Highland Railway brake van

As my first step in modelling the Highland Railway pre-grouping, I thought I would start with an iconic Highland 6-wheel goods brake van, from the Lochgorm kit. The etch is reduced from 7mm and 4mm scales, but has proved a practical proposition. (For an example build in 7mm, see petesworkshop).

Construction is nearly complete: I still need to fit the chimney, handrails and couplings. Some filling is needed around the "birdcage" lookout. Most of the brake rigging is missing, but I don't think it would be visible. There should be tie rods between the bottoms of the W-irons, but I don't see how to fit these without inhibiting movement of the W-irons.

Axleboxes and springs are not included in the kit. I built them up in plasticard and fixed them around the footboards. They are much reduced in depth to allow for movement of the W-iron assemblies. The J-hangers are included in the kit but I soon gave up trying to put them together in this scale! Instead I made some crude replacements from plasticard and lengths of wire (still quite fiddly). They don't stand up to close scrutiny but at least there is something there!

The third photo shows the underside of the van. I build the chassis basically as described in the kit instructions. Each axle is fitted in its own W-iron assembly. The rightmost of these is rigidly soldered to the van floor. The leftmost is held by fold-down tabs that allow the axle to pivot in the centre. The centre assembly is allowed both to pivot and to move side-to-side (I had to file some material off the inside of the solebars and the backs of the top-hat bearings to allow this). It is held by a 0.010" steel spring wire which is soldered to fold-down tabs at either end. It runs up and down my Inverneuk layout ok, but time will tell if this system works satisfactorily out "in the wild". Wheels are 2mm Association coach wheels.

Judith Edge 06 shunter

I have been working on and off for several months on a Barclay Class 06 shunter, based around an etch from Judith Edge (shot down from 4mm).

First stage was to build up the main bodyshell using the parts provided:

This prototype has a rather narrow bonnet (something like 7mm inside width) that won't fit most types of motor, so it presents something of a challenge to design a workable mechanism. Particularly as it is my first scratchbuilt chassis!

The next photo shows the body attached to the basic structure of the chassis. The frames are made from thin PCB, and spacers are solid brass (as per Nigel Cliffe's DY1 article). The Judith Edge etch does include frames but I wanted to use the PCB method with solid brass spacers to maximise weight.

The third photo shows the spacers more clearly. They are tapped for the 12BA screws that hold the frames on - the screw heads will be hidden behind steps eventually. They are drilled to a clearance fit for two further screws which attach to captive nuts on the top of the footplate (inside the cab and front bonnet), thus holding the body and chassis together. The third axle bearing in each frame will support the jackshaft.

I decided to try one of Nigel Lawton's "micro-motors" as these are narrow enough to fit in the bonnet, thus keeping the cab empty. I spent quite a considerable time pondering how to fit in a mechanism and also experimenting with how to mount the motor etc. I settled on the arrangement you see below, with a 3-stage reduction. The initial stage is via one of Nigel Lawton's rubber band drives, followed by a conventional Association 21:1 worm, and finally 14:20 spur gears. The latter are the new metric M0.3 gears, as these had the most suitable diameters. Due to the narrow width I was severely limited in the choice of gears to fit on the wormwheel cross-shaft. There was also a limitation due to the rather small 7mm driving wheels. The overall reduction works out at something like 108:1.

The intermediate gear shafts are held in a simple "gearbox" folded up from a scrap part of the kit etch. The "motor mount" is simply a piece of PCB hollowed out to an interference fit. It is bolted on to the gearbox so that the whole can be dismantled and the motor and/or rubber band drive can be replaced. Notice also the resistor between the motor and frame, recommended because these motors are rated only for 6V.

Amazingly, the mechanism now fits inside the body. However, it is rather temperamental, and I'm in the process of "tweaking" the setup to get the motor to turn happily in both directions. I got it to work initially but rather infuriatingly ruined the alignment somehow while modifying it to fit in the body! The problem is that the gearbox needs bending slightly to achieve minimum resistance on the worm and the correct meshing distance for the gears. In theory this will allow me to correct for my inaccuracy in marking, drilling and folding it up. In practice it is remarkably difficult to get right. Hopefully I will be able to get it turning OK, fit the wheels, and be able to move along the track! I'm not particularly confident in its running abilities, but it is after all my first chassis.

More on Building Construction

I found this photo of one of my low relief warehouses/sheds under construction. As you can see, the main structure is built out of styrene sheet. It's based on a photo of a prototype at Dingwall.

