By Martin Haywood

Having been hankering for a Simplex of some kind for a while, my intrigue as to the quality of 3D printed models, and an impending 16mm WWI military event, seemed a good opportunity to obtain one. For those who rejoice in round numbers, this project coincided with the 100 year anniversary of the very first Simplexes being deployed in France.

What do you receive from the 3D printer?

Plastic but fantastic: No machining tags or sprue to sand down. It is not sold as a working piece so there are no instructions included.

Firstly, a lot of credit goes to Simon Dawson of Rue d’Étropal who designs his own scale representations of WWI railway items and sells through the Shapeways website. This particular model is extraordinarily strong and remarkably light, with only very minor structural flexibility at the brake wheel and radiator pipe supports. All very charming and well detailed, but it’s immediately apparent this little workhorse is not ready to run! So, what do I need to do it, and what do I want to do to it?

A minor fault in the model is that a notch needs to be cut in the bonnet for the radiator pipe. A round file barely dented the plastic so it got brutishly hacked out with a craft saw and pliers. The radiator grills are from wire mesh, followed by a plasticard fan bracket and a fan from a 1:18 scale car.

Painting and detailing

Rather than sourcing a specific colour, I had a half-empty olive drab matt acrylic spray can (Humbrol no.155) that needed using up. The plastic has a slightly grainy feel and took the paint in like an old friend. A second coat was only required in order to get into the nooks and crannies. No primer was used. If the green spray wasn’t available at the time it would currently be in grey and black guise, similar to the real-life example at IWM Duxford.

Hooked pins glued into drilled out plasticard offcuts make the couplings, which are in turn superglued to the frame. Although perfectly functional I would prefer the model to have prototypical couplings pre-fitted or provided as a spare add-on.

With the loco now starting to look the part it was time to add a few extra details: a chequered footplate (scored plasticard) and clutch pedal (bent O gauge wagon brake shoe), followed by direction and gear levers which are bent sewing pins attached to the inside of the bonnet.

Basic detailing picked out in black helps break up the mass of green.

The driver is an alien

The 3.75” tall range of Space Precinct figures, which are out of production but widely and cheaply available second-hand, populate much of the railway. Modified with craft tools, ‘Jasper’ has been cut to fit the accurate but awkward low seat. Once posed in a happy position his legs and hips have been superglued, with only his arms and head left movable for direction changes. His helmet and gas mask holder are Blu-Tack, with straps made from a brown paper envelope.

Would you guess they were twins? Before and after hand painting in acrylic using small custom mixes of colours.


This is the difficult bit. Having used Faller Mini Play-Train (set no.3515) chassis on several occasions, they are perfect for slow-running small locos. No cutting or modifying will be done to the underside of the Simplex.

The Faller 3515 chassis has its motor positioned vertically in the cab, requiring a lot of surgery to make it fit the Simplex.

As I will be slinging the motor horizontally, gear side down, the Faller chassis needs to be cut in two. The non-motor end will need trimming back near to the axle supports as the motor will occupy this space. Most of the plastic frame and guards at the motor end have to go, with great care not to cut, saw or break the gear and plastic wheels. It is advisable to continually trial the positioning, and test that the motor works between incisions.

The motor end was superglued, first taking note of squaring to the axleboxes and height simultaneously. Because I know I will only get one chance to fit this, I find that applying a bit too much superglue (just so it pools) gives a little bit more time for minor adjustments before it cures and you’re stuck for good. It isn’t a precise way of working but an ugly joint out of view is of no concern. The same method applies to the non-motor end – just check everything before committing to the glue. In honesty mine is slightly out of true laterally, but it is close enough to run smoothly.

The axles only just aligned inside the axleboxes. There is some play in the non-motor end which can tolerate some horizontal and vertical errors.

The motor slants towards the front end, but not too low as to dig into debris between the rails.

An electrical circuit for the minimalist

The battery holder was constructed using the Faller terminals nut-and-bolted to a plasticard piece that fits under the bonnet. The original wires from the motor are stripped back, wrapped around the bolts and squeezed up to the holder by each nut. No soldering and no switches. To turn on, put the battery in. To turn off, take the battery out. Reverse is achieved by flipping the battery around.

There is enough room under the bonnet to use AA rather than AAA if you want more power.

The finished model in operation weighs just 120g and powered by a rechargeable 1.2V AAA, which may be considered to be a bit light and weak. That said, it does deceive with its pulling ability – comfortably capable of hauling seven empty Tri-ang Big Big tipper wagons up minor gradients.

Finished but not finished

This project was achieved over two days (including paint drying time), and I’m very pleased how ‘Daisy Cutter’ turned out. Typically this isn’t to be the end of the story, with deliberations to be made over number plates, hinging the bonnet, adding engine parts, covering the wheels and weathering and so on.

Post construction showcase

Notable websites

Rue d’Étropal:

Model Simplex 7-tipper haulage demo:

2017 Addendum

A year on from completion and the petrol tractor now sports LR199 plates from Narrow Planet. It has become a regular runner on the railway and, apart from recharging the battery, has so far required no maintenance or repairs.

Model Simplex short film