A general view of the Elvin stoker coal distribution head. Note the two mechanical shovels.
The Elvin Mechanical Stoker
The Elvin type of stoker was available in the 1920s. The whole system was somewhat different to the more traditional form of mechanical stoker. It is to be assumed that as the device was not a great success as it seems not to have been generally adopted despite the manufacturer's claims for superiority over other stoker systems. Notably it was claimed to lead to greater fuel efficiency.
As was often Porta's approach he advocated the adoption of technologies which, first time around, had either been a failure or were just never very popular. The Kordina being an example. In the case of the Elvin stoker reference to it and the Patadon type can be found in several of Porta's locomotive proposals, including his to the A1 Trust in the UK.
Specifically Porta referred to the stoker system head - that is the final coal distribution system. As is recorded elsewhere, for example David Wardale's book on the Red Devil etc, Porta did not favour the more common type of mechanical stoker system where coal is distributed around the grate by coal jets. It was one of his observations that the Gas Producer Combustion System often performed best when hand fired. However with high output locos hand firing is not an option and even on lower output locos mechanical firing is desirable. So following a comprehensive review of the technical documentation on stoker types Porta recommended future development of mechanical stoker distribution systems focus on the Elvin and Patadon types. No data is to hand on the Patadon type however a little is available on the Elvin type as shown below.
No steam distribution jets are used, rather the coal is flung from the distribution table by mechanical shovels, the idea being it mimics, as closely as possible to action of a shovel in the hands of a fireman. The system also makes it easier to achieve a washbowl shaped fire important with modern applications of GPCS.
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A general view of the Elvin stoker coal distribution head. Note the two mechanical shovels. |
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A plan view showing the distribution effected by one shovel. |
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For historical interest here is a full Elvin stoker schematic. Click on the image to view an enlarged version (97kb). Readers are free to speculate as to the potential weak spots in the design! |
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Also for historical interest this book 'The Elvin Mechanical Stoker - Road Service Hand Book' is available here in Adobe PDF format. (2.59MB) |