The collar beam will, unless the roof settles or spreads, be in compression ; bat, as the latter contingency may possibly occur, it will be better to provide for its becoming a tie beam by tenoning it to the principal rafters and securing these with inns or iron straps.
Not much difficulty will be experienced in making this drawing. Set off the walls to the given span, bisect the span and erect a centre line. Draw the corbels resting on the springing line, and with a radius of 19 ft. describe the soffit of the arch and the back 9 in. farther out. Next draw in the collar beam tangent at the crown, and the two principal rafters at a pitch of 450 tangent to the arch; the remaining iines are parallel to these and can easily be followed from the example. It is a good method in all drawings to get in the most important or essential member first, constructing those of less importance around it as circumstances suggest.
Doors.—The framed, Iedged and braced door in solid frame shown in Figs. 1 to 3, page 59 is a strong door of the ledge and batten type used for coachhouses, warehouses, etc.
The stiles and top-rail are of equal thickness, in this case 2 in., and are grooved to receive the boards. The middle ami bottom rails, termed " ledges," are usually half the thickness of the framing, the remaining half being occupied by the boards or " battens " ; these are grooved and tongued together with straight tongues, the two outside boards being rebated and tongued to the frame, as are also the top ends of the remainder. The boards are nailed to the ledges and braces with wrought nails. Braces should rake downwards towards the hanging stile for the purpose of throwing the weight upon the hinges, and be notched into the ledges as shown. The ends should not be taken into the angles, as this has a tendency to push the shoulders off. Barefaced tenons are cut on the ledges, and the top edges of the latter " weathered " to carry off the water. These doors are usually hung with hook and eye straps. The frame is out of 4} in. X 3 in. deal, solid rebated and beaded; 4 in.
Figs. I to 3. Projections of a Framed, Ledged and Braced Door in Solid Frame. Figs. 4 to 6. Projections of a Framed and Panelled Door. Figs. 7 and 8. Enlarged Details
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