Author Topic: Packing a Marine Chronometer for Shipping.  (Read 4023 times)

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Offline W1RC

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Packing a Marine Chronometer for Shipping.
« on: September 22, 2016, 07:25:05 AM »
A marine chronometer is a highly accurate precision timepiece usually found in a highly crafted wooden box often on a gimbal mount to keep it level at sea. 

Accurate timekeeping is essential for precise navigation to determine the longitude where the ship or aircraft is located.  The most common of these were made by the Hamilton Watch Company of Lancaster PA.  The Model 21 (1941) and 22 (1941 and later) are very different but both were made for the US Navy.  Currently they sell for $1000 to $4500 on eBay and are highly sought-after items.  The least expensive chronometers, the Kirova MX6 and the Polyot, are Soviet made and are decent copies of a German chronometer.

Packing these things properly is very important if you want to minimize the possibility of damage in shipping. These instruments are very delicate and can be easily damaged if not prepared and packed correctly for,shipping.  Cost to repair a broken balance staff or detent locking jewel,can run $500 and higher.

Here is how I do it so it will stand up to the shipping company's scrutiny in the event of a claim which they would probably try to weasel out of paying on the grounds that the item was improperly shipped.

Just about all chronometers have a "wind indicator" that shows how many hours have elapsed since it was last wound.  It usually shows  0 (fully wound) to 56 (completely unwound).  Do not ship a chronometer completely unwound (at 56); it is advisable to,let it run down to 48 then gently stop the balance wheel with a light finger touch or an artists camel hair paintbrush is the best way to do this.

Now you must put something under the balance wheel to keep it from moving. This miscalled "corking the balance".  A small cork wedge or piece of paper folded a couple of times placed very carefully under the balance wheel on two opposite sides should do it. Just be sure it keeps the balance wheel from moving but not too much pressure and is equal on both sides. Make sure there is not too much pressure on the pivot points and that it is equal.  If you are not comfortable doing this then take it to a clockmaker or jeweler and have them do it. Otherwise the balance staff or the pivots may be damaged in shipping.

Remove the chronometer from the gimbal mount and pack the bottom of the wooden box with plastic supermarket bags tightly balled up. Replace the chronometer and use more bags and pack on all sides until it is solid and cannot move in the wooden box. Place a piece of cardboard under and on top of the glass to protect it. This is very important. Then use large bubble wrap to surround the entire wooden box and pack it in a cardboard box. Then get a larger box and some sheet styrofoam you can buy at Home Despot in the insulation department. It is cheap and you can pack the inner box inside the outer container surrounded by several sheets of styrofoam, about 3" insulation on each surface. Insure for full value.

As far as a choice of shipping carrier the key thing is to ship by the method whereby the package is in the carriers custody for the least amount of time.  The most cost effective metho to accomplish this is USPS Priority Mail with the Fragile Handling option. When it comes to the risk of damage it seems that the three major shipping carriers are equal because all packages are subject to ape-like handling who don't give a rat's rear end about what is inside the packages they are tossing about.  The USPS Fragile Handling option costs $ additional and promises special care but it is too new and no one knows what it really offers in terms of minimizing the possibility of damage.

Finally insure for the full value even though it is expensive.  When selling a chronometer it is wise to charge $35-50 for shippimg to cover packing, shipping and insurance.

Dr William Morris, a retired physician who lives in New Zealand is, in my opinion. An expert on the subject. A visit to his excellent Web site is well worth the time and is most informative.

Here is an excerpt from his Site that discusses the importance of properly preparing a chronometer for shipping:

"Marine chronometers don?t like being moved around. This may seem to be a strange statement to make about instruments that spent their working lives on bridges of ships at sea, so it needs some explanation. When the balance wheel is oscillating back and forth it is unconnected with the rest of the chronometer for most of the time and it is only when it is releasing a tooth of the escape wheel or receiving a push (?impulse?) from it via the escapement that the two are connected. If the instrument is suddenly rotated at the wrong time, two teeth of the escape wheel may be released instead of one (?tripping?) or the impulse jewel may be struck amiss or the detent damaged (you can read in the book about how these parts work). The main message of this paragraph is that moving a chronometer around needs care. It is particularly vulnerable to damage if it is fully run down, so it should be moved when it is at least partially wound, as this keeps the escape wheel locked in the correct position. If it is to be transported it should be partially wound and the balance wedged unless it is going to make only a short trip in your hands or resting on your knees. When carrying it from one place to another move deliberately and avoid sudden rotational movements as, for example, when turning to close a door behind you."

Bill wrote "the book" on the subject called THE MARINER'S CHRONOMETER: STRUCTURE, FUNCTION,   MAINTENANCE AND HISTORY,and is available from and costs about USD $38.00

I highly recommend Bill's book to anyone interested in marine chronometers.