Figure 2-1. Linkage Arrangement (For Non-Linear Fuel Systems) - Woodward UG-5.7 Dial Installation And Operation Manual

UG Dial Governor
A linear linkage arrangement is used in applications where the governor output
shaft positioning is directly proportional to the torque output of the prime mover.
Thus, the governor output shaft travel will be directly proportional to the amount
of fuel delivered to the prime mover.
A linear linkage is a linkage arrangement which provides as much movement of
the governor output shaft per increment of valve movement at light loads as it
does at heavy loads.
In applications where a governor is controlling a butterfly valve, such as on a gas
engine, a linear linkage should not be used.
This is due to the inherent design of the butterfly valve which requires only a
small amount of valve travel (for example, 10°) to bring an engine from no load to
half load. By contrast, this design requires a much greater movement of valve
travel (for example, 30°) to bring the engine from half load to full load.
In order to improve governing control at light loads, a compensating linkage is
devised ("non-linear" linkage). This linkage provides greater movement of the
governor per increment of valve movement at light loads than it does at heavy
loads. Figure 2-1 illustrates the relationship between governor output shaft and
butterfly positions obtained with simple linkage of maximum non-linearity. When
installing this linkage, make sure that the two following conditions are obtained
when the linkage is in the no-load position:
1. The lever which is attached to the governor and the connecting link is in line
with the governor output shaft and the point of attachment of the connecting
link to the butterfly lever.
2. The butterfly lever must be at 90° with the connecting link.
See also Table 5-2 for a satisfactory relationship between governor output shaft
travel and butterfly valve travel in a non-linear system.
For more information on non-linear linkage, please refer to Woodward
Application Note 50516, Governor Linkage for Butterfly Throttle Valves.

Figure 2-1. Linkage Arrangement (for non-linear fuel systems)

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Manual 03040
Woodward