Marchford Creek

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

  1. Bullhead

    Bullhead Active Member

    Today, I made a mock-up of the Marchford Creek control panel.
    upload_2018-6-8_23-24-44.png

    The black dots on the track diagram show roughly where the various led indicators will be. For some reason I decided to use surface mount leds and resistors – so, 52 tiny components (that I can barely see) to be soldered to a pcb with sub-millimetric accuracy. Let’s do this! Note: On the real thing, the switches will be in a straight line! The upper row of 6 on-on dpdt switches are for the Tortoise point motors, the lower row of 4 (on)-off-(on) dpdt are for the uncoupler coils, each switch activates one coil in each direction.

    The indicators will show for the traverser – alignment, occupation and over-run, for the rest of the scheme, turnout position and uncoupler activity. As the layout control is by DCC, nothing else is required.
    upload_2018-6-8_23-25-8.png

    Here’s one I made earlier, this time attached to enamelled copper wire for use in a small building. VERY fiddly but worth the effort.

    upload_2018-6-8_23-26-35.png



    Also this week, I’ve put some time into preparing artwork for the various pcb’s that are required. This has taken much longer than anticipated but is moving on well now. These circuits are for the IR detectors for the traverser (top left), the uncoupler coil arc suppression circuits (bottom left) and a Tortoise test rig. More to follow on these.
     
    jonte, chrisb, JimG and 1 other person like this.
  2. Bullhead

    Bullhead Active Member

    Progress in the next couple of weeks is going to be slow to non-existent due to a major project at home. This involves decorating four rooms and moving my “railway” room to a different location. Long term the benefit is more working space for me and regaining of the “spare bedroom” by the domestic authorities – every one’s a winner!

    Some progress over the weekend.

    upload_2018-6-20_13-18-15.png

    All the holes for uncoupler armatures and point motor mountings have been marked and drilled.

    upload_2018-6-20_13-18-51.png

    The track bed areas and positions of structures have been marked out.


    upload_2018-6-20_13-19-13.png

    Wiring looms have been added to the Tortoise point motors.

    upload_2018-6-20_13-19-57.png

    And finally, the cut-out for the control panel has been ..er.... cut out.

    Hopefully more to follow before too long.
     
  3. Bullhead

    Bullhead Active Member

    As expected there has been almost zero progress at Marchford Creek over the last three weeks. My work room has become a spare bedroom and all my gear is piled up near its new location waiting for some electrical work to be done before the new space can be made ready for use.

    I have managed to finish the artwork for the circuit boards…
    upload_2018-7-19_22-32-3.png
    …and transfer it to some transfer film ready to apply to the boards for etching. Depending how the process goes, I will share details later.
    upload_2018-7-19_22-32-28.png
    A drilling template has been made for the control panel, which will be made from this piece of aircraft aluminium. I came by a stock of this many years ago and it's very useful stuff.
    upload_2018-7-19_22-33-7.png
    I have no experience of or access to CAD programs so have ended up using Microsoft Power point of all things. This is used a lot in my work and the drawing functions are very easy to master.
     
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  4. Bullhead

    Bullhead Active Member

    It is difficult to believe that more than two months have elapsed since my last post. It has been a busy summer but sadly not with modelling projects. As the days get shorter and the evenings lengthen, it is time to get back to the work bench. Unfortunately, my new workspace has not been completed yet so the kitchen table has been pressed into service for now.

    To get back in the groove, a simple van kit proved to be an ideal quick warm up project. A ratio SR uneven planked van from my to-do pile was selected. This kit has nice crisp mouldings and it all fits together very well. It waits now for wheels, buffers and a few other details before painting.
    upload_2018-10-5_22-11-10.png
    [​IMG]

    Next up was to complete the electronic circuits for Marchford Creek previousy described. Initially, I had mixed results using Press’n’peel transfer film to get the artwork onto the boards. After some trial and error, the board preparation was changed to include a 1500 grit polish followed by careful cleaning and the iron temperature was optimised to get complete release of the image from the film. I’d be very happy to share more details of this process if anyone is interested.

