In my previous post, describing my design method, I wrote:  “This method also means that I do not need to make any of my own measurements but simply rely on the drawing being accurate and traceable”

 

A lot of early railway drawings were far from accurate!  I found the following in a collection belonging to William Strickland, an American architect:

 

 

According to Wikipedia, “William Strickland's Reports are the starting point of American railway engineering, and represent the state of knowledge as the first railways were planned in that country." - so that’s where they went wrong 🤠

 

I should also add a caveat that the drawings I use need to be complete.  In the case of ‘Eagle’, there is only the side-elevation by E.T. Lane, so a lot of details that might be be revealed by plan and end-elevation views remain as guesswork. This guesswork can, however, be informed by other sources of information.

 

There are fortunately more drawings of the contemporary engine ‘Aeolus’, albeit from a different manufacturer. The general layout of items such as smokebox doors and back-head controls can be assumed to have been reasonably standard at that time, so I drew on my earlier model of ‘Aeolus’ for these details. I also know that ‘Eagle’ was based on similar engines built by Sharp, Roberts & Co. for the standard gauge. This knowledge enabled me to make further deductions about the layout of the frames, which were inside the wheels for the broad-gauge.

 

In addition, there is the curious omission of springs on the rear axle in the ‘Lane’ drawing, although springs are clearly shown on similar standard-gauge engines from the same builder. Even more curious is that the much later drawing by G.F. Bird (Locomotive Magazine 1901) of the sister engine ‘Lion’ also omits rear springs.! I strongly suspect that, although purporting to be ‘Lion’, this Bird drawing was actually based on Lane’s earlier drawing of ‘Eagle’, although the Sharp, Roberts valve gear, shown on the Lane drawing, is missing.

 

 

‘Lion’ – drawn by G.F. Bird – Locomotive Magazine 1901

 

I made the decision to add rear springs to my 3D model.

 

Splashers

 

To return to the problem of modelling splashers … I have tackled similar splashers on other broad-gauge engines but those shown in the Lane drawing pose additional problems. There appear to be no backs to the splashers, which removes any potential means of support in a model. The drawing does not indicate how these splashers were attached to the frames of the engine, either.

 

After some thought, I adopted the following method:

 

I first traced the outline of the outside valance from the Lane drawing and used this to extrude into a solid component of 4 mm depth.

 

Splasher Component based on Lane drawing

 

This gave me a robust structure to place over the wheels but which needed thinning on the underside to clear the wheel flanges. I moved this component into position relative to the rest of the model and added extensions on the inside, to butt up against the main frames of the engine. I also reduced the thickness by using the ‘offset’ tool on the underside faces, so that the splashers would be clear of the wheel flanges. Finally I added some tabs to the extensions which I intended to fit into matching slots cut into the frames. I have often complained about the absence of alignment tabs on commercial kits, so I felt that I should not make the same omission on my own model!

 

Underside of splasher after adding extensions

 

Now, after adding various details, including springs, buffers, and lines of rivets, which are easily created with the aid of the ‘pattern on path’ tool, I had a set of components ready for printing.

 

My 3D model of Eagle in Fusion 360

 

One further detail that I have considered is the ‘box’ that appears behind the smokebox in the Lane drawing, where the front axle might normally have been expected to be placed. According to Ahrons (‘British Steam Locomotive’, p.39): “The exhaust passages of Sharp's engines of 1839-1842 were peculiar. Both exhausts were discharged from the cylinders into a cubical box placed midway between the inside cylinders, and the blast pipe was connected to the top of this box, which was intended to act as a form of " air vessel " to equalise the blast. It caused considerable back pressure in the cylinders.” I am guessing that this may be the box shown in the Lane drawing behind the forks of the valve gear.

 

Printing

 

That’s the hard part finished, so now it’s a matter of exporting the files for each of my components from ‘Fusion 360’ into the slicing program ‘Cura’  I use this program to align each component in an appropriate orientation on my printer bed and I also check the ‘preview’, after slicing, to ensure that all the parts should print correctly. At this stage, I found that the driving wheel spokes were a little too narrow, so went back to Fusion 360 and used the face offset tool to increase the spoke widths by 0.1 mm.

 

After these minor adjustments, it was then simply a case of loading the GCODE files onto a memory card, inserting this into the printer, selecting a file on the touch screen, and pressing the ‘Print’ button.

 

After several short printing sessions, my ‘kit of parts’ looked like this:

 

3D-printed Collection of Parts

 

I was especially interested to see whether my planned method of assembling the frames and splashers would work. The slots in the frames needed a little cleaning out with a scalpel but, after that, everything fitted together neatly. The splashers themselves are very fine and not too robust – this will not be a model for the grandchildren to play with!

 

Frames and Splashers after assembly

 

I used my now-standard method of applying a low-temperature soldering iron to ‘weld’ the splashers to their associated frames.

 

Using a soldering iron to join the splashers to the frames

 

I was pleasantly surprised by how well my printer managed the boiler fittings, including the safety valve housing, which is only 1.6 mm diameter.

 

3D-printed Dome and Safety Valve Cover

 

The boiler, smokebox, and firebox fit together over a 14 mm diameter brass tube, which provides weight to the model and aligns these parts on a common axis:

 

3D-printed Boiler, Frame, and Wheels

 

Chasssis

 

Next, I need to think about assembling the chassis. Because I only have a side-elevation drawing, there will have to be some informed guesswork, especially as the drawing gives no information about boiler supports or other structures.

 

I shall pause here and do some more research before continuing with painting and final assembly.

 

Mike