THE CRANK HANGER.
The crank-hanger is of the one-piece construction, and is made from a five-inch disk of sheet steel, which is drawn into the shape of a tube through the medium of five separate operations; and this tube, when finished, is about two and a half inches in diameter. The four lugs to carry the rear forks, lower main tube and diagonal stay, are then drawn and formed upon it, this, however, requiring a total of twelve operations to complete it. The part requires annealing after every operation, the process of drawing and forming having a tendency not only to lengthen the fibre of the metal, but to harden it. The quality of the metal used in making this hanger must necessarily be of the best, and after the metal has survived all these operations it must also necessarily be perfect, for any crack, seam or flaw in it makes it useless and consigns it to the scrap heap.
MAKING CRESCENT
CRANK HANGER.
STAGE 1.
MAKING CRESCENT
CRANK HANGER.
STAGE 2.
MAKING CRESCENT
CRANK HANGER.
STAGE 3.
MAKING CRESCENT
CRANK HANGER.
STAGE 4.
MAKING CRESCENT
CRANK HANGER.
STAGE 5.
The seat-pillar lug or group, while not altogether seamless, is of the one-piece construction, also having the three lugs drawn and formed upon it. The rear fork jaws are also stamped out of crucible sheet steel, and are of what is known of the semi-hollow construction.
The little brace which is usually placed between the rear forks and back of the crank-hanger and called a bridge, is generally made by a short piece of tubing and brazed to the two rear forks. The makers of the Crescent, who use a D-shaped rear fork, which is drawn to a round shape where it is offset and where it joins the rear lugs on the bottom bracket, make this bridge of two pieces of sheet steel, which are pinned and brazed together and are carried down on each side of the rear forks for several inches in a peculiar lipped shape. It is an expensive method of bridging the rear forks, but greatly adds to the strength at this point and prevents any serious lateral deflection of the frame when the pressure is applied to the cranks on either side. They are the only makers who form their sprockets out of a piece of crucible sheet stamped steel. As it is now made to fit a three-sixteenth chain, which is so popular and which they use, they do not show the wide opening on the flanges of the sprocket between the teeth.
WORKING DRAWING DIAMOND FRAME MODEL. ([See Page 52]).
[Fig. 1] shows the circular steel blank as made by the first operation on a large double action drawing press. It is then drawn into a cup shape as shown in [fig 2]. The practicability of the result obtained is noticeable at once. The edge of the cup is smooth, and there is no wrinkling, cracking or buckling in the steel, and it is still of the same thickness as the original sheet. It is again drawn by successive operations into a cylindrical shape as shown in [fig. 3]. The end is cut off, and the next operations form the lugs as shown in [fig. 4], until the final operation gives the result as in [fig. 5], when the crank-hanger is ready for the joining of the frame tubes. It requires ten days to complete a finished crank-hanger. A marvellous piece of work this certainly is, and it is doubtful if the result obtained in stamping this crank-hanger can ever be equalled by the working of forgings, and the whole result might be summed up by saying that it is “distinctively Crescent.”