Marchford Creek

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

  1. Bullhead

    Bullhead Western Thunderer

    By my standards, I’ve made quite a bit of progress with wiring this week. The DCC distribution system is complete. The un-coupler electromagnets have been connected to their control board, which now looks a lot neater. All the point motor wiring has been routed and tidied up with spiral wrap. Next on the agenda is to complete the IR train detection system for the traverser.
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  2. Bullhead

    Bullhead Western Thunderer

    My plan for this weekend was to construct the IR train detection equipment but on gathering the components and reminding myself how it all went together, the realisation struck that I had bought two different types of IR receivers and no transmitters. A quick order placed will remedy that by Monday but a different project was needed.

    I turned my attention to the layout lighting. Some time ago, having read up on the subject from various sources, I bought some led strips in warm and cool white to enable a suitable mix to be formulated for my daylight setting. Three long and two short strips seemed a good way to start to suit the layout’s geometry and I opted for three in warm and two in cool for the first trial in colour balance.

    This worked well for colour but needed a little adjustment in position to give the best overall effect. Having got everything set up it seemed a good idea to position all the buildings and have a photo session to test the overall appearance, colour balance and shadows. All these pictures were taken on my phone using just the layout led lighting. Hope you like the results.

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    The arrangement of led strips. For test purposes, these have just been positioned with masking tape. The inside of the “lid” has been given a coat of white paint to help to reflect light.

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    The layout box with lights on. The yellow glow at the top seems to be a camera effect and is not visible to the (my!) naked eye. The electrical panels have been positioned for effect. Note removal of the traverser winder to facilitate forthcoming painting of the front facia. Having a new deadline, I may even be able to do the planned upgrade to electric motor operation!

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    Driver’s eye view coming off the traverser.

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    His day’s work done, Jim sits under his shelter. Looking out through his sad rectangular eyes, he wonders if the Marchford Creek scenic department will ever arrive!
     

    Attached Files:

    Lyndhurstman, adrian, 76043 and 5 others like this.
  3. Bullhead

    Bullhead Western Thunderer

    Hello All,

    It has been far too long since my last post. I’m still here, pressing on with Marchford Creek as fast as spare time allows.

    The final control PCB has been completed. This one is the receiver board for the infra-red train detection system and will operate the track occupation indicators for the traverser. Again, this uses surface-mount components on a home-etched pcb. I will post more on this part of the system soon.

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    The layout lid and front facia have been given a coat of primer and I have sourced a rather restful shade of sage-ish green that will be used to finish them off.
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    In odd moments here and there, I have been testing the track and doing a few tweaks on some rough spots and a couple of places where the flangeways were a bit tight.

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    Testing showed that one of the wing rails in the slip needed improvement to get the geometry spot on and to open out the flangeway to the correct clearance. Having completed the replacement, running is much smoother. There are still a few uneven rail joints needing attention and a good number of dislodged cosmetic chairs to be replaced (again!). I remind myself that that some additional time invested now will save loads of trouble in the future!

    One thing I have been able to do recently is some reading. Specifically, I have revisited some of the material on the Scalefour Society website (particularly the extremely useful and comprehensive contribution by Will Lichfield) about springing vs compensation for rolling stock. The general opinion expressed seems to be that springing gives far superior running compared with compensation. Further, CSB (continuous springy beam) suspension appears to offer a construction method that is no more difficult to achieve than beam compensation. In addition, it looks like a straightforward option to make wheelsets removable, retained securely by the suspension beam itself. This appeals to me as it means wheelsets can be set to gauge and quarter away from the chassis. I would be interested in any thoughts or feedback on this subject from those with experience of the techniques.

    Another topic that I’ve been researching and experimenting with is loco pickups. Whilst looking at suspension, I came across a pickup design in Will Lichfield’s material that jumped out at me. Will uses a hard brass wire support (0.7mm) with a springy pickup wire fabricated from phosphor-bronze or similar mounted on it. I have used 0.25mm beryllium copper for my prototype springs. The big advantage of this method is that the length of unsupported pickup wire is reduced as the coil spring section is reinforced by the 0.7mm brass core. The next challenge is to figure out the best way to configure a sub assembly for attachment to a completed chassis.
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  4. Bullhead

    Bullhead Western Thunderer

    Some recent progress or two steps forward and one back.

    The infra-red emitters have been mounted on gantries above the traverser, one to show track occupation and the other to indicate over-run.

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    The gantries were soldered up from brass strip and are bolted to the parapet walls of the traverser. In order to give the widest possible effect, the track occupation unit is mounted at 45°.

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    The receivers are mounted in the corresponding positions between the rails. The holes are quite deep which should help to prevent triggering by any stray light. The electronic design for the unit came from here http://www.ho-ptit-train.be/html_en/cablage_04_en.html

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    My frequent vague allusions to “possible motorisation of the traverser at some future time” have moved closer to reality with the sourcing of this little gem.

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    It’s a 6v motor with 298:1 gearing obtained for just a fiver from Pimoroni. Slightly inconvenient that it needs a 6v power supply but that is easy enough to rig up. Initially, I had considered letting the motor stall at each end of its travel as the stall current is low. However, the amount of torque it produces is phenomenal for its size so an end-stop microswitch will be used at each end to cut the motor current. A two-pole centre off dpdt switch will reverse the motor supply and a push-button switch defeats the end stop microswitches to start the thing moving.

