frame than an articulated underframe, also, no hinged connection had to be maintained. reduced hammer blows on the track resulting in lower maintenance cost. two sets of drivers with four wheels each could have lighter (as much as 25%) running gear than a locomotive with all four axles coupled together, smaller and lighter moving parts ensured less wear and tear. baldwin's chief engineer believed that the 8-coupled, two-cylinder locomotives of the time were at or near practical limits in terms of steam flow, cylinder efficiency could be improved at high speed by getting the same power from four smaller cylinders with proportionately larger valves. valve travel in s1's cylinder was 7-1/2”, the lap was 1-7/8”, the lead was 5/16”, exhaust clearance was 0.25”, valve diameter was 12”.