It was, Michael, because I’d not known it had happened until I tried to contact the firm.

…

Julie –

I took a short cruise on the paddle-steamer ‘Waverley’ a couple of weeks ago. Her expansion-links and die-blocks are even more complicated than a locomotive’s, possibly for relatively easy maintenance as you can’t always just stop a ship in mid-ocean to repair the main engines! The link is double, with two parallel but side-by-side rather than fore-and-aft bars joined by bolts and spacers; and the die-blocks are flanged round the bar sides. Lots of bronze blocks and pads, too.

I think my far simpler engine will use gauge-plate or mild-steel expansion-links with either leaded-bronze or cast-iron die blocks.

I have used cast-iron for the split big-end journals, running on the mild-steel crankshaft. Well, I say mild-steel… it was heavy and rusty. It would not have been some exotic alloy certificated to the nth degree, neither is it free-cutting, but my source was a scrapped axle from a restored, narrow-gauge quarry tramway wagon of unknown make and age.

Though drawing my engine parts using Alibre, I can’t design the entire engine, or the rest of the steam-wagon, that way. I might be able to use TurboCAD in orthographic mode for plotting the valve-gear, as the 2D option is good for geometrical constructions. Otherwise I’d need do so by hand. TC in 2D is also good for General Arrangements, but even in its 3D model mode, I think the “Deluxe” edition at least, lacks the sort of animation feature built into Alibre Atom. (“Deluxe” is the name IMSI gives to its basic editions of TurboCAD!)

My design guide is K.N. Harris’ version of LBSC’s Stephenson’s Link Motion for his Maid of Kent 5″-gauge locomotive. I’ve also a copy of Martin Evans’ Manual of Model Steam Locomotive Construction, for some indication of port dimensions, etc.; and our club has a useful library of assorted full-size and model engineering text-books.

Although I had copied in Alibre, Harris’ expansion-link design, I realised the simpler end-suspended form with that end taking the fore-gear, as on a traction-engine, is appropriate, because road vehicles don’t run in reverse very much. I wonder if may even be slightly more efficient because the suspension-link is relatively a lot longer, reducing the lateral displacement. That redrawing was difficult because the original was dimensioned very awkwardly, needing plenty of arithmetic to untangle.

To be honest I don’t know what valve-gear my originals, by Hindley, used because the inverted-vertical engine is enclosed! So I can take some liberties with its design, and only you and I would know. However, one of the few archive photographs shows the rear of the engine had two curious little (pressed-steel?) excrescences on its “quickly detachable cover” (quoting the catalogue). By their positions I suspect these gave clearance for the ends of the expansion-links of Stephenson’s Link Motion.

Ironically off-topic on my own question!

I have just acquired a “simple” construction for part of Stephenson’s Link Motion but to be honest my projejct is highly speculative and I am forever making replacement parts, or modifying ones already long made.