Talk:Caledonian Railway 72 Class

Classification

I am struggling with the classification of these engines. The 72 Class is OK but the others are a muddle. According to BR Database [1] BR 54461 to 54476 are all 113 Class. According to Rail UK [2] they are 713 and 918 Classes. Can anyone explain? Biscuittin (talk) 15:53, 21 June 2012 (UTC)

The British Locomotive Catalogue 1825-1923 by David Baxter (vol.4 pp.100-101) has them all as the same class with identical dimensions but in two series. The first series (Nos. 113-124 BR 54461-66) were built at St Rollox works whereas the second series (Nos. 928-937 BR 54467-76) were built by the North British Locomotive Company. I have no idea where '918' comes from. --Das48 (talk) 16:33, 21 June 2012 (UTC)

Baxter shows (p.91) that the Caley 918 Class were 4-6-0, not 4-4-0. McIntosh, built 1906. --Redrose64 (talk) 18:00, 21 June 2012 (UTC)

Thank you. Biscuittin (talk) 18:20, 21 June 2012 (UTC)

Pressure conversions

There seems to be something wrong with Wikipedia's pressure conversion system: 175 psi (1,210 kPa), 180 psi (1,200 kPa) - higher in psi but lower in kPa. I make them 1,207 kPa and 1,241 kPa repectively, using the factor given at Pascal (unit). Biscuittin (talk) 18:32, 21 June 2012 (UTC)

It's to do with the number of significant figures. 175 has 3 sig fig, but 180 has two (the 0 doesn't count). On conversion, they're rounded to the same degree of precision, so 1,210 has 3 sig fig (the 0 doesn't count) and 1,200 has two (the 00 don't count). You can force the accuracy by adding a final positional parameter: |0| gives 175 psi (1,207 kPa), 180 psi (1,241 kPa) whilst |-1| gives 175 psi (1,210 kPa), 180 psi (1,240 kPa). I'd go with the latter because it maintains the consistency of three significant figures. --Redrose64 (talk) 19:21, 21 June 2012 (UTC)

Thank you. Biscuittin (talk) 19:37, 21 June 2012 (UTC)