When the amount to which the leather has been stretched is an unknown quantity (as is commonly the case), the workman cuts the belt too short, to an amount dictated solely by judgment, following no fixed rule. If, as in the case of narrow belts, the stretching be done by hand, the belt is placed around the pulleys, stretched by hand, and cut too short to an amount dictated by judgment, but which may be stated as about 21⁄2 per cent. of its length.
But the stretch of a belt after it is put to work proceeds very much more rapidly if it has been stretched in the piece and not in the strip, hence it gets slack in the course of a few hours, or of a day or more, according to how much it has been stretched; whereas one properly stretched in the strip will last for weeks, and sometimes for months, without getting too slack.
Fig. 2660.
| 2,000 | 1⁄4 | 3. | 2,050 | 3⁄16 | 3. | 1 | 2,150 | 3⁄16 | 3. | 2 | 2,175 | 1⁄4 | 3. | 3 | |
| 1,400 | 9⁄32 | 2. | 12 | 2,000 | 1⁄8 | 3. | 2,625 | 3⁄16 | 3. | 4 | 2,325 | 7⁄32 | 3. | 4 | |
| 2,000 | 1⁄4 | 2. | 11 | 2,075 | 3⁄16 | 3. | 1 | 2,375 | 7⁄32 | 3. | 4 | 2,175 | 7⁄32 | 3. | 5 |
| 2,075 | 1⁄4 | 2. | 12 | 2,700 | 7⁄32 | 3. | 3 | 2,600 | 7⁄32 | 3. | 4 | 2,275 | 5⁄32 | 3. | 7 |
| 2,450 | 1⁄4 | 2. | 13 | 3,025 | 9⁄32 | 3. | 7 | 2,575 | 11⁄32 | 3. | 8 | 2,225 | 7⁄32 | 3. | 10 |
| 2,475 | 1⁄4 | 3. | 2,975 | 5⁄16 | 3. | 6 | 3,200 | 9⁄32 | 3. | 10 | 2,175 | 3⁄8 | 3. | 10 | |
| 2,575 | 11⁄32 | 3. | 2 | 2,875 | 9⁄32 | 3. | 7 | 3,475 | 11⁄32 | 3. | 13 | 1,850 | 11⁄32 | 3. | 11 |
| 2,675 | 11⁄32 | 3. | 2 | 3,075 | 11⁄32 | 3. | 8 | 3,450 | 9⁄32 | 4. | 1,950 | 1⁄4 | 3. | 11 | |
| 2,650 | 3⁄8 | 3. | 2 | 2,900 | 9⁄32 | 3. | 6 | 3,150 | 3⁄16 | 3. | 15 | 2,225 | 1⁄4 | 3. | 10 |
| 2,800 | 1⁄4 | 3. | 1 | 3,050 | 5⁄16 | 3. | 6 | 2,850 | 1⁄4 | 3. | 13 | 2,275 | 3⁄16 | 3. | 7 |
| 2,700 | 1⁄4 | 3. | 3,150 | 7⁄32 | 3. | 5 | 3,000 | 3⁄16 | 3. | 10 | 2,600 | 1⁄4 | 3. | 5 | |
| 2,650 | 1⁄4 | 2. | 13 | 3,000 | 7⁄32 | 3. | 4 | 3,400 | 1⁄8 | 3. | 6 | 2,550 | 1⁄4 | 3. | 4 |
The results of some experiments made by Messrs. J. B. Hoyt & Co. on the strength of the various parts of a hide are given in [Fig. 2660]. One side of the part of the hide used for leather belting was divided off into 48 equal divisions, each piece being 113⁄4 inches long, and two inches wide, the results of each test being marked on the respective pieces. The first column is the strain under which the piece broke; the second column is the amount in parts of an inch that the piece stretched previous to breaking; and the third column is the weight of the piece in ounces and drachms.
From the table it appears that the centre of the hide which has the most equal stretch has the least textile strength, while in general that which has the most stretch has the greatest textile strength, but at the same time the variations are in many cases abrupt.
A single belt is one composed of a single thickness of leather put together, to form the necessary length, in pieces, riveted and cemented together at the joint, or sewed or pegged as hereafter described.
A double belt is similarly constructed, but is composed of two thicknesses of leather cemented and riveted, pegged, or sewed together throughout its whole length, as hereafter described. The object of a double belt is to increase the strength without increasing the width of the belt. Belts are usually made in long lengths coiled up for ease of transportation, the length of belt required being cut from the coil.