Friday, 13 August 2021

August 2021 Meeting

This month there was a certain optimism that we could at last see a possible light at the end of the Covid tunnel, maybe a perceived chink of light was enough to spark speculation that we might be able to meet face to face again in a month or two. Our Zoom contact has been very worthwhile spanning over a year and to great extent keeping the spirits up. Reuniting Lightermans Yard both physically (the main parts of the layout are currently located either side of London) and with ourselves, and replacing our 40 minute Zoom sessions, with 4 hours of convivial discussion and running trains, is something worth looking forward to. 

Alan: Apart from the work done for the 2mm Association - major shed work has been taking place with the big hammer!

Howard: Tom wants to use servos for the track he is building for Richard’s cameo. I suggested some HobbyKing servos based on advice from MERG.

  • For semaphore signals, we [MERG] recommend the HobbyKing HKSCM9-5V digital servo. This completely eliminates any tendency to twitch at power up and is completely quiet when the drive pulses cease.

  • For turnouts, we [MERG] recommend the HobbyKing HK15178 analogue servo. Although this can suffer from a power-up twitch, it is ideal where a small amount of pressure is desired to hold the switch blade against its stock rail. Again, it is completely quiet and draws no current when the drive pulses cease.

    There is only a small difference in price between the two HobbyKing servos recommended above, so it makes sense to choose the most appropriate servo for the job.

    Tom intends to control the servos with MERG’s SERVO4 board, and the latest version has eliminated power-on twitching. (HobbyKing are currently out of stock of the HK15178).

    1. Howard also supplied a servo tester to be powered with 6V of AA batteries. He made up a 6way connector for the power supply – this only fits one way so avoids incorrect polarity. The tester is very useful as a standalone test to ensure servos work; it can also set the servo horn to its mid-point to maximise movement in either direction when in use. Where the servos connect to the tester, he marked the edge of the PCB with a black pen to indicate where the brown wire should go (on some servos this lead is black).

      Yet More Experiments with trackwork

      Having watched Laurie Adams’ “2mm Track Talk” Youtube videos, I decided to experiment with his method of feeding power. Laurie used 0.7mm brass wire flattened and soldered in place of the outside Easitrac plastic chairs (2mm magazine p 38 April-May 2017). I had some 0.8mm brass wire but found it impossible to squeeze flat with pliers. Perhaps my wire is hardened; furthermore I do not have a strong grip.

      I found I could get a reasonable effect using single stranded wire of 0.6mm (Rapid Electronics 01-0601) using the ends of a ratchet crimping tool. I was then able to get a good effect on the 0.8mm brass wire using the same technique.

      Molex Crimping tool (Rapid 85-0262)

      flattened wire and brass wire (below)

      A reasonable approximation to a chair can be made if the flattened end is first trimmed.

      Obviously, using them to bond the switch rail to the stock rail still needs the wires to be connected together. I used the brass rod on one and the wire on the other to compare them – the wire is more flexible and I have lots of it! The appearance is acceptable, and would probably be un-noticed after painting and ballasting – I found it hard to get a decent photograph.

      I also used brass sleepers on a piece of copper clad point sleepers.

      I have abandoned my idea of drilling and tapping the Finetrax cast frog to take 14BA bolts, but instead just drilled the hole and pushed some of the wire into it and soldered it to the top of the cast frog. I can use the same idea for the Easitrac cast frogs. I like this method as it is easier than soldering the wire to the underside of the cast frog and having to thread it through the baseboard. My preferred method is to lay the track and then attach the droppers later.

      Richard and Tom: An interesting locomotive from Kato appeared in the press, feels like another diorama  might be forming in the mind - Poplar Docks anyone?

      Progress on 'Clyde'; A companion way for workers' access to the hull, and a way to close the scene.

      Pete TownsendI'm sorry but there is nothing to report from Somerset this month. 

      I have been so busy with the garden that modelling has had to take a backseat.

      I was also a bit dispirited, a while ago I got a nice looking 3d printed Lord Nelson class from Shapeways.  It was advertised  as n gauge, but as it's one of my favourite locos I went ahead. When I got it I checked the overall length of the loco and tender and both were exactly correct for 2mm. Like a fool, I didn't check any other measurements. I went ahead and built a chassis, painted and lined it and was quite pleased with the results. The first time that I ran it on the layout  it fouled the road bridge. Too high.

      I then checked all the measurements.  The tender is spot on.  The loco is right in all dimensions including the footplate height, but somehow the designer has managed to make the body a full 2mm too high. I can only think that this was to take some proprietary mechanism.  It towers above the rest of the stock. A lot of time and effort wasted. Any future 3d printed bodies will be thoroughly checked before building.You have been warned! 

      Next meeting, Sunday 12 September. Location to be announced

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