Trasandino Chileno 2-6-2 Locomotives in Chile

Class 4 (Locobase 20295)

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).

Locobase 20294 describes both the origins and character of the Trasandino (Chilean Transandean to its English owners) and the two all-adhesion tank locomotives that arrived in 1889. As that entry notes, this short connector on the Valparaiso-Buenos Aires main line laid several segments of rack when grades were too steep to allow the usually sufficient steel-steel adhesion of wheel and rail to grip.

After purchasing a single Shay from Lima Locomotive Works (works number 925), the railway turned to the well-known German builder for these two "rack and adhesion" locomotives. All the dimensions grew considerably, but the Belpaire firebox and boiler were apparently too small; see Locobase 20296 for an enlarged stablemate.

The specs show the cylinders used to turn the drivers on the less-steep sections. The rack drive, said Dewhurst, "is slung between the first and second coupled axles, and has two sets of rack pinions".A separate set of cylinders located under the smokebox were of identical diameter but a 450 mm (17.75 in) stroke drove the pinions.

Reversing the motion when descending these rack sections meant the cylinders acted as "dynamic" brakes (decades before diesels adopted them). Clean air came into the cylinders via a bypass below the blast pipe and repression valves allowed the compressed air to escape. One can imagine the heat this procedure generated and Borsig supplied an injector to squirt cooling water into the valve chests.