ORBITA SKELETON AUTOMATIC WATCH
by Paul Flannery

Several months ago I posted a review of an extremely cheap hand wound skeleton watch on a popular wristwatch bulletin board. A few months later I received an E-mail from Chuck Agnoff, President of ORBITA Corporation (the watchwinder company). Chuck had just returned from China where he had purchased several automatic skeleton watches in order to demonstrate his watchwinders in action at trade shows and exhibitions. During our discussion he informed me that ORBITA was not going into the watch business, but that he was considering a promotion to give these watches away "free" to retail purchasers of his multiple head watchwinder as a sales incentive. He was however hesitant to start such a program until someone with a little more knowledge of watch mechanics and operation had a chance to look at the product and provide some critique. Having read my review of a similar style watch, Chuck decided to ask me if I could provide him with an honest appraisal. As I was planning to write another review, this opportunity was just too intriguing to resist.

The Watch:

The watch is a classical design, 39mm in diameter and 10.3mm high with center seconds, leaf shaped hour and minute hands, a cut away dial and skeletonized movement.
The case is gold plated with a highly polished screw in stainless steel exhibition case back which is marked with a water resistance of 5 atm. This water resistance claim is supported by a rubber gasket under the case back and an O-ring seal mounted inside the crown. Both the front and rear crystals are made from flat mineral glass. The alligator style strap is stamped "GENUINE LEATHER ANTI-ALLERGIC" and fastens with a substantial gold plated tang buckle.

The Dial:
All but the outer five millimeters of the white painted dial has been removed in order to display the movement. The center of the dial has been cut away and the face gold plated. The dial markers are gold plated Arabic numerals at the 12, 3, 6 and 9 o'clock positions and baton markers for the remaining hours. A minute track of black printed batons complete the dial markings. The numerals and batons are genuinely applied markers as opposed to the embossed dial surface often seen on inexpensive watches. Twelve fluorescent dot markers are also present at each hour position, although these seem somewhat redundant as all the hands are painted a dark metallic blue and have no fluorescent coating whatsoever. However you could find these invaluable should you urgently need to find your watch in the dark! 

The Movement:
The movement is of Chinese origin with 20 jewels and a frequency of 21600 vph. The drive train layout is that of a manual winding 17 jewel center seconds design. The additional jewels are used in the automatic winding system which I shall endeavor to describe later. All bridges and plates are unplated grained brass which have been decorated with laser engraving.

You may notice that there are no photographs of the front of the movement with the dial removed. This is because the dial is glued rather than screwed to the top  carefully removed if it ever became necessary I did not wish to tempt fate at the time.

The Drive Train:
.The transmission system begins at the mainspring barrel which stores the energy to drive the watch. The mainspring provides the movement with an autonomy of forty two hours. The top surface of the barrel, shown here partially wound, slowly turns the gear train which drives the hands under the regulation of the escapement.

The top surface of the barrel gear has been cut away to leave a three spoke pattern. This gives a clear view of the mainspring when looking at the watch face, which allows a visible indication of the amount of stored energy in the mainspring. An unwound spring will push towards the outside of the barrel while a fully wound spring will be pulled inwards towards the barrel arbor. 

The automatic winding wheel pinion winds the barrel ratchet wheel (marked red) clockwise as shown by the top yellow arrow which in turn winds the mainspring. The ratchet wheel is prevented from unwinding by the click spring (colored dark blue). The stored energy in the mainspring can therefore only be released by clockwise rotation of the barrel gear (marked in green) as shown by the bottom yellow arrow.

Looking to the side of the movement the entire mainspring barrel can be seen. This is the side of the barrel which is wound by the automatic winding system. The image below shows the sections of the mainspring barrel components, highlighted for clarity. 

The gear train can be seen on the upper image on the left and is numbered for clarity. From the mainspring barrel (1) the power travels to the center wheel pinion (2). This is the wheel to which the minute hand is attached. The center wheel drives the third wheel (3) which drives the fourth wheel. This movement is a directly driven center seconds design which means that the fourth wheel is located in the center of the movement below the center wheel (2), and so cannot be seen in the picture on the left. The second hand is attached to this wheel by a long pinion which passes up through the center wheel. The fourth wheel is driven from the escape wheel (4) whose rotation is regulated by the balance assembly (5) which is detailed in the following paragraphs. Finally, the center wheel gearing is reduced by the minute wheel (7) to drive the hour wheel (6) onto which the hour hand is attached.

All the wheels from the center wheel to the balance are jeweled. This is known as a "Jeweled To The Center" design and this accounts for 17 of the 20 jewels used in the movement. Very basic finishing of wheels and bridges combined with poor alignment of some of the jewel mountings disclose this movements low cost, mass produced origins.

The lower image on the left shows a close up of the escape wheel (A) and the pallet lever (B) which releases the escape wheel teeth. Two banking pins on the underside of the base plate (C) prevent excessive movement of the pallet lever and over rotation of the balance wheel. 

The balance assembly consists of a smooth laser poised  three arm balance with a flat hairspring. I was hoping for a Breguet overcoil, but you can't have everything. The balance wheel swings on a cap and pierced jewel pair which are retained by a tri-shock spring. A regulator arm at the ten o'clock position (in the right hand image) allows for regulation adjustment and a movable stud carrier at twelve o'clock allows centering of the balance jewel for beat adjustment. The stud is held in the stud carrier by a small screw and the balance spring held in the stud with a brass tapered pin. 

