N.Y. Comp. Codes R. & Regs. tit. 17, § 922.4
For locomotives, the maximum allowable stress per square inch of net cross-sectional area on fire box and combustion chamber stays, shall be 7,500 pounds. The maximum allowable stress per square inch of net cross-sectional area on round, rectangular, or gusset braces shall be 9,000 pounds.