NATIONAL SUREAU OF STANDARDS REPORT

3689

IMPROVEMENT OF NAVIGATIONAL LIGHTS

By

Ray P. Teele

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

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©Office of Basic Instrumentation ©Office of Weights and Measures.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

0201-20=2316 October 5, 195*+

NBS REPORT

3689

IMPROVEMENT OF NAVIGATIONAL LIGHTS

By

Ray P. Teele

Sponsored by

Bureau of Ships

Department of the Navy

Washington 25 , D.C.

Project Order 10768/53

NBS.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, r

unless permission

25, D. C. Such pc

cal ly prepared If

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

ir In part, Is prohibited

standards, Washington

report has been specifireport for its own use,

IMPROVEMENT OF NAVIGATIONAL LIGHTS

By

Ray P, Teele

This report describes the optical components for

two types of navigational lights designed to give improved optical performance while decreasing the physical

size compared to currently used navigational lights.

Consideration was given to features that would permit

retracting the navigational lights when used on submarine vessels. It is understood that the mechanical

design will be carried out by the Bureau of Ships. However, models were made up to serve as possible prototypes.

1. CYLINDRICAL MODEL

The cylindrical shape would lend itself to retraction. The bottOiii could be equipped with rings and

operate as a piston inside of a tube extending through

the fairing or into the hull of the vessel. The top of

the unit could be shaped so as to be flush with the fairing or hull when the unit was retracted.

1.1 Mast Head Light

The optical unit for the mast head light is shown

in Section B-B of Figure I. The optical unit is essentially a channel and in production could be made from

channel brass (or other metal) and serve as the mechanical support between the top and bottom of the complete

light unit. The forward edges should be bevelled and

made as thin as possible while having adequate mechanical

strength.

The optically important dimensions, a and b, are

related by the relation a/b = tan 22.5°. The dimension,

a, is the distance of the filament from the plane containing the forward edges of the channel. The dimension,

b, is half the width of the channel measured outside at

the forward edges.

An alternate construction is shown in Figure II.

In this case the section of the metal cylinder at the

back of the unit must serve as the support for the top

and bottom of the unit and would need to be quite thick

to maintain the top and bottom parallel to each other

and to exert adequate pressure on gasket material to

seal the glass cylinder against entrance of water.
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1.2 Side Lights

The optical unit for the side lights is shown in

Section A-A of Figure I. This optical unit is symmetrical about the horizontal center line, A-A. One unit

serves for both port and starboard lights, being installed with the opposite end up in one light as compared with the other light. This interchangeability

would simplify stocking and storing problems.

The optically important dimensions are, as for

the clear unit, a and b, for the side cut-off and on

the forward axis through the filament for the forward

cut-off. The arched shield for the forward cut-off has

sufficient length to permit relamping; its shape need

not be held to close tolerances.

1.3 Lamp Bulbs

Lamp bulbs were designed for these units. They

are characterized by having spherical bulbs with medium

prefocus bases. The filament is a single coil at the

center of the spherical bulb and at right angles to the

axis through the base. The bulbs are especially

selected to be free of striae, stones, bubbles and

other imperfections. Although made up specifically

for this project by one of the large lamp manufacturers, they would not be too costly in production in

quantities A description of the lamp would be: bulb,

G-16 1/2; base, medium prefocus; rated volts, 19;

amperes, 2.6; filament, C — 6

;

light center length,

2 3/32 inches; maximum overall length 3 1/16 inches.

The criteria for selection of the bulbs for quality are

the same as now commercially used for lamps for medical

instruments, for example, as used for the trade number

981 lamps. The life can be specified as desired between

100 and 1000 hours.

l.b General

Each unit is equipped with a standby lamp. The

optical performance is the same with either the regular

or standby lamp in operation.

All surfaces of the optical units are painted with

flat (matte) finish black paint.
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In production an opaque coating should be applied

to the outer glass cylinder over all portions through

which light does not pass. (Paint was used on the models

but would not be durable in actual service} The opaque

coating on the models has been omitted at the back of the

side units to permit examination of socket arrangement

and wiring „ In all units the #3 terminal of the plug is

the common lead.

2. SEALED “BEAM UNIT

A sealed~beam unit was designed. The principal

advantage of this unit would be ruggedness and small

size. It could be used in a housing similar to a traffic-signal standard with a regular unit and a standby

unit in the same housing. A red coating has been developed by the Westinghouse Lamp Division which is suitable for use on these lamps. However, a durable green

coating has not yet been perfected. While the coated

red or green bulb is preferable it is possible to use

a clear bulb and external colored glass disk. At a demonstration of an early model of this sealed-beam

unit it was decided by the Bureau of Ships representatives to concentrate on the cylindrical model. However,

an improved sealed-beam lamp was already on order at

that time. <

The improved sealed-beam lamps were delivered subsequently and their performance is such that, in view of

their ruggedness and small size, they might be used in

some service applications. A fog lamp housing was

obtained to house this unit and it is suggested that

it be considered along with the other models. The

cut-off is not adjusted to be exactly 112.5 degrees in

this sample. This adjustment would need to be made for

the exact dimensions of the final housing decided upon

if the unit seems to have sufficient merit.

