Full size loco boiler material. Copper Inner firebox = ½" to 5/8". Tubeplate 5/8" to 1". Studs = 7/8th inch or 1".
Use hardened pins of 2" (scale) diameter in valve motion, which equals 3/16" actual for 5" gauge.
BOILER LAGGING. Some years ago a friend and I experimented with different thickness and types of lagging to see how easy it was to reduce the heat escaping to the outside world. Partly this was to protect the paint, but also any lost heat is inefficient. Obviously the thickness of lagging that one can use on a small model without it being totally out of scale is minimal. In fact, to be fully effective, the lagging would need to be several inches thick.
However, we did find that the most effective was to use two thin layers of Kaowool lagging, with ordinary aluminium kitchen foil in between, and this was more efficient that a single layer of lagging of the same thickness
STEAM OIL.
Steam oil is specially formulated for the purpose. Do not use car or general oil in steam engines. Most of the model engineering suppliers stock steam oil, which comes in different grades for large or small engines. Your local model engineering society may also have stocks, or be able to tell you where to get it.
Run out of steam oil? Lard, or a vegetable oil can be used as a temporary substitute. With small models, a cooking oil will work as a temporary measure.
Boiler leaks. There are numerous "traditional "remedies for leaky boilers. These range from adding oats to the water (not good if you use an injector as it will probably get blocked), through to throwing a couple of cow-pats into the boiler. Horse manure is often quoted as a remedy, but this is probably due more to its availability when many engines were engaged on agricultural work, rather than to its effectiveness compared to other ingredients.
When finishing with your engine at the end of the day, squirt a drop of steam oil into the safety valve casing. It will prevent the spring from rusting and keep the mechanism lubricated..
A locomotive / traction engine should never be run using the remaining steam after the fire has been extinguished as this will draw cold air through the boiler tubes, which may weaken the end joints on them.
