646 Application of Iron Rods to compensate [Nov. 



being bolted through the piano, are each further secured by two wood 

 screws. 



The exact spots for fixing the clamp at both extremities of the 

 rods, must be determined, according to circumstances, by the judg- 

 ment of the individual applying them, because pianos vary in their 

 internal construction ; on which account also, it is obvious, that they 

 would be applied, with the greatest advantage, by manufacturers in 

 the first construction of the instruments, as the makers would have it 

 in their power to accommodate the internal arrangement of the pianos 

 to the most desirable position for fixing them. 



The rods should be applied to new pianos, before warping takes 

 place ; they may be put to old instruments, though not with equal 

 advantage, from the circumstance of the blocks of wood placed at the 

 end, under the sounding board, together with the iron bar, which is 

 screwed at one end on to the block, bearing the tuning pegs, fixed at 

 the other to the metal plate, on which the strings are hooked, being 

 thrust, by the warping of the instrument, out of their places ; for 

 when a piano has been straightened, they will be found to have 

 parted from those original bearings, on which mainly depended the 

 strength of the piano. However objectionable this loss of bearing 

 may be, the power of the rods is nevertheless the more clearly indi- 

 cated by their sustaining the piano in its straightened state against 

 the tension of the strings. 



Fig. 3, B, is the bridge ; ff are holes cut obliquely through it, to 

 lighten it; g g g are the places where the rods cross it; the bridge 

 is *2\ inches thick, and with the plank h h above it, in depth 3| or 3f 

 inches ; the dotted lines at I and L shew the body of the piano, 

 across its breadth. 



Fig 5, K, is the bolt that fixes the clamp E, by passing through 

 the block, (bearing the tuning pegs,) the bed of the piano, and by a 

 nut and screw fastening below the clamp. The whole of fig. 5, is 

 represented upside down. 



The rods are of round iron wire, T 3 ^ of an inch in diameter. Hither- 

 to, not less than three rods have been put to a piano ; but perhaps 

 two might be found sufficient. It is possible to draw the rods too 

 tight, especially when first put on, and if the piano was much warped; 

 for the instrument does not accommodate itself to the new tension for 

 some time : it will therefore be necessary, until it settles, to examine 

 it daily ; for if the rods are not slackened by turning the adjusting 

 screws, the strings might be endangered. 



Many pianos may be seen with the end plank M. figs. 1 and 2, 

 split ; occasioned entirely by the pull of the strings. The bolts GG. 

 figs. 2 and 6, secure the plank against this failure. The block 