    The boards pictured below are for the IR train detector and control panel. 1. After transfer of the artwork ready for etching. 2. After etching and removal of the transfer film. 3. Tinned ready for assembly.

    upload_2018-10-5_22-11-49.png
    upload_2018-10-5_22-12-21.png
    upload_2018-10-5_22-14-32.png
    [​IMG][​IMG][​IMG]

    This board carries the arc suppression circuits for the uncoupler electromagnets described in an earlier post.
    upload_2018-10-5_22-14-58.png

    [​IMG]Having produced all the etched boards, I completed this test rig (yes, another one!) for Tortoise point motors. It allows the function of the motor to be checked in each direction along with both the internal switches and allows easy set-up of the point throw.

    https://www.youtube.com/watch?v=FvFb4I3qzu4

    A Tortoise connector is fitted to allow testing straight from the box. For units with wiring already attached, this sprung pcb connecter block can be used. These are available in different configurations from Rapid Electronics and are a nifty and cost effective way to create removable connections between items.

    upload_2018-10-5_22-16-3.png

    [​IMG]

    Next on the agenda is assembly of the control panel and IR train detection boards.
     
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  5. Bullhead

    Bullhead Active Member

    A bit of progress was made today with the High Level Hudswell Clarke.
    The crew are ready for work.
    HC Crew.jpg

    Pickups and wiring have been added so the chassis is now complete apart from the rear sandboxes, which need to be added after the wheels to leave clearance for a wheel press to be used.
    HC chassis 1.jpg

    HC chassis 2.jpg

    Finally, some touching up and weathering has been added to finish off the cab interior painting, completed by the addition of some real coal in the bunkers. This was crushed to a reasonable looking size and fixed with PVA over the liquid lead that had been added as ballast in the bunkers. The lead was mixed with epoxy and pushed into position to avoid any long-term effects caused by the possible reaction between the lead and PVA.

    HC cab 2.jpg
    HC cab 1.jpg
     
  6. PaxtonP4

    PaxtonP4 Active Member

    It's been years since I've seen home etched PCBs. I thought everyone sent them off to China these days. It's one hell of an effort to do it your way - I admire your persistence.
     
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  7. Lyndhurstman

    Lyndhurstman Western Thunderer


    Nice. I presume you don't have an issue with rim scraper and compensated axle? I've moved towards back-of-the-wheel-rubbing because I couldn't get a trade-off between pickup pressure and freedom of movement.

    Nice work. I particularily enjoy your eye for colour and patina on the non-ferrous fittings. And the duckboards look sutiably grotty. Good stuff.

    Cheers

    Jan
     
    Bullhead likes this.
  8. Bullhead

    Bullhead Active Member

    I've not looked at the economics of getting one-off boards made and there are only four to do. Being a bit miserly I decided to stick with the diy route. Back in the 80's I used individual rub down transfers for each solder pad and track! Compared with that, this method seemed like a breeze.
    Best, Peter
     
  9. Bullhead

    Bullhead Active Member

    Hi Jan,
    Thanks for your kind comments. I looked long and hard at the pickup method and decided to go with the scrapers. They are made from 0.25mm beryllium copper wire and with the extra turns are very springy. On bench testing, they stayed in contact very well with the wheel rims as the wheels moved vertically without exerting too much drag. If I can get my track nice and flat they won't have too much flexing to do!
    Best, Peter
     
    Lyndhurstman likes this.
  10. PaxtonP4

    PaxtonP4 Active Member

    You get 10 boards (100 x 100) for about £12.
     
  11. richard_t

    richard_t Active Member

    Double that if you have to pay import duty and PO/Carrier charges. HMRC/Border Force seem to be having a crack down at the mo.
     
  12. PaxtonP4

    PaxtonP4 Active Member

    No - you are entitled to import goods up to the value (including post) of £15 VAT and Duty free.
     
  13. richard_t

    richard_t Active Member

    The 15ukp limit includes the postage as well - which typically takes it over the limit.