7.
Tachymetre
slower, such as a bicycle, you must use a shorter
distance because the elapsed time must fall within
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
100
mph, 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
25
mph over the
quarter mile.
Example No. 2
– To measuring something much
7.2
-
60
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:
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.
TACHYMETRE DIAL = 3600 / Elapsed
Time In Seconds
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.
Example No. 1
– A car covers one mile in
30
31
60
40
20
0
8
2
4
6
9
3
12
6
N
S
W
E
5
0
1
1
5
2
0
25
30
35
4
0
4
5
5
0
55
SPECIAL
FORCES
1000XL
UNDERWATER
DEMOLITION
TEAM
CHASE-DURER
BLACK STEEL
1000FT DEPTH
9
3
12
6
31
60
40
20
0
8
2
4
6
9
3
12
6
N
S
W
E
5
1
0
1
5
0
2
25
30
35
4
0
4
5
5
0
5
5
SPECIAL
FORCES
1000XL
UNDERWATER
DEMOLITION
TEAM
CHASE-DURER
BLACK STEEL
1000FT DEPTH
9
3
12
6
A
START/STOP
A
START/STOP
