The jerk in the ride

Jerks have everything to do with acceleration or deceleration and Newtonian inertia

I recently travelled on two trains — (a) 22418/22417, Mahmana Express, New Delhi to Varanasi and back; and (b) 12314/12313 Rajdhani Express, New Delhi to Sealdah and back. Both are good trains. Hence, both have relatively smooth rides. However, the ride on Mahamana Express was smoother than on Rajdhani Express and this wasn’t subjective assessment. This sounds contrary to a priori expectations. Surely, Rajdhani is a better train. Since others might have had similar experiences, here are speculative thoughts on what is a complicated outcome. Perhaps, routes and, therefore, tracks were different.  Let’s stick to common terrain between the two trains, New Delhi to/from Varanasi/Mughal Sarai. Even along that stretch, Rajdhani was “jerkier”. 22418/22417 doesn’t quite follow a straight line route between New Delhi and Varanasi. From New Delhi it heads up to Moradabad, Bareilly and then comes down to Varanasi via Lucknow.  12314/12313 has more of a straight line run from New Delhi to Mughal Sarai, via Kanpur, Allahabad. Hence, tracks are indeed different, but since both tracks are in the same part of the country, even though there are minor differences because tracks of the two trains are sometimes in different zones, this track difference argument isn’t convincing. Ownership/maintenance of the rake is also a red herring — Mahamana is owned by Northern Railway and Sealdah Rajdhani by Eastern Railway.  

Perhaps, it has something to do with the locomotive pilot’s skills. Skills are important. However, since two different loco pilots (up/down) delivered a jerkier ride on Rajdhani, we can probably discount this. Perhaps, it has something to do with a train’s speed. Sealdah Rajdhani has an average speed of 79 km/hour and a peak speed of 130 km/hour; Mahamana has an average speed of 56 km/hour and a peak speed of 100 km/hour. Speed has nothing to do (directly) with jerks. Jerks have everything to do with acceleration/deceleration and Newtonian inertia. Unless the argument is that a train with a higher average speed accelerates/decelerates on more occasions, one can’t link average speed/peak speed with jerks.  Perhaps, it has something to do with the length of the rake and the coach’s position. When the locomotive’s motion changes, that’s transmitted to coaches and the farther a coach is from the locomotive, the greater will be the jerk.  Mahamana has a rake with 18 coaches, Sealdah Rajdhani a rake with 20 coaches — not much of a difference. What was the distance between our coach and the locomotive? For 12314 and 22418, there were four coaches between our coach and the locomotive. For 12313 there were 15 coaches between our coach and the locomotive, and for 22417 there were 14. This answer wasn’t satisfactory.

FORCE AT A DISTANCE: When the locomotive’s motion changes that is transmitted to coaches and the farther a coach is from the locomotive, the greater will be the jerk. Photo: iSTOCK

Perhaps, it had something to do with the locomotive. Sealdah Rajdhani has a WAP-7 locomotive. Mahamana sometimes has a WAP-7 locomotive and sometimes a WAP-5 locomotive. As I have mentioned in these columns before, “W” means broad gauge, “A” means “electric” and “P” means passenger. On the days we travelled, did Mahanama have a WAP-5 or WAP-7 locomotive? I don’t know and neither did the train superintendent, whom I asked. If I have got my locomotive livery right, they were WAP-5s. There are technical differences between WAP-5 and WAP-7 and one can debate the superiority of one over the other. (It is by no means obvious that regardless of the number of coaches and load, WAP-7 is superior.) That being said, I have found no compelling reason why WAP-5 should give us a smoother ride than WAP-7. One is therefore left with only one cogent reason for jerkiness. This has to do with couplers. Sealdah Rajdhani has an LHB (Linke Hofmann Busch) rake, Mahamana has an ICF (Integrated Coach Factory) rake. LHB coaches are safer and superior to ICF coaches, but there is an issue.  

We aren’t talking about train sets with integrated rakes, not yet.  Therefore, the locomotive has to be coupled to an end-on generator car in case of Sealdah Rajdhani, a seating-cum-luggage rake (SLR) in case of Mahamana, and coaches have to be coupled to each other. Broadly, there are two kinds of couplers, screw coupling and centre buffer coupler (CBC). Though this isn’t invariably the case, an ICF rake like Mahamana will normally have screw coupling and an LHB rake like Rajdhani will have CBC. CBC anti-climbing devices make LHB coaches safer in case of accidents (fewer fatalities). But this also makes an LHB rake jerk more. However, some newer ICF coaches have CBC coupling, to make them safer. It is more a coupler issue, not so much ICF/LHB. There have been attempts to improve couplers such as Schaku couplers used on EMUs. Schaku is a tongue-twister, unless you know German. It is an abbreviated form of Scharfenburgkupplung. These are semi-permanent couplers and that adjective underlines the key issue. Coaches are coupled to each other and locomotives coupled to coaches. They will occasionally have to be uncoupled. Historically, Indian Railways (IR) has felt that a locomotive pilot, guard or gangman should be able to uncouple coaches, for instance, in case of accidents. If that’s important, couplers will be cruder and jerkier. Can you imagine Delhi Metro coaches being uncoupled on tracks? They can still be uncoupled, but by trained engineers in workshops. That’s exactly what a train set or fixed rake means. There is a parallel with every roadside mechanic being able to “repair” old-model Ambassadors and Fiats earlier. No longer, and that’s the transition IR will also have.

The writer is a member of the National Institution for Transforming India Aayog. The views are personal