Saturday, July 30, 2022

How I constructed a Glyn Valley Tramway Glyn loco



After carefully studying the drawings in Bernard Rocket's excellent book (Glyn Valley Locomotives: 16mm scale drawings, Theodore Press, 2007) and various photos of the Beyer Peacock Glyn, my next job was to figure out how to break it down into pieces which could be 3D printed. Normally, I try to ensure that, where possible, flat sided parts are printed horizontally to minimise the layering effects which are inevitable with 3D printing. However, as the bodies of the GVT tram locos have curved corners, I decided to try creating the sections of the body so they would print vertically. 

3D Drawing

The body was broken down into six main sections: the skirt, the lower body, the smokebox, the cab, the tank and boiler tops and the roof. Smaller parts such as the smokebox door, chimney, toolbox, doorways and sandboxes were drawn separately. I used Tinkercad, which is my preferred 3D CAD package having tried others and, although I mastered their main drawing techniques, I struggled to produce viable (ie printable) parts. 

As can be seen, the 'tools' in Tinkercad are basic shapes which are reshaped and joined together. If you think about it, a steam locomotive is basically a few cuboids and cylinder shapes bolted together.

OK, there is a bit more to it than that, but you get the general idea.

Once all the parts had been drawn and joined together virtually on-screen to make sure they fitted together ....

.... the individual parts were exported as .STL files, imported into my slicer program (Cura) and then transferred to my 3D printer to be printed out.


The actual construction of the loco was very straightforward. I decided to use the motor block from a Bachmann Streetcar - because I happened to have a couple in my bits-box. Of course, any powered chassis or motor block/bogie can be used as the skirts hide a multitude of sins (unless you decide to construct the model with its skirt flaps raised).

My first task was to remove the track pick-ups from the motor block as my model would be battery powered. The block was disassembled, by removing the six screws holding it together.

The tiny screws holding the spring wipers were removed .....

..... and the harness was then taken out completely (and put into another bits-box - who knows when it might become useful?)

The motor block was then re-assembled ...

After a test-fit, I realised I needed to cut additional slots in the running plate of the main body-part for the wheels, if the block was to sit at the right height for the skirt. This was achieved with my trusty razor saw.

The block was now a cosy fit.

The skirt was now glued to the underside of the running plate.
NOTE: I use thick (High Viscosity) superglue from Tool Station (but make sure you go through the age verification process or it won't be delivered!)

.... and the motor block checked again to make sure the body was the correct height above the track.

Holes were marked and drilled for M3 screws to hold the block in place ....

..... and nuts were screwed on. It's not often I have such an easy solution to attaching my loco bodies to their motor blocks!

The smokebox door was then glued into place 

Then I realised I needed to cut a couple of notches in the front of the tanks behind the smokebox to clear the wheels of the motor block (if your moto block doesn't have such large wheels then you won't need to do this).

The smokebox and front of the tanks could then be glued into place.

The tank/boiler top section was then test fitted. As I wanted this to be removable, I glued a couple of pieces of 2mm thick plasticard to the insides of the tanks to stop it from slipping down (just visible on the left of this picture.

The cab was now glued into place. It took a bit of jiggling to make sure it was sitting accurately on the body but hopefully its position is fairly easy to figure out - it has to butt up to the tank top section so make sure this is in place before gluing the cab.

The insert into the base of the cab roof was then glued in, making sure it was centrally located. Note that the cut-outs are aligned with the front of the roof (where the ventilation holes are placed) to give clearance for the cab windows.

The access flaps were then glued into their spaces in the skirt. Note how the step hole aligns with the door of the cab .......

..... and just forward of the door into the smokebox section. You could glue these in the open position but that might reveal that you have no cylinders, coupling rods or motion).

The cab door was then attached (handle to the rear) .....

.... as was the door to the smokebox section (handle to the front). These can be glued open if you so wish - quite a few photos show these doors left open when the locos were running.

The chimney was then glued into place.

With the body more or less complete, I turned my attention to the trailing bogie. This is not essential as it will be hardly visible beneath the skits, but I'll know it's there. I used a set of IP Engineering 20mm dia wheels (again because they were in another Bits Box). The axle was placed in the slot and the pivot piece was glued into place.

The pivot for the bogie was then bolted on using the same screws holding the motor block into place. If you are using a different chassis or motor block you may need to make your own arrangements (or not fit the bogie at all - it isn't essential - and does take extra faffing when placing the loco on the track).

A self-tapping screw was used as a pivot.

After gluing the toolbox on the the right hand side of the tank top, just ahead of the filler, the loco was now in a state to be test-run. A temporary battery pack was fitted and wired-up with a make-do on-off switch.

Finishing and painting

The main disadvantage of printing items vertically is the clearly visible striations which mar an otherwise smooth surface. I noticed that additional ripples seemed to emanate from the rivet heads.

These undulations required a fair bit of rubbing-down and some filling with Squadron White Putty in order to get a reasonably smooth finish. The body was then given a couple of coats of primer (Halford's grey) from a rattle can aerosol before being rubbed down again and at least three coats of Halford's satin black were applied.

The backhead was also painted black with detailed picked out on gold, copper and red. NOTE: This was printed on my cheaper lower quality printer which is why the finish is not as smooth.

Nameplates were drawn in Tinkercad and printed out using a resin printer to provide finer detail.


I used my tried-and tested approach to wiring up the loco.

Three 18650 li-ion cells with tags (from Ecolux) were wired-up through a 3S battery protection board to act as a power-source.

Holes were drilled through the running plate for the charge socket and switch ......

..... and then everything was wired-up to a Micron MR603a receiver/controller. This is compatible with Deltang equipment which enables me to continue using my Deltang transmitters which, until now, have been my go-to radio control system ( see Getting started with Deltang).

The floor of the tanks section was raised 7mm using an offcut of PVC foamboard, to provide clearance for the top of the motor block and wheels.

The loco could now be tested more thoroughly.

Satisfied that all seemed well, I added 3D printed loco lamps to the front and rear, fitted with 5mm bi-colour red/white LEDs. These were wired-up to output pads 1 and 2 on the MR603 to provide directional lighting. which changes colour dependent on whether the loco runs forwards or in reverse. 

I also added a MyLocoSound British Steam soundcard - wired up as below. The trigger for the whistle on the soundcard was connected to output pad C on the MR603. The speaker was mounted in the roof of the cab which is where I usually place them as it allows the sound to escape, it is fairly unobtrusive and easily accessible.
Buffers and my own less obtrusive LGB style hook and loop couplings were added so the loco was now ready for some serious test running.


The GVT Beyer Peacock loco seems to me to be a really good choice for someone wanting to try their hand at creating a battery powered steam outline loco to run on their railway. The cavernous body provides plenty of room for batteries, radio control equipment and a soundcard. The skirts mean that any sort of 45mm or 32mm gauge powered chassis or motor block could be used,

I have, however, been finding that the Bachmann streetcar motor block I have used is somewhat under-powered when compared with my other locos which use LGB motor blocks. Presumably, streetcars don't really need to be powerful as they usually tow nothing more than a single trailer. I might experiment with using a different motor block - I do have a slightly larger wheelbase USAt block in the Bits Box - or alternatively, I might even explore constructing my own chassis.

However, in the meantime, I am enjoying watching an all-black loco chuffing around the garden.


All the .STL files for the loco can be downloaded from the forum
NOTE: You will need to register with the forum to access the 3D files download section where there are a large number of rolling stock and lineside accessories available for free download.

There is no registration fee for the forum but if you feel you would like to make a contribution to its upkeep and running then there is a link to the forum's PayPal account in the introduction to the 3D print files section