Comments by "deezel_fairy" (@deezelfairy) on "SmarterEveryDay" channel.

@scrambledmandible They don't have unlimited torque but they produce 100% torque from 0 rpm to max rpm providing steam flow can keep up at the higher rpm's. Steam cylinder is just like a hydraulic cylinder so steam pressure (psi) X Cross sectional area of cylinder(s) piston = force generated by cylinder.
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