LACMTA, the transportation authority of the Californian metropolis Los Angeles, has ordered 235 metro trains from the Japanese rail vehicle manufacturer, Kinkisharyo. For these Electric Multiple Units (EMU), Toyo Denki ordered innovative new light rail drives from ZF. The transmissions were developed at Friedrichshafen and are produced at the U.S. location in Gainesville, Georgia.
Low weight and high reliability are the two essential qualities for the construction of electric metro trains. Since every kilo saved in the vehicle is available for efficient passenger transport, the operators and thus also the manufacturers of metro trains search for suppliers which contribute to weight reductions, without losing any operational reliability.
The weight reduction opened up an opportunity for both ZF and propulsion supplier Toyo Denki for the City of Los Angeles. Although ZF has used for decades in Europe, for the first time, the aluminum housings are in an EMU metro transmission for North America. Compared to the previously spheroidal casting process, this reduces the transmission units' weight by 15 percent. That way, the rail vehicle manufacturer can save more than 200 kilos per railroad car and is thus able to meet the demanding requirements of the LACMTA train operator. This innovative lightweight design which is also easy to service was a decisive element in the use of the ZF gearbox for LACMTA. Also important, the ZF engineers had placed an additional focus on long service intervals during product development.
The two-stage transmission meets all technical requirements in being developed in Friedrichshafen, where ZF's Special Driveline Technology business unit is located. "However, it was clear right from the start that we would industrialize the transmission in the US and, therefore, the coordination of the teams consisting of a total of 15 developers in Friedrichshafen and at the Gainesville production location was very close," says Alan Dittrich, project manager at ZF. This process also involved Rapid Prototyping procedures which enabled a development time of only eleven months. "In this process, we also benefited from the experience of the ZF Group, for instance in the area of materials technology, FEM calculations, and acoustics know-how," says Mr. Dittrich.
An additional advantage in this context was the use of standard ZF labyrinth seals. Usually, contact-free labyrinth seals optimal in terms of wear have to be developed and adapted for the corresponding transmission. Thanks to the application of the ZF standard, the development time was significantly reduced.