The first locomotive built in 1873 at SLM works in Winterthur was Cog-Wheel-Engine Nr 7 for the Rigi line. In 2009 it was to run again from Vitznau to the culmination point on the Rigi. However, the chimney on the upright boiler exceeds the height of the loading gauge of todays' electric trains, and clearance underneath the road bridge at Vitznau was insufficient for chimney and contact wire. The problem was solved by installing two contact wires, spread apart to give enough space for the chimney whilst being close enough to the track centre-line to avoid dewirements. Electrical clearance is just sufficient to allow the steam train to operate under live wires.