Mumbai EMUs Overshooting Platforms

by Prakash Tendulkar, April 2006

This first appeared as a two-part article in the IR-Technical mailing list and is reproduced here by permission of the author.

The 1928 stock on WR and 1925 stock on CR had a monopoly on the tracks as far as EMUs were concerned in the Mumbai section until 1950. They were vacuum braked, and had minimal instrumentation in the cab, such as a vacuum gauge and a brake cylinder gauge, no speedometer, no circuit breakers, and just one circuit for a bell. Their ceilinsg were higher, and they had good oscillating fans and side vents above windows creating an airy atmosphere even during monsoon when windows and doors were closed.

Even during peak hours till early-60s, they carried a reasonable load.

In 1950, Metro Camell, Hitachi, Breda and other companies supplied new EMU sets. They were all compatible with each other, and were provided with electro-pneumatic brakes as well as self-lapping air brakes. Although the bell circuit remained single, they did have some circuit breakers instead of fuses. They had driving motor coaches so the motorman could at least fix the leading motor coach. Fans were of the oscillating type and good, tube lights provided light, and seats were Formica covered.

By the late 1960s, the crowds increased. The 1950 stock coaches started developing sags in their chassis and IR installed support beams to reinforce them. Strange as it may sound, the 1928 stock never developed this problem till they were discontinued well after a decade later.

In 1961-62, WR received the first batch of EMUs built by Jessop and Co., with traction gear supplied by English Electric. Originally intended for 3000V DC on ER, they were converted for 1500V DC operation and were delivered brand new to WR. These rakes had smaller windows, and non-oscillating fans made by Usha (near Kolkata). But from a driving point of view, they were revolutionary. The driving trailer had circuit breakers, two types of bell circuits, good capacity air compressors, and of a total of 9 coaches (against 8 coaches for older EMUs), 3 were motor coaches.

The traction motors were fantastic. Even during peak hours on long run such as Andheri-Borivali, these rakes would touch 120km/h.

Unfortunately, they developed a snag of brake loss. A fine running rake would overshoot a platform unexpectedly. The motormen involved in many of these cases had excellent track records.

A Senior Foreman at Mumbai Central was able to identify the issue. His name was Shri Ali and he was almost illiterate but with a wonderful mechanical aptitude. He found that the arms holding the brake shoes for motor coach moved vertically up and down (depending upon direction of travel) and did not remain perpendicular to their contact points. He devised a bracket to limit such travel and it was the happy end of that story.

At this time, WR was scrapping some of 1928 stock rakes, except for the motor coaches. These spare motor coaches were used to convert 8-coach rakes into 9-coach rakes for 1928 stock EMUs. For 1950 stock EMUs that were still running strong at this time, Jessop supplied trailer coaches with wider windows to add them as idlers to make 9-coach rakes.

The first batch of rakes meant explicitly for WR and CR operations came from ICF. A unit contained 6 coaches instead of 3. A 9-coach rake would have 1.5 units, i.e., 3 driving trailers, 3 motor coaches and 3 trailers.

Around late 60s, WR started experimenting with composite brake pad to replace cast iron brake pads. The cast iron brake pads worked fine but they needed replacement every few days as against every few weeks for composites. Initially, Ferrodo was the sole supplier of composite brake pads but later many vendors joined the list. Composites needed lower brake cylinder pressure to deliver the same brake power, thus increasing the life of the compressor.

My experience with the first batch of composites was not very good. They never delivered predictable braking power many times. With vacuum braked rakes, entering platforms at 60-65km/h was easy; with EP brakes the margin went to 65-70 kms/h. With composites, I never dared to enter a platform faster than 60km/h. This was a motorman's decision and not mandated by management.

Now, over a period of time, the population of travelers has increased. WR has 12-coach rakes with 15-coach rakes in the planning phase. Crowded trains result in travelers hanging on to the windows and ladders of motor coaches and so on. Brake power has limitations and with overcrowding, the limits have exceeded what adhesion can provide.

Now WR and CR have mandated that rakes should not run faster than 45km/h when entering platforms for scheduled stops and that the guard must alert the motorman that the train is scheduled to stop at next station. Regardless, overshooting is becoming common based on my talk with friends at WR, both motormen and management. Overshooting is taken seriously and the offending motorman is eligible for dismissal, if proven guilty.

Unlike the old days when high school graduation was enough to be a motorman, today you will see motormen with a Master's in Engineering.

I do not know what to predict. In February 2005, I realized that I could not maintain time even though I am an aggressive driver. The new AC/DC EMUs have better braking power since they utilize regeneration rather than relying solely an air brakes. But there is a limit on what wheels can perform on tracks within the coefficient of adhesion.

Both WR and CR have exceeded that limit today.