A. They should be opened just enough to admit sufficient air to produce
perfect combustion, but not enough to cool the fire-box. The dampers
should be closed when the engine is drifting or when at rest and the
fire is cut very low or is out entirely.
30. Q. About how much smoke do you consider an oil burning locomotive
should make under adverse conditions, when the engine is steaming well,
but is being crowded by the engineer?
A. Only a light smoke should show at the stack.