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Scratch Building

See also DIY Casting and Wagon Making

The Choices...

Here I speak as a scratch builder who has always been so. Scratch building is not the easy option -however it may be the only option that you have if the object of your desires is to be realised. The first thing to do is to grab all and any information on the object, the internet is rife with JPGs etc -so mine it for them. The second thing to do is to start drawing... I have an A4 sketch pad that is plastered with doodles. Do not expect the first drawing to be correct, expect the tenth drawing to near it. What the drawings will tell you is what is going to be the best method of making your object. Once you have the finished drawing you can then place objects on it to see if they will fit or how much the drawing will have to be modified to make them fit.

As far as possible try to plan in modules. This will allow you some added flexibility as you will simply have to modify that module rather than the entire model. This allows you "get it wrong" without affecting anything too much. If this is your first piece of scratch building then I would advise you to work from a plan or home made scale drawing. Decorate your plan with information about where the parts are to come from and supplier parts. I own a set of plans for a PEAK 45 loco that has practically had to have an index... Locomotive Design Co supply plans and PDH drawing supply books of 00 scale drawings from which you may order specific drawings at any scale.

Do not be afraid of doing it differently to the original. It is a model and you must accept that. THUS it is quite permissible to make Diesel and Electric locomotives with plywood and plastic bodies. With a steam loco it does have to be metal due to the heat. Purists may wish to opt for Brass but Steel is cheaper. Boilers HAVE to be made of Copper in the UK as there is no existing certificate method for steel boilers. You may Weld, Braze, Rivet or Silver Solder the Copper together. But this operation does require minimum of two people -one of whose job will be to act as fire watch as the amount of heat used can set fire to nearby wood equipment or melt plastic equipment. Do not laugh -but I have the remains of a Workmate that was incinerated and a bottle torch whose controls melted into my gauntlets.

The next problem you will have -is how to power your model...


In the case of a live steam loco this means pistons, valve linkage etc. Only if you have either experience of building a live steam system or have the support of someone who has, would I say that you use this path. Every steam builder has their own favourite linkage to move the valves and I have to admit that mine is the Stephenson. This is because it is so simple and easy to make. The "typical" piston size is 1 inch stroke by 1/2 inch bore at a pressure of 80 psi. Your boiler shell will have to be pressure tested hydraulically at 200% working pressure and then tested at 150% working pressure with all the fittings installed. This test must be repeated every 14 months.

The G3S uses "the Orange Book" for boiler certification. If you are running at a GTG then the Insurance says that you must be certified -3BAR rule or not. If you run your loco privately you may by all means blow yourself up...

Gas tanks that are refillable (i.e. Ronson valves) have to have a certification that lasts for three years to the day. Non refillable disposable tanks do not require certification.

As a Scale we do have a few "byes" to help us...

The shell pressure test is conducted at twice the working pressure. This holds true for the lifetime of the shell. Should you alter the boiler (fit another bush or pipe) then the boiler has to be hydraulicly pressure tested again. The steam test is a t1 50% of the working pressure and this (due to a printing error) has to be preformed every 14 months -rather than 24 months.

However certain "scale parts cannot take the pressure of the steam test. The chief culprit of these are the gas regulators, these would explode at the pressures used. THUS they and similar items may be removed the ports blanked off if the additional pressure will ruin them. The pressure gauges are tested annually against a certified gauge and the true max pressure reading marked in red paint. There must be a drain cock fitted to the base of the water gauge to allow "blow down".


For some reason people seem to disparage the electric powered loco. At G3 scale most electric locos carry; a battery pack, an R/C system, and ESC. Allied to this there may be such things as smoke generators, sound cards etc. Yes there are track powered systems and OHL systems -the former more for exhibition layouts and the latter is for the dedicated... Having on board power raises the question -how much of it do I need? The manufacturers of the electric motor should be able to supply a few figures as to the working voltage and current requirements and most importantly the torque rating in gramme-cm. The major figure you are looking for is the one marked Stall, as this is the amount of force that the motor generates when it stalls (ie stops) under load. There "should" be a maximum current rating at this point that will define the size of the ESC and the cable ratings to take that much power. What some people refuse to realise is that a battery is also a bomb. If the battery shorts then the loco burns. Design your model for the battery pack to be easily removed for charging.


There have been some very successful models made at Gauge 1 -however as yet none at Gauge 3.

Building it

Assuming that you are going to build a steam outline model powered by electric motors -where do you source the parts from? You can quite easily find laser cutters who will cut your parts for you out of sheet ply or thin steel to produce bodywork from. The frames that you will mount everything on can come from the same sources or you can cut them from sheet with a hacksaw. Several people have used power scroll saws to make interior support frames for diesel locos. I normally use MDF for internal support partitions and then use thin ply and face that with sheet ABS for the exterior.

Rolling Stock

The shot below shows you the three completed practice pieces, all were made with simple hand tools.

The Practice Wagon

While building a scratch built loco is a work of dedication and lots of four letter words the humble wagon is something that you can use as a test object to hone your skills with. If you are new to G3 and have looked at the delectable wagon models from Williams Models and Garden Railway Specialist and then thought, "I can't afford that!" -you are probably right. However as time progresses you will find the price to be very realistic. If you are not sure if G3 is for you then try this simple wagon.

The wagon is based on the Railway Clearing House 5 plank, which at the time held the same social position on the railways as a road side skip does now... The wagon is made from pine strip wood bought from B+Q or Wickes -nothing special.

