In 1973, Lou Ross, of Arizona, designed and developed this large 3.5 cubic inch opposed twin for possible use as a target drone engine for military applications. It burns methanol on glow ignition with castor oil mixed in for lubrication. His unique style of casting the crankcase integral with the cylinders is typical of his line of smaller model airplane engines that are well known among the collectors, however, only a few examples of these larger drone engines exist today.