It is believed that the sealed-beam unit would

prove to be the most rugged in actual service as well

as the easiest to maintain in first class working condition.

3. MEASUREMENT OF CUT-OFF OF UNITS

The various models and one of the present masthead lights were measured on a semi-automatic recording
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goniophotometer to determine the cut-off characteristics.

The present mast-head light delivered to the Bureau together with the lamp currently used in this model were

found to have either an incorrect socket position or an

incorrect light center length for the lamp. We were

assured hy telephone that both unit and lamp were those

currently used. The difference between the filament location for a horizontal beam and the actual location of

the filament in the unit delivered to this Bureau is

approximately 1/4 inch.

The angles in the vicinity of the cut-off are determined with an expanded angle scale as marked on each

graph sheet. The major portion of the horizontal traverses

was run with an angle scale of 5 degrees per line on the

graph; the expanded angle scale is 0.5 degree per line on

the graph.

3.1

Present Mast-Head Light

The cut-off of this unit, as can be seen from Graph I,

is accomplished in approximately 5 degrees.

3.2

Improved Mast-Head Light

The cut-off of this unit, shown on Graph II, occurs

in 1 1/2 degrees.

3.3

Improved Port Light

The side cut-off of this unit, shown on Graph III,

occurs in 1 1/2 degrees. The forward cut-off occurs in

2 degrees.

3.4

Improved Starboard Light

The side cut-off of this unit, shown in Graph IV,

occurs in 1 1/2 degrees. The forward cut-off occurs in

2 degrees.

3.5

Larger Improved Mast-Head Light

The cut-off of this unit, shown in Graph V, occurs

in less than 1 degree.

3.6

Sealed-Beam Side Light

The entire beam is shown in Graph VI, together with

expanded angle-scale of cut-off region at each end. The

entire range of the cut-off is about 8 degrees but the
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effective cut-off is about 1/2 of this value (from

zero to about 60 percent of the side increase in intensity) .

4. REDUCTION IN SIZE

The present mast-head light is 10 1/2 inches high

and 29 inches wide. The side boards are “swept back*1 and the overall depth is about 1 foot (the central

body is 9 inches deep).

The small size improved mast-head light is 7 1/2

inches in diameter by 12 inches high. The larger size

improved mast-head light would be about 9 inches in

diameter by 12 inches high in complete unit form. The

optical unit is 7 1/4 inches in diameter; a surrounding

glass cylinder and top and bottom plates wculd increase

the diameter to about 9 inches in a completed unit. The

improved side lights are the same size as the improved

mast-head light. Two photographs showing comparative

size are appended to this report.

The sealed-beam lamp Is 4 3/8 inches in diameter

by 2 1/2 inches deep. When this is mounted in an automotive fog light housing with the light baffle on the

front the complete unit is 5 inches in diameter and

3 1/2 inches deep.

5. SUMMARY

An improved cylindrical navigational light with

internal control of the cut* off angle has been developed. The smallest practical size has a cut-off of

about 1 1/2 degrees as compared to about 5 degrees for

the current lights. A slightly larger unit (about 1 1/2

inches greater diUmeter) would result in a cut-off of

less than 1 degree. Either cylindrical model is approximately the same size as the central body of the current

lights. No side “boards' 1 are used with the new lights.

A sealed-beam unit was developed which would have

optical characteristics comparable with those of the

current navigational lights. The advantages of this

unit would be its small size, ruggedness, and ease of

maintenance in service.

This report covers the optical units in prototype

housings. Details of mechanical design are to be

worked out by the Bureau of Ships.

Photographs showing the comparative size of the

current and improved mast-head lights and the optical

components (from left to right) for a side light, the

large mast-head light, and the small mast-head light

are appended to this report.

One fault that exists in the current model is the

presence of reflections in the edges of the prisms of

the Fresnel lens. hese reflections cause difficulty

at close ranges. The improved units all use smooth

outer or cover glasses and such reflections are avoided.

The smooth outer glass is, of course, much easier to

clean than are the Fresnel lenses now in use.
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Photograph 1

Present mast-head unit on the left and improved

mast-head unit on the right

Photograph 2

Optical units of improved navigational lights.

Side-light unit on left, large mast-head unit in

center, and smallest practical mast-head unit on

right.

Photograph 3

Sealed-beam unit for side lights compared with

present mast-head light. Ruggedness and small size

are the principal advantages of the sealed-beam unit,

which has cut-off characteristics comparable to those

of present lights.

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

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Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

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Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

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publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.