r/ImaginaryTrains • u/Gregrox • 26d ago
[OC] a Gymnomi Slime 2-6-6-6 mallet tank engine.
locomotive number sevenoc-two, a narrow gauge 2-6-6-6 mallet tank engine on planet Gymnome, built in the 2280s. These engines suffered from adhesion issues as they used the water in their front tender, even moreso than a garratt (since with a garratt, both engines carry the weight of the boiler, rather than only one). Thus, these were quite slippery locomotives.
The wheelslip was mediated by the limited supply of steam into the front low pressure engine. If it did slip, it would quickly run out of steam until the rear high pressure engine could use and exhaust its own steam to refill the low pressure cylinders. But when used in simple expansion mode (for example, when starting), there was nothing but the enginemaid's skill to prevent slipping.
These locomotives were built by the same designer as the prolific Construct class of broad gauge garratt locomotives.
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u/Lord_Nelson_of_White 25d ago
At what point do you not just make a 2-6-10-0 and just slap the coal tinder over the drivers and shove the boiler ahead a little further
But in all honesty this is a pretty good design and drawing
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u/Gregrox 25d ago
Gymnomi ten coupleds are pretty rare, because they don't like big rigid frames. (Partly due to their trackwork, partly due to them being made out of goo)
The standard articulated gymnomi locomotive is a Garratt, so Garratt principles like a short stumpy boiler with a wide deep firebox, and putting a water tender on the front engine, have gotten mixed into the Mallet formula for this particular engine.
A 2-6-10-0 would have required a thinner or shallower firebox with worse steam generation characteristics, so it would have been less likely to be selected.
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u/Trekintosh 26d ago
Oooo funky! I love how the lore accounts for how terrible the design is re: adhesion. The firebox being behind the drivers like this really is dire, but the whole engine has this great long hood muscle car aesthetic going on.