LAST EDITED ON Jun-15-04 AT 08:22 AM (EDT)
Ryan,maybe a little outdated, but perhaps an interesting bit of trivia. First and foremost, I do live in a country with some mountain terrain (also known as the alps) which is crossed by several North-South and East-West mainline routes. In the 1870/80s, when these routes where designed & built, some local engineers came up with the concept of "cog-wheels" and "rack-track" allowing trains to climb grades of a magnitude no adhesion-based train could ever concur, with grades of up to 12,5% or even 14% being technically feasible (even more on touristic roads featuring light excursion traffic only).One of these engineer (by the name of Abt) was what we would nowadays call a feaverish lobbyist. He was trying to convince all these RR companies setting up trans-alpine routes to save on route length and thus cost by using his technology. His equation was - seemingly - fairly easy: If rack-track was used, then many tunnels, bridges etc. could be saved, and the overall track length would be shorter.Despite all his lobbying, only excursion RRs going to mountain tops, and short branch lines bought the concept. All the major through-fares went for adhesion-only, typically using grades around 2% to 2.6% This translated into building helicydal tunnels, viaducts, landfills etc. to allow trains to reach the top, but despite the longer track resulting from this decision, the overall concept proved to be more succesfull than rack-track following a direct line across the terrain. You may wonder why this is so.- First and foremost: Steeper grades on the one hand require shorter trains on the other hand - the power of the engine is as much a limiting factor as the braking capabilities on the downhill leg. So when your 30-50 car train arrives at the foot of the hill, it is not very economical to break it into 3-5 parts which need to be pulled over the steep grades individually.- Second: it might be sufficient to have specially equipped locomotives with cog-wheel axles for pulling trains uphill, but reliable braking is another factor. Basically, also the unpowered cars of your train need one cogwheel per car or even per truck - depending on grade and weight - for braking purposes. Now if you run an international route through the alps with lots of foreign cars ending up on your train, it is a burden to ask every single operator out there to equip its fleet with this additional piece of technology (sure, it could be done, but it is a competitive disadvante when your competitors' routes do not require it). Otherwise, additional "brake vans" would need to be inserted in your consist as helpers protecting the cog-wheel-less cars from causing spectacular, but terminal run-aways. - Third: Speed limits on rack-track are usually very low. When we talk about the 1880's, then typically a steam powered train would have been limited to as little as 12-14kph (under 10mph) uphill, and maybe 8-10kph (5-7mph) downhill. Modern day electric rack-track motors may go as fast as 40kph uphill (~25mph) and 25-30kph (~17-20mph) downhill. Now go figure: When a pure adhesion train can run the entire 2% ramp at a constant 80 kph (50mph) without having to slow down for rack-track sections inbetween, then the short-cut effect the rack-track offers distance-wise is minimized or even outweighted by the loss in average speed associated with it.- Fourth: rack track is expensive to maintain. The most expensive parts are,
- a) on a combined adhesion/rack-track system, the entry and exit sections to the rack-track where you have to make 100% sure that the cogwheel on every single one of your engines and cars is brought up to the correct speed and phase. By this I mean that it must turn just the right way to meet the rack-track precisely & smoothly - otherwise you risk to derail your train: Imagine the "hump" of the rack track meeting the "hump" of the cog-wheel, resulting in your train being lifted slightly. Then add some speed, and difficult terrain, and down you go. Typically, trains need to enter rack-track-sections at speeds that are equal or below the speed of a walking person (typical limits here are 8 kph / 5mph).
- b) Points in a rack-track section. Lots of moving parts there to get the rack section for the other track out of the way for both wheels and the cog-wheels of your train.
- c) manpower to frequently grease, check, and maintain the rack track which is facing much more tear and wear than the pair of standard rails your wheels roll on.All these factors contributed to the alpine mainlines being build in the traditional way. Over the years, with the increasing efficiency of electric (or in your country diesel-electric) power over steam engines, this decision has even more so turned out to be the way to go. While adhesion based freight and passenger trains were not that terribly fast in the days of steam, the difference has become even more noticeable today. I remember having read that around the 1910's, the trans-alpine RR operators were already proud of steam engines when they allowed them to go at 45 kph / 30mph on the grades under ideal conditions (light train, dry weather). Modern motors now go about twice that speed, under any condition, or even faster with light trains, or tilting-technology trains etc. Same with regard to the tonnage of trains, which has multiplied from a few 100 tons in the days of steam to 1500 (metric) ton trains on the 2.6% grades (remember, we are still using the old-fashioned chain couplers over here, which is a limiting factor). Tests to open the routes up for 3000 metric tons trains are underway for a couple of years now... Hope that gave you some feed for thought and another perspective on tracks vs. terrain Cheers,Lukas a.k.a Swissie
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