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    Here is the motor duly installed in a bracket fashioned from some aluminium u channel. The coupling to the motor is a piece of 4mm id polyurethane tube which is a tight fit and is further restrained using cable ties. The whole assembly works ok but is excessively noisy. A number of modifications are under consideration to cure this.....

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    Attached Files:

    Simpas, chrisb and cbrailways like this.
  5. Bullhead

    Bullhead Western Thunderer

    Hello All,

    Things have been a bit slow at Marchford Creek over the summer months as there have been lots of other things to do. I have made some significant progress though and thought it was time for an update.

    The most obvious sign of progress is the painting of the exterior cabinet surfaces. The inside of the lid and the backscene panels are now primed and ready for scenics to be applied.
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    I attempted to fit a self-adhesive photographic backscene but ended up with more creases than I could shake a stick at! This, I should stress, was entirely down to my own ineptitude and impatience, not the quality of the product. Having reconsidered the possibilities and viewed some how-to videos, I’ve decided to have a go at painting the backscene myself. A few practice sessions have given me some confidence that this could work. More on this to follow.

    The daylight lighting led strips have been permanently fixed into position in the lid. An additional blinder was added to prevent direct visibility of the lighting strips from normal viewing angles.
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    A separate night-time light bar was made up on a 500mm strip of copper-clad circuit board using 2x cool white and 3x blue smd leds. This bar is mounted on the inside of the front facia and gives a nice moonlight effect to the scene. The two different levels of light are selected from a front panel switch.
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    The rather inadequate traverser motor previously installed has been replaced with something a bit beefier. A motor mount incorporating two layers of rubber sheet was contrived in order to minimise noise transmission. The flexible coupling to the shaft is a piece of tight-fitting polyurethane tubing.
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    Wiring is officially complete! Everything is connected to something else and it all works as designed after a bit of tweaking and the correction of a few mistakes. The main control panel has switches for the Tortoise point motors. Led position indicators for the points are driven by one of the switches built into the motors while the other looks after frog polarity. Uncoupler magnets are powered from biased switches so that each switch operates one electromagnet in each direction. The spare contacts on each DPDT switch are used for the led indicators on the panel. The position indicators for the traverser are simply connected to microswitches operated by the movement of the table. Switches at each end must close in order for the positive indication to be given. Finally, the infra- red system for indicating track occupation on the traverser works very well and I'll post separately on this in the near future.
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    The next phase will be a period of intensive testing of track and electrics with the aim of flushing out any gremlins before scenic work (finally!) begins. Should be fun!
     

    Attached Files:

  6. Bullhead

    Bullhead Western Thunderer

    As promised, some more detail about the traverser monitoring system on Marchford Creek.

    The idea of this system is to give the operator at the front of the layout a positive indication that the traverser deck is correctly aligned with the exit track and a reminder of where stock is berthed, without the need to look ‘round the back’.

    Traverser deck position as previously mentioned, is simply taken care of by two microswitches at each end of travel. Once both switches close, the relevant panel led lights to confirm position. Simple screw adjusters allow for fine tuning of the position at which the switches operate.

    The traverser mechanism operates via a push to make switch and a DPDT centre off switch. At each end of its travel, a microswitch cuts the power to the motor. For the return journey, the direction of travel is selected with the DPDT switch, the pushbutton then overrides the power off microswitch to get things moving. Once the microswitch has closed, the unit continues on its way until the other side is reached and the second microswitch cuts out.
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    In order to give an indication of track occupation on the traverser, an infra-red (IR) system has been adopted. This uses the principle that an item of rolling stock positioned between an IR emitter and receiver causes a panel led to illuminate. I found a suitable design published online here http://www.ho-ptit-train.be/html_en/cablage_04_en.html
    The four independent IR units are mounted on a single pcb as previously described. This and the mounting arrangements for the transmitters and receivers have been described earlier. Each traverser road has two detector units, one angled to give the maximum possible coverage along the length of the track and the other positioned at the end to give an operator warning of an impending collision with the end stop. The IR units proved to be easy to make and are very reliable in operation.

    The following pictures illustrate the control panel indications (top left corner) for different distributions of stock. The green light indicates correct track alignment, yellow shows track occupation and red warns of imminent collision with the end stop!

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    Brian McKenzie likes this.
  7. Bullhead

    Bullhead Western Thunderer

    Hello All,
    Once again, modelling time has proved elusive in the last few weeks. I have managed to complete testing on the electrics and sorted out a couple of mistakes in the wiring. Next step was to try to get something moving. After some track cleaning I retrieved my 48DS from the drawer and did a good clean on the wheels and pickups. Here is a short video of the results.




    A few tweaks are required here and there but generally, I'm very pleased with the running achieved.
     
    Last edited: 7 November 2019 at 21:08
    Bill Campbell, AJC and Lyndhurstman like this.
  8. Lyndhurstman

    Lyndhurstman Western Thunderer

    Well done. A great clip. And a great thing to see. Nice trackwork, too.

    Cheers

    Jan
     
    Bullhead likes this.
  9. Bullhead

    Bullhead Western Thunderer

    Thanks Jan, much appreciated.
    Cheers
    Peter
     
    Lyndhurstman likes this.