How I constructed a pair of diesel locos from downloaded 3D files

Having acquired a 3D printer (see How I assembled my (very) cheap 3D printer) and printed out various small items for the railway, I felt the need to tackle something a bit more ambitious. On Thingiverse, I discovered Arockstone had uploaded the parts needed to make a small diesel loco based on an IP Engineering motorised chassis. In addition, Clarionut had made some additions and modifications to the parts to produce a slight variation on the basic loco.

The parts for both the original loco and the variant were downloaded and printed out. They were cleverly drawn so that for most of the parts, no additional supports were needed, apart from the cab roof and the handrails. I eventually gave up on the hand rails as I decided they were very fragile and I decided they could easily be made from brass rod.

A .pdf document describing the construction process as also downloaded and I used this to guide the assembly of the parts. 

The underframe was constructed first ......

A straightforward process of joining five parts together using, in my case, thick (High Viscosity) Superglue from Tool Station.

The four sides of the cab were then attached, .....

...... followed by the three sides of the engine compartment.

For one of the locos, I bought the IP Engineering budget chassis kit recommended in the instructions but, for the second loco, I decided to use the 3D printed chassis supplied with the kit. Brass top-hat bearings (from IP Engineering) were inserted into the axle holes.

20 mm diameter wheels and axles were bought from IP Engineering as was a small motor and some gears. These were put together using the relevant holes in the chassis frame.

From past experience, I have learned that the pulling power of such a chassis is greatly enhanced if Delrin 8-tooth sprockets and chain are added. These were purchased from MotionCo and, after a bit of fiddling, fitted to the chassis.

At this stage, I decided to do the wiring. I found that two 14500 (AA sized) lithium cells fitted snugly inside the control panel in the cab which is provided with the variant, together with a Deltang Rx65b receiver/controller.

A SPDT slide switch was fitted to the aperture at the base of the panel fascia.

The charge socket was positioned between the wheels on one side of the loco.

The wiring for this loco follows my usual pattern, the only difference being that I replaced the toggle switch with a slide switch:

The two component parts of the bonnet top were then glued together and slotted into the top of the engine compartment.

After some test running to ensure that the loco ran smoothly, the mechanism and wheels were masked with tape ready for a visit to the paint shop.

A couple of coats of Halfords grey primer were applied from a rattle-can aerosol. These were carefully rubbed down .........

......and another couple of coats applied.

The underframe and cab interior were then masked .........

...... and a couple of coats of Halfords Rover Brooklands Green applied from a rattle-can aerosol.

The underframe was then brush-painted with black acrylics and the buffer beams picked out in red, 

Various details were now added, such as the windows......

...... the exhaust pipes. .......

..... and headlamps, which were fitted with tiny LEDs.

As I decided not to try fitting the 3D printed handrails (which I found tricky to print and then tidy-up), I painted some cast whitemetal handrail knobs (from Garden Railway Specialists) the same shade of green .....

...... and threaded some 1.5mm diameter brass rod through them.

Holes were drilled in the cab sides ........

...... and the handrails glued into place with thick superglue. The excess handrails were snipped off after the glue had set.

The diesels were then coupled-up ..........

...... and given a few test runs.

I then decided to install couplings and buffers so they could be used with my rolling stock. As the buffer for the stock on my railway is higher than the buffer-beams on the locos, I created some risers for the buffer beams from plasticard .......

..... on to which the buffers could be attached

Bespoke hook and loop couplings based on my generic design were then fashioned from wire and attached to the buffer beams at the requisite height to engage with those on my other stock.

..... and more test running was carried out.

At first, only one loco was powered but it soon became apparent that, to cope with the 1:40 gradients on my railway, both would need to have motors installed, and so the second loco was duly equipped - with its motor connected to the output from the Deltang Rx65b.

In addition, name and number plates were designed in TinkerCAD and 3D printed.

The diesels have entered service and do stirling work on the Copper or and Sand Quarry trains.

Conclusion

Since constructing these diesels, I have gone on to designing my own locos in TinkerCAD and printing them out - see for example, How I constructed a Schull and Skibbereen Nasmyth and Wilson loco. One of the things I have learned from constructing these little diesels is to ensure that the loco is broken down into a series of parts which are simple to print, with no (or the bare minimum) of support structures needed.

I have not, as yet, started producing my own powered chassis - I generally use motor blocks from ready-to-run locos. But my next project will be to design, draw and 3D print a complete loco from scratch.