Tuesday, January 29, 2008

Explosive Decompression

So, there you are, cruising along at 36,000 feet and the cabin door blows out. Will your watch crystal pop out or not? Would you really care? If so, read on . . .

The force on the crystal is the pressure differential between the outside and inside of the watch, multiplied by the area of the crystal.

Most planes are pressurized inside to about the equivalent of 8,000 feet and airliners fly at around 36,000 feet, so therein lies the pressure difference which is about 52700 Pascals. See here for an ICAO standard atmosphere calculator.

My Gallet Navigator's watch, for example, has a crystal of 30 mm diameter.

I figure the force to be 37 Newtons or 3.8 kg or 8.4 lb. Not a lot, really. Therefore it's probable that the crystal will stay in place, although your ears won't be up to much for a while!

best regards,


Friday, January 25, 2008

Rate your Collection the Geeky way!

When you've collected more than a few watches, there comes a time when you want sell one or two - or you're unsure which ones to keep.  You look at one and you want to keep it but it's lume is poor - or this other one keeps perfect time but it's ugly, etc, etc.  Then, when you've looked at them all, you have to remember what you thought about each one.  There is also a problem for many folks in actually organizing their thinking in such matters especially at my age!  However, the world of programming provides a possible solution to organizing your thoughts and spreadsheeting can provide the memory and even rank your collection!

Without going into it too deeply, modern programmimg relies heavily on objects, properties of objects, and values of those properties.  If we take "watches" as a class of objects, then we could define an object in that class as an "ana-digi".  Now, having chosen analog-digital watches to think about, we would then decide what properties of analog-digital watches are important to a collection.  Those properties are your choice, but I would choose something like "form, function, condition & value".  After deciding what these named properties represent, you can rate each of your watches by giving a score to each property and then adding them up.  The one with the least points would be the first to go if you were culling the collection.

Co-incidentally, it happens that I own several "instances" of ana-digi watches - a Breitling and various Citizens.  So I tried the concept out in a spreadsheet.  Unfortunately, it didn't really seem to give realistic results.  The Breitling came out last, and that's not really what I would do.  It came last because of it's ugliness (the form property) and it's a bit beaten up (the condition property).  I realized that the concept itself was a little too simple.  In the spreadsheet, each property had equal weight - whereas, when considering tool watches such as these, surely function carries more weight than form or condition?

So, back at the spreadsheet, each property was assigned a weighting factor.  Now, changing the condition of a watch had less effect than changing the function and, lo, reasonable results were obtained.  Here is the sorted result:

ranking table

"A lot trouble for only three watches", you might say and I agree.  But there are folks with twenty or more diver's watches - what if Wifey says "you can't buy any more unless you sell a few?".  If you would like to download the spreadsheet to play with, I've posted it here.

Best regards,


Tuesday, January 22, 2008

The most precious watch metal

Many people think that the most precious metal available in a wristwatch would be platinum or possibly palladium. Surprisingly, that is incorrect. The most precious metal found in watches is probably staring up at you as you glance at the time. I refer to rhodium - often used to impart a good shine to watch hands or dial markers because of it's high reflectance. There's quite a good article on rhodium as it relates to jewelry here.

Today's (1/22/2008) prices for precious metals tell the tale . . .

Best regards,