Indian locomotive class WDM-3

Henschel

Industry	Locomotive manufacturing
Founded	1887
Headquarters	Germany

Overview

The Indian locomotive class WDM-3 represents a series of diesel-hydraulic engines engineered by Henschel specifically for Indian Railways in 1962. The designation "WDM-3" indicates a broad gauge (W) locomotive powered by Diesel (D), intended for Mixed traffic (M), and classified as the third iteration (3) in its series. These units entered operational service during the period from 1970 to 1971, with a total production count of eight locomotives manufactured between 1962 and 1970. Their withdrawal from active duty occurred at the Gooty facility in 1995, after which they were fully retired.

It is important to note that these diesel-hydraulic locomotives are distinct and unrelated to the ALCO-built WDM-3A, despite sharing a similar nomenclature.

Introduction

The hydro-mechanical transmission for diesel locomotives, known as the "Suri transmission," was invented by Man Mohan Suri, an Indian Railways Mechanical Engineer. This innovation was evaluated by the National Research and Development Corporation and subsequently patented in India during 1956-57. By 1962, the Railway Board opted to investigate the application of the Suri transmission in high-powered locomotives to fully leverage its advantages. Consequently, the Board authorized discussions with West German companies for the development of locomotives rated at 5,000 hp, alongside negotiations with ALCO for 2,600 hp units that were already being produced at Diesel Locomotive Works in Varanasi.

Selection of locomotives

From 1962 to 1964, the Railway Board considered acquiring and developing locomotives equipped with the Suri transmission across different horsepower categories, including 5,000 hp, 2,500 hp, and 2,600 hp models. Technical evaluations at that time suggested that locomotives with greater horsepower would offer superior benefits due to improved power-to-weight ratio. Nevertheless, procurement decisions were contingent upon reasonable pricing and satisfactory performance assurances.

In September 1964, tender invitations were sent to three West German manufacturers, resulting in bids from two companies for 5,000 hp locomotives powered by two 2,500 hp Maybach engines. By June 1965, a Technical Committee was established by the Board to assess these proposals. Their mandate included evaluating the technical feasibility of developing Suri transmission for 5,000 hp locomotives and identifying necessary measures to minimize operational issues related to 20-cylinder high-speed Maybach engines under Indian conditions.

The Technical Committee's report in December 1965 concluded that investing in 5,000 hp locomotives would not yield economic advantages when considering capital expenditure and maintenance compared to dual-coupled 2,600 WDM-2 locomotives. Additionally, the Committee found the 5,000 hp units unsuitable as standard equipment due to limitations posed by track and bridge infrastructure, hauling capabilities, challenges with multiple unit operation practicality, and reduced operational flexibility.

Production

In September 1966, a locomotive manufacturer based in West Germany invited bids from two companies, extending the original deadline from 15 September to 28 September. Both companies submitted their proposals, which were evaluated by the Tender Committee. Upon review, the Committee determined that the proposal from Henschel was superior in both technical specifications and cost-effectiveness. Consequently, the Committee recommended awarding the contract to Henschel. Following a technical assessment, the Research Design and Standards Organisation of the Railways also rejected the offer from the other contender (designated as "firm B"). Additionally, the Committee highlighted that Henschel's warranty conditions were more favorable than those presented by firm B.Template:Fix/category

Henschel provided quotations for locomotives equipped with either Suri or Mekydro transmissions. Although the Suri transmission carried a slightly higher price tag (DM 67,500 more per unit), it demonstrated greater efficiency—achieving a final stage efficiency of 92%, compared to Mekydro’s peak efficiency range of 80-83%. The Committee projected that this increased efficiency would translate into fuel cost savings. Assuming daily operation of approximately 400 km with fuel consumption at 4 liters per km, the anticipated annual savings per locomotive were estimated at around Rs. 20,000, even accounting for a modest 5% efficiency gain. Based on these factors, the Committee advised placing an order for six locomotives featuring Suri transmissions and two with Mekydro transmissions from Henschel. The expected FOB value was about 10.4 million DM (equivalent to roughly Rs. 2.08 crores). The Railway Board approved this recommendation and issued an advance letter of acceptance to Henschel in December 1966.Template:Fix/category

