Friday, 30 November 2012

Magnetic Coupling Trials

I spent a couple of hours today, despite the freezing weather, preparing a length of garden track and running a 12-coach test train round the reverse curves on a 1 in 50 gradient. This was the first fully "live" trial of the "McBogle (or DOGRF) Magnetic Coupling" (see previous post). The couplings between coaches 1, 2, 3, 4, 5 and 6 were to the Mk.1 design using a single 3mm x 2mm magnet on each coupling. The couplings between the loco and the first coach, which were taking the greatest load, were Mk.2, with an opposite-polarity pair of 2mm x 2mm magnets. None of the couplings failed during the trials, which comprised several low-speed runs up and down the test track. (Higher speeds were not possible this time because of undiagnosed limitations in the control or  power distribution equipment, i.e. it couldn't supply enough current for a Hornby class 50 pulling 12 coaches up 1 in 50 at more than a scale 20mph.)

  1. Both the Mk.1 and the Mk.2 magnetic couplings have a more than adequate holding force for a 12-coach train of 160g coaches on a 1 in 50 gradient with reverse curves of radius 4ft and greater. Tests were carried out at scale speeds of 20mph and lower.
  2. The Mk.2 is easier to use, as identical couplings wll mate with each other. Before the start of the trial it was necessary to change the Mk.1 couplings between the loco and first coach for Mk.2 because one of the Mk.1s was the wrong polarity.
  3. Further tests are needed to assess the long-term reliability of the adhesive joint holding the magnet to the "pipe", with the stress of regular coupling and uncoupling.
  4. (Not related to couplings.) An unexplained gap between two lengths of track on a reverse curve has now grown to about 5mm (it was about 3mm in the summer). It is now causing regular derailment and needs investigating.
  5. (Not related to couplings.) A rail joiner near the top of Quarry Bank has no wire jumper and is not making good contact.

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