page_title: South African Class 16C 4-6-2
section_title: Trofimoff piston valves
hierarchical_section_title: South African Class 16C 4-6-2 / Modifications / Trofimoff piston valves
caption_attribution_description: Deutsch: Trofimoff-Schieber der 41 1144-9 komplett, geschlossen
context_page_description: The South African Railways Class 16C 4-6-2 of 1919 was a steam locomotive.
  During 1919, the South African Railways placed ten Class 16C steam locomotives with a 4-6-2 Pacific type wheel arrangement in mainline passenger service. Another twenty entered service in 1922. Unlike the earlier Classes 16 and 16B, these locomotives had combustion chambers.
context_section_description: During 1931, A.G. Watson, CME of the SAR at the time, fitted engine no. 851 with Trofimoff type by-pass piston valves as an experiment. The Trofimoff valve was claimed to afford ideal conditions when drifting.
  It consisted of two fixed discs, secured to the valve spindle, and two junk rings, each carrying a Bull ring and four valve rings and both free to move longitudinally on the spindle. When the regulator is opened, steam forces the loose valve bodies against their respective fixed discs, and they then act as units similar to ordinary piston valves. When steam is shut off, the loose valve heads become detached from their respective discs and remain in their idle positions near the centre of the steam chest, while the valve spindle and fixed disks continue their reciprocating motion with the spindle sliding freely through the now stationary loose valve heads, and with the steam and exhaust ports now in commu­ni­cation. With both ends of the cylinders now in commu­ni­cation, the use of ordinary by-bass or snifting valves became unnecessary.
  Further similar experiments were carried out on Class 5B no. 726 in September 1931, Class 16B no. 805 in July 1932, Class 16DA no. 876 in August 1932, Class 15CA no. 2852 in March 1933 and finally on Class 15A no. 1961. The results of these extended tests did not prove entirely satisfactory and all these engines were gradually refitted with standard piston valves and snifting valves.
caption: Trofimoff valve, closed
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