Re: 18-24"gauge adjustable.

Dan, the Mancha ModelA Trammer was multi-gaugeable with extended axles and 3 x one inch spacers to allow sales to mines with either 18-20-22-24 inch track. These ring type spacers were quickly reduced to a single 3" spacer on the ModelB as by that time the 20"and 22"ga seemed to have dropped from favour, Arizona being the exception. There weren't very many multi-gauged mine trackages in the dual-gauge sense.
Mancha modelA photos Darryl Killian



Macha modelB


However while Skip is correct in that the 18"ga was the most common, it was mainly underground and surface use at mines with compressed air, storage-battery motors or trolley motors. Very rarely 18"ga was worked with steam and very rarely were there 18"ga tramways similar to the Coronado.

Arizona seemed to be a 20"ga stronghold and to have 20"ga underground as well, the reason was the increased capacity for the copperore related to their style of mining which differed from the standard average gold or silver mining. The Homestake in Sth Dak had 22" surface tramways with 18" underground later regauging the 22 back to 18". The sight of a 22"ga Airmotor hauling a train load of piggybacked 18"ga timbercars to be put on the hoist is most odd.

Porter Airmotor 18"ga