Friday, May 30, 2008

My ideal rotating Bezel

I prefer hours - good for other time zones, like eBay, or for living by solar time with one eye on the real world. But, on the other hand, I often need to time something in minutes. I also find that uni-directional bezels are a pain because I don't actually scuba-dive daily. And how do you set half-hours on a 60-clicker?

So, in my mind, I just bought this SandYathon:
creation

The bezel would be narrower of course, but you get the idea. Mine would probably not have clicks but, if it did, it would have 120, not 60. Being a little old-fashioned, the hours would be subdivided into halves and fourths. The minute divisions would go all the way around as shown. Maybe the hour numerals would be Roman to readily distinguish them from the minutes. It could look quite good and nowhere near as cumbersome as the above creation.

For example, this Jupiter Pilot has two scales on a really narrow bezel and is still quite readable:


Best regards,

xpatUSA

Thursday, May 29, 2008

Sexagesimal Time

Old measure wasn't much of a problem BC (before computers). We mixed together all kinds of units and bases but we were quite used to them. The Brits coped quite admirably with pounds, shillings, pence and even the occasional sovereign up until the early 70's when Heath took them kicking and screaming into the E.U., or EEC as it was known back then. To this day, Americans still struggle on bravely with tons, pounds, ounces and grains in everyday life - not to mention gallons, pints and fl. ounces!

Although most countries are metricated now, the time of day has remained supremely sexagesimal to this very day. The time of day is represented as hh:mm:ss. This format is based on the Babylonian positional numbering system, with colons separating the positions. The Babylonians inherited sexagesimal counting from the Sumerians and improved the system by adding positional significance (by powers of 60) and the concept of the number zero. They still used chicken-scratchin's (cuneiform) to represent the values of each position and each value was represented in base 10 notation using a grouping of the two symbols for one and ten. This symbol grouping was not itself positional and so simple addition gave the value, see table below. For example 23 is represented by 2 eyeballs and 3 wine-glasses, i.e. 2x10 + 3x1 = 23.



Because the number of hours in a day is less than 60 (on this planet, anyway) our time-of-day representation is truly sexagesimal and follows the Babylonian system with the addition of colons as separators and the use of Arabic numerals instead of cuneiform.

There is an interesting property of the hh:mm representation. It is either a fraction or an integer number depending on how you look at it, but the representation itself does not change. For example, let's say a timer shows a elapsed time of 3 hours and 40 minutes, which is written as "3:40". In our decimal system (i.e. positional base 10), that would be 3.667 hours or 220 minutes. In sexagesimal, 3:40 represents either 3x60^0+40x60^-1 hours or 3x60^1+40x60^0 minutes but the bolded numbers do not change and the colon remains where it's at.

But what if there were more than 59 hours involved, for example three days, 13 hours 43 minutes and 22 seconds? "Easy!", you say, "just write 85:43:22" - but sorry, that is not a true sexagesimal number because 85 is more than 59! To be truly "sexy", it would have to be written 1:25:43:22 which is 1x60^1+25x60^0+43x60^-1+22x60^-2 and which is also thoroughly confusing! Indeed, this is why we still have a DMS function (angular Degrees, Minutes and Seconds) on our engineering calculators due to the mixed bases of decimal degrees with sexagesimal minutes and seconds.

Best regards,

xpatUSA

Wednesday, May 28, 2008

Unusual Hamilton GG-W-113 bridge

I've serviced a good few Hamilton GG-W-113's over the past year and have become accustomed to various engraving styles used to designate their 17-jewel Cal. 649 ebauche ETA 2750. Some are even marked "seventeen 17 jewels unadjusted" with no mention at all of "H W Co Inc" & "649".

But, until today, I've never seen this style - the movement is from a one-piece case model dated May 1982:

hammy bridge
close up

The turned circle is about 2.4 mm dia, just under 1/10" !! The inked (?) lettering is not real sharp.

xpatUSA

Sunday, May 25, 2008

UV-excited lume shots

Having recently purchased a 38-LED 2-Watt UV lamp, I decided to take some lume shots. UV light is best for charging photo-luminescent paint, see my article on watch lume. Here's the set-up:

the setup

When I switched on the lamp, the watch lume glowed like it was on fire!! However, the first shot was a little disappointing and there seemed to be no camera setting that brought out the brightness. It seemed that the UV itself was messing up the shot by over-exposing the camera sensor in spite of the UV filter on the lens:

first try

So, I tried charging up the lume and then switching off the UV lamp before taking the shot. I ended up with 5 seconds exposure at f/22; consequently, much of that prized initial brightness was lost (f/22 is my standard aperture setting - I leave it there for a good depth field from the 60mm macro lens). Had I shot at say f/8 for a shorter time, the lume would have come out brighter. Still, even at f/22, the resulting pictures came out well and were combined in Photoshop without any processing other than cropping and re-sizing.

A re-lumed 1900's Trench watch:
trench watch

A re-lumed Hamilton GG-W-113:
113 leftie

A Hamilton MIL-W-46374D with replacement Luminova hands:
Hamilton with Khaki hands

In the last shot, the lumed seconds hand sweeps through the 5 secs exposure and the rapid fall in brightness of Luminova, even during that short time, is quite evident.

Best regards,

xpatUSA

Saturday, May 24, 2008

Review of a Broken Watch

Hi All,

This 1981 watch sits on my work bench all the time. The only functions that work correctly on it are the chronograph and the countdown timer.

