Reading time - the Breitling Bezel (part 2)

Great Scott! How many functions are there?

Today we will 'go back' into the many functions of the Breitling bezel (really any pilot watch bezel) and how to read them. In the last part we discussed simple multiplications and divisions. In this part, we will explain some conversions (as most pilot bezels default in miles) from miles to kilometres and vice versa.

First off, let's just reiterate that we are only using the outermost 2 scales on the watch. The outer sliding track printed on the bezel, and the inner fixed track printed on the outer circumference of the dial. The scales are logarithmic in spacing, and printed with very small text, so most of these calculations are a fairly close approximation. Let's also not forgot the decimal dilemma. 10 on the outer scale is also 0.1, 1, 100, 1000, etc, much the same as for the other numbers on the scales.

We use the same calculation on the bezel to convert miles to kilometres, as we do for miles per hour to kilometres per hour (and vice versa, to go from kilometres to miles etc.). For example, let's say we want to find out exactly how fast Marty McFly and Doc got that steam locomotive to travel, when they said 88 miles per hour.
First, 1 kilometre is approximately 0.621 miles. So we align 62.1 on the outer scale, with the 10 (in red) on the fixed scale. Then on the outer scale, find 88. The inner track will display the kilometres conversion (either kilometres, or kilometres per hour) which for us says about 14.15.
This obviously isn't the speed as that would have been very easy to reach, even for a steam locomotive. So we move the decimal place to find approximately 142 kilometres per hour (flat out on straight track, most steam locomotives back then topped out at 40 to 50 miles per hour). The exact answer is 141.6 kilometres.

In much the same way, if you have kilometres you need converted to miles, you do the reverse, without touching the bezel. To find out how many miles it is across Australia, you look for 3860 (kilometres across Australia) on the inner track, to read your miles off the outer track.
Your scale doesn't have 3860? You're only partially correct. It does have 38.6 which is the same number as far as our logarithmic scales are concerned. Looking now to 38.6 on the fixed inner track, we read off the outer bezel a hair under 24 (or 2400). The correct answer being closer to 2398.5. Not too bad an approximation when you compare the width of Australia with the circumference of your Breitling.
In this way, once you align 62.1 with the red 10 a shown above and below, all conversions for all numbers from 0 to infinity can be calculated at a glance.

We will return again with more Breitling Bezel tutorials as there are still many more uses for it.

Andrew