SZU Be 510
Class SZU Be 510 designates an EMU of the Swiss railway Sihltal Zürich Uetliberg Bahn (SZU), procured for the Uetliberg railway. These EMUs can operate on the DC Uetliberg line and on AC lines such as the Sihl Valley line. No other multi voltage equipped motive power shall be deployed, as SZU intends to change over to all AC operation. History. The Be 510 EMUs were developed by Stadler Rail for the special requirements of SZU. Sihltal line and Uetliberg line have different railway electrification system but the two lines share the double track from Zurich Giesshübel  through the underground Selnau station into the station under "Bahnhofplatz", track 21 and 22 of Zurich main station. Whilst the Sihltal line uses the 15 kV AC system like all SBB lines, the Uetliberg line has a 1.2 kV DC overhead line which, looking uphill, is shifted to the right of track centre. Previous electric trains can run under one voltage only, AC trains collect power from the centre overhead, DC trains from the off centre contact line. The Be 510 trains were bought for the Uetliberg line, but to allow flexible operation and considering plans to convert the Uetliberg  line to AC electrification, a multi system EMU was specified. With the pantograph in the centre standard 15 kV AC is drawn. The pantograph moved to the right allows collection of 1200 V DC, the unique supply up the Uetliberg line. These six EMUs are intended for the transition of the Uetliberg railway to AC overhead, future trains will be AC only. A current benefit of AC capability is that the new EMUs can be parked away from the DC depot, space there being scarce. Technical description. Each set consists of three car bodies, the middle has two motored bogies . Both end cars have one non-motored bogie at the outer end and are supported by the middle car at the inner end, like a Stadler GTW. All cars have low floor sections at the doors, rising over the bogies. Access from the platform is at level. Traction equipment is concentrated in the middle car. Designing the car body to be strong enough to support transformer and air conditioning equipment on the roof whilst limiting the weight proved difficult, delaying delivery by about a year. Each end car has a driving positions and a pantograph. To allow lateral movement each  pantograph is mounted on a sledge. At standstill the sledge can be moved by from the centre to the side. Contacts on the sledge engage with fixed contacts on the car roof to route the current to either the AC (centre position) or DC equipment. The pneumatic cylinder allows movement to the right only, but, should the EMU be turned, provision can be made for movement to the other side with a simple intervention at the workshop. The vehicles can travel on the entire 15 kV AC network of the Swiss railways. They are equipped for multiple unit operation of  up to three car sets. Platform restrictions limits train length to (two sets), normal operation on the Uetliberg line (S 10) is a rake of two Be 510 sets.