Marchford Creek

Discussion in 'Entries' started by Bullhead, 7 February 2018.

  1. Bullhead

    Bullhead Member

    Hi Jonte,
    Very kind of you to say so but I'm only recycling bits of what others have done before.
    Thanks for your interest,
    Peter
     
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  2. Bullhead

    Bullhead Member

    Thanks Colin. No engineering background I'm afraid, it's all guesswork and bodgery! It is great fun to build these little gadgets and they can speed up production of components required in multiple. On reflection, it might be better if I spent more time working on the layout itself!
    Best, Peter
     
  3. Pushpull33

    Pushpull33 Member

    I feel the same, I seem to spend more time making bits and posting on my blog than actually building a layout. I have just made a selecting mechanism for my fiddle yard, now to find the time to post about it.
     
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  4. Bullhead

    Bullhead Member

    Sounds interesting. Look forward to seeing how it works.
     
  5. Bullhead

    Bullhead Member

    In order to test couplers installed on rolling stock and finished electromagnets, a very simple test rig was constructed.
    upload_2018-4-15_20-49-46.png
    This enables coils to be rapidly interchanged for evaluation and allows for easy testing and adjustment of coupler units fitted to stock.
     
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  6. Pushpull33

    Pushpull33 Member

    Hi Peter. Good job done. I was just wondering about the length of the coil below baseboard level, wondering if it would still work the same if it could be made shorter. Colin
     
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  7. Bullhead

    Bullhead Member

    Hi Colin. As I'm using Tortoise point motors, there is plenty of space below board level for these coils. I guess they would work ok if made shorter as long as the number of turns was similar. It might be necessary to use a chunkier bit of steel for the armature too.
    Best, Peter.
     
  8. Bullhead

    Bullhead Member

    Uncouplers on Marchford Creek will be activated from biased toggle switches mounted on the control panel. When switching a DC inductive load such as the uncoupler coil, arcing can occur between switch contacts reducing switch life. To control this effect a snubber circuit is employed as shown below, together with a flyback diode across the coil.

    upload_2018-4-20_13-20-11.png

    RL is the electromagnet coil. The capacitor (C) must be a non-polarised type, I have used a value of 0.22uF with a working voltage of 63V. The resistor (R) is 68R. This needs to be a 0.5W type. For the diode across the coil a 1N4001 should be ok for a 12v circuit.

    upload_2018-4-20_13-21-15.png

    The effect of this circuit has been tested in my ..erm.., “electrical test area”.

    upload_2018-4-20_13-20-51.png

    I don’t have any instrumentation suitable for measuring the effect so I can’t absolutely prove that it works but it does seem that there is far less sparking when test contacts are opened with the snubber/diode in circuit. I’ll take that as a win!
     
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