| Chicago Burlington & Quincy Railroad 4-8-4 Class O-5-A 5625 at Eola, Illinois on December 14, 1952, photographer unknown, print by Tom Klinger, Chuck Zeiler collection. Number 5625 was assembled by the CB&Q at West Burlington, Iowa, completed in October 1938, sold for scrap in March 1954. In 1942 this locomotive was fitted with the Franklin steam distribution system employing poppet valves. Note the lack of eccentric rod. One of the primary objectives of the system was to employ relatively small diameter poppet valves, both for intake and exhaust, in this permutation five valves of both types (in the online patent design search, it was two supply poppets and three exhaust poppets) grouped in a manner to maintain the cylinder port clearance volume at a minimum. In poppet valve locomotive engines, especially of relatively large size, the cylinder port walls, because of their rather extended area, have been subject to warping, as a result of thermal changes. Any such warpage is likely to be reflected in distortion of the valve seats and the detrimental effect of such distortion is more serious with large diameter poppet valves than with small diameter valves. The employment of multiple small diameter valves is therefore of advantage in overcoming difficulties due to valve seat distortion. Although poppet valves operated well enough when they were carefully maintained, they could not stand up under the abundance of power that was packed into the Class O-5 Northerns. After a trial life of a few years, number 5625 was retired in 1954 and eventually scrapped, rather than invest money converting it back to original status. |