CARPENTRY. 



i rue- 

 Carp 



PLATE 

 CXXVIII. 

 Vig. 1. 



fluently the joggles, in the arches of circlet, making 

 ic other extremity. 



( \tniln-r fit-it nit, a u- thov timbers whii-h are sup- 



ported uj.on purlins over the cellar biams, and sup- 



the boarding for a leaden platform ; for tins 



purpose they have an equal declivity from the middle, 



ui nui'-r to cause the water to descend equally on 



1e of the roof. 



( 'r>, X // i; or ( 'i>i;i;i>i!!, the form of the joints which 

 the tie be<tm* and w:ill plates make with each other. 

 And here, as in every other case of jointing, the parts 

 must be reciprocally reversed to each other, so that 

 the protuberant part or parts of the one, are the rais- 

 ed or indented parts of the other ; and the parts which 

 the bottom or bottoms of the recess or recesses are 

 parallel to, are those which form the sides perpen- 

 dicular to the surfaces from which the joints are made. 

 The best method is by cutting a groove across the 

 fibres in the beam to be let down, to correspond to a 

 rising in the plate, formed by recessing the plate on 

 each side of the rising. Another method is, by 

 an external and internal dovetail ; but this last me- 

 thod is almost antiquated. 



Fig. 1 . shews the form of a truss similar to that 

 on the Pantheon in Oxford street, London, when it 

 was converted into an opera-house. The design was 

 made by Mr James Wyatt. It was consumed, as well 

 as the theatre, about the year 1792. The extent of 

 the building within the walls was about 80 feet. 



Fig. 2. shews the truss of the roof of the church 

 of St Paul's, Covent-garden, designed by Mr Hard- 

 wick, and executed by Mr Wapshot, in 1786. 



Scanning-. 1 ?. 

 In. by In. 



A A, the tie beam cambering 6 inches 

 in the clear of the walls, the whole 

 length being 72 feet, and the clear of 

 the walls 50 feet, 2 inches, ..... 16 



BG, BC, queen posts which are in the 

 shafts, ................ 8J 



DE, straining, or collar beam, .... 10 



FG, king post, 14 inches broad at the 

 joggle at the shaft, ......... 8 



HI, HI, struts, ............ 8 



KL, KL, straining braces, or auxiliary 

 rafters, at top 8 inches square, and 

 at bottom .............. 10 



JM, m, TH, i, puncheons, or blocks, to 

 support the principals, ....... 8 



NO, NO, principal rafters supported 

 by the puncheons, by the queen posts, 

 and by the tie beam at the lower end, 

 and king posts at the upper end, be- 

 ing 8^ inches square at top and bot- 

 tom ................. 



p, p, p, &c. purlins, supporting the 

 same rafters, ............. 9 



GR, GR. small rafters for supporting 

 the boarding and covering, ..... 6 



SS, wall plates ............. 12 



X 12 



x 

 X 



X 



x 



X 8 



10 X 8-| 



X 



X 



10 



Fig. 3. 



The distance of the trusses is about 10 feet 6 inches: 

 each tnibs contains about 198 solid feet of timber. 



Fi)r. 3. represents the truss of the roof of the Royal 

 Hospital at Greenwich. The design was by Mr James 



VOL, V, PAHT II. 



537 



t, author of the Antiquities of Athens. It wa C *-.i 

 executed by Mr Samuel Wyatt, about the year 1785. 



Scmntlimgt. 

 In. by In. PL * 

 AB, tie beam, being in length 57 feet, 



and 51 feet in the clear of the walls, . . 14 X 

 CD, iron kn.g post, 2 X 



EF, r.F, qifeu p.iHts, 9 X 



GH, GH, &c. struts 9 X 



IK, straining beam, 10 X 



HL, straining piece, 6 X 



MN, MN, principal rafters 10 X 



OP, camber beam, 9 X 



p, p, Purlins, 4 X 



12 "* 



9 

 12 



I 



7 

 7 

 6 



The timbers of this roof are well disposed, but the 

 iron king post is of little more use than supporting 

 the middle of the tie beam. 



The remaining figures in Plate CXXVIII. thew 

 the various joinings, in roofing, of king posts and 

 principal rafters ; of tie braces and principal rafters ; 

 of principal rafters and tie beams ; of struts and truss 

 posts ; of dragon pieces, angle ties, and wall plates, 

 with the various methods of bolting and strapping 

 these various parts together. 



Fig. 4-. No. 1. represents the method of joining and Fig- * 

 strapping the principals and king posts. In this figure ^' ' 

 the principals meet each other without the interven- 

 tion of the king post, which is omitted, in consequence 

 of the shrinking of the wood between the joggles. 

 Fig. 4. No. 2. exhibits the method of fixing the king No. 2. 

 post and tie beam, showing the manner of strapping the 

 same. Fig. 4. No. 3. Shows a section of part o? the No. 3. 

 king post through the mortice for the keys, with the 

 manner of wedging the same. Both the mortice and 

 the resisting piece of iron on the upper side of it, are 

 cut with a greater vertical dimension, than what the 

 width of the two wedges are, so that the head of the 

 mortice through the wood goes higher than the head 

 of the mortice through the iron ; so also does the 

 bottom of the mortice in the wood go higher than 

 the bottom of the mortice in the iron. 



Fig. 5. shews the manner of securing the king post, Fig. ~>. 

 principal rafters, and tic beam. No. 1. shews the form No. 1. 

 of the joggle joints, and the manner of strapping the 

 king post and principals, the king post intervening ; 

 but it is to be hoped, that thisinte: vention will be re- 

 linquished in practical works. No. 2. The manner of No. -. 

 bolting the lower end of the king post and tie beam, 

 the nuts being double, and their directions, in two 

 planes, intersecting each other at right angles ; and 

 also at right angles to the intersection, which is also 

 the axis of the bolt ; and the one direction perpendi- 

 cular, and the other parallel, to the plane of the truss. 



Fig. 6. shews the method of hanging the beam, and Fig. (i. 

 supporting it at the foot of the struts. No. 1. The 

 two rafters, suspending a double or branched rod for 

 supporting the lower ends of the struts. 



Fig. 7. represents the method of securing the lower F '- T - 

 end of the principal to the one end of the tie beam. 

 No. 1. The two parts secured together by means of aii No. 1. 

 eye bolt. No. 2. The manner of cutting the tenon. In ^' " 

 this, the principal is thinner than the tie beam, so that 

 the end of the tenon forms the outer abutment, and 

 the part on the inside of the rafter at the bottom, the 

 3 Y 