You can also see my method for representing the corrugated-iron roof. I glued a sequence of lengths of wire to a piece of plastic with suitable spacing. To produce the sheeting, a piece of aluminium foil is cut from a suitable piece of scrap food packaging (shown left). This is thicker than usual kitchen foil, helping the rigidity of the finished sheet. It is pressed by hand over the wire former with the help of a fingernail in each groove. The resulting sheet of "corrugated iron" is then glued on to the building and painted.

Below is the finished building in place on the layout (the green building). Using metal foil rather than scribed plastic --which I had previously used for the goods shed roof--allowed me to model the exposed end of the corrugated sheet, along with the collapsing gutter!

Putting in the Stops

At long last, I've added a buffer stop to the siding in front of the goods shed.

Rather than use one of the new Association etches, this one is scratchbuilt, based on a Highland Railway example (plate 162 of "Highland Miscellany by Peter Tatlow; drawings by the same author of what appears to be the same stop are in the Highland Railway Journal No.10, 1989). Bullhead rail was bent to shape and soldered to form each side of the structure (8 pieces in all). The 1'x1' timber baulk is laminated from two lengths of PCB point sleeper.

Picture Post

With a new camera I'm now able to take pictures again, so here are some of the layout in its current state. There are a few more details needed but it's getting there.

First Steps in DCC

I've finally taken the plunge and purchased an NCE Power Cab system (from Digitrains). This comes with everything you need to get started except a locomotive decoder.

As a first experiment I have converted a brand new Farish Class 24. This is an ideal choice as it is "DCC ready", meaning there is an internal circuit board with standard 6-pin decoder socket, and no need to modify the chassis. The socket comes fitted with a "blanking plug" for ordinary analogue operation.

I believe the idea is to buy a decoder with an integral 6-pin plug and simply plug it in. However, the decoder I bought at the same time as the system was a Digitrax DZ125 without a plug, just with 7 bare wires. These are colour-coded as follows, where the first column gives the numbers of the (labelled) sockets on the loco PCB, according to the NMRA standard:

1 (orange) motor right

2 (gray) motor left

3 (red) right rail

4 (black) left rail

5 (white) front light

6 (yellow) rear light

- (blue) light common

Note that there are 7 wires but only 6 sockets. The blue wire is not needed - the standard is apparently such that if it is not connected then the lights are supplied using the track as the common instead. As I had no plug I unsoldered the socket from the loco and soldered the individual wire ends instead (a bit fiddly and not what the maker intended!). The decoder sits happily where the blanking plug was initially located.

(Note: Sorry there are no photos as my camera is broken).

With some trepidation I assembled a circle of Setrack (the wheels have not been changed yet), put the loco on the rails, connected the Power Cab, and turned it on. It picked up the loco straightaway with the default factory address of "3," and I was able to drive it away with no further ado. One benefit of DCC showed immediately: I could turn the headlights on or off independently of whether the loco was moving (well, it impressed me anyway). When you change the direction on the controller, the lights change colour too.

I then followed the "Getting started" instructions in the Power Cab manual to easily program a long address for the Class 24. In the default state the operation was not smooth, increasing in 28 discrete steps from standstill to ridiculously fast. I expected it to be a lot of work to remedy this, but in fact it was simple. Following the instructions in the manual again (at least to begin with), I rapidly obtained fantastic running by programming the Class 24's decoder through the following procedure:

(1) Change the start voltage - configuration variable (CV) 2: I tried increasing this in single steps (these variables take values from 1 t0 255) until the loco just starts moving on speed step 1 (initially there was not enough voltage until speed step 2).

(2) Change the maximum voltage CV5: I lowered this to get a more reasonable top speed.

(3) Change the mid speed voltage CV6: I put this mid-way between my new values for CV2 and CV5 (not sure if it was necessary to set this independently).

With these settings the loco was able to run at a reasonable range of speeds, from an incredibly slow crawl to a reasonable pace. I then got adventurous and fiddled with CV3 (acceleration rate) and CV4 (deceleration). By default these are set to 0 so the loco moves instantly at the new speed, creating an undesirable jerky effect. By setting a non-zero acceleration I found that the loco could move very smoothly from one speed to the next, despite the fact that there are only 28 discrete speed steps on the controller. Nice. I opted for only a small deceleration rate so that the braking is also smooth, but is quick enough that I can control where the loco stops.

That concludes my DCC experiences so far. Unfortunately I only have one "chipped" loco as yet, so I can't experiment with controlling multiple locos at once. Although, on Inverneuk this will be something of a challenge. Time to order a decoder for the 08 I think...

Seen at Model Rail Scotland

I spent an enjoyable day at the SECC last weekend including a stint on the 2mm stand with Inverneuk.

Andrew Peggie managed to film Mick Simpson's Class 25 at work shunting the yard...