Locomotive dynamics: What effects can partial balancing of reciprocating parts produce in steam locomotives? Consider the typical residual unbalance when only a fraction of the reciprocating mass is balanced to limit out-of-balance forces. Choose the correct option.

Given data

• Topic: partial balancing of reciprocating masses in locomotives.

Concept / Approach
Full balancing eliminates primary shaking forces but may be impractical; partial balancing reduces them at the cost of other residual effects.Residual unbalance leads to: (i) hammer blow (fluctuation of wheel–rail vertical load), (ii) swaying couple (rocking due to out-of-phase forces left and right), and (iii) variation in tractive force along the stroke (longitudinal fluctuation).

Step-by-step reasoning
Step 1: Partial balance → some primary (and secondary) components remain.Step 2: These components generate alternating vertical and horizontal forces and couples.Step 3: Each listed phenomenon is a known consequence; therefore all occur together.

Common pitfalls
Assuming partial balancing removes hammer blow; it only reduces amplitude.

Final Answer
All of the above