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
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.
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.