Part 2 - some details of the new caliber GP4500

Apr 03, 2007,00:06 AM

In 2006, Girard-Perregaux added two more base calibers to enhance the manufacture´s movement portfolio; a suiting movement for every purpose and four different base calibers is a number not every manufacture does offer:

Girard-Perregaux caliber families

Within this portfolio, the new caliber GP 4500 marks the largest movement with the longest power reserve.

But it is not just large; the height of 3.95mm is to be regarded comparably thin if compared to other, late introductions among the swiss manufacture-made movements.

And there´s a number of interesting details:

The first encounter with GP´s new "power plant" caliber 4500 leads to a surprise; long gone seem to be the days of unfinished plates, but the first impression is dominated by the decorative elements featuring "Geneva Stripes" both in circular and horizontal patterns, as well as extensive "Perlage" particularly under the dial:

GP caliber 4500 (prototype), dial side

GP caliber 4500 (prototype), bridge side

GP caliber 4500 (prototype), bridge side, different view

The GP 4500 combines design elements of the caliber 3000-range by Girard-Perregaux, in that likewise large bridges and plates hide most of the moving parts.

The visual relationship does not come by surprise; it is a manufacture-made movement representing complete development and design work by Girard-Perregaux.

Yet the new GP 4500 is not an enlarged caliber 3000, but a completely new development from scratch.

It took the brand 4 long years to finalize the details, with extensive tests before announcing this new caliber; a series of 15 prototypes, all cased up and ready to wear, stood daily life and practical use for well over a year on the wrists of GP staff.

"Our basic approach was to create a large movement, suiting the contemporary trend towards larger watch cases" states Nicolas Dehon, GP´s chief movement engineer.
He adds, the development started with "two major considerations, to create a movement which is sturdy enough to stand daily wear over a long time. And to do so in exceptional performance quality"; a rugged, accurate, powerful movement to ensure future owners will find their expectations of a manufacture-made watch fulfilled.

GP caliber 4500 explosion drawings (notice the large barrel)

Nicolas Dehon explains the basic approach, which started with a large barrel.

The new caliber was intended to prolongue the power reserve of GP´s ultra-thin caliber 3000 range while offering a high stability of timekeeping results; to achieve this, a high amount of energy is required. As with all mechanical watches, this energy is provided by the mainspring, which finds it´s place inside the barrel. The longer and subsequently, stronger, the mainspring is choosen, the more space is required for the barrel; in the beginning, the size of a barrel determined the size and place of later movement components to be integrated. A stronger mainspring provides practical benefits down the road; not just the power reserve of the movement to be increased (notably, 25 percent increase over the GP3000 range), but it is promising to deliver a more constant power flow, which is likely to support an improved timekeeping.

The "double 3rd wheel"

In order to save available space and allow for a likewise large balance, an already well-tested development by SOWIND Group was added - the "double 3rd wheel".

Every mechanical movement requires 3-4 wheels, which transport the energy of the barrel and mainspring towards the escapement, which accounts for the timekeeping. This gear train, often called the "going train" or
"power train", requires to be designed with care: the more power the movement will have, the force the individual gears need to deal with, suggesting to be likewise large and sturdy.

Within the gear train, the 3rd wheel is a so-called "double wheel"; by using this solution, which is highly unconventional among modern movements, it is possible to minimize the size of the 4th wheel, which allows for more space for the barrel.

For an in-depth analysis of an earlier application, the JeanRichard caliber JR 1000, please have a look at Suitbert´s review:

The "double 3rd wheel" did proof to offer practical advantages and to work very well, thus it is a natural choice it is used for the GP4500 as well.

Here´s the gear train, as found in GP´s latest addition:

GP caliber 4500 gear train

While the drawing is not to be regarded a technical drawing, both the gear train and the recessed section in the movement base plate may give an idea of the barrel to consume most of the movement´s space - this one is all about power supply!

The use of the "double 3rd" wheel keeps in mind three applications:

- the use in central second watches

- the use in sub-second watches

- the use with a module fitted in complicated watches

For all applications, the "double 3rd wheel" will eliminate tangential play of the seconds hand pinion, which will avoid the "fluttering" performance of other central seconds movements. This phenomenon goes back to the alignment of the wheels; in conventional movements with indirect central second, the seconds hand pinion requires a friction spring to support proper fit and prevent from a "skipping" motion of the hand. The "double 3rd wheel" rules out this tangential play, thus avoiding the unfavorite "skips" of the seconds hand.

