As a trial run before SAR mechanical engineer David Wardale was granted permission to proceed to rebuild a Class 25NC 4-8-4 locomotive to the Class 26 Red Devil in 1979, he was allowed to carry out modifications to a Class 19D locomotive.
The locomotive selected for the experiment was Krupp-built no.
2644, a particularly poor-steaming member of the Class at the time.

A gas producer combustion system (GPCS) and dual Lempor exhaust were installed, along with some other small improvements.
The Lempor had a four-jet blastpipe with extended petticoats to provide truer ejector proportions.
To accommodate the arrangement, the smokebox was extended by 300 millimetres (11.8 inches).
Steam flow in the cylinders was improved by streamlining the edges of the piston valves which were each equipped with an additional valve ring to reduce leakage.
The firebox was modified to the GPCS system wherein principal combustion is effected using secondary air introduced above the firebed through ducts in the firebox sides, while primary air was restricted through dampers and a redesigned grate.

Firebox turbulence was created by steam jets and clinkering was inhibited by introducing exhaust steam under the grate.
Sanding was improved and de-sanding jets were installed to clean the rails after the locomotive had passed.

The modifications improved the locomotive's steaming rate and enabled it to achieve significantly higher power and significantly lower fuel consumption than other unmodified Class 19D locomotives, the coal savings and increased output being in the order of 20% to 25%.
The success of this experiment convinced the SAR management at the time of the viability of the project which culminated in the Class 26 Red Devil.
As a trial run before SAR mechanical engineer David Wardale was granted permission to proceed to rebuild a Class 25NC 4-8-4 locomotive to the Class 26 Red Devil in 1979, he was allowed to carry out modifications to a Class 19D locomotive. The locomotive selected for the experiment was Krupp-built no. 2644, a particularly poor-steaming member of the Class at the time.
A gas producer combustion system (GPCS) and dual Lempor exhaust were installed, along with some other small improvements. The Lempor had a four-jet blastpipe with extended petticoats to provide truer ejector proportions. To accommodate the arrangement, the smokebox was extended by 300 millimetres (11.8 inches). Steam flow in the cylinders was improved by streamlining the edges of the piston valves which were each equipped with an additional valve ring to reduce leakage. The firebox was modified to the GPCS system wherein principal combustion is effected using secondary air introduced above the firebed through ducts in the firebox sides, while primary air was restricted through dampers and a redesigned grate.
Firebox turbulence was created by steam jets and clinkering was inhibited by introducing exhaust steam under the grate. Sanding was improved and de-sanding jets were installed to clean the rails after the locomotive had passed.
The modifications improved the locomotive's steaming rate and enabled it to achieve significantly higher power and significantly lower fuel consumption than other unmodified Class 19D locomotives, the coal savings and increased output being in the order of 20% to 25%. The success of this experiment convinced the SAR management at the time of the viability of the project which culminated in the Class 26 Red Devil.
South African Class 19D 4-8-2