whatever the answers are, I will bet not one of them has a shred of evidence to support it! Most boilers I can think of have the feed exactly there. Only place I have not put one is on the smokebox end as I thought it would probably get too hot, but again nothing to support this by way of fact.

On my traction engines both the pump and injector feeds are part way down the boiler barrel, comfortably in front of the firebox and at, or below, the water level.

Andrew

hi david,

an extremely good question!

the simple answer from fullsize is that it is the worst place to feed water into a boiler, and is only done in miniature out of convenience or bad design.

why 'worst place'? surely if this is the hottest part of the boiler then ideal place to feed water? no, because it upsets the water circulation, plus additionally if below the water line you get considerable or increased scale forming in the check valve which will make the check valves unreliable.

Churchward, Maunsell etc carried out a great deal of experimentation in fullsize and the best place to feed water was the front 1/3rd of the barrel. Churchward used a sloping tray inside the boiler from the top feed points.

ive fitted check valves to the backhead on some of my locos but all are taken via internal pipes to the front 1/3rd of the boiler and above the water line.

in the smaller gauges you might not have much choice where to put them in 2.5 and 3.5"g. most of LBSC's own locos as opposed to his published designs had top feed!

cheers,

julian