Pine Bluff daily graphic., 1912-07-31
TiE FREE BRIDGE
 AT FORT SMITH
Continued from page Onr5-

: the abutments serve =io lro4r.t the ends of the embankmnHs fHm e16s- ion at high water periods. They are supported on piles, N4iug Wer. Atiy- en to bearing on tac bed rgeh below the river. The central portions of fbp abutments support tn6zapars. and con sequenly they are, iha tBe niprs sunk into bed rock by tde uneumatjc 1 tube process.
 The earth embanhM1az5 eonslitut-
 ng the approaches Ire protected q from erosion during high water by rip-.rap on their upstream slopes. and they are paved with ,n}eng4sn. The approach at the Van BuTcn end of the bridge is spread SD as to carry railway tracks curyin9 both up and down steam to cross Dr io connect with the Iron Noun aib }5Hr.
 The spans provide 2 total traffic deck 50 feet W de ill the clear between hand rails. The truss $ are placed A feet inches apart, center 10 center. and between them provision js made for double track ele2rie railway. The area is also flooyed over with creosoted plank, so that it may be used by rapidly moving vehicles. such as automobiles, and in tae III dale of the bridge between the atreef railway tracks two additional rails are placed so that a standard steam railway of the heaviest modern type may cross the bridge on this central track During the use of she b,tid2a hv a train. the street railway cars may follow or precede the ira II; but. oh account of the presence eff the train Cn the bridge street cars cannot cross the bridge in the oppasine di 1ection. It would, of course. have been structurally practicable to make the bridge wide enough and strong enough to carry standard steam railway trains on two electric railway tracks and thus have avoided
 this interference with street rail-. way cars opposing trains, but to do so would added more than s20O 900 to the cost of the bridge, q sum many lmes larger proporti5nally than the benefit it would have afforded. In fact the commission had not avail able adequate funds to build bridge large enough and heavy enough for a double track steam railroad. and it was only by adopting this unusual construction that the use of the bridge by steam railways was made possible. Outside of The ,russes on cantilever brackets two roadways each Il feet wide in the clear between the guard rails are prov ded. These roadWays are paved with creosote3 wool blocks, and afford ample pro- vision for all the vehicular traffic the bridge will ever be required to carry. outside these roadWays there are two sidewalks for each five feet in the clear for the use of pedestrains.
 Saved Sls,O00.
 Another unusual feature of the bridge s the movable span, which is made to lift vertically, instead of to swing horizontally, to permit the pas sage of boats. The lifting span thus provides a channel 1S0 feet wide Ill the clear on the water line, and a vertical clearance of B feet at high water, or about 80 feet at low water.
 Fms affords an eXN ptionally wide clear channel and ample head room for the passage of the highest river steam beats. The lift span is exact SDdHS that machinery house is provided on the top of the center of t, and is counter'balanced by concrete counter weights ccnnected to it by steel wire ropes, which run over cast steel sheaves 10 feet in diameter, placed on the tops Of the towers, at it's ends. The counterweights weigh the same amount as the span and the machin- cry house and the machinery, so that the work to be done by the machinery Is only to overcome friction and in- ertla. Each corner of the span is connected, to the counterweights by eight steel wire ropes inches in diameter and each having a breaking rength equal to more than the en- tire lead imposed upon the group of ght ropes at the corner. The hoist ing engine in he middle of the span consists of train of gears actuated by an electric motor and operating four drums, to which are attached ! ropes which run over the sheavas at he corners of the. span and connect
 the tops and bo toms of the lower .egs The revolution of these operat- rg drums in one direction winds on ne ropes which lead to the tops of | the towers and plays eff those which | lead to the bottoms, lifting the span through the force eXerted by the [ ropes on the sheaves at the corner of the span. The reversal of the direc- ion CT rotation of the drums brings the span back to rest in position for service. The span can be lifted to it's full height or lowered in about ne minute.
 The use of the Tiff span in the bridge affected an economy amounting to about $1S,000 as compared with the cost of the ordinary swing span; and it possesses the additional and peculiar virtue that n case the navi- gable channel of the river should shift from its present position in any other direction, it is practicable at comparatively small cost, and with ut !nterrupting the traffic, on the bridge, to move the towers, counter weights, and machinery on the span to any other span. and to make any of the nine spans movable. This is II ,rn,tn T .I,