15-12-2012, 04:00 PM
The Hartnell Governor
1The Hartnell.pdf (Size: 1.33 MB / Downloads: 409)
INTRODUCTION
Stationary steam engines, traction engines, portable and semi-portable engines all require some
method of steam regulation to enable the operator to maintain adequate control over the machine.
A device known as a governor is the piece of equipment used for this purpose.
Numerous types of governors have been designed and put into use. It is widely accepted that the
Watt governor may be one of the oldest, if not the oldest, design which can still be found in use
on numerous applications around the world today.
This article, although introducing the Hartnell Governor to the best of my ability, assumes the
reader to have an understanding of the basic functions of governors in general.
Mr. Hartnell* designed his governor circa 1875 and at the time it was considered to be of superior
design to other governors of the day. It rotated between 500 and 600rpm and by utilising
smaller fly balls and less parts, the internal friction was less than that of others.
His original design consisted of the previously accepted method of a spring loaded rotating
sleeve which altered the position of a bell crank and valve rod connected directly
to a control valve fitted into the steam inlet pipe. The control valve either reduced or increased
steam admission to the engine as required. When the steam engine increased in speed, possibly
due to reduced loading of the engine, the fly balls would be forced out by centrifugal force thus
moving the sleeve against, as in this case, spring tension. As the fly balls moved out, the central
sleeve would be forced upwards which in turn moved the bell crank, valve rod and control valve
in the correct direction to minimise steam flow and therefore decrease the speed, of the slightly
over revving engine, back to its normal operating speed.