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| Re: Linked Sets (1639417) | |||
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Re: Linked Sets |
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Posted by Stephen Bauman on Sun Feb 23 22:32:49 2025, in response to Linked Sets, posted by GonzoUSN on Sun Feb 23 21:48:58 2025. I assume Mr. T. Dude will give a more complete explanation.As an outsider with engineering experience I see three advantages. First, there is commonality of equipment. An air compressor can handle two or more cars. This results in a weight savings. Second, multiple unit trainline signals are incorporated into the couplers. The coupler connections have proven to be troublesome. The linked cars eliminate the troublesome connectors. Third, elimination of cabs does provide more passenger space. I see many disadvantages. First, the coupler connection problem could have been resolved by using more modern (post 1900) signals for the trainlines. They did not have to incorporate the connectors in the couplers. They could have used cables with better connectors. They could have used optical or radio connections from the late 20th century. Second, the IRT patented a cab design that was available for passenger use when it wasn't used by a train operator. The BRT and the IND did not want to pay the IRT royalties to copy their or a similar design. Third, there's a lack of flexibility. The half train length sets means that many train lengths are either too long or too short for passenger loads most of the time. One workaround has been to alter service levels (train frequency). This creates a big problem with a trunk/branch system like NYC. The way to avoid merging conflicts is to operate balanced merges. The use of unbalanced merges results in delays at merge points. Fourth, there's a safety problem in case brakes have to be cut out in lead car. This means a tripper won't have any effect until a powered car tries to pass it. Trippers were originally placed sufficiently far from the impact point so that the train would stop should the second car tripper be actuated. That was 60 feet from the front tripper. Should the first 5 cars have their brakes cut out, that distance would now be 300 feet. They did compensate when the Archer Ave Subway was built. The diamond crossover was placed 300 feet from the terminal station entrance. The result was that a stub station with tail tracks that should have handled 40 tph could handle only 12 tph. Fifth, if a single car needs unscheduled maintenance, then 4 or 5 cars are out of service. This reduces availability or requires more spares. Spares are more costly because 4 or 5 cars cost more than a single car. |
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