Spark arrester

We're talking about Sentinels hare and the exhaust up the stack can get rather hot. You can get flames out of the chimney without too much effort as there are no smoke tubes. You will never see that on a conventional steam loco as the smoke tubes will extinguish any flame.

 

Yes, but how hot does a flame have to be to melt steel? As hot as an oxy-acetylene burner, and I can hardly believe that the flames coming out of the chimney are as hot as that.

 

The flame will probably not melt the steel but it will tend to increase the oxidation and degrade the material. If stainless steel is used it should have a much longer life.

As an aside I use stainless steel mesh as spark arresters in 3.5" and 5" gauge locos. It is made of 1/64" wire on a 1/16" pitch. The mesh does not need to completely surround the blast pipe and petticoat, a semicircle behind the petticoat is sufficient. I expect that any large lumps of char that pass either side hit the smoke box door and break up rather than sweeping 180 degrees around the front of the mesh.