Fig. 289. Scissors Beam.
Braced Collar Beam.—This is a modification of the last type, but is adapted for thick walls only. The tie rod braces (A, A) have to be brought down low to give a good bracing action, and this arrangement is capable of considerable ornamentation.
The steeper the pitch the higher up would be the inner and lower brace posts (B, B) which were supported by the top of the wall. This form is not available for wide spans, and is shown to illustrate how the development was made into the succeeding types.
Fig. 290. Braced Collar Beam.
The Rib and Collar Truss, Fig. 291, is the first important structural arrangement which permitted the architect to give full sway to embellishment. The inwardly-projecting members (A, A) are called Hammer Beams. They were devised as a substitute for the thick walls used in the Braced Collar Beam Truss, and small brackets (B, B) were placed beneath as supports.
Fig. 291. Rib and Collar Truss.