Complex sentence: For ease of maintenance, the boiler, firebox and smokebox were encased in steel sheeting that resembled a modern diesel locomotive, a major departure from traditional steam locomotive design, allowing the engine to be cleaned using a carriage-washing plant.
Split into simpler sentences: For ease of maintenance, the boiler, firebox and smokebox were encased in steel sheeting, which meant that the engine's shape resembled that of a modern diesel locomotive. That was a major departure from traditional steam locomotive design, allowing the engine to be cleaned using a carriage-washing plant.