When replacing worn pins in the striking trains, care should be taken to get them the right length, as on account of the large amount of end shake in these movements they may slip past the levers without operation, if too short, or foul the other parts of the train if too long. For the same reasons bending the levers should only be done after exhausting the other sources of error and then be undertaken very slowly and cautiously.
The notes of a cuckoo are A and F, just below middle C; these should be sounded clearly and with considerable volume. If they are short and husky in tone it may be due to holes in the bellows, too short stroke of bellows, removal of the bellows weights, E, [Fig. 103], dirt in the orifices of the pipes, or cracks in the pipes. Holes in the bellows, if small and not in the folds of the kid, may be mended by being glued up with paper or kid, or a piece of court plaster which is thin enough to not interfere with the operation of the bellows. If much worn a new bellows should be substituted. Cracks in the pipes may be mended with paper.
The orifice of the pipe, if dirty, may be cleaned with a piece of mainspring filed very thin and smooth and carefully inserted, as any widening or roughening of this slit will interfere with the tone. Sometimes a clock comes in which has been spoiled in this regard, then it becomes necessary to remove the outer portion or lip, A, [Fig. 103], of the slot (which is glued in position) and make a new inner lip, B, or file the old one smooth again. The proper shape is shown in B, [Fig. 103], while C and D show improper shapes which interfere with the tone.
Fig. 103. Cuckoo bellows and pipe. A, outer lip;
B, inner lip; C, D, incorrect forms of lip.
Much time and money has been spent in trying to avoid the inherent defects of this portion of the clock; sometimes the lips will swell or warp and close the orifice; sometimes they will shrink and make it too wide; in either case a loss of purity of tone is the result. Brass tubes, if thin enough to be cheap, give a brassy tone to the notes; compositions of lead, tin and antimony (organ pipe metal) are readily cast, but give a softer, duller tone of less volume than the wood. Celluloid lips to a wooden tube were at first thought to be a great success, but were found to warp as they got older. Bone lips are costly; so there is nothing at present that seems likely to displace well seasoned wood, where discriminating lovers of music and art demand purity and correctness of tone, reasonably accurate time, artistic sculptural effects and durability, all in one article—a high class cuckoo clock.
When sending a clock home after repairing, each of the chains should be tied together with strings just outside the bottom of the case so that they will not slip off the sprockets and the customer should be instructed to hang the clock in its accustomed position before cutting the strings and attaching the weights.