The daily Gate City and constitution-Democrat. (Keokuk, Iowa) 1916-1922, 1916-07-24
The Nelu keokuk Hamilton
Bridge Is NoU Complete

| eye-bar bottom chords. The swing
span consists of. two riveted spans,
made partially continuous by eye-bar
connections to the tower over the
pivot pier.
AS most of the old substructure was
In good condition, the new super
structure has been placed on the old
piers, with the exception OF one which
was partially rebuilt. On account of
a difference In the floor depth, the old
piers have had to be cut down and
capped with concrete. The old center
pier is hollow, consisting of circu-
lar wall under the drum with CEN
trail column under the center casting.
in preparing this for the new super.
structure the circular wall and central
column were covered with rein
forced concrete slab.
| An improvement has been obtained
!, In the new structure through the sep
aration OF the highway traffic from
the rail traffic by placing the former
on an upper deck. This has necessi-
tated viaduct 600 feet long on the
west side OF the river and one Of $50
feet on the east side. Owing to the
fact that the business district of Keo-
kuk Is at considerable elevation
above the railroad tracks, the ap-
proach viaduct on the city side Is
convenience rather than detriment.
| On the east side Of the river an in
cline on per cent grade is neces-
sary. The removal of the highway
traffic from the lower deck has per
mttted reduction Of the distance be.
tween trusses. to 16 feet inches for
the eight short spans and 20 feet 6
inches for the others and the use Of the
ordinary loor beam and stringer floor
system, with an open timber deck.
The upper deck has a creosoted
wood block roadway for the team
traffic and a sidewalk feet inches
wide, cantilevered out on the south
side. The floor is carried on wooden
stringers having to 10 foot spans,
supported on Inch 42-pound I-beams,
spanning from truss to truss. On the
eight short spans the highway deck
is carried on top of the top chords of
the trusses. In the draw span and the
two curved chord spans the deck is
carried between the trusses, longitud-
inal Orders being provided just in
side of each truss to carry the floor
system, these Orders being support
ed at each post by connections to the
cross frames.
The Swing Span.
The center of the swing span Is OF
the rim bearing type and has four
support loading arrangements. The
bottom chords Of the trusses pass d.
rectly ever the drum and the concen-
tration of the end posts and the tower
posts are transmitted directly through
the bottom chords of the drum, there
being no intermediate loading girders.
The rollers are secured between two
concentric rings; a stiff structural
ring on the inside and lighter
flexible ring on the outside, the In
eide ring. being rigidly connected to
the center of the system of stiff ra-
dial struts. With this arrangement
the roller shafts are simply short ak
les connecting the rollers of the two
rings.
Two sources of power are provided
for operating the bridge machinery.
a 37L horsepower motor operating on
a 2-cycle, 440-volt circuit, and a IA
horsepower, 2-cycle Fairbanks-Morse
marine gas engine, operating at 500
revolutions per minute. The machin
cry is arranged SO that it may be
operated by either, the single unit
performing all functions in either
case. The motor will be used ordi-
narily, the gas engine serving merely
as an alternative source of power in
case of a failure of the current. The
motor is connected to the machinery
by hand operated clutch. which may
be thrown into gear either with the
swing machinery or the longitudinal
shafting connecting to the machinery
at each end of the span.
The longitudinal shafts are con-
= IL, 4o1,@ ~
lifts and the rail locks, but through
peculiar trip arrangement these
clutches are alternately operative
and imperative thereby automatically
effecting the alternate operation of
the end lift and the rail lock in the
proper sequence. Thus in opening
the bridge, the end machinery first
withdraws the rail lock and with the
completion of this function, the
clutches are shifted automatically,
putting the end lift machinery in mo-
ton to lower the end Of the bridge.
The operator, observing the compile
ton of this operation on a mechanical
Indicator, shifts his hand clutch and
the bridge commences to swing.
When the bridge is being closed all
Of the operations are reversed.
The end lifts are of type which
serves TO center dne DTluSe hutoHdt-
ically and will readily overcome the
warping effect resulting from the I'M
equal expansion Of the two sides Of
thesstructure. The ends OF the spans
are raised by forcing the toggles
from an inclined to vertical posi-
ton. the rollers at the lower ends OF
the toggles being in contact with the
inclined bearing surfaces. As the
toggles are raised, the rollers roll !
down the inclines to the lowest posi-
ton, after which any further move
ment of the toggles serves to center
the ends of the span.
The rail locks are of the sliding |
tongue type. A new development in
this case is the use of steel ties I'M
der the ends of the rails, a measure
adopted because of the rapid crushing !
of wooden ties as a consequence of
the impact obtaining when the wheels
pass over the gap in the rails The