The Works Of Messrs. Schneider And Co.

THE SCHNEIDER PAVILION AT THE PARIS EXHIBITION. 331 at the latter date the dismantling of the scaffolding was begun, and tlie Pavilion was conipletcd and painted with the help of lighter apparatus. The trusses were erected in succession, by putting in place at the same time the two half trusses, which balancée! each other ; when one truss was put in place and joined to the preceeding ones, it was left and the next one was erected. A platform for working and skifting the scaffolding was put clown level with the base of the trusses; it consistée! of an iron flooring above tlie Moulineaux Rail- way cutting, and of a provisional flooring with scaffolding on the river side. The lifting apparatus consistée! of the following parts (see Figs. 1064 to 1070, Plate CLXX.): 1. A central fixed column. 2. Two inside rolling scaffolds, acting as supports for the trusses in course of érection. 3. Two travellers, carrying the large movable trucks for raising the pieces. 4. A double steam winch, with the necessary mechanism for lifting and skifting the pieces. The central wood column was fixed ; it served to regulate the whole construction. The top joint was wedcred in this column. The latter consistée! of eight o round wood uprights, 25 centimètres (9-^ in.) in diameter, placée! on a circumference 7 metres (23 ft.) in diameter. It was tied and stayed in tlie usual way. The top flooring, above the top of the trusses, was 28.20 metres (92 ft. 6 in.) above the base of the trusses ; it had the shape of an octagon, 10 metres (32 ft. 10 in.) in diagonal. In the centre of the flooring was placée! the pivot round which the two travellers turned. The two movable scaffoldings were placed diametrically opposite each other, under the sectors formed by the two half trusses already erected, and under tlie two half trusses in course of érection. They contained several platforms placed in redan, the ends of which followed the curvature of the trusses. The top platform was 23.46 metres (77 ft.) above the base of the trusses. These scaffoldings travelled on two coneentric lines 6.80 and 17.47 metres (22 ft. 4 in. and 57 ft. 4 in.) in radius. Each one was carried on four rollers, the two rollers on the outside rail being 4.56 metres (15 ft.) apart. Each traveller contained a top horizontal flooring rectangular in plan ; the flooring was supported by two parallel beams on which was the track for a truck. These beams, placed over the central column, rested on tlie column at one end, and at the other on a vertical wood tower ; the latter travelled on two coneentric rails 2 metres (6 ft. 6 in.) apart (see Figs. 1064 and 1068, Plate CLXX.). The outside rail was the same as that of the movable scaffolding. In plan the top flooring of the two travellers were almost diagonally opposite each other ; the vertical shaft round which they pivoted was in a line with the central column. The space allotted for the Pavilion did not allow surrounding the trusses by the travellers ; it was not possible, therefore, to place the of the double covering had already begun. It was, there- fore, important to ascertain, in view of the nieasures to be taken during érection, what was the set produced in the trusses under varions loacls. The set due to the bending moments was rigorously calculated, taking into account the varions sections of the trusses, from the first courses to to the top. The fixed position of the top joint had to be . insured until the placing of the last truss, for the following reasons : (a) The trusses built on the saine pattern at the Cbalon Works had to be found, on érection on the spot, with the same dimensions as regards chorcl and abscissa ; (6) under the weight of metal, the top of a truss subsides when left free ; tlie trusses last erected would not, in this respect, have undergone the strain which the first under- went, and they would not all have been in the same state as regards wear and working. It has been calculated that the top of the truss subsides 5 millimétrés (f-j- in.) under the weight of metal. That part of the double covering from the wallplate to purlin No. 4 raises the top by 12 millimétrés (T7K in.), and that part which is on the purlins Nos. 3 to 1 causes it to subside 2 millimétrés (j-V in.); an increase of 10 deg. Cent, in temperature causes the top to rise by 5 millimétrés (T:!T in.). This involved a double wedging of the ridge ball to prevent it from rising or sub- siding. It has been found, besides, that for preventing a truss from subsiding by 5 millimétrés (T3T in.) it was neces- sary to create a reaction on the top, with a lifting force of about 650 kilogrammes, equal, for the twelve trusses, to a load of 7800 kilogrammes (7 tons 15 cwt.) on the axis of the central column. When the trusses had been put in place and had to be released, it was necessary to know, in order to regulate the fixing of the purlins, what were the variations in the abscissæ of the half trusses variations which were the more important at the spandril near the purlins Nos. 7 and 8, the double covering flattening the trusses, while the campa- nile produces a bulge greater in extent than the flattening. The resultant is an increase is the abscissæ up to 11 milli- métrés (T7-g- in.). When the closing sectors were put in place, the bolts holding the purlins near the spandril had to be easeel to let the trusses set freely, so that the theoretical conditions could be maintained. The horizontal displacement of the top was ascertained in a truss, half of which was in the sun, and the other half in the shade ; this would be of 2.7 millimétrés (.105. in.), for a difference of 10 deg. Cent, in the temperature of the two half trusses, and is of no great importance, considering the dimensions of the Pavilion. The circumstances under which the Pavilion had to be erected led Messrs. Schneider and Co. to make use of very powerful tools and appliances, which enabled them to put the building together with great rapidity. With these appliances, of great power compared with the tonnage of tlie metallic parts to be clealt with, the object aimed at was fully attained. The érection of all the heavy work only lasted thirty-five days, from February 15 to March 20; i