First things first. True Mallets are compound locomotives, so the front cylinder shape has to be modified. From the Backwoods fret, select another rear bunker which has bending lines and cut two rectangles to the correct size and bend them to obtain the cylinder shape.

Sand or file off all the details of the cylinder ends of the front chassis.

Now for the cylinder ends. Cut two pieces of thin sheet and solder them together. Drill a hole in the centre and turn on a mandrel and sand until round and the right diameter. Separate, fill the holes with solder, sand flat and punch the bolts around the cover with a sharp point or rivet tool.

Its not perfect but very small!

the Roco as delivered

the valve gear is not perfect but better than most

the nub of the matter....the motor is retained by the boiler casting which is very bulky.

Rear chassis

The cab and rear bunker just pull off. There are two plastic covers on the tank tops where the fillers are modelled. Remove these and you can then unscrew. Everything then falls apart including the motor! Unscrew the keeper plate and remove the wheelsets and cylinders.

Now saw off the front section a shown below. Best to wrap the gear train with Selotape to prevent ingress of filings.

Then remove the motor cradle using a cutoff blade. Best to keep cutting along the line until thin enough to break off. You will have to let it cool a few times though.

Destruction is over now. Wash the chassis in white spirit to remove any dust, then warm water and detergent.

Now replace the wheels, cylinders and keeper plate. The chassis needs to be wired up now. I have left the wires long as I will be fitting a chip soon. Now just stick on the motor and the cylinders with 5minute epoxy. There you have it, the rear chassis complete. Now we have to make the attachment to the body.

Check that the chassis fits into the body. Relieve any impediment with a cutoff disc and burrs. Using another bit of the Backwoods kit that has a fold line, make a small bracket for the rear mount. A nut is already soldered onto the body section.

Drill through the centre of the cylinders with a 1.6mm drill.

The front support is made from thick Plasticard. This will glue perfectly well to the brass with epoxy provided the brass is roughed up with the sander and the plastic cross hatched with a scriber. Obviously the chassis must sit parallel to the body.

Now glue the rear of the keeper plate to the rear brass bracket. Take care to avoid getting glue onto the gear and that the chassis is dead centred. Once hard, two additional brackets are glued on. Remember, both chassis hang on this fixing. When the chassis is removed, these brackets are also soldered.

The front is fastened onto the plastic with the two short self tapping screws that were removed from the body when dismantling the loco. Drill through with a 1.3mm bit and fasten the chassis onto the body.

Front chassis

This is almost total destruction! The chassis, sadly, cannot be motorised. Completely strip the chassis, remove the gears and chop off the end and motor bearing as shown below and reassemble. Any, you now have a lot of spare parts! Glue the cylinders into place. There has to be a great deal of weight bearing down onto this chassis to make sure the wheels go round. Thanks heavens for lead shot!

Oops! I have just realised that I cannot have a steps soldered under the side tanks. They would foul the swinging bogie. That was why I had steps  on the front and then forgot why!

Stick on the front rear bogie support. The rubbing strake is a thin wire which is sanded down so that the loco is level.

Glue front pilot to chassis and then the new cylinder wrappings. Check that all wheels are contacting the ground. This is essential. 

Above is the flexible joint between the two chassis. It is built onto two plates which glue to the chassis ends.

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The front pilot is completed with the fitting of a Langley cowcatcher, Greenwich coupling which is side sprung. The photo above shows the locomotive negotiating a 12" radius. Lead shot is added to fill the water tanks, and bunkers.

Weight distribution between front and rear is a big issue. The minimum weight should be added to the front to ensure that the wheels go round on the front bogie. The maximum weight is needed at the rear to gain traction. I have had to play around with this a little until obtaining an acceptable distribution.

Space has to be left for the DCC chip. the rear buffer beam, cowcatcher, detail and coupling is also added.

Unlike the prototype, completely out of scale hands will pick up this engine. If mishandled, the front bogie would be torn off. We have fitted  a retaining plate to prevent this. When on the track, the surfaces do not contact.

the front bogie retaining plates.

A good clean and the loco goes for priming with U-Pol Acid #8

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Time to ship it off for painting and lining.

painting tips

I will never use mat black on models. Always add some white. I prefer weathered locos, and the photo below shows the start of the process.

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