The automatic winding system:
The primary purpose of this Orbita promotion is to assist in clearly and visually demonstrating the function of an automatic watchwinder. It therefore seems reasonable to go into a little more detail describing the automatic winding components. The method used in this movement utilizes a cam driven, double ratchet system to provide bi-directional winding.
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With the winding rotor removed, the rotor mounting can be examined. The mounting consists of a keyed shaft which is supported by a ball bearing. The bearing is secured to the movement by a finely grained steel rotor plate, which is held in place by three screws. The images above show the exhibition back and winding rotor, the base of the movement with the winding rotor removed and the rotor ball bearing.

An Explanation Of The Winding System.
Rotation of the winding rotor in either direction causes the two winding arm pivots, fixed to a mounting stud (shown by the green dot) to follow a path around the center of rotation (shown by the red circle). This causes the two winding arms (yellow) to move back and forth in a sinusoidal motion as the arms are pushed and pulled by the mounting stud. As the two arms meet the pivot at different angles, one arm will either lead or lag the other by an angle of approximately 45 degrees depending on the direction of rotation. The right hand arm is shaped to push the winding wheel, the left hand arm to pull. The result of this motion is that one arm is always acting as a ratchet to prevent the mainspring from unwinding while the other arm is returning to its original position. Jewels are provided at the mounting stud (green dot) and on the top and bottom of the winding wheel. These 3 jewels, combined with the 17 jewel transmission system, account for the 20 jewels used in the entire movement.
The steel click spring (shown in blue) also rides over the much larger ratchet wheel teeth at the point indicated by the cyan dot. This provides a fail safe to prevent uncontrolled unwinding of the mainspring should a problem with the ratchet arm mechanisms occur.
The right hand image shows a greatly magnified section of the winding wheel detailing the very fine winding wheel teeth and how they engage with the right hand winding arm.  

An interesting note on the movement is that there is no way of manually winding the mainspring. Although automatic watches are designed to be worn every day, almost every automatic movement in production is able to be manually wound in order to supply some energy into the mainspring if the watch has been left to completely unwind.  The inability to manually wind the movement is not a significant problem as the escapement will function after only a few turns of the rotor. The foreseeable problem with this arrangement comes from a watch servicing point of view, as follows:  When a fully, or even partially wound watch is brought in for servicing or repair the stored mainspring energy must be released before any work is carried out on the movement. Failure to do this will result in this stored energy being suddenly and violently expelled when the first load bearing bridge is removed. This will result in the servicer spending the next five hours on his or her hands and knees on the floor looking for unfeasibly tiny gears and even more unfeasibly tiny springs!  In order to release the mainspring energy the click wheel or spring is lifted away from the wheel it engages with a small screwdriver while the crown is held firmly between thumb and forefinger. Pressure on the crown is then slightly released and the crown is allowed to rotate slowly until the mainspring is fully unwound.  The lack of manual winding on this movement means that there is no connection between the mainspring barrel and the crown as can be seen from the image of the keyless works below. There ARE Breguet teeth on the clutch (yellow arrow), however no winding pinion is present to engage it.

The design of the Orbita movement requires that for the mainspring to unwind, both the mainspring barrel click spring and both winding arms must be disengaged simultaneously. This means that for servicing it was probably intended that the rotor, winding wheel and winding arm assemblies should be removed prior to releasing the mainspring tension. This allows the mainspring to be unwound by just releasing the click spring retaining the mainspring barrel, it does not, however, shed any light on how to release this tension in a controlled manner?

Performance Observations:
Setting of the exact time is made slightly more difficult by the lack of a hack feature which applies a mechanical brake to the balance wheel to halt the movement when the crown is pulled out to the hand setting position. As a hack feature is not present, the movement may be manually 'hacked' by applying a slight reverse pressure to the crown while it is in the hand setting position. Hacking this movement successfully proved more difficult than most, and requires a fair amount of patience especially when fully wound. But at least the visible movement allows direct observation of the reducing balance amplitude if your attempts are proving successful. Daily rate results for the five standard testing positions are shown in the table below:

The consistently fast results suggest a surprisingly well manufactured movement. All mechanical watches need time to settle after manufacture, and I will allow this watch a few weeks of daily operation and then check the timings again. After the settling of the oils and lubricants I would expect a reduction in the overall friction of the movement. This will cause the balance amplitude to increase with a corresponding reduction in the daily rate. If this does not significantly improve the accuracy then a simple adjustment to the regulator should bring the accuracy up to COSC threatening tolerances!

Subjective Similarities:

As the majority of low cost watches are based to a greater or lesser extent on existing designs from the great Swiss watch making houses, I have searched around to find designs to which this watch can be compared.
At present I have arrived at two: On the left is a Zenith Skeleton and on the right a Blancpain Skeleton Ultra Thin.

Notable similarities to the Zenith can be seen in the case and lugs, other comparisons include the rotor shape.

The Blancpain similarities are obvious in the layout of the dial and hands.
The Blancpain also has a similar overall design, though obviously with a much shallower case.

Conclusions

The size and weight of this watch, combined with a surprising attention to detail as can be seen in the (relatively) well finished case, mineral glass, movement construction and good quality strap and buckle, combine to give an overall impression of a watch which costs significantly more than it actually does. I have found myself wearing this watch for day to day use where it has attracted comments from both enthusiasts and non enthusiasts alike. In its own right this would make a worthy addition to anyone's watch collection. As a free gift I certainly don't expect  Orbita will be getting complaints.  And, if you're not buying a winder, but would like a Skeleton, you can always call Orbita  and see if they'll sell you one! ...

Orbita produce a wide range of  AC  and DC automatic winders. The image above shows the Orbita Skeleton watch mounted on a cherry finished Watchwinder from the Geneva Series.  

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