Maintaining gauge along the length of the turnout switch blades can be a bit of a problem so I’ve decided to use some of Bill Bedford’s brass slide chairs. We’ll use one either side of the tie bar (to avoid melting the plastic slide chairs when the tie bars are soldered in place), together with another one or two along the length of the switch rail. All the others will be C&L plastic slide chairs. The photo shows the brass and plastic slide chairs.
I’ve finally sorted out the catchbox design for the lever frame, so I think I’m on the home run with the lever frames. Both the locking frames have been fitted into their final positions, and I’ve attached the signal box lever frame, and satisfied myself that everything will work when I finally assemble the whole lot.
However, having assembled the signal box lever frame with its locking frame, I’ve come to the conclusion that the drive mechanism connecting the levers to the tappets (using 1mm diameter wire) is not positive enough - there’s too much spring in the mechanism, so that it’s not entirely clear whether a lever is locked, or whether it’s just a bit stiff to move. This seems to be a recipe for disaster if anybody unfamiliar with the locking sequence tries to pull a locked lever - something will break.
I’ve devised a better solution using a stirrup made of 4mm by 0.5mm nickel silver strip folded into a long U shape. An 8 BA bolt in the end of the U provides the attachment to, and the adjustment for the tappets in the locking frame. A few hours work, and I’ve made and fitted the 32 new stirrups - a great improvement on the brass wire.
March 2013. This month seems to have gone very quickly, with seemingly not a huge amount of progress. We have finished fixing the cosmetic chairs and the slide chairs, as well as starting work on fitting the tie bars. The main area of progress has been painting the sides of the rails a rusty colour - not the most interesting of tasks, but complete now.
I haven’t made a lot of progress on the lever frame - the main thing left is to make the catch handles and catch boxes for the signal box frame.
Chris has started work on the footbridge. We have a Churchward Models kit, which is a pretty good representation of the bridge at Plumpton - and as good as we can get I think, without scratchbuilding.
I have worked out what I want to do with the base-boards, and we should be ready to start construction in May - hopefully it will be warmer by then,
Finally, I have drawn out my wiring diagram. The turnouts, signals and gates will be operated electrically from the lever frame, and in addition there will be switches for section control, Alex-Jackson electromagnets, and two sound modules for whistles. At some point in the future I intend to build block instruments and bells for communication with the fiddle yards, so I need to add some wiring for that as well.
The principles of my wiring are as follows:
- a control box containing transformers for various voltages (5V AC, 15V AC, and 21V DC) with separate transformers for the loco controllers. Mains power is restricted to this lockable box for safety, and is nowhere else on the layout (ie no mains powered transformers under the layout or control panel).
- 5V AC, 15 V AC, 21 V DC feeds to the control panel and all the baseboards to provide different voltages for different applications
- common earth for trackwork, so only one wire is required for each section
- a ‘control’ earth to be wired throughout the layout to provide the earth for the loco controllers (ie the common earth from the track)
- a separate ‘technical’ earth to provide a separate earth for turnout motors, AJ’s etc. The two earths are joined together at the control panel, and connected to mains earth. Experience shows that earthing all these functions together on the layout can cause back-feed through the loco controllers (so that locos move when turnouts are operated). Joining them together closer to mains earth avoids this problem.
- turnout and signal motors to be powered from either 5V AC or 15V AC line (depending on the motor), using diodes to switch polarity and hence reverse the direction of the motor. This requires only one wire from the lever frame to the motor.
- AJ’s powered from the 21V DC line.
- self isolating sidings, so that when a turnout is thrown against a siding, locos in that siding cannot run.
I’ve successfully used computer ‘D’ connectors on Brighton Road so will use the same technique again. These have the advantage of being relatively cheap, and in a variety of sizes (9, 15, 23 and 37 pin), but the pins are fairly fragile so care has to be taken when connecting the plugs and sockets. They are fine for relatively low current DC applications, but I don't know about DCC which uses higher current.
I like to use a coherent colour system for the wiring, so that as far as possible, the wire for a particular function (a turnout for example) is the same colour all the way from the lever frame to the motor. The cheapest way to get a large variety of coloured wire is to buy computer cable designed for the D connectors - for example 36 way cable, with 36 distinct colours, and to strip off the outer sleeving.