Hammerblow (railway)
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Hammerblow is a force that steam locomotives and some diesel locomotives create as they move. It is the result of a compromise made when a locomotive's wheels are balanced to off-set reciprocating masses, such as connecting rods and pistons, in order to keep the ride as smooth as possible. However, hammerblow occurs with the downward force of the wheel's balance weight onto the railway track, with the potential of causing damage.
[edit] Principles
The aforementioned reciprocating balance on the wheels attempts to prevent the worst of the reciprocating forces at play on a locomotive, though as a compromise, this extra mass on the wheel causes it to be out of balance vertically, therefore creating hammerblow.[1] Therefore, if reciprocating balancing is increased, it may appear that a locomotive is running smoothly, but at a high cost in hammerblow, especially at high speeds.[1]
Locomotives are balanced to their individual cases, especially if several of the same design are constructed (a class).[1] The normal operating speed is ascertained, resulting in each class member being balanced accordingly.[1] Usually the reciprocating weight is balanced between 45 to 50% of total balance weight.[1] High speed locomotives were the key recipients of such treatment due to the increased level of forces involved, and the exponential factor of stress on the track at these higher speeds.[1]
