Developing a Manual Point Control System.

Discussion in 'Workshop Benches' started by gormo, Sep 11, 2020.

  1. gormo

    gormo Staff Member Administrator

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    G`day Folks,
    I`ve used some masking tape to rough out the routes for the cables on the underside of the baseboard. It`s not dead accurate ,it`s just a guide.


    DSC09693.JPG


    Now this is where we`ve gone back to the drawing board.
    You may remember back at the start of this thread that I had come up with a point actuator made from a tile spacer as per below

    DSC09595.JPG


    Well it`s good in principle, however when it`s fitted under the baseboard the wire connection to the point, approx. 20mm, acts a bit like a lever and twists the nylon arm of the tile space, rather than moving the point. Basically the nylon material is not rigid enough to allow it to work properly in that formation.
    Back to the drawing board !!!
    So instead, I`ve used a short piece of cable with a wire through it bent at 90 degrees to go up to the point through the baseboard, and the other end is connected to a tile spacer bellcrank which gives a change of direction for the wire run. The cable is held by 4mm cable clips. I`ve also cut a terminal block brass insert in half and slid it over the wire to act as a limiter for the throw of the lever. There is also one at the other end of the cable to restrict the throw in the opposite direction.

    DSC09703.JPG


    DSC09705.JPG


    Sorry the pic is blurry, but the cable was then fitted properly to the underneath of the board according to my temporary route selection. It`s important to have straight wire and to lay the cable straight as well. This will reduce friction and allow the wire to travel smoothly through the cable.


    DSC09704.JPG

    Now we have a second back to the drawing board situation.
    The tile spacer bellcrank used in this situation below struggles with the load applied by one meter of cable being pulled or pushed at a right angle. Once again under heavy load the tile spacer bends, this time in the horizontal plane.
    So they are becoming horses for courses, in that they need short runs because they can`t take too much strain. The situation back at the point is fine because it`s only a couple of inches of cable to deal with, but in the situation below I`m afraid it`s a no go.


    DSC09706.JPG


    So I`ve gone back to my original design of bellcranks made from plastic / nylon molding cut into wafers and fitted with a post and terminal block inners as connectors.
    These suckers can handle the strain.

    DSC09709.JPG

    I`ll insert a short video showing a bit about how they are made and how they are used.



    I have lots of spares, but I just have to put them together.

    DSC09711.JPG

    Connections to the point levers are working out fine. I am putting two right angled bends in the wire to set it off the back of the board and line up with the rocker arm properly.


    DSC09708.JPG

    The tile spacers were a disappointment, but I guess I had never tested them to the extent that was required on this build.
    You live and learn plus, you`ve got to have a crack at this stuff to see if it works......but you can`t win `em all unfortunately.....:scratchchin:
    More as it happens
    :tophat:Gormo
     
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  2. Walkingthedog

    Walkingthedog Full Member

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    Tile spacers are very easy to snap, they are made that way. Your new idea looks much better. Any chance the holes could become distorted after a time. Perhapes a piece of brass tube in the holes might be advisable.
     
  3. gormo

    gormo Staff Member Administrator

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    G`day Walkingthedog,
    Well you would think the holes would become distorted??.......when I first built these bellcranks, I put a couple on a test rig and every time I went out into the shed I would do a few hundred rapid movements back and forth. I wanted to see what it would take to break it.........25,000 moves and one bellcrank failed.
    Surprisingly, you don`t seem to get the wear you would expect with a thread rubbing on the insides of the holes, I have been using them for seven years now without any serious problems.
    One bellcrank failed and there were a couple of minor adjustments
    I think there is so little movement required in them that they wear really well.
    So I`m looking forward to wearing another one out on the layout.......just to see how long it takes....:avatar:
    This is a rather long winded way of saying....I don`t think brass sleeves are necessary.:avatar:
    :tophat:Gormo
     
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  4. Walkingthedog

    Walkingthedog Full Member

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    Appears you have given them a thorough road test. In that case ignore everything I typed after the word "better". :thumbs:
     
  5. gormo

    gormo Staff Member Administrator

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    :avatar::avatar::avatar:....Ok mate.....thanks for the input anyway.
    :tophat:Gormo
     
  6. Walkingthedog

    Walkingthedog Full Member

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    Really enjoyed this thread.
     
  7. Keith M

    Keith M Staff Member Moderator

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    Presumably by limiting the wire travel using the 'half-connectors' you then don't need 'Omega loops' to prevent or take up overtravel at the point. It's certainly a clever way of point actuation based on real life, but it's only do-able if you can turn the board upside down to do the install, it'd be a nightmare to attempt on an already fitted in place board.
    Keith.
     
  8. gormo

    gormo Staff Member Administrator

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    Yes you`re right there Keith,
    No need for omega loops, just set the point in position and then slide the half connector to the end of travel and lock it off......no danger of pushing the point blades too far.
    I agree the system is not for layouts fitted in place, as it needs really good access to set it up properly. It would be difficult and frustrating doing everything upside down, that`s why I`ve always had my layouts set up so that sections can lift out or up if required.
    :tophat:Gormo
     
  9. gormo

    gormo Staff Member Administrator

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    G`day Folks,
    Well I think there`s probably not a lot left to update in this thread after today`s update.
    As you can see below, the connections under the baseboard have been completed.
    The wire in tube is working very well, although I think a one metre run is probably starting to get near the limit of best practice. I`m not sure actually, so it may be good for much longer lengths, but there`s only one way to find out..........test it....:scratchchin:


    DSC09718.JPG

    The most critical piece of the whole system is the wire...........it must be straightened and used in straight runs. Subtle bends in the wire or introduced curves in the cable will start to introduce friction and extra play in the system and basically start giving some grief.

    This is how I`ve approached the baseboard join. One simple brass connector that can release the wire link between it and the bellcrank on the left. The wire, when released also from the bellcrank on the left and the connector on the right, will slide out of the way until required for a permanent connection.


    DSC09719.JPG



    DSC09720.JPG


    Wire connections to the levers have to be connected in sequence, left to right, to allow proper access to the locking screws on the rockers. For example, to connect the rocker on the far left, the four rockers to the right of it would be drawn back against the back of the lever frame box, thus allowing clear access to the locking screw on the rocker on the left.


    DSC09721.JPG

    I have a video demo of the system working, albeit still in the workshop



    So now I`m looking at the wiring and fitting the boards back in place. I also have to add combing to the box and signage, so once the combing and signage are in, I`ll do a further update to finish off this thread.
    Hope you`ve enjoyed it so far.
    :tophat:Gormo
     
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  10. Walkingthedog

    Walkingthedog Full Member

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    I see you have still used a couple of tile spacers. I think what you have done is excellent and has the cogs in my brain whirling.
     
  11. Sol

    Sol Full Member

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    Ingenious is not the word :thumbs:
     
  12. gormo

    gormo Staff Member Administrator

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    Thanks Walkingthedog,
    Yes there are five tile spacers used to make the connections near the points. They only have to deal with shorts runs of wire and loads, so they are fine in that situation.
    I hope you don`t get a headache with all those cogs whirling........:avatar:
    :tophat:Gormo
     
  13. gormo

    gormo Staff Member Administrator

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    Thanks Ron.......:thumbs::thumbs::thumbs:
     
  14. Toto

    Toto I'm best ignored Staff Member Founder Administrator

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    As I said before ..... one of my favourite " gormoventions " the pulling of the levers to change positions cannot be bettered in my opinion to give some realism to operating. The finish of the lever framework is top notch.

    Long may yer lum reek. :avatar: ... an auld Scottish saying.
     

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