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Breitling Navitimer Slide rule
The Breitling Navitimer is a watch equipped with a slide rule , even in this computer world it can be a very usefull tool for basic math , such as multiplication , divisions , money conversion ......
The Breiling Navitimer has not been the first Breitling equipped with the slide rule as you can read very often . In fact it is the Chronomat , introduced in 1942
you can have a look here to a Breitling Chronomat equipped with the first Breitling slide rule

The 1942 slide rule is different from the one of the Navitimer (except the Navitimer 92 with this "1942" type) it is an inverted scale type and you can see hereafter how it works. In 1952 Breitling introduce another type of slide rure We will try to explain hereafter the basics of this tool Note that each Navitimer is supplied with a complete instruction manual for the slide rule + a "training" model (see the scan just below)

To multiply with the Navitimer, use the unit index (number 10) in red on the inner scale . Always set the multiplier (the number by which another is multiplied) opposite the unit index on the inner scale and read the answer on the outter scale opposite the multiplicand (number to be multiplied by another) appearing on the inner scale To multiply 7x12 set 12 (the multiplier) on outer scale opposite unit index (10) on the inner scale . Opposite 7 on the inner scale, read the answer 84 on the mobile dial. To divide with the Navitimer alsoi use the unit index (Red 10) place the dividend on the outer scale opposite to the divisor on the inner scale . Opposite the unit index read the answer on outer scale To divide 120 by 4 place 120 on outer scale opposite to 4 on the inner scale. Read the answer,30 , on outer scale opposite unit index (10) You can view and download the complete instruction manual of the slide rule of a vintage 1967 Navitimer : click here You can view and download the complete instruction manual of the slide rule of a modern Navitimer : click here Navitimers can also be used to convert Hours in Minutes (not all models have this scale but if you want some details about this scale : click here Navitimers can be used as tachymeter, pulsometer or telemeter : click here to get the tutorial

Many other math calculations can be acheived using the slide rule such as : calculating ground speed , calculating miles per minute , rate of climb or descent .... but also simply money conversion : something VERY usefull for us Europeans ! we have just swap our money for Euros ! The Navitimer slide rule is for sure THE sympol of this watch , even if some other watches have one and if very few owners use it. Just remember the time where calculators where not in your pockets and where this instrument was always with you Slide rules are still used by some pilots : the picture on the left shows a E6B flight computer with circular slide rule similar to the Navitimer slide rule. Please find hereafter some links about slide rules : Basic slide rule instructions (HP museum site) The Slide rule universe The Slide rule site Eric's Slide rule site A Java fully functional slide rule on your computer 