Our next planned outing should be TINGS near Leamington Spa in early September although the show web site is curiously shy about our presence and that of another 2FS layout of this parish which I'm told will be in attendance.
There are still a few more buildings needed and some of these may appear before September but I think it's time to make a start on another aspect (get it?) of the infrastructure - the signals.
St Ruth needs a lot of signals so there is zero chance that they will be finished any time soon but they certainly won't get finished until we start on them.
The first thing we need is a plan. This has been work in progress for a long time - the original plan was created before the control panel and then drawn using a PCB design tool. The printout became the template for the control panel. Our understanding of the way we will operate St Ruth has now moved on so there have been some changes such as adding full running signals to allow departures via the east crossover. I re-drew the control panel overlay using some free software called 'Dia'. The new plan is rather closer to the conventions used by the drawing office at Reading but it wasn't possible to get it exactly right because of limitations of the tool.
Here is a PDF of the new plan. It is oddly shaped in places because it needs to fit over the existing switches on the control panel. struthsigplan.pdf
We've tried to avoid inventing our own arrangements and have tried to find precedents from the prototype as much as possible. It's probably best described as a hybrid of the pre and post 1938 plans for Penzance with the addition of the branch line and goods loop. The signals for the east crossover are based on the postwar arrangement at Newquay which also gives us an excuse for a GWR backing signal. The trickiest part was the branch because there doesn't seem to be a perfect precedent for a single line junction joining a double track line within the limits of a terminus station. The closest I've found is the arrangement of the spur from Barnstaple North into Barnstaple Junction but it's not a perfect match and is only partly GWR.
I am sure that signalling lawyers could pick hols in the plan but we've done our best to stick to the rules and get it right. Looking at the plan again I am thinking of some further minor changes - arm 62 might become a disc because it only covers shunt moves unless the branch points fail again and 65 should probably be lower than 15. The three doll bracket might also gain a slotted distant arm for the next box to the east.
So far we have one signal which is mostly finished. This is the starting signal from the arrivals platform (number 68) and is one of the very few single arm signals on the plan. It has the extra advantages of lacking a rule 55 diamond and having its balance weights hidden below platform level. The intention is to operate all of the signals using servos as described in MRJ 201. This signal has been fitted with a servo on a test rig and seems to work OK.
The signal also has a working lamp. This consists of a tiny white LED to which some enamelled wire is soldered. This is contained inside a short length of heat shrink sleeving in which two holes are drilled for the lens and backlight. A short length of 1mm styrene rod is pushed into the top and the whole thing painted black. It is pretty close to the shape of a GW signal lamp but perhaps a little 'chunky'. The power feed for the lamp comes via a resistor under the baseboard and then up the ladder as
described in the 2mm handbook. The lamp man's platform is some thin double sided PCB with one side used for structural solder joints and the other side used for the lamp power feed.
There is still some more 'development' work to do. We haven't yet finalised our servo controller approach. I used a 555 timer circuit (see photo) to get the thing working initially and we tried out a MERG SERVO4 unit yesterday. There will be some more head scratching about powering the LEDs on multi-arm signals because the easy thing to do would be to wire them in parallel but I'm told that having LEDs in parallel sharing a single resistor is a bad idea. I'm sure that using the first few signals at a real exhibition will also reveal some more problems for us to think about. The jury is still out on the colour for the post. I tried metalcote 'steel' but this was too dark so the signal was repainted in light grey which looks less wrong. I now have some metalcote 'aluminium' which I will try on the next signal.
Here are some pics of the signal on its test rig and temporarily fitted to the platform at St Ruth. The clear signal was a bit of a cheat because the photo was taken before the servo was fitted. The servo is now in place, albeit with no controller or wiring yet.
Now I'm working on the second signal. This one is rather more complex and provides lots of new challenges for me to think about, but more about that another day.