Burlington weekly free press. [volume] (Burlington, Vt.) 1866-1928, 1888-01-06
IGLECTRIC LIGHTING.


Street Lighting.
[From the Engineering and Building Rccord.l
This question invol, es the following
points
First-A form of construction of towers
that will require minimum horizontal
space for base, be inaccessible to boys
climbing, and offer least obstruction to
view along the street
Second-Strength to resist high winds.
Third-Ready means of ascending to
the lights, so that an attendant may care
for lamps without breaking the circuit.
Fourth-Perfect accessibility of all parts
for frequent inspection and painting.
Fifth-The proper height for towers in
order to yield the best practicable results
i. g., to enable the light to reach its effect
i've limit without unduly robbing its i'm
mediate surroundings.
The system of electric-lighting from
towers is of very recent date. Their con
struction has been subject to gradual
change and development,
At the outset square pyramid tower
was most used, made with inclined posts
at the corners united by horizontal struts
and braced both in the plane of the sides
and horizontally. These horizontal braces
prevented the ready arrangement and
operation of an interior elevator, so resort
was hal to triangular tower similarly
braced on it's exterior faces, but requiring
no interior bracng. This left free space
for an elevator, but, in order to insure
strength, the tower was tapered from the
top t. the base so that with an altitude OF
say $50 feet the spread at the base was
about IS feet
This formed no great objection where
the tower could be located in park or
NM lad mil hi in n Il "A
city or town these towers had to be loca
ted at street corners. 1t was found nee
essary, therefore, to have the tower span
the street or sidewalk so that one corner
Of the tower might rest near the corner of
the street. and the other two corners of
the tower rest adjacent to the buildings.
This was unsightly and inconvenient, AS
frequently i'll cities the space between the
sidewalk and the building is occupied by
vaults or openings, and tower foundations
placed there would often he very much In
the way, uecessitating the shifting OF
tower location from point where it ought
to be to some other locality where it is
possible to erect II.
Again, with pyramidal tower not
guyed the wind pressure caused great
strains and required heavy members, and
necessitated frequent adjustments and
repairs. Assuming the same wind pres
sure per foot of height on the pyramidAl
tower as is permissible for the prismatlc
one, and that the former Is not guyed and
that the latter Is perfectly Guyed, then for
equal dimensions the unguyed tower
would be strained at least four times as
much rs the other for the same wind
pressure.
The development and improvement of
pyramidal and other forms OF tower grad
ually led to that here described.
1t is essentially a triangular prism, six
feet on "A side, built in II vertical sections,
each ~ feet long, supported on single
base column and guyed at two points.
The centre lengths of all sections are
equal, and members, to considerable de-
gree, Interchangeable.
The foundation is generally located just
inside the angle of the curb at the street
corner, and consists of a double platform
of two inch oak plank laid crosswise car
rying pier, three feet square, of hard
burned brick set in mortar of hydraulic
cement and coarse sand the pier Is cap
| ped by stone BIB XG that receives the
base casting, the latter secured by six
| | Is anchor bolts through the masonry
| and bearing on an iron ring underneath
| the platform. A tubular column IA feet
| high screws into the base casting and re-
ceives struts at the top connecting it with
| the prismatic tower. A light elevator
| platform runs in the interior of the tower
| and is carried by single endless cable
| passing over fixed upper sheaVe and a
| lever, pivoted at the short end and coun-
terweighted on the free long end the
| outer part of the cable carries a counter
! pOise nearly balancing the loaded elevator,
| Two stationary guide-cables pass through
| the car and are engaged by clutch which
! holds the elevator stationary and only
permits ascent or descent when released
| by pressure of the occupants foot.
| The towers have suitable lower and up
per platforms with ratings, and mast and
arms for the lamps All the compression
| members are of best ap-welded tubing,
quality maleable iron, that have ri BIS to
which are bolted the forked ends screwed
to each end of all the wrought-iron diago-
| nal rods.
There are two sets of four guys each
one leading from point II feet below
| the upper platform and the other from q
point about "a feet lower down on the
tower, The guys are each 7-l6-inch
| galvanized wire cable, connected by Il
| turnbuckle to an eye-bolt in an oak post IA
| inches square by 10 feet long that is set
vertically six feet in the ground at about
| 100 feet from base of tower and receives
two guy robes IN the same vertical plane.
| The iron-work is painted one coat of as
| phaltum, and the posts two coats of lead.
The towers are erected by first putting
| together the top section, then hosting up
and building on the next beneath il, and
SO on until completed. The weight of Il
complete tower, elevator, etc, inclu ding
| guy ropes, is about 1900 pounds.
The entire wind surface, including
lamps, hoods, and mechanism is calcu
lated at 50 square feet, but this should
probably be increased so per cent for OBJ
lique and indirect exposure.
This form of tower has been subjected
to terrific storms. AT Evansville, Ind IL
of them were subjected to three cyclones,
one of which destroyed large numbers of
houses, barns, aud shops, and, in fact