Model Engineer, Volume 182, issue number 4089, 12-25 March 1989, page 312 has a simple design; basically a stainless steel cone shaped mesh running between the outside edges of the blower ring and the petticoat pipe.
Model Engineer, Volume 186, issue number 4139, 9 February 2001, pages 122-124 inc., has a discussion on the desirable characteristics, design constraints, and manufacture of spark arrestors for locomotives in our sizes, together with a more exotic design which includes an oil separator, although this last item could be ignored if neither required nor desired.
The spark arrestor part is simply a tube (‘drum’) of expanded stainless steel mesh smaller than 10 gauge running from the outside edge of the blast pipe/blower nozzle to the outside edge of the petticoat pipe. An example in the text is given of a 5″ gauge ‘Lion’ using 32 mesh gauge bronze wire, however this has been found to be too fine and clogged ‘after a few hours running’.
Both these designs are visually unobtrusive as they are inside the smokebox and invisible when the smokebox door is closed.
Regards, etc. Phil
Edited By Weary on 02/05/2010 19:33:11
Edited By Weary on 02/05/2010 19:34:17