You will need

  • 6mmsq pine (2.4m)
  • 6x18mm pine (2.4m)
  • 6x35mm pine (2.4m)
  • 13mm brass tacks
  • hardboard nails
  • small sheet of 3 layer ply
  • M3 x 25 pan head screws
  • M6 x 30 BZP coach bolts
  • small piece of plastic sheet circa 60 thous thick.
  • 13mm plastic edging strip 1 metre.

Cut the piece of ply to produce a rectangle that is 225mm long and 110mm wide. Cut the front and side pieces from the length of 6x35mm to make the sides of the wagon. Groove the pieces on each side with a nail at 7mm intervals. Stick the sides to the base and edges to each other. Cut the edging strip and glue over the outside corners. Saw the 6x18 strip to make the stretchers of the wagon and the buffer beam. Ensure that the outer edge of the outer beam is 95mm from the other, this makes room for the wheels. Glue these to the wagon. Cut the 6mmsq strip to go from the base of the buffer beam to the top of the wagon end and glue it there. Drill 1.5mm holes in the 6mm sq strip in the centres of each "plank" at the end of the wagon. Gently file a slope on the sq piece so the top is thinner than the bottom. Glue Hardboard pins into these holes. Do not bother cutting the spare ends until the glue has set hard. Drill 1mm holes into the plastic edging on the wagon corners and glue in the brass pins. As above wait for the glue to set before trimming. File/grind the domed ends of the coach bolts flat. Drill the buffer beams to give 77mm separation of the M6 bolts. The "Oleos" that cover the threads can be made from any plastic tube -or wound tape. Some artistry with a file and grindstone will turn a penny washer into a hook which you can solder or epoxy to the M3 screw.

This is what your practice wagon should look like

The wagon can be expanded to produce a box car with the roof made from cardboard or thin flexible ply.

Wheels, axle guards, various dress up parts etc are available from Williams Models and Garden Railway Specialists. Both suppliers produce parts for RCH1923 wagons.

The following thee articles will show you the real life wagon in production. The things to think about while detailing your wagon by Mike Williams and the finely detailed scale model by John Candy.

The Practice Toad

No other guards van is so distinctive or well known. The std GWR Toad is a grey and white icon. However there exist several variations that have evolved after 1949. BREL "Crash Study" Pink striped grey Toads with blue and yellow chequers, Black Toads, Departmental Yellow Toads, Blue Toads, Green Toads etc etc!!! Whatever collection of wagons that your loco is pulling for some reason it always looks "correct" if there is a Toad at the end.

There are several suppliers of Toad kits and Toad dress up parts. The remains of the ply and wood used above will supply you with a Toad to practice with. Cut the base of the Toad to 333 x 110mm. Cut the sides to 333 x 85mm. Section out the rear platform at 115 x 100mm high. Cut the rear piece to 110 x 40mm. Cut the front piece 1100 x 100 (you want two of these). Round the two pieces with a fret saw to produce the curved roof. Assemble as above the runners are 6mm sq pine and the rear arch is cut from layers of 6mm sq pine. The roof is a piece of breakfast cereal packet glued into position.

The under frame is made from 12mm channel, (either aluminium, plastic or steel), or just plain wood strip.

What you do with your practice Toad is up to you but based on personal experience there are several suppliers of parts to complete your raw Toad with. The following is an article on fine detailing a Toad -again by John Candy

The Practice Hopper

This is based on the LMS 20 Tonne hopper wagon. Parts for this were common with the RCH1923 Wagon and this wagon is made from 60thous sheet ABS or Plastikard with Plastruct mouldings. You will need to made a large 90 degree frame to align sides with -this can be made from left-over ply and 6mm sq strip. At this point you will probably need to buy 5mm sq steel bar or brass U channel as this is used to make the hopper chassis frame.

This as such is the plan for the hopper.

The rear supports are glued to the base plates and angle Plastruct re-enforces the joint -as well as being correct to the hopper.

The rear support is then edged with flat Plastruct strip. You may glue on fake rivets as sold by Cambrian models if you like at this point because it will be easier to do so than further along assembly.

Make up a right angle assembly frame from scrap 6mmsq and ply. This will become a powerful tool for later use. Stick the sides to the base and re-enforce the angle joint with tape while it sets solid. Then do the other.

Stick the angles rear support to the ends.

It is now time to make the chassis frame. In this case it has been made from U section brass (as it was on sale at B+Q). The side runners are cut to the length of the rear supports -so that it rests on their ends. The four transverse pieces are cut to the width of the support pieces. You can either silver solder, this is advisable, or epoxy the pieces together.

The frame is now dropped onto the wagon body and aligned with the ends of the support pieces. Some heat distortion may have occurred so don't be afraid to twist and hammer until it does. Bond with epoxy the frame to the hopper body.

Here a set of GRS white metal axle castings for the RCH wagon have been bonded to the frame. Some additional Plastruct "I" girder has been stuck to the sides of the frame. More angle will be used to resemble the original at the corners.The buffer beam is as for the wagon.

If you have tried the above and found them to be, "well it's not THAT hard", then you can find plans for wagons and various others sold by Locomotive Design Co or start trawling the internet for the original drawings.

This is a drawing for the LMS10800 which was a unique loco but was based on US practice as a "Switcher". This evolved into the familiar BR class 20. It is given freely for you to use. If however you would like to try something else then the National 2.5GA sells a plan for a NER EF-1 under the name "NEaRLY". This was drawn in 1923 and the author won a prize for it -justifiably so! I have built this model, it actually was my first G3 loco. It has proved to be a very robust and trustworthy model. However it is easier to make the body out of 3mm ply than sheet tinplate....

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Page last modified on March 13, 2020, at 11:19 AM