Voith Turbo-Transmissions - Double Circuit Transmissions For Railcars

Double Circuit Transmissions For Railcars

In 1969, the smaller T 211 turbo-transmission was developed as an alternative to hydro-mechanical bus transmissions, being designed for diesel railcars in the low power range of 200 to 300 hp (149 to 224 kW). Similar to the first turbo-transmission, the T 211 used a linked converter-coupling combination but it also had a high-speed gear for greater efficiency. Additionally, a reversing gear assembly was added and an optional hydrodynamic retarder could be installed if required. The converter had a hydrodynamic circuit diameter of 346 mm (13.6 in), while the fluid coupling had a slightly smaller diameter of 305 mm (12.0 in). And due to its high-speed gear, the main shaft could run significantly higher at 4,170 rpm. As a result, the T 211 r had reserve power, which was reflected by its reinforced mechanical components (gears, bearings and shafts) as well as the transmission controls. At the same time however, the diameters of the converter, coupling and retarder remained unchanged. The overall flow rate within the hydrodynamic circuits was increased to accommodate the higher power rating of 205 to 350 kW (275 to 469 hp). At 350 kW (469 hp), the main shaft ran at just under 5,000 rpm which resulted in rotational speeds for the (empty) converter of 74 m/s when the vehicle reached its maximum speed. To ensure adequate cooling of the converter during high-speed operations, a stronger hydrodynamic fluid pump was installed, which supplied 3.5 l/s of oil through the heat exchanger during the travel phase and 9.0 l/s when in the braking phase, with the retarder rotor also serving as an additional circulating pump. When viewed from the outside this T 211 r transmission differed from its predecessor, the T 211 re.3 with 320 kW (429 hp), only slightly through the addition of a built-in electronic control unit and an enlarged air filter.