But this effect is of benefits for use with modules as well; a more equal motion of the seconds pinion is promising to support an improved and more equal performance.

GP caliber 4500 gear train

At the same time, the "double 3rd wheel" allows for a trick:

It is one of exceptionally few movements which are capable to indicate the seconds in different positions!
This allows for truly creative dial designs, which are different from what is seen so far.

The "double 3rd wheel" supports the pinion of the seconds hand, which can be attached in three different positions without changing the movement or adding a module:

- a small second at 9 position

- a small second at 10.30 position

- a central second

Quite a neat trick; where other movements demand additional height by a module, which is an issue particularly in watches sporting a rectangular or curved case, the GP4500 allows to freely choose the dial layout without ressorting to modules.

Such allows not only to find different applications for the movement, but for unusual case designs at the same time!

Uni-directional winding

But the GP4500 doesn´t end with an unusual wheel in the gear train; actually there´s a variety of other details, which set it apart from others.

Like with the GP3000 caliber range, the new GP4500 offers unidirectional winding; the rotor winds the movement in one direction only, while spinning free in the other direction. Practical tests, as far back as 1970´s and conducted by several brands, did turn out this solution to be superior to bi-directional winding in terms of efficiency.
Thus it is a natural choice for a movement intended to offer practical benefits for the owner and the choice of

GP caliber 4500 automatic winding

All automatic winding movements require a gear train with "reverser unit" in order to transfer the motion of the rotor towards the barrel with it´s mainspring.

This reverser unit ensures a connection between both in one direction, while uncoupling in the other.

There are several solutions in practical use for younger movements, such as rocker mechanisms or satellite wheels. One consideration when thinking of constructions to offer practical advantages is to keep things simple; the large rotor supplies considerable energy towards the strong mainspring, hence the stress and wear on automatic units including the reverser mechanism is a consideration important for later longevity of the completed watch. The less parts a reverser mechanism integrates, the larger these can be in order to allow for a strong built and reduced wear, as well as improvements for lubrication (what is not there does not need to be lubricated) and reduced danger of problems.

The reverser unit within the GP4500 caliber can be described as construction of "satellite" gears; but instead of installing an individual gear train, all necessary gears are integrated parts of the reverser wheel!

Sounds different - and it is:

GP caliber 4500 reverser wheel and parts (left above: complete wheel)

The practical application of the reverser wheel is a seemingly simple one on first view

GP caliber 4500 reverser wheel,
with central rotor and bearing (center above)
and balance (left below)

but the drawing may give an idea this solution is an ingenious simplification.

Nicolas Dehon points out two more advantages, in that the reverser wheel is the only wheel above any of the movements bridges. This accounts for the "technical" appearance of the GP4500 and the large space of the bridges, which subsequently improves the movements stability. This is certainly well in line with the quest for a manufacture-made movement intending to offer some practical benefits! As a welcome side effect, this allows for different decorations; the more surface space there is, the more stripes (or whatever decoration Girard-Perregaux decides to choose) can be applied.

The practical difference, which should be apparent to all future owners, is an increased efficiency:
Reversing the winding direction to "free motion" of the rotor requires the reverser mechanism to change the gearing; the rotor and automatic unit is coupled or uncoupled from the barrel and mainspring.

A critical aspect is the so-called "dead angle"; this describes the part of the rotor motion required to actually make the reversing mechanism switch winding on or off.
The more it is, the less efficient winding will be - if a good portion of the 360-degree-arch of the rotor motion is used to activate the mechanism, there´s simply not just that much way left to make the barrel wind up.
This is a concern particularly in daily wear, when the watch on the wrist receives motion impulses in various directions. Each time the reverser mechanism will switch and within the many many wrist shakes of the day, there´s hardly the same motion of the watch and the movement as on a watch winder.

Therefore a short transition or switching period is of great benefit to improve the winding efficiency; the faster the mechanism responds to a motion of the wrist, the better it will wind.

For the GP4500 caliber, the "dead angle" of the movement is less than 15 degree; this is considerably less than other movements on the markets and in a practical perspective, it means hardly any motion of the wrist will get lost for winding the movement!

As we see, the seemingly simple construction with it´s likewise plain appearance on first sight offers some practical benefits.

"Zirconium" ceramics ball bearings

Like all late production movements by Girard-Perregaux, the new GP4500 caliber will include GP´s ceramic ball bearings, whose practical benefits and features are subject of this earlier introduction:

GP caliber 4500 prototype; reverser (right below), central rotor bearing (middle)


GP caliber 4500 prototype; rotor bearing 
A barrel bridge with a button

Coming back to the barrel, the new GP4500 caliber utilizes a feature not seen often, but with practical benefits: the barrel bridge.

