Tachymetre - Chase-durer Squadron Commander Operation Manual

Using the TACHYMETRE scale
The TACHYMETRE dial is mainly used to compute an average speed after noting how long it takes to travel a
fixed distance (like one mile or one kilometer), but it can also be used to compute many other things.
The dial is a logarithmic scale that uses this formula to compute:
Time In Seconds
The chronograph second hand indicates 1/10, 1/4, 1/2, 1, 10, 100 or 1,000 etc. units (miles, objects, pounds
etc.). When stopped, the second hand points to the number on the TACHYMETRE scale by which the number
of units (1, 10, 100 or 1,000 etc.) must be multiplied to obtain per-hour production rate or per-hour speed.
MPH
CHASE-DURER
12 12 10
10 2
8 2
9 3
8 4
6 4
6 6
SQUADRON
COMMANDER
31
60
50 10
40 20
30
Example No. 1 – A car covers one mile in 30
seconds. The second hand, stopped as the mile
marker is passed, reads 120 on the TACHYMETRE
scale. Average speed of the car is 120 x 1, or 120
miles per hour.
Although decimal units (100 liters, 1 mile, 10
kilometers) make computing simple, in practice, the
TACHYMETRE scale can be used to calculate
velocities and production rates from any number of
units.

Tachymetre

A
START/STOP
TACHYMETRE DIAL = 3600 / Elapsed
MPH
CHASE-DURER
12 12 10
10 2
8 2
9 3
8 4
6 4
6 6
SQUADRON
COMMANDER
31
60
50 10
40 20
30
Example No. 2 – To measuring something much
slower, such as a bicycle, you must use a shorter
distance because the elapsed time must fall within
7.2 - 60
the second range.
For this example, it took 36 seconds for a cyclist
to travel 1/4 of a mile. Reading the TACHYMETRE
dial displays a speed of 100mph, but the cyclist only
traveled 1/4 of a mile, so the actual speed would be
1/4 of that or an average speed of 25mph over the
quarter mile.
7.
A
START/STOP