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Talk:0-6-0+0-6-0

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Fairlie?

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Is the Fairlie an 0-6-0+0-6-0 or an 0-6-6-0T (as most Fairlies) ? Andy Dingley (talk) 20:40, 18 September 2016 (UTC)[reply]

It seems to depend on its configuration. Single Fairlies with this wheel arrangement, with a six-wheeled engine unit and a six-wheeled unpowered bogie, would be 0-6-6, if such an engine existed. Double Fairlies, like the pair used in South Africa with their two swiveling six-wheeled engine units, were designated 0-6-0+0-6-0, like a Garratt. -- André Kritzinger (talk) 22:32, 18 September 2016 (UTC)[reply]

Single Fairlies are described as 0-6-4T or 0-4-4T under Whyte - their bogie articulation is simply ignored.

For double Fairlies, they are described as 0-4-4-0T or 0-4+4-0T^[1] The "+" rather surprised me, as I see this as bogies under a single rigid frame, and there is no connection between the bogies, but then the drawbar forces are taken directly by the nearest bogie, rather than the frame.

What I can't find though, are any sources describing the bogie units as "0-6-0" individually, i.e. the 0-6-0+0-6-0 form. Andy Dingley (talk) 00:13, 19 September 2016 (UTC)[reply]

The "+" in 0-4+4-0 would be quite right, except that it should most likely rather be 0-4-0+0-4-0. Remember, it's not bogies under a single rigid frame, it's separate complete swiveling engines with or without leading and trailing wheels. As on a Garratt, the inter-engine connection is the loco frame itself which permanently connects two separate swiveling engine units, not a drawbar or linkage connection between powered bogies as on most diesels and some electrics.

South Africa used only two Fairlie types, the three Modified Fairlie classes, the Class FC, Class FD and Class HF, which were apparently unique to South Africa (like the Union Garratt, an apparent attempt to bypass BP's Garratt patent), and one Double Fairlie class, the pair of CGR Fairlies. As to the Modified Fairlies, there seems to be agreement on the Garratt-type wheel arrangement notation.

In the Double Fairlie article, I altered the 0-6-0+0-6-0 notation in the article to 0-6-6-0 about two weeks after I created the article, because I "believed" the info contained in the article on 0-6-6-0. Then, during a major revision of the whole kaboodle of SA locos this year, I found that all three my main sources are unanimous on the wheel arrangement notation of the Cape Fairlies as 0-6-0+0-6-0. The quotes are verbatim.

Espitalier & Day: "The "Fairlie" engine of 1875 had a wheel arrangement of 0-6-0+0-6-0 and was built by the Yorkshire Engine Company..."^[2]

Frank Holland: "The Fairlie engine was built by the Avonside Engine Co and was of the 0-6-0+0-6-0 type."^[3]

Jean Dulez: "The Fairlie 0-6-0+0-6-0 design was built by Avonside and delivered in 1875, works double Nos 1096/1097, CGR No E7."^[4]

I strongly suspect that all references to Double Fairlies and Péchot-Bourdon locomotives in Mallet-type Whyte wheel arrangement notations are in error. The only difference between Double Fairlies, Péchot-Bourdon locomotives and Garratts are their upper structure designs – in respect of their engine units, they are all identical in principle. I can't speak for Single Fairlies, really, but from what little I know about them, they should all fit into the more usual three-digit Whyte notations like 0-4-2, 0-4-4, 0-6-4 and the like. -- André Kritzinger (talk) 14:19, 19 September 2016 (UTC)[reply]

In summary, it seems to me that the distinction between the Mallet-mode and Garratt-mode of wheel arrangement description arose from their construction. On a Mallet, only the front engine unit swivels while the rear engine unit is rigid in relation to the locomotive frame. On a Garratt and similar designs like the Kitson-Meyer, Union Garratt, Double Fairlie and Modified Fairlie, both engine units swivel. I suspect that this distinction was what led to the Cape's Double Fairlies of 1876 being described as 0-6-0+0-6-0 and not 0-6-6-0. André Kritzinger (talk) 18:07, 1 November 2016 (UTC)[reply]