The formal contract for supplying the locomotives was finalized with Henschel on 23 June 1967. The company guaranteed that the locomotives would be manufactured according to agreed specifications and would function correctly. Furthermore, Henschel assured reliable operation of the Suri transmission system. This warranty remained valid for either 24 months following commissioning in India, or 26 months from shipment departure from Germany, or until each locomotive had covered 300,000 km—whichever occurred first.Template:Fix/category

Performance of locomotives

The eight WDM-3 locomotives arrived in India during the latter half of 1970 and were commissioned between August 1970 and May 1971 at Gooty under Southern Railway jurisdiction. By August 1975, expenditure related to these units amounted to Rs. 3.37 crores. Initially deployed mainly for freight operations within the Guntakal Division, they began service on express passenger routes starting November 1972.Template:Fix/category

In July 1971, Southern Railway reported to the Railway Board that defects had emerged in the transmission systems and converter turbine wheels of these locomotives, causing operational failures. Following manufacturer recommendations, adjustments were made to components such as torque converters, turbine blades, and mechanical clutches, which resolved these technical problems. Despite these fixes, overall performance remained below expectations; recorded inefficiency averaged between 15.5% and 45.3% from commissioning through April 1973.Template:Fix/category

By April 1973, the Railway Board requested a comprehensive performance evaluation of these locomotives. It was found that WDM-3 units exhibited lower horsepower (under 2,600 hp), lighter axle loads (76 tonnes compared to WDM-2’s 110 tonnes), and reduced converter efficiency at low speeds. These factors resulted in diminished hauling capacity—approximately 23% less uphill and 25% less downhill relative to WDM-2 locomotives—particularly noticeable on steep gradients.Template:Fix/category

Maintenance expenses for WDM-3 engines were higher; for example, cylinder head repairs cost Rs. 6,851 compared to Rs. 2,632 for WDM-2 units. Additionally, failure rates were elevated for WDM-3s, averaging one failure every 43,379 km between fiscal years 1971-72 and 1974-75 versus one every 112,893 km for WDM-2s during the same period. Fuel consumption was about 20% greater in WDM-3 locomotives (regardless of transmission type) than in their WDM-2 counterparts. Engine damage associated with Suri-equipped units necessitated operating those transmissions solely in hydraulic mode.Template:Fix/category

Repeatedly reported major faults affecting transmissions and engines prompted manufacturers in November 1973 to advise that these transmissions should be operated purely hydraulically. The Railway Board consented to this adjustment plan, which entailed removing Suri transmissions and converting them into simpler hydraulic Mekydro systems. This retrofit was completed on all Suri transmission-equipped locomotives between December 1973 and January 1974.Template:Fix/category

A Southern Railway report compared fuel consumption between WDM-2 and WDM-3 models using liters per thousand gross tonne-kilometers—a metric only valid when trailing loads are comparable. However, since WDM-2 and WDM-3 hauled significantly different trailing loads on steep grades, this comparison was not meaningful in practice. In cases where both locomotive types pulled similar loads—such as on the Brindavan Express route between Madras and Bangalore, where higher speeds were achieved—the WDM-3 demonstrated approximately a 4% fuel consumption advantage over WDM-2 units. Despite this potential benefit, restrictions tied to their initial procurement limited WDM-3 usage mainly to freight operations; although later authorized for passenger service use, scarcity of imported spare parts compromised reliability further. Consequently, these locomotives were phased out by around 1990.Template:Fix/category

Loco shed

The entire fleet of eight WDM-3 locomotives was initially assigned to the Diesel Loco Shed, Gooty (GY), which operates under the Guntakal Railway Division located in Andhra Pradesh. During that period, the region was managed by the Southern Railway zone. Currently, the Guntakal Railway Division is part of the South Coast Railway zone.

See also

• Rail transport in India § History
• List of diesel locomotives of India
• Rail transport in India
• Indian locomotive class WDM-2