Fig. 42 shows a type of truss that has been extensively used for church roofs, by Mr. D. S. Schureman, architect, of Rockford, 111., and possibly by others. The half-tone illustration, Fig. 43, shows a truss of this type over the Second Congregational Church of Rockford, where the trusses have a clear span of 80 feet, and are 51 feet apart. The space between the trusses is spanned by two Howe trusses. The roof is of slate. The timbers used in these trusses are 10" x 12", the kingpost is 9 feet long, and the bottom of the king-post is 14 feet above the foot of the truss.
Fig. 42. - Hog-Chain Scissors Truss.
In the truss shown in Fig. 42 the horizontal beam at the foot of the king-post is put in merely to support the ceiling construction, and is not needed as a part of the truss. The rods R R, merely support the ends of the horizontal beam and a part of the ceiling, and would not be needed if there was no ceiling to support.
Although this truss somewhat resembles the scissors truss, the mechanical principle of the two trusses is entirely different.
In this truss the tie-beams T T are in tension, for their full length, and all of the other timbers are in compression. The truss is prevented from spreading by the ties T T, and the rods B, E, C (one on each side of the truss). By tightening up on these rods, the strut beam is raised at the centre, and the feet of the truss drawn in. The rods A, K, B and C, H, D support the end of the short braces.
Fig. 43. - Trusses in Roof of Church at Rockford, 111. D. S. Shureman, Architect.
While this is a true truss, the author does not consider it as good a truss as that shown by Fig. 38, which gives about the same lines. The stresses in the truss, Fig. 42, are considerably greater than those in the truss, Fig. 38, and the connections are more difficult to make. The truss shown in Fig. 42, however, is but little affected by shrinkage of the timber.