Building O Gauge Online

At the kind of level of detail we have in this locomotive we are in to what is termed "Fine Scale". I have no wish to put anyone off coming up to this level in O Gauge, quite the contrary, the diesel and electric part of the hobby needs more of us. Everyone and everything starts somewhere and as a beginner at this level, something like this Class 31 locomotive could quite easily take you 12 to 18 months to build.

Sometimes, time spent looking and reading before engaging in a short period of building will pay huge dividends because you will appreciate fully the sequence of construction and how, often, the fitting of some parts will affect how other parts fit later in the build.  

So lets take a closer look at the cab units on this locomotive and highlight the areas of construction that need to be addressed. Below are a few photographs of one of the cab units, untouched by me other than to remove the paint by soaking in cellulose thinners.

The bottom left photograph above shows something that is actually quite difficult to achieve. The builder has managed to get a large blob of solder to fill a gap that is very nearly 1.5mm. If the kit needed support at this corner then Modern Motive Power would have included it. Solder is NOT designed to gap fill like this and cannot be relied upon to do so and retain strength - DO NOT use solder like filler.

The bottom right photograph shows  the underside of the cab unit. There are two basic mistakes here. The first is, there is way too much solder. In this example the builder has not even tried to remove the excess but there are countless numbers of pictures on various forums around the Internet that show just how hard some people work to remove what they have just applied. If your going to remove most of it, why apply it in the first place? The trick to good soldering and kit construction is to use the minimum required to do the job. Solder should flow like a liquid. It should not form clumps or solidify as you are applying it. With enough heat and flux that is suited to the job you should be able to apply a tiny amount of solder to the tip of the iron and then drag it along the joint. Most of the solder will end up within the joint and anything you leave at the edges will be a thin film and very easy to remove with a glass fibre pen. It should be noted that we do not use acid based fluxes that are commonly sold to modellers in various strengths. Our flux is water based, very mild and suited to all the materials commonly found in kits like this one. This flux is available in our WebShop.

The second mistake is a common one that most beginners and even some who should know better make. The rule of thumb is that if there is a half etched line, you fold into it so that it is on the inner face of the fold. This is not always the case, folds that are over 90 degrees and almost all 180 degree folds are normally done with the half etched part external. Here our original builder has made this classic mistake. Reference to the CAD drawings supplied with the kit and any reference photographs would have prevented this. If you do make this mistake (and we all have) you will usually only get one shot at putting it right and the fold will be weak so will need a bead of solder run into it to give it strength.

The above photograph shows the nickel silver parts from the cab bulkhead after removal. At some point our original builder has decided that soldering is not his thing. These items did have quite a lot of solder internally. It's not unusual to find thin folded items like these with solder along the internal edges of the joins, it helps them to retain their shape while fitting and soldering. As the builder has not managed to get any of the folds to be even close to 90 degrees quite a lot of the solder had run out and was making the fitting of some parts near impossible as some are designed to butt up against each other. To compound the problem the builder has decided glue is better than solder and has filled most of the items with epoxy resin, most of which was on the inside but significant amounts had found it's way onto the outer surfaces.  I hate glue. Unless you are prepared to put your hand deep into your pockets, most of the commonly available adhesives will not grip the surface of most metals enough to form a permanent bond. This shows up most on resin kits where the manufacturer has the builder applying lots of fine detail in metal or structural metal parts. Any movement of the more flexible resin or plastic will weaken the bond where the metal is attached. This coupled to the fact that some plastics and resins and many adhesives are not UV (ultra violet) stable is a recipe for disaster.

Here I suspect the parts were not clean when the adhesive was applied as it was easy to remove as the item in the centre of the photograph shows. All these parts needed the tabs that held them to the fret removed and the folds made as good as possible.

None of the castings survived. These had been both soldered and glued using an EvoStik type of adhesive. Luckily everything within the cab that was a casting is available in generous quantity in the Modern Motive Power - Diesel Locomotive Detailing Set, something all serious modellers of modern outline locomotives should have at least one of.

So, this brings us to the series of photographs below which show both cab units reconstructed. All the basic errors have been corrected although I introduced a new one by getting the chairs slightly wrong in one cab, see I told you we were all capable of it!

I have added all the pipe work to the various castings on the bulkhead. This is well worth doing and very easy, it's just basic forming of shapes using brass rod (0.45mm dia). If you want you could use copper wire of the right diameter which is slightly easier to form as it is softer. Drill all the castings to accept the rod or wire prior to fitting. These holes will provide an anchor point for the rod or wire while you solder it. Leave a small gap between the various pipes and the bulkhead, enough to get a cigarette paper between, this will aid painting them in the various colours later. Where a long run of rod or wire runs from roof to floor I have used small stand off's made from bits of scrap fret to keep the pipes clear of the bulkhead.

Everything you see here apart from the castings started life as a flat item on a fret. Fine scale modelling at this level is all about creating complex structures that are as close to the prototype as possible by combining lots of parts folded or laminated to achieve the end result. Plastic kits cannot and and never will be able to achieve anything like this level of detail. A lesson we can learn from our friends who model steam locomotives in 7mm fine scale , none of them are using plastic or resin for major body parts, why should we be different?