In column 12, 0.2300 - 2⁄3(0.2300 - 0.1940) = 0.2060.
Also 0.2715 - (0.2715 - 0.2060) × 0.17 = 0.2604, and 0.2604 × 60 in. = 15.62 in. = diam. of step belonging to the same belted pair as the 30 in. step of cone a.
The effective diameters will be:
| 12 | in. | 18 | in. | 24 | in. | 30 | in. | on cone | A, | |||
| 33 | 27 | .92 | 22 | .16 | 15 | .62 | „ | B, |
and the actual diameters when belt is 0.22′′ thick:
| 11.78 | 17.78 | 23.78 | 29.78 | in. |
| 32.78 | 27.70 | 21.94 | 15.40 |
and the length of belt is found to be:
[3.2252 - (3.2252 - 3.1310) × 0.17] × 60 in. = 192.55 in.
In all the preceding problems it should be noticed that we arbitrarily assumed all the steps on one cone, and one of the steps on the other cone. It will be found that all of the practical problems relating to cone-pulley diameters can finally be reduced to this form, and can consequently be solved according to the methods just given.
For those who find difficulty in interpolating, the following procedure will be found convenient: Estimate approximately the necessary length of belt, then divide this length by the distance between the centres of the cone pulleys; now find which one of the 33 lengths of belt (per unit’s distance apart of the centres) given in the [table] is most nearly equal to the quotient just obtained, and then take the vertical column, at the head of which it stands, for the companion to the right-hand column. Those numbers of these companion columns which are on the same horizontal line will be the companion steps of a belted pair. The table is so large, that in the great majority of cases not only exact, but otherwise satisfactory values can be obtained by this method, without any interpolation whatever.”