Timber

You have a few choices. A 4mm wheel will probably do the job with an extended axle. According to my maths a 80" wheel in S Scale is 31.7mm diameter. in 4mm scale 31.7mm is equivalent to 7'11". So you need to finsd a 7'11" 4mm wheel ideally OO or EM with a decent tread and put it on a axle that will allow the right B2B. Alan Gibson makes a 8' wheel. This will be close enough, but he will not supply the axles or at least he did not last time I asked. So you will need to get someone to cut 1/8 steel bar to the right length so that you can push the wheels on to give you the right back to back. Alternatively if you get the wheels I could 3D print centres that would enable a Markit S Sclae axle to fit. But that would come with a caution that these are big wheels and any plastic wheel of this size is going to be relatively weak....On the S Scale forum page there are some examples of my wheels - the most recent with a video clip is in the "what is on your bench" blog. You then need to fit crank pins. These should be chosen depending on existing crank pin diameter - I like Markits but I am sure others will do the job. You also need to think about pickups....if the existing wheels are steel for pickup purposes you will need a wire to get from the tyre to the axle. If the pickup is off the tyre then these may need to be adjusted with a new tyre - but this should not be too difficult. The above is just a suggestion, it may not work as I have not seen your model but as with all things there is usually an answer. Hope that helps.

Next up is fitting the compensation beams. There are two on the etch. They fit through the chassis using two 10BA screws with a half nut acting as a spacer between the compensation beam and the side of frame. The beam is held in place with a nut and the screw cut to length then soldered,

Finally on this leading wheel a 6BA bolt is used to provide the rocking compensation. A bolt is held on both sides of the frame with 2 nuts, only the bottom nut is soldered (taking care not to solder the bolt). Top nut is then removed. Bolt can be cut to length later in the build. The bolt runs on the wheel axle, not pretty but it works fine for me.

Early prototypes had a splasher behind this leading wheel. There is a strip on the etch to make this. Simply role the strip and using an old 3'6" wheel possition so that the splashe is 1mm from the wheel, I find it easier to solder the curve and then cut, The bottom of the splasher has a small lip away from the wheel.

Once in possition the top is folded onto the "n" and soldered. This provides 1.5mm of metal for the wheel to run on both sides...dressing out with a file may be necessary as this wheel sits low in the "hornblock.

Starting at the front of the frames, the first thing to do is to make the "hornblocks" for the leading 3'6" wheel. On the etch there are two small "n" shape etches. These are soldered into the frame below the fold.

Thank you for the feedback Joseph but I am planning to offer these only in S Scale - just simply sharing what I make for myself. If anyone wants to reuse then that is great if not then that is fine also.

The rails are folded and soldered flat.....

All folds are into the etch. The bearing and hornblocks are a little different, I have used a system where Gibson bearings fall into rails and then are folded into spaces in the chassis. The system works, there is maybe a little more lateral movement than other systems but it is very simple and for me works fine. If required the rails can be removed and High Level hornblock and bearings used. This will require more alignment as the folds in the Gibson bearing system help maintain alignment.

Starting with the chassis. This is a single etch that can either be folded for pickup operation or seperated to use the frames for split axle. The chassis is simply folded, placed on a flat surface top side down and then soldered.

Thx The locomotive is a simple build, the boiler and fittings are all available in a single 3D print. As with any print it will require a little smoothing.

The second is for the Tender. This is a larger etch as it includes the parts for early and late variations and also the parts for both straight and curved steps, The Albion had curved steps whereas its sister locomotive the Volunteer class (that I am also building) had straight steps.... I have not itemised all the parts on this etch...I will explain when I get to that part of the build.

The etches are on two sheets. Both 0.45mm NS. The first is for the locomotive.

Whilst there are many photos and articles on the internet, accurate drawing information was relatively hard to find. The basis of the locomotive design is taken friom HMRS drawing number 26238 (Albion 2-4-0 small passenger) and HMRS 25461 1200 gallon 4 wheel tender. The challenge with the HMRS locomotive drawing is that it is an early GA and there are discrepancies between the drawing and early photos. These discrepancies are in the boiler design not the overall dimensions. To reflect later builds of the engine I found the drawing on page 60 of Russell's "A pictorial record of Great western Absorbed Engines" the most useful and one that i refered back to on many occasions. From what I have learnt, whilst the locomotives did go through various rebuilds, the boiler dimensions did not change. Only the exterior only the boiler fittings, chimney, cab and tenders changed. I have 3D parts for both early and late fittings.

The locomotive is best known as the Cambrian "Albion" Class locomotive but the design was used extensively across many companies. My model is of the Brecon and Merthyr USK and WYE locomotives. I am not sure if the B&M locomotives every carried a closed cab but I have added one to the etch as most of these locomotives where rebuilt with close cabs at some point in their life. Many finished life being converted to tank locomotives. There are many articles and photos on internet for this locomotive but the best link I have found that is a good picture summary of most of the locomotives built to this design can be found on page two of this tribute to Rev Awrdry of Sodar island fame. Click on the link page and scroll through the photos. https://sodorislandforums.com/thread/6234/agents-reports?page=2

Over the next few weeks I will detail the build of the following locomotive using etched and 3D printed parts. The parts are available to members at cost. Where possible the model has been built to scale. However, similar to my other models it is a very simple representation of the prototype. The overall construction is very simple and can be improved if required. The chassis is for pickup operation but could easily be adapted for split axle. The available parts support closed and open cab versions of this locomotive together with parts to make early and late versions of the tender.

if you look at some of my S Scale blog posts I have examples of driving wheels I have made using Fusion 360......you may need to use a top end 3D printer via shapeways to ensure concentricity but anything is possible. There are other examples on RMWeb of people doing similar things.

wonderful CAD work (and modelling)......what do you do for wheels?

Fantastic thank you! - the loco is non restored I picked it up at auction for as modest price compared to a Gauge 1 equivalent.....

It is a Hornby motor through a HL Gearbox. The thing that has made the most significant improvement to my locos performance is the pickup system I am using. I have started using plunger contacts from http://www.coda-systems.co.uk/catalog/info_PC7BS.html. They are not cheap - but the quality of operation is better than anything else I have used. There are no moving parts in the chassis so decent sized wire can be used to connect the pickup to the motor. I use the pickups with the lightest spring. It sits in an insulated 2mm wheel bearing from Markits. Chassis is drilled out 3mm after painting and the plastic bearing superglued to the frame. I connect the wires before fitting as the bearing cannot take any heat. Hornby motors are great value for money. I have to modify the HL Gearbox by using a tapered reamer to open up the motor mounting. I make it a tight push then super glue the motor in as there are no fixing holes. But it seems to hold firm and true.

Thx - Etches are etched with beading....the splashers are 3D brass prints as an integrated piece with the springs. Here is a clip of it running....

Not so many post recently so I thought I would get our mojo back and post what is on my bench....It is a rebuild of a Sharp Stewart Small Saddle Tank for the B&M. I built one a few years back but this is a complete rebuild with 3D printed body and Saddle Tank together with 3D printed wheels. The coupling rods are temporary and will be properly joined rather than joined on a crank pin. It has a very long High Level Gear set with a Hornby Motor under the Saddle. I will post an update when it is finished.

I am starting to build an S Scale model of a Old I Class MW and found this article very inspirational. Super model engineering.

A masterpiece.....my model may not be so good :-). But very good shots. Thank you.

composite sir, my mistake