Complex sentence: The locomotives were rotated occasionally and all three had service spells as the O'okiep engine, but by 1910 they were no longer used on the Nababeep line since the trains had become too heavy.
Split into simpler sentences: The locomotives were rotated occasionally and all three had service spells as the O'okiep engine. By 1910 they were no longer used on the Nababeep line, since the trains had become too heavy.