The term "slag" applied to a series of model engines does not refer to the products of a particular manufacturer - rather, the term "slag" denotes a type of engine which is characterized by one rather alarming feature - the absence of a ferrous cylinder liner.  Indeed, the slag engines went even further than this - they used aluminium alloy pistons operating directly within the aluminium alloy bores! The origins of the "slag" handle applied to such engines is unclear - all that can be said is that they generally exhibited standards of quality which were well below average. They also didn't last long in service. Most of them were sparkies, although a few examples were marketed as glow-plug models during the late 1940's.

These engines originated exclusively in 1940's America. They appeared under a variety of trade-names - Syncro, Rogers, Thor, Genie and Buzz, to name a representative sample. However, they all had a common source - regardless of the applied brand-names, they were all manufactured by the Judson Company of Philadelphia. They sold in very large numbers, mainly because the corners cut in their construction allowed them to be offered at very low prices. Most of them ran as supplied, although they didn't wear well.

Perversely, the slag engines have developed into something of a "cult" series among model engine aficionados, who are curious to learn for themselves just how bad these engines really were! Examples can be found in many present-day collections. In this, they reflect the ongoing interest shown in such woeful offerings as the G.H.Q. and the Deezil.

A detailed article covering the production history of the slag engines and reporting on present-day efforts to actually run them will appear on this website in due course.