3304 & 3306 – “Non-Adjustable Dashpot” Governor

The non-adjustable dashpot governor is the standard governor for the later engines. It controls engine rpm with less hunting (oscillation of engine rpm between faster and slower than desired rpm) than the earlier standard governor.

The “non-adjustable dashpot” governor gets its name from the function of some of the parts in the governor. These parts work together like a “dashpot” or shock absorber to make the rpm of the engine steady. Governor piston (6) moves in cylinder (3) which is filled with fuel. The movement of piston (6) in cylinder (3) either pulls fuel into cylinder (3) or pushes it out. In either direction the flow of fuel is through hole (2) in the bottom of cylinder (3) and through orifice (1) to the inside of the housing. The restriction to the flow of the fuel by orifice (1) gives the governor its “dashpot” function. The fixed size of orifice (1) makes the “dashpot” function non-adjustable.


NON-ADJUSTABLE DASHPOT GOVERNOR
1. Orifice. 2. Hole in bottom of cylinder. 3. Cylinder. 4. Governor spring. 5. Weights. 6. Piston. 7. Dashpot spring. 8. Seat. 9. Riser.


DASHPOT GOVERNOR PISTON
6. Piston. 7. Dashpot spring. 8. Seat.

When the engine has a decrease in load, the engine starts to run faster. The governor weights push against riser (9). Riser (9) pushes against governor spring (4) with more force. The additional force starts to move riser (9). This puts more compression on governor spring (4) and starts to put dashpot spring (7) in compression.

Dashpot spring (7) is in compression because the fuel in cylinder (3) behind piston (6) can only go out through hole (2) in the bottom of cylinder (3). The rate of flow through hole (2) and orifice (1) controls how fast piston (6) moves. As the fuel goes out of cylinder (3), piston (6) moves into the space from the fuel. This lets compression off of dashpot spring (7) gradually.


NON-ADJUSTABLE DASHPOT GOVERNOR CYLINDER
2. Hole in bottom of cylinder. 3. Cylinder.

When governor spring (4) and dashpot spring (7) are both in compression, their forces work together against the force of the governor weights. This gives the effect of having a governor spring with a high spring rate. A governor spring with a high spring rate keeps the engine rpm from having oscillations during load changes. When the engine rpm and the engine load are both steady, governor spring (4) works alone to keep the engine rpm steady. This gives the engine more sensitive rpm control under steady load conditions.

When the engine has an increase in load, the engine starts to run slower. The governor weights push against riser (9) and seat (8) for governor spring (4) with less force. Governor spring (4) starts to push seat (8) and riser (9) to give the engine more fuel for injection. Seat (8) is connected to piston (6) through dashpot spring (7). When seat (8) and riser (9) start to move, the action puts dashpot spring (7) in tension. Piston (6) has to pull fuel into cylinder (3) from the governor housing to take its space so that it can move. This makes the movement of seat (8) for the governor spring (4) and riser (9) more gradual.

During this condition, dashpot spring (7) is pulling against governor spring (4). This gives the effect of a governor spring with a high spring rate. A governor spring with a high spring rate keeps the engine speed from having oscillations during load changes. It lets the engine have just enough fuel for injection to keep the engine speed steady.

The functions of the other parts in the governor housing are the same as in the earlier standard governor.

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