Jump to content
 
  • entries
    54
  • comments
    185
  • views
    41,481

Right back where I started from


Ian Morgan

950 views

It is over 12 months since my last posting on this blog. A quick recap of the project so far is in order.

 

Way back in July 2010, the 2mm Scale Association celebrated its Golden Jubilee with a special Expo in Oxford. Prior to this, a layout building challenge was issued for layouts up to 9.42 square feet to be exhibited at the Expo. I built Freshwater for this challenge. As a change from my normal use of relays to operate points, I decided to try servos for the new layout. I joined Merg to get access to their Servo4 kits. After some teething problems, I managed to get the layout working just in time for the Expo with a temporary control panel with a switch for each point. Although the layout operated nicely all weekend, there had been no time to create any scenery. It was just track on white painted baseboards.

 

I did want to have route selection and a proper control panel, but there was a problem with the servos that I wanted to fix first. On powering up the layout, one or more servos would decide to move rapidly to one extreme or the other, despite being restricted in their movement by the point mechanisms. Sometimes they would draw so much current, the power supply voltage to the PIC controllers would not rise high enough for the PICs to start operating and get the servos under control. I had to resort to switching the power off and on a few times until things sorted themselves out.

 

My last posting on this blog describes the introduction of the Merg CBus layout control bus, the introduction of DCC, and a lot of work on power supplies in an effort to resolve the servo startup problems. The problems persisted and I was beginning to lose interest in the layout.

 

The introduction of a new Merg kit for a servo mounting started me thinking again. I had done everything I could with the electronics - maybe the problem was with how I had mounted the servos. I had them directly driving the point mechanisms which meant they were only using a small segment of their available movement. The new servo mounts are arranged so that the servo can sweep through its entire range while the rod connecting to the point mechanism only moves a few millimeters. It would no longer matter if the servo wanted to move to an extremity on powering up. It could do so quite freely.

 

So, a start was made removing the existing servos and their mounting blocks and fitting the new mounting kits (with 5mm shaved off their overall height to fit within the hinged cover panels). At the same time, I decided to replace the under-board point tiebars I had originally fitted. Although they had worked OK, they did not have any way to adjust the distance between the point blades. The old ones also had a microswitch to change the frog polarity, whereas the new mounting also has microswitches nicely mounted on them. My new under-board tiebars, therefore, did not require microswitches.

 

blogentry-11458-0-65780100-1370198796_thumb.jpg

 

All this work has now been completed with a couple of weeks to spare before this year's 2mm Scale Association Expo in Wallingford. Unfortunately, the viewing side of the baseboard is pretty much the same as it was in 2010 - ballasted trackwork sitting on plain white baseboards. But, like the duck, calm and serene on the surface but peddling like mad underneath.

  • Like 4

5 Comments


Recommended Comments

  • RMweb Gold

Good to see FW back Ian - I always liked this layout and would be a shame not to see it finished.

 

How is the new arrangement working now - did you get a test one done to your satisfaction first before tackling them all?

Link to comment

Ian

Good to see the Servos have not been ditched altogether. I am now a strong advocate of these, and will certainly use them again.

 

Looking at the underside of DCC layouts, it seems to me that there is always a mass of conductive tape, with soldered leads flying off to all the track work. Do you find this useful? Do you feel that it saves time, or is more effective than conventional wiring?

 

Richard

Link to comment
  • RMweb Premium

bcnPete, the layout will be completed - I have accepted an invitation to the Basingstoke show next March, so it needs to be presentable for then. Hopefully, now the rewiring is complete I can now make a start on the scenery. The layout has spent most if its life upside-down so I could work on the wiring. That is why I did not want to start scenic work just yet. Once I start on the scenic side it should not take long as there are only about 5 buildings to make. I am also experimenting with 3D printing for part of the station platforms, but more of that later.

 

RichardW1, 2mm finescale track does not use rail joiners, and the rail has a small cross section, so it is good practice to have lots of power feeds to each length of rail. This is not a DCC thing, but it is beneficial for DCC wiring too. On previous layouts I have used twin-and-earth mains cable, stripped to just the copper, soldered to small brass screws forming bus-bars beneath the tracks, then soldered fine dropper wires from the rail down through the baseboard to the nearest bit of bus-bar. Although effective, it took effort and a large soldering iron to work with the thick copper wire. Using the copper tape has proved a quicker and easier method, and so far has worked OK. It is still there after 3 years, although soldering near the end of a length of tape does upset the glue.

Link to comment
  • RMweb Gold

I had been thinking of trying servos but it does seem a bit troublesome. When I first used Tortoise motors they were so easy to fit and need no adjustment. We need a servo control that would do the same. Your solution of allowing the servos full travel seems to be a possible. Could you then operate them with a simple changeover switch? I am planning a mini layout that I will be able to take in the motorhome and room for tortoise motors will just not be there so I am considering what approach to use.

I will be nice if you get round to scenery. There is a lovely scene just down the line where the road bridge from Freshwater crosses the river. The one with the tidal doors and the church in the background. The old line is a lovely walk.

Don

Link to comment
  • RMweb Premium

Tortoises are very nice, but they are also very big and expensive. Cobalt motors operate the same way, and are smaller and, I think, cheaper, but still larger than a mini-servo. I might try them on my next layout (if I every get around to doing one).

 

Servos are controlled by varying width pulses, so you do need some electronics between an on/off switch and the servo. Merg do a simple Servo4 kit which can be used to control up to 4 servos from on/off switches. You will also need a set-up box (another Merg kit) or a computer with a serial port and modem cable to use some free software to set up (configure) the Servo4 initially. You have to set the throw and the speed for each servo during this configuration. Once set, you no longer need the set-up box or computer. For some reason, the Servo4 comes configured with zero throw, so until it is configured it looks like it is not working as the servos will not move when the switches are thrown.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...