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S< KT <.i:nl M> 



137 



the cross struts .r, y, z, etc., being inserted to hold the radial 

 struts firmly in position. The feet of the various radial 

 props rest on the sill M N. These fan-like timber struct mvs 

 are set up at intervals of from 3 ft. to 6 ft, depending upon 

 the quality of the soil penetrated. 



Pin. 63. Sketch Showing Radial Roof Strutting, Belgian Method. 



Centers. Either plank or trussed centers may be employed 

 in laying the roof arch in the Belgian method, but the form of 

 center commonly employed is a trussed center constructed as 

 shown by Fig. 0*4. It may be said to consist of a king-po>t 

 truss carried on top of a modified form of queen-post truss. 

 The collar-beam and the tie-beam of the queen-post truss are 

 spaced about 7 ft. ajKirt, and 

 the posts themselves are left far 

 enough apart to allow the pas- 

 sage of workmen and care be- 

 tween them. The tie l>eam of 

 the king-post truss is damped 

 to the collar-l>eam of the queen- 

 post truss by iron bands. On 

 the rafters of the two trusses are fawN-m-o! timU'is, with tln-ir 

 outer edges cut to the curve of the roof arch. These centers 

 ;m >ct up midway between the fan-like strutting frames j.r. \i- 

 ously descril>ed. They are usually built of square timbers. 

 The tie teams are usually *> x 6 in., and the struts and posts 

 4 x 4 in. timbers. The reason for giving the larger sectimril 



Pin. . Sketch Showing Konf Arab 

 Center, Belgian Method. 



