Locomotive numbers 92165-92167 were built with a mechanical stoker, which was a helical screw that conveyed coal from the tender to the firebox, where it would be directed to the required part of the grate by high-pressure air jets controlled by the fireman [REF].
The only modification which did deliver any noticeable benefit was the fitting of 92178 with a double blastpipe and chimney during its construction.