The barrel and it´s powerful mainspring is housed under a separate bridge, which provides increased stability.

In addition, the barrel bridge is fitted with a push button; this allows to release the barrel and unwind it, before removing it during service work.

A seemingly simple mechanism, but a very handy feature for all watchmakers to work on this!

GP caliber 4500 prototype; release button

This message has been edited by PeterCDE on 2007-04-03 00:35:37

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Comments: view entire thread


Some thoughts on the new ref. 25820 Vintage45 "Square" and GP´s new caliber 4500

 By: PeterCDE : April 2nd, 2007-23:58
Dear enthusiasts, following up to our previous introduction , i´d like to have a closer look at GP´s new pre-SIHH introduction reference 25820, dubbed the Vintage 45 "Square" or "Carree": Vintage 1945 Carrée At the beginning of the 90s, well before "vinta...  

Part 3 - some more details of the new caliber GP4500

 By: PeterCDE : April 3rd, 2007-00:07
As we´ve seen, the new GP4500 caliber incorporates some practical, new solutions to improve the efficiency, longevity and durability of this movement. It is promising to be an accurate, sturdy timekeeper for a long time to come. But is it a nice movement ...  

Thanks a lot for this exciting pics and insights

 By: Alexander from Germany : April 3rd, 2007-06:42
Peter, that's a great thing what you're again doing for us! Amazing pictures I love very much. And I'm particularly glad to learn about and understand now this movement in a way I would like to be able to understand the 3XXX mvts. as well, which have not ... 

Oh, there´s something for you!

 By: PeterCDE : April 3rd, 2007-12:06
Hi Alexander, thank you a lot! That´s much appreciated and the pleasure is completely on my side! In terms of the GP3xxx range, have a look here. There aren´t many chances to get much closer than this: Sure it´s n... 


 By: Alexander from Germany : April 4th, 2007-03:42
thanks again for this hint, I didn't note this study before, best wishes for the feast days, Alex

My pleasure!

 By: PeterCDE : April 4th, 2007-12:06

Thank you Peter

 By: pr7 : November 2nd, 2007-09:07
Hello Peter, first I wanna thank you for this indepth look. I was wondering about how GP will provide the same moment with the central second position with a double third wheel, but with the second at 9 with a singular third wheel? Because in my opinion t... 

Like this?

 By: PeterCDE : November 2nd, 2007-11:59
Hi Philipp, something like this? These are prototypes and in fact the GP4500 caliber with central second! While i can´t share details on upcoming models, at least it seems such is being evaluated very closely... Does this help a bit? Cheers, Peter...  

More technical...

 By: pr7 : November 3rd, 2007-15:16
Hey Peter, hmm... that's not really what I meant, but also nice pictures of course. In part 2 you showed us a picture with details of the different variations of seconds. And if GP produces the second at 9 they perhaps will have different torques and thou... 

Oh, that´s what the double third wheel is made for

 By: PeterCDE : November 3rd, 2007-16:23
G'day, regardless the attachment of the wheel driving the second hand, amplitude and performance will always be the same. As noted, that´s what the double third wheel is made for; the second hand pinion always engages the same wheel, eliminating the need ... 

We're getting closer :o)

 By: pr7 : November 4th, 2007-03:45
Hello Peter, yes in this case you're right. But what if you use the second wheel to display the small second at 9 without the second hand pinion like on the picture with only a single third wheel. You definitly will have less engagements in your going tra...  

Well, i think that´s not possible

 By: PeterCDE : November 4th, 2007-06:30
G'day, i´m rather tempted to trust GP´s engineer in this one Actually attaching a seconds hand onto the second wheel is a rather unconventional thing to do and as said, regardless the position of the second hand there´s no difference otherwise. In this i ... 

Difficult issue

 By: pr7 : November 7th, 2007-00:32

Hi, Philippe,....

 By: SuitbertW : November 4th, 2007-06:57
....I believe GP opted for this design for beeing flexible and vesatile. Of course one could use the classical small seconds design and use the fourth wheel directly to display the second. But, than you're also bound to design the train around it - i.e. o... 

strange arrangements on pictures

 By: robert_bob_stefan : November 5th, 2007-02:48

The black dial looks smart

 By: Jokoh : April 3rd, 2007-02:01
Can't wait to "feel" it on my wrist thanks Peter cheers joe