3304 & 3306 – “Adjustable Dashpot” Governor


“ADJUSTABLE DASHPOT” GOVERNOR
1. Governor housing. 2. Governor control shaft. 3. Needle valve.

The “adjustable dashpot” governor is for electric set engines which must operate at very near constant rpm under changing loads.

The “adjustable dashpot” governor gets its name from the function of some of the parts in the governor. They work together like a “dashpot” or shock absorber to make the rpm of the engine steady. The governor has a piston (6) that moves in a cylinder (5) which is filled with fuel. The movement of piston (6) in cylinder (5) either pulls fuel into cylinder (5) or pushes it out. In either direction, the flow of fuel is through a hole (9) in the bottom of cylinder (5) and through passages in the governor housing which are connected by needle valve (3). The passages in governor housing (1) connect the fuel in governor housing (1) with the fuel in cylinder (5) through hole (8).


“ADJUSTABLE DASHPOT” GOVERNOR
3. Needle valve. 4. Governor spring. 5. Cylinder. 6. Piston. 7. Riser.

When the engine has a decrease in load, the engine starts to run faster. The governor weights push against riser (7) and seat (11) for governor spring (4) with more force. The additional force starts to move riser (7) and seat (11) which puts more compression on governor spring (4) and starts to put dashpot spring (10) in compression.


“ADJUSTABLE DASHPOT” GOVERNOR CYLINDER
5. Cylinder. 8. Hole (in governor housing). 9. Hole (in bottom of cylinder).

Dashpot spring (10) is in compression because the fuel in cylinder (5) behind piston (6) can only go out through hole (9) in the bottom of cylinder (5). The rate of flow through hole (9) controls how fast piston (6) moves. As the fuel goes out of cylinder (5), piston (6) moves into the space from the fuel. This lets compression off of dashpot spring (10) gradually.


DASHPOT GOVERNOR PISTON
6. Piston. 10. Dashpot spring. 11. Seat.

When governor spring (4) and dashpot spring (10) 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 speed from having oscillations during load changes. It lets the engine have just enough fuel for injection to keep the engine speed steady.

When the engine has an increase in load, the engine starts to run slower. The governor weights push against riser (7) and seat (11) for governor spring (4) with less force. Governor spring (4) starts to push seat (11) and riser (7) to give the engine more fuel for injection. Seat (11) is connected to piston (6) through dashpot spring (10). When seat (11) and riser (7) start to move, the action puts dashpot spring (10) in tension. Piston (6) has to pull fuel into cylinder (5) from governor housing (1) to take its space so that it can move. This makes the movement of seat (11) for the governor spring (4) and riser (7) more gradual.


“ADJUSTABLE DASHPOT” GOVERNOR
3. Needle valve. 4. Governor spring. 5. Cylinder. 6. Piston. 7. Riser.

During this condition, dashpot spring (10) 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 rate of flow of the fuel into and out of cylinder (5) is controlled by the adjustment of needle valve (3). While the engine is running, the needle valve is adjusted so that the governor action is fast enough to keep the engine running at a steady speed under changing loads. The rest of the parts in the dashpot governor and their functions are the same as in the earlier standard governor.

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