LORUS ROTARY SLIDE RULE Quick Manual

NRFRS
ROTARY SLIDE RULE
C H A R A C T E R I S T I C S
With this rotary bezel type slide rule, a wide
v a r i e t y o f c o m p u t a t i o n s r e q u i r e d b y p i l o t s
are possible.
• Ordinary multiplication, division and rule-
of-three calculation
• Calculation of time, speed and distance
• Conversion between nautical miles, statute
miles and kilometers
S C A L E S
The rotary slide rule consists of
A ) a dial ruler fixed on the dial and
B ) a r o t a t i n g e x t e r n a l s l i d e r u l e ( r o t a r y
beze l).
The outer circumference of the rotary bezel
is graduated at an interval of 3 deg. to form
a u t i l i t y b e a r i n g c o m p a s s , a n d t h e i n n e r
c i r c u m f e r e n c e i s p r o v i d e d w i t h a l o g a r i t h -
m i c s c a l e g r a d u a t e d f r o m 1 0 t o 1 0 0 a n d a
d i s t a n c e c o n v e r s i o n s c a l e ( K M , 1 0 0 0 F T ,
NAUT, STAT).
T h e o u t e r c i r c u m f e r e n c e o f t h e f i x e d d i a l
ruler is marked with the same logarithmic
scale (10 – 100) as the rotary bezel, and the
inner circumference is graduated with a time
scale.
Time index
(reference point for
time conversion)
Logarithmic scale
on fixed scale*
* A n y v a l u e o n t h e l o g a r i t h m i c s c a l e i s r e l a -
t i v e , f o r e x a m p l e , " 1 9 " a s s u m e s a n y v a l u e s
that are the n-th power of 10, multiplied by
itself ... 1.9, 190, 1900 ...
O R D I N A R Y C O M P U T A T I O N
[ M u l t i p l i c a t i o n , d i v i s i o n a n d
t h e r u l e - o f - t h r e e c a l c u l a t i o n ]
A Multiplication
[Problem] 30 x 40 = ?
[S olution]
1) B r i n g 3 0 o n t h e r o t a r y b e z e l i n l i n e
with 10 on the fixed scale.
2) Read the scale on the rotary bezel cor-
responding to 40 on the fixed scale.
It is 12 (= 1.2 x 10
3) Calculate the number of digits follow-
ing the formula in "Hint for calculation
of exponents".
[Ans wer ]
B Division
[P roblem] 120
[S olut ion]
1) B r i n g 1 2 o n t h e r o t a r y b e z e l i n l i n e
with 40 on the fixed scale.
2) Read the rotary bezel scale corresponding
to 10 on the fixed scale.
It is 30 (= 3 x 10
3) Calculate the number of digits follow-
ing the formula in "Hint for calculation
of exponents".
[Ans wer ]
C Rule-of-three calculation
[Problem] 30/10 = ?/40
[S olution]
1) B r i n g 3 0 o n t h e r o t a r y b e z e l i n l i n e
with 10 on the fixed scale.
2) Read the scale on the rotary bezel cor-
responding to 40 on the fixed scale.
The reading is 12 (= 1.2 x 10
3) Calculate the number of digits follow-
ing the formula in "Hint for calculation
of exponents".
[A nswer ]
A - 2)
B - 1)
C - 2)
H i n t f o r c a l c u l a t i o n o f e x p o n e n t s
Any number can be given by an exponential
expression as follows.
Assume A = a x 10
M ult iplication:
Then, the product of A and B is expressed
by C (= c x 10
Division:
The quotient of A/B is expressed by
C (= c x 10
C O M P U T A T I O N F O R N A V I G A T I O N
[Calculation of time, speed and distance]
A l l t h e e x a m p l e s h e r e c a n b e c a l c u l a t e d a c -
cording to the following formula:
Time calculation
A
[P ro blem]
Ground speed
Distance to fly :
Time to fly
[S olution]
1) A d j u s t 2 0 o n t h e r o t a r y b e z e l t o t h e
time index on the fixed scale.
2) Read the fixed scale at a position cor-
responding to 10 on the rotary bezel.
The reading is 30.
3) For the purpose of determining the number
of digits, the same rule as with the division
applies. Thus, the answer is 30.
[Answer]
mark at the 12 o'clock position
B Speed calculation
[Problem]
Ground speed
Distance to fly :
Time to fly
[S olutio n]
1) Adjust 10 on the rotary bezel to 30 on
the fixed scale.
2) T h e v a l u e o n t h e r o t a r y b e z e l c o r r e -
sponding to the time index on the fixed
scale is read to be 20.
3) For the purpose of determining the number
o f d i g i t s , t h e s a m e r u l e a s w i t h t h e
d i v i s i o n a p p l i e s . T h u s , t h e a n s w e r i s
200.
[Answer]
mark at the 12 o'clock position
1 20 0
40 = ?
3
120
C = c x 10
).
z
z = x + y if c
z = x + y + 1 if c < a, b
).
z
z = x – y if a
z = x – y – 1 if a < b
SPEED = DISTANCE/TIME
:
:
30 (minutes)
:
:
200 MPH
60
SPORTS
Utility bearing
compass scale
Logarithmic scale
on rotary bezel*
1
).
1
).
A - 1)
B - 2)
C - 1)
, B = b x 10
x
. (10 > a, b, c
z
= >
a, b
= >
b
200 MPH
100 miles
?
?
100 miles
30 minutes
12-97
1
).
, and
y
= >
1)