A. Horlock and Co. 0-4-0 (2020 Lockdown Challenge Loco)

[musket the dog]

Hello Everyone,

If you can cast your mind back to the height of lockdown in the UK last year there was a design competition posted on the forum, the the prize being a motor block of your choosing to help bring a prospective design to fruition.

2020 Design Competition

My proposal was for a A. Horlock and Company 0-4-0, freelance but heavily inspired by the original locomotives of the Padarn Railway. Happily, one of these locomotives survives, the Fire Queen of 1848.

Fire Queen

A few years prior to the competition I had already sketched out a rough plan for the locomotive using the Autodesk CAD program. Like a 2D sketch I used the 3D CAD to roughly arrange the Hartland Mack motor block and the original wheels to check I could create something that would be vaguely recognisable as a Padarn loco but in keeping with the proportions of the rest of my stock. It had always been a bit of a 'definitely,maybe one day' project, it was part of the fictional history of my railway but not in keeping with the era I wanted to model. The competition was a good excuse to look at actually getting around to making it and to my pleasant surprise I won.



I never get around to anything quickly and so here we are over a year later beginning to make a start. Jonathan (who ran the competition) was kind enough to also supply me with a set of 58mm driving wheels for the locomotive. This required a slight redesign of the loco as originally I had planned on using a set of LGB wheels from one of their small 4 wheel motor blocks.




I took the opportunity to redesign most of the loco in the end. The Holock locos have been described as being 4-wheeled versions of the Crampton type. One of the features that distinguishes Crampton locomotives is that they do not have frames like a conventional loco, instead everything is bolted to the boiler like a traction engine. The bigger wheels required me to change the boiler diameter, which in turn meant that I had to modify all the other components.

The model will be tender driven by the Mack block and the engine will free wheel. Having no frames there is no convenient way to leave the valve gear out and claim that it is hidden at the same time. I have attempted to model valve gear on my scratch builds in the past but have always bottled it in the end. There's really no escaping it with this engine though and so having meticulously studied the 'Handbook for Railway Steam Locomotive Enginemen' I gave it a go. Something I can do in CAD that I can't manage in a sketch is to animate the model. If I had got something wrong by either over or under constraining the valve gear, the model will not animate. I can then also use the model to show if any of the parts are colliding into each other and need tweaking.

 

[musket the dog]

My usual method of building is based around plasticard and plastic pipe, when making large flat surfaces, like a water tank, I prefer to start with a large, flat piece of material. Detailed components are are provided by white metal castings or 3D prints. This build will lean more towards 3D printing because of the technical aspects of the locomotive.

For boilers I use standard plastic plumbing pipe and this was the plan originally. However with the new wheels I could no longer get a 40mm pipe to fit and in my eyes 30mm pipe looked far too small. Instead I will print the boiler to 35mm. As well as the custom size, printing the boiler brings 2 additional benefits. The first is that I can include all the points that the boiler mounted components attach to into the model. All I need is a variety of holes, but I can remove the chance of me messing up a measurement and getting something in the wrong place. Any error in the location of the mountings will change the relationship between the wheels, pistons and valve gear. The second is that I can print the boiler with a icosidigonal (22 sided) cross section. This is so I can have nice flat surfaces to attach the miniature timber for the boiler cladding.



The first component off of the line was something a little smaller. On a previous build where I had also used a Mack motor block I printed inserts for the wheels to add axle extensions so I could make the loco outside framed. For the tender I designed a generic, vintage spoke pattern to push into the wheel. My install of CURA became corrupted and lost all of my printer settings. A single insert was printed while I am still recalibrating.

 

[Gareth]

A very interesting project I live a few miles from Penrhyn Castle and I am very familiar with the loco !! Its a real mis mash of locomotive technology and Maritime technology of the day. I can tell you one thing it use to have big problem it it slipped due to rail conditions The coupling rods frequently broke or buckled and as there was no frame as such vibration caused problems as well ! Her sister Jenny Lind had a make shift wooden cab . I don,t think Fire Queen had one . Keep up the good work I look forward to the end result !!

 

[musket the dog]

Another small update:

I've been having to self isolate for the last few days, which has provided me with a lot of time to keep the printer running.

I have been experimenting with some different size printer nozzles. The first I have been trying out is a 0.6mm nozzle (up from the standard 0.4). The benefits of a larger nozzle is to reduce print times on larger parts and provide a stronger bond between layers. This comes at the expense of layer detail. I have used the larger nozzle to build the larger parts of the structure; the boiler and the rear subframe. Detail here is not as important as the boiler will be clad in timber and the frame will be mostly hidden by the wheels.






The other size I have been trying out is 0.2mm (half the default size). This allows the print resolution to be pushed right down to a 0.06mm layer height at the expense of printing time. I have been trying out some detailed parts with the smaller head such as the front covers for the cylinders.