Here it is, in all it's glory!

bench navihawk

It was quite a fancy watch in it's day. 60g of heft, 20mm lugs, 13mm thick and a 41mm slide-rule bezel. It sports gold trim on the bezel, gold pushers, a white dial and the well-known Citizen C300 movement. This movement has a common fault: everything seems fine until you pull out the bottom right-hand pusher to reset the watch after a battery change or to change between regular and summer time. Nothing happens. The contact inside the movement has failed. However, the chronograph function is unaffected (nothing to set) and is perfect for watch regulating with it's 24 hr capacity, 1/100 sec resolution and especially the "split time" feature. The split time feature lets you check the regulation after a few minutes of running without stopping the chrono - this gives you an early check on the goodness of the regulation. The slide rule bezel still works smoothly and I do use it to calculate the daily rate of a watch. Here's how:

 

Assume that the watch ran for 60 minutes and the split time measurement said the the watch was off by 0.85 sec. Realistically, this means somewhere between say 0.8 and 0.9 secs (accounting for human reaction time). Set 1440 (the number of minutes in a day) on the outer scale next to 60 (minutes elapsed for this example) on the inner, like so:

timed over 60 mins

 

Look for 0.8 to 0.9 (secs error) on the inner scale. On the outer scale, we see that this corresponds to between about 19 and 22 secs per day error.

19-22 secs/day

For me this watch is akin to my trusty Wenger pocket knife, and I'd be quite put out if it died on me!


Best regards,

xpatUSA

More Oil Migration

It was so fascinating to see those stress patterns that I just had to play a little more. This time, the goal was to simulate the gap between a cap and a pivot jewel such as found on a balance cock. The top of a pivot jewel is slightly curved and the bottom of a cap is flat. When oiling balance pivots, the goal is to provide sufficient oil to form a ring of oil around the end of the pivot between the jewels.

Another blob of motor oil was placed between the crystals not far from the middle and two clothes pins provided the necessary fringe pattern to simulate the juxtaposition of a flat surface and a curved surface. Sure enough, the blob headed for the thinnest gap - albeit very slowly, The pics below show the position after 6 hours elapsed time (that radial shadow line is a deep scratch outside on one of the crystals):
oil blob
oil blob

It appears that there comes a point where the blob stops moving, since it did not go all the way to the center. This point is likely when the molecular attraction force between the oil and the surface of the glass is equal to the motion force that is due to the decreasing gap (or gap force gradient). When the gap decreases the oil spreads out, thereby increasing the attraction force between the oil and the surface. Also when the fringe lines are wider, the gap gradient is smaller.

These experiments have shown quite conclusively that oil tends to move to the narrowest gap and stay there. So fears of random oil migration if a watch is left in drawer are groundless. By the same token, running a watch occasionally to "spread the oil around" is a waste of time IMHO. Also, since the oil moves as a blob, insufficient oiling will leave dry zones - not a good thing.

Sorry about the terminology, I never really studied capillary action or tribology for that matter!

Best regards,

xpatUSA

Friday, May 23, 2008

Oil Migration - Moebius vs. Mobil

Oiling a watch movement is serious business. If you use the wrong oil, there's plenty of people out there to wag their finger at you and say "I told you so!". On the other hand, Swiss watch oil is pretty expensive and some might be tempted to seek alternatives.

On a whim, I decided to compare Swiss watch oil with automotive synthetic oil. After all, motor oil is designed for a much harsher environment than the inside of a watch. I took two flat glass 30mm watch crystals, cleaned them with alcohol and held them together with a small plastic clothes pin. Using a watch oiler, I put 1 'measure' of the following oils at the edge where the crystals were touching - a slight chamfer on the edges formed a convenient 'V' to touch the oiler to.

Mobil 1 5W/30 synthetic motor oil (upper)
Moebius 9010/2 sythetic light train oil (middle)
Moebius 941 synthetic pallet jewel/escape teeth oil (lower)

I was completely unprepared for the result!



As I touched the oiler to the edge of the crystals, I noticed that, not unexpectedly, each oil blob moved inward a little, leaving no oil at the edge. I noticed also that an optical fringe effect was actually indicating the interfacial stress caused by the clothes pin pressure. "Must take pictures!", I thought. While I was setting up the camera, I noticed that the motor oil seemed to have changed shape and moved a bit!. As you can see from the above shots - it eventually moved a lot, disappearing under the clothes pin in less than an hour!! The first shots were a couple minutes apart; the last four were taken at 5, 10, 15 and 60 minutes elapsed time.

The motor oil moved in the direction it did because the attractive molecular forces were greater on the side nearer to the clothes pin. Attractive forces are higher when two surfaces are closer together as shown by lower spatial frequency of the fringe pattern toward the pin. However, the blob stayed essentially whole because of it's own surface tension except where some some surface irregularity caused it to shed a small piece (conflicting attractive forces exceeded the shear strength of the oil).

I conclude that Swiss oil does tend to stay in place as advertised, and that oil can migrate away from where you put it - leaving dry, un-lubricated areas if the forces of capillary action so dictate, or if you just don't put enough.

I have to say that this is an astounding sequence of photos, made alive by the wonders of today's Internet technology. Do forgive me if I sound a little immodest!

Best regards,

xpatUSA