Usage:
D346, D348, D349 Engines With Hydramechanical Governors
Reports indicate there are questions about the difference between the values for the spacer thickness in the governor torque control group and the static fuel setting specifications shown in the Fuel Setting And Related Information microfiche, Form SBFY1108.
NOTE: The Torque Control Group spacer thickness is not the same as the amount of rack travel between the Full Load and Full Torque readings.
Illustration 1. Hydramechanical governor components.
The governor for these engines is mounted vertically while the rack moves horizontally. The governor movement is transmitted to the rack through a bellcrank. The bellcrank arm that connects to the rack is longer than the bellcrank arm that connects to the governor. Therefore, when the governor moves the bellcrank a certain distance, the bellcrank moves the rack a greater distance. The bellcrank amplifies the movement of the governor.
Example
The information used in this example is from Fuel Setting And Related Information, Form SBFY1108, 0T3131 for D348 PC-TA, Serial No. 98S2610-98S2730.
Illustration 2. Part of OT3131 Fuel Setting And Related Information.
From the Torque Control Group information in Illustration 2, the total torque control group spacer thickness is 3.20 mm (.126").
From the Static Fuel Settings information in Illustration 2, the difference between the Full Load reading and the Full Torque reading is 4.35 mm (.171"). If the arms of the bellcrank were of equal length, the two values would be nearly equal. But, since the arms of the bellcrank are not of equal length, when the governor moves from the Full Load to Full Torque position [3.20 mm (.126")], the rack moves 4.35 mm (.171").
Also, in Illustration 2, note the difference between the Static Fuel Settings and the Dynamic Fuel Settings for these engines is 0.91 mm (.036"). The figure previously used for this difference was 0.76 mm (.030"). Testing has shown that 0.91 mm (.036") is correct.