Hammer Blow - Solutions

Solutions

One solution to this was the duplex locomotive, which spread the driving power over multiple sets of pistons, thus greatly reducing hammer blow. Less successful was the triplex locomotive.

The Soviet Union used a different solution to hammer blow with their 2-10-4. The cylinders were placed above the centre driving axle. Unlike nearly all steam locomotives, the pistons had rods on both ends which transferred power to the wheels. The idea was to balance the driving forces on the wheels, allowing the counterweights on the wheels to be smaller and reducing "hammer blow" on the track.

The usage of inside cylinders (which was rare in the USA) results in a more stable locomotive and thus reduced hammer blow. Many European tank engines had inside cylinders to reduce the wear and tear on shunting yard tracks from frequent and heavy use. Outside cylinders are easier to maintain, however, and apparently for many US railroads this was considered more important than other considerations. The maintenance costs associated with the nigh-inaccessible inside cylinders on Union Pacific's 4-12-2 locomotives may have hastened their retirement.

Steam turbine locomotives lack pistons, valve gear and other fore-aft reciprocating components making it possible to balance the wheels and connecting rods to eliminate hammer blow. Steam turbine locomotives were tried by several companies around the world in the 1930s and 1940s (such as the Pennsylvania Railroad's S2 6-8-6 and the LMS' Turbomotive). Whilst many of these turbine locos suffered problems in service (usually excessive fuel consumption and/or poor reliability) they did prove to be free from hammer blow and offered a way of achieving high power outputs and speeds without causing track damage.