Garratt - Competitors, Look-alikes, and Variations On The Theme

Competitors, Look-alikes, and Variations On The Theme

The Garratt was, obviously, not alone in the field of articulated locomotives. Aside from the well-known Fairlie and Meyer types, the Garratt had contemporary and similarly-designed competition in the form of the Union-Garratt, Modified Fairlie and Golwé. Of these, the closest was the Union-Garratt, a type originally conceived owing to the perceived necessity for a rigid connection between a bunker or tender and a firebox fed by a mechanical stoker. Though it could be argued that the NZR G class locomotives were Union-Garratts (having their bunkers mounted on the boiler frames, rather than on the hind engine unit), a more concrete example can be seen in the two South African Railways Union Garratts of classes GH and U.

The Union-Garratt did not enjoy the success of the standard Garratt. It was soon evident that mechanical stokers could function perfectly across the connection between a Garratt's boiler and engine unit, making the rationale for the Union-Garratt obsolete. The Union-Garratts' extended boiler frames and the position of the bunker and hind water tank upon those frames meant that they suffered from many of the problems which beset the Mallet design; the SAR U and GH classes had much heavier axle-loadings than Garratts of comparable size, weight and power, and the movement of water at the extreme ends of the long main frames generated high wear on the hind pivot between the boiler and engine unit. The Union-Garratt, like the Golwe and Modified Fairlie, was not perpetuated on anything like the scale of the Garratt, and no known examples survive.