Steam loco air and vacuum brake hose siting.

Someone, hopefully might know the answer to this. Looking at a loco head on the vacuum brake hose is to by tradition to the left of the draw hook on locos built on lines that were built using that system only. Locos originally built for lines using air brakes only also had them on the same side. However, when vacuum braked locos were additionally fitted with air brakes as well - LNER K2 2-6-0s come to mind here - the vacuum hose was shifted to the right of the draw hook and the air hose fitted to the left. With air braked locos fitted additionally with vacuum brakes - LB&SCR Atlantics for example - the air hose stayed where it was on the left and the vacuum hose placed to the right. So why the shifting of vacuum brake hoses on originally built vacuum brake only built locos?

 

Can I add a supplementary question (or two)? How are the hoses arranged on coaches and wagons? Does this have a bearing on how they are arranged on the locos?

Steve B

 

I'm not sure it is as clear cut as you are making out. For example, looking at some SR vac-only locos, those derived from Eastleigh practice (such as the S15 or Q) have the vac bag on the right of the draw hook, as did many Drummond locos. I've seen Maunsell moguls with vac bags in both orientations relative to the draw hook, though I haven't gone so far as to see if there is correlation between side and whether the loco was either (a) Brighton or Ashford built or (b) originally RH or LH drive.

All of which suggests to me that there is an element of drawing office custom involved, rather than any specific standard. I wonder whether @Steve B is onto something when considering the match up between position of the hoses on a loco and on the carriages from the same company.

Tom