Trasandino Chileno Kitson-Meyer Locomotives in Chile

Class Z (Locobase 20297)

Data from P C Dewhurst, "Locomotive Practice of the Chilian Transandine [sic]", Locomotive Magazine, Volume 20 (15 June 1914), pp. 161-169 (data on p. 169). See also Ian Thomson, "The Transandine Railway: a Hundred Year Long Financial Disaster that Still Attracts Investors", pp. 1-8, archived at [], last accessed 21 October 2017. Works numbers were 4488 in 1907, 4598 in 1908, and 4664 in 1909.

Dewhurst celebrated these engines as representing a "great advance on previous rack engine practice." (Locobase suspects Dewhurst meant Chilean Transandean rack practice.)

Noting that the Argentine Transandean #40 had the same specs (Locobase 20298), the author added that the latter two Chilean locomotives' only difference was an considerable extension of the bunker and rear tank.

Its unusual layout put one set of adhesion axles under the Belpaire firebox and boiler with a small rack engine (13"/330 mm x 14/356 mm) diameter x stroke nested between the first and second axles. Farther back under the long wheelbase, a second set of adhesion cylinders turned the six drivers in a rear bogie. In addition, a 18" (457 mm) x 19" (483 mm) rack engine drove two rack pinions (i.e. between 1 and 2 and between 2 and 3). Another system intercepted the exhausting steam and returned the condensed water to the boiler through a direct-acting feed pump.

The railway soon discarded two of the installations that interfered with effective power maintenance. Dewhurst commented that the condenser sapped energy from the blast just when the engines running in the tunnels had both the rack engines and the adhesion cylinders. At that point, he said "it was not possible to maintain steam without using all the available blast." Likewise, the small rack engine's demand for steam on rack sections meant that four adhesion cylinders and two rack engines competed for the boiler's output. This forced the shutdown of the adhesion cylinders, leaving them "to be dragged along at a loss." Using just the large rack engine and the two adhesion cylinders actually reduced the time needed to traverse the rack sections.

Still, as Ian Thomson reported, the "locomotives were working close to their physical limits for a considerable proportion of their time"; consequently "maintenance was heavy". The Abt rack and pinion "led to a lot of mechanical wear, which further increased maintenance costs".

An engine that is paid for has many advantages over possibly better replacements (even electric traction didn't yield much of an improvement) and these Zs proved long-lived and successful.