The Pickering Governor
The Pickering governor was an American design, they were either imported or made here under licence in the UK by Joseph Evans of Chepstow. Very much an 'off the shelf' device they were made in a range of sizes defined by the steam pipe diameter they fitted on and were bought by some of manufacturers rather than build a governor of their own or bought by end users to fit to their engines after installation.
The Pickering is a throttle governor, this means that it is fitted on the steam line into the engine and controls the speed of the engine by operating a throttle valve which restricts the flow of steam from boiler to engine.
The governor drive pulley and shaft (on the left) is driven from the engine crankshaft, this causes the pair of bevel gears (d) to rotate, these are linked to and rotate plate (b1). Three balls are mounted on three spring steel strips (a) which are fixed to plates (b1) and (b) as these rotate centrifugal force causes them to fly outwards against the spring pressure, as the springs bend this pulls the top plate (b) downwards, concentric tube (c) slides down over inner tube (c1) allowing the central rod (e) to move downwards. At the base of this rod a double seated balanced throttle valve (f) and (f1) closes and reduces the passage of steam into the engine through flange (h) from the inlet flange (g).
As the engine speed reduces the springs (a) straighten and the top plate (b1) rises, lifting rod (e) and opening the valves (f) and (f1) increasing steam flow into the cylinder.
Speed control is adjusted by the key and worm (i) which rotates the pinion (k) and either tightens or releases spring (j) this increases or decreases the pressure on lever (m) which applies more or less pressure on the collar (m1) which is fitted on the central shaft (e) and makes it more or less easy for the governor mechanism to open or close the throttle valve.