having difficulties selling $10k watches with the "same" work as a $2k watch, all other things being equal. Making the base movement a tad larger means that it will run, all other things being equal, more smoothly, since you are increase the mass of the moving parts. Think of the old record players: some of the substantial price differences among, say, Thorens models were based simply on the weight of the platter that the record revolved on and the motor to drive it (I'm simplifying, but that's the basics), and I've known audio freaks who weighted their records down and let the record player run for 20 minutes so that the speed would stabilize to an immeasurable variation before they'd put the diamond on the vinyl. To increase the accuracy of the seconds count (NOT the beat!) you can either increase the weight of the balance wheel or you can increase the speed, with speed ultimately winning out up to the mechanical limits.
Credits to John F.;-)
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