All the explanations I have seen for fireless locomotives state only they use hot water and steam, the same principle as bottled l.p.g., so I wonder how a mix of steam and compressed-air would work. Indeed, if it would work at all.
Steam alone, without water, would not work: the pressure and temperature would drop far too rapidly.
Compressed-air supplied via a pressure-regulating valve (distinct from and upstream of, the locomotive’s regulator) would be more effective but still have a rather short range. The elaborate unit in the cab of the Ambérieu example suggests this mode; but could such a pressure-regulator have been applied to using steam as well, to keep the reservoir conditions stable?
I’d guess the Austrian locomotive was intended for hotwater / steam operation.
Wikipedia states they used steam or air, not both.
Try this for a direct, authoritative, answer:
http://www.theengineer.co.uk/content/in-depth/the-week-in-1914
which credits Andrew Barclay & Sons, of Kilmarnock, as pioneering these locomotives, and building 114 of them (at time of original press, in 1914). It also states these could stand in steam for a day, and move the normally short distances back for re-charging at as low as 15psi!
An extra safety feature cited by The Engineer, and new knowledge to me, was that the rubbing surfaces and buffers had special facings to prevent sparks. Particularly important in highly-gaseous areas, or sites like Holton Heath that made and used raw nitro-glycerine, one of the least stable of compounds.
Holton Heath was the Admiralty’s main factory for the gun propellant ‘Cordite’, based, like Dynamite, on nitro-glycerine and a stabiliser. The site was derelict for many years but is now a modern industrial-estate. The main Weymouth-Poole-London line passes it, with a halt used at peak times; and for some years a private siding branched off there to serve a fertiliser warehouse.
Note that comment about the optionally-extra Brakes in Hudson’s own catalogue. I can’t imagine many advertising types these days being that candid!
The description refers to ball-bearing axle-boxes. Those at Norden have roller-bearings, but it’s entirely possible Hudson modified the design, or the Norden ones were by a different manufacturer.
I understand there is somewhere near Norden a former tramway tunnel under the main Wareham – Swanage road. I don’t know where, so have not seen it, but it is apparently one of the oldest railway tunnels in the country – which would mean oldest anywhere.
Norden is some miles inland but one of the tramways crossed the heath to a pier on a remote part of Poole Harbour. I can just remember seeing what I now know was a Hunslet diesel locomotive working at Norden, in the early-1960s so probably not long before these narrow-gauge railways became disused.
The Ball-clay, white and very fine-grained, does not occur in Purbeck in broad strata or spreads like many sedimentary rocks, but in discrete, scattered lenses in river-sands and gravels, hence the large number and scatter of the mines and (now) opencast quarries. It should not be confused with the white “clay tips” around St. Austell. That is not clay but highly-pure silica sand, and I surprised it was ever a waste product from that area’s ball-clay mines.
I used a piece of scrapped axle from one of these wagons for my Steam-wagon’s single-piece crankshaft. I have no idea of the steel’s grade, but it turns very nicely with HSS tools.