The Norden Bomb Sight manual

GYROSCOPE

A.

Review

1.

Defini-

tion.

2.Explanation

When bombing with a cross wind condition and

when drift is

encountered the rate end solves the

problem

exactly

as in case of

no cross wind or

drift.

Refer to

the

cross trail drawing, Fig.4l,

to see how the sicht corrects for cross trail.

Trail is set

in on the cross trail knob (M-3)

and trail mechanism. (See cross trail drawing M-6).

When the trai!

arm is rotated, the

eccentric disc

and rolier are

displaced

from the center of the

dove

tailand

disc respectively a distance pro-

portional to trail.

The cross hairs are placed on the target and

checked to see whether the

fore and aft cross hair

moves off the target in a transverse direction. If

it does, rotate the turn knob until the fore and aft

hair is again

on the target and then the course

knobs

may be double gripped to keep the hair on the

target.

Refer to cross trail drawing to see what

happen

when the

course

knobs are double gripped.

Since

the dovetail is a part

of the sight stem, and

since

the

sight

stem is fastened to the stabilizer,

the sight stem

will turn with the

independently

stabilizer and

of the sight. As the sight stem pivots,

the eccentric disc will pivot through an arc and in

so doing

the

stud, which fits in the slot

of the

cross trail carriage, will move the cross trail car-

riage in a transverse direction.

This transverse

movement is translated through bell crank and

cross

trail connecting

link to the cradle differential

lever and to the

telescope which is tilted

an

ular distance

that will subtend cross

ang-

trail on the

ground.

(The

cross trail drawing,

Fig. 41, shows

exactly the relationship between the triangles form-

ed by the movement of the dove

tail and

sight stem

and the

tilting

of the optics and

resulting tri-

angle). As is

shown, in order to keep the fore and

aft hair on

the target

the plane's ground track

is upwind of the collision course

cross trail dis-

tance

and parallel to the collision course.

Fig. 42 shows why there is no transverse move-

ment

set

of the cross trail carriage unless

trail is

in on

the

cross trail mechanism.

Synchronization is accomplished in the same

manner as when

bombing with

no cross wind.

A gyroscope is a flywheel so mounted that only

one point,

its

center of

gravity,

in a fixed

position, the wheel being free to turn in any dir-

ection about this. point.

Such a whee! has three

angular degrees of

freedom.

The wheel or rotor revolves in bearings in a