GEARS
The material used for all gears on the Liberty engine was selected at the option of the manufacturer from the following standard S. A. E. steels, the composition of which are given in Table 12,
| Steel No | X-3,340 | 6,140 |
| Carbon, minimum | 0.350 | 0.350 |
| Carbon, maximum | 0.450 | 0.450 |
| Manganese, minimum | 0.450 | 0.500 |
| Manganese, maximum | 0.750 | 0.800 |
| Phosphorus, maximum | 0.040 | 0.040 |
| Sulphur, maximum | 0.045 | 0.045 |
| Nickel, minimum | 2.750 | |
| Nickel, maximum | 3.250 | |
| Chromium, minimum | 0.700 | 0.800 |
| Chromium, maximum | 0.950 | 1.100 |
| Vanadium, minimum | 0.150 |
All gears were heat-treated to a scleroscope hardness of from 55 to 55. The heat treatment used to secure this hardness consisted in quenching the forgings from a temperature of 1,550 to 1,600°F. in oil and annealing for good machineability at a temperature of from 1,300 to 1,350°F. Forgings treated in this manner showed a Brinell hardness of from 177 to 217.