Talk:Blackburne Thrush

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Displacement

Bore and stroke given yield 116.8 cuin and 1913.5 cc, NOT the 88.97/1500 shown. AMCKen (talk) 06:22, 26 December 2010 (UTC)[reply]

Have you got a new reference that supports that claim? MilborneOne (talk) 13:05, 26 December 2010 (UTC)[reply]

It is not necessarily the displacement that is wrong, you need a ref to change this, not a calculator. - Ahunt (talk) 15:23, 27 December 2010 (UTC)[reply]

That's why I didn't change it. I want to know which numbers are the correct ones 'cause some or all of these were incorrect. I see Nimbus227 has obtained better figures than Lumsden. It was:

"Bore: 3.16 in (91.5 mm)" 91.5mm is nearer 3.6 inches

"Stroke: 3.78 in (97 mm)" 97mm is nearer 3.82 inches

Using the 'inches' gave c. 88.9cuin and c. 1457cc. The mm gave c. 1913cc (c. 116.8cuin)

Still, 81mm is nearer 3.19" than 3.16 and 96.8mm is nearer 3.81" than 3.78. In fact, I'd wager the engine was originally engineered at 3 3/16" by 3 13/16". : )

AMCKen (talk) 07:01, 31 December 2010 (UTC)[reply]

It is very hard to say what the original spec would have been, but keep in mind that manufacturing tolerances could be quite wide back then and that sets of oversized and undersized pistons and cylinders could have been matched to make working engines, creating a wide degree of variance in the actual manufactured bore, stroke and displacement. Also the displacement was probably measured using the oil method and not just calculated, meaning that while the stated bore and stokes could be "nominal" the displacement could be the average of engines measured or even just one single result, which would account for it not correlating to the calculator. Such are the methods in use when a lot of these engines were made. It means that all the numbers could be accurately measured and reported but not agree mathematically. It is precisely for these sorts of reasons that Wikipedia doesn't allow original research as instead of adding accuracy it maybe misrepresenting historical realities. - Ahunt (talk) 12:18, 31 December 2010 (UTC)[reply]

So the historical reality is that no one knows for sure what ANY engine really displaces? May as well go with the calculated value from the bore and stoke. : ) AMCKen (talk) 20:44, 1 January 2011 (UTC)[reply]

Well certainly there is a great degree of variance due to the factors mentioned above which is why we use the values given in a reliable source instead of using original research. - Ahunt (talk) 20:53, 1 January 2011 (UTC)[reply]