Mixing and Placing Concrete.—A Ransome mixer holding a half-yard batch was used. The mixer was driven by an electric motor. The concrete for the piers was a mixture of 1 part Portland cement to 7 parts gravel; for the arches, the concrete was mixed 1 to 5. The gravel was piled near the mixer, a snatch team being used to assist the wagons in delivering the gravel into a pile as high as possible. Run planks supported on "horses" were laid horizontally from the mixer to the gravel, so that big wheelbarrow loads could be handled. The barrows were loaded with long-handled shovels, and the men worked with great vigor, as is shown by the fact that four men, shoveling and wheeling, delivered enough gravel to the mixer in 8 hrs. to make 100 cu. yds. of concrete. We have, therefore, estimated on a basis of six men instead of four. The mixer crew was organized as follows:
| Per day. | |
| 6 men shoveling and wheeling | $12 |
| 2 men handling cement | 4 |
| 1 man handling water | 2 |
| 1 man dumping concrete | 2 |
| 2 men handling dump cars | 4 |
| 2 men handling hoisting rope | 4 |
| 4 men spreading and ramming concrete | 8 |
| 1 engineman | 4 |
| 1 foreman | 5 |
| Fuel, estimated | 3 |
| — | |
| Total | $48 |
The output of this crew was 100 cu. yds. per day. The concrete was hauled from the mixer in two small dump cars, each having a capacity of 10 cu. ft. The average load in each car was ¼ cu. yd. Ordinary mine cars were used, of the kind which can be dumped forward, or on either side. The cars were hauled over tracks having a gage of 18 ins. The rails weighed 16 lbs. per yard, and were held by spikes ¼×2½ ins. Larger spikes would have split the cross-ties, which were 3×4 ins. Only one spike was driven to hold each rail to each tie, the spikes being on alternate sides of the rail in successive ties. No fish plates or splice bars were used to join the rails, which considerably simplifies the track laying.
Fig. 162.—Trestle for Service Track.
Two lines of track were laid over the bridge. The tracks were supported by light bents, the cross-tie forming the cap of each bent, as shown in Fig. 162. The bents were spaced 3 ft. apart. There were two posts to each bent, toe-nailed at the top of the tie, and at the bottom to the arch sheeting plank. Two men framed these crude bents and laid the two rails at the rate of 150 lin. ft. of track per day, at a cost of 4 cts. per lin. ft. of track. As stated, there were two tracks, one on each side of the bridge, but they converged as they neared the concrete mixer, so that a car coming from either track could run under the discharge chute of the mixer; Fig. 163 shows the arrangement of the tracks at the mixer. The part of each rail from A to B (6 ft. long) was free to move by bending at A, the rail being spiked rigidly to the tie at A, leaving its end at B free to move. To move the end B, so as to switch the cars, a home-made switch was improvised, as shown in Figs. 163 and 164.
Fig. 163.—Arrangement of Service Tracks at Mixer.
Fig. 164.—Improvised Switch for Service Cars, General Plan.