Steam domes

A simple question but no doubt with a complicated answer.

Are steam domes decorative or functional on model locos.

Both Eric.

The one on my Scamp is permantly attached to the boiler so acts as a steam collector, with two safety valves top side, whereas the one on my Simplex was covering the steam collector, thus decorative.

Which miniatures fall into either categoryI have no idea, but the Collecrive will no doubt come to the rescue.

Just need to do the side tanks and minuscule 'cab' and Scamp will be done.

Geoff - Must steam her up as haven't done so in ages.

Edited: Second sentence to correct something, but I've forgotten the word that explains

Edited By OuBallie on 02/05/2015 10:37:30

Probably marginally functional. The purpose of the steam dome is, of course, to supply steam with the highest possible dryness fraction. It does this by simply being further away from the water/steam interface where there is inevitably some mixing of steam and water droplets.

If you have superheating I suspect it won't make much difference, but if using saturated steam then every little helps.

Andrew

hi eric,

the outer dome casing is of course purely decorative.

whether a dome is required depends on lots of factors not least whether the loco is superheated, what type of regulator, and what type of overall design of boiler.

with a tapered barrel belpaire firebox Churchward carried out extensive tests and experiments, ultimately deciding that a dome was unnecessary and that 'dry' steam could be collected from the top front corners of the very carefully designed belpaire firebox. this was before most of his 'standard' designs were fitted with superheaters, and the regulator was in the smokebox. allied to this one could argue that there simply wasnt room within the loading gauge for the Dean type dome.

i personally think that in miniature a dome of Victorian proportions is an advantage for lots of reasons incuding due to our lower boiler pressures and the arguement that turbulance and bubbling of the boiling water doesnt quite scale in size.

but i would also never build a miniature loco without superheaters.

cheers,

julian