What is Fluid Flywheel | Diagram, Advantages and Disadvantages

What is Fluid Flywheel 


It is also known as Fluid clutch or fluid coupling which couples the driving member with the driven member through a media of fluid. It consists of two members in which one is a driving member and the other one is driven member as shown in Figure. Among them, the driving member is connected with the engine flywheel and the driven member is connected with the transmission shaft. These two members are not made to contact with each other. The driven member is free to slide on splines provided on the transmission shaft. The two rotors are filled with a fluid of required viscosity. Radial ribs are provided to form a number of passages to avoid the formation of eddies. They also guide the fluid to flow in the desired direction.

Read more: Construction and Working Of Fluid CouplingOpens in a new tab.

Fluid Flywheel Diagram : 

fluid flywheel
fluid flywheel

When the engine is started, the driving member called the impeller starts to move inside the housing containing oil. Pockets of moving driving members are completely filled with oil. Due to this, the centrifugal force forces the oil outward radially. The pockets are designed in such a way that the splashed oil will strike the pockets or vanes of the driven member. Hence. it is forced to move in the same direction. When the engine speed increases. the oil which is coming out from the pocket of the driving member strikes the pockets of the driven member with greater force. Thus, it tends the driven member to rotate at the same speed.

Characteristics of a Fluid Flywheel: 

  • Stall speed The stall speed is defined as the highest speed at which the pump can turn when the output turbine is locked and the maximum input power is applied. Under stall conditions all of the engine’s power would be dissipated in the fluid coupling as heat, possibly leading to damage.
  • Slip The runner speed is almost equal to that of the impeller only when the efficiency of liquid coupling is highest. But usually the runner speed is less than that of the impeller. The (speed) lag of the runner behind the impeller is known as slip. This (speed) slip varies with many factors such as engine speed, vehicle speed, and engine and vehicle load.
  • Slip is given as (N1-N2)/N1 where N1, N2 are speed of driving and driven

Advantages of Fluid Flywheel :

1. It gives smoother power take-up than the centrifugal type when the engine IS accelerated.
2. The fluid in the coupling behaves as a cushioning agent between engine and gearbox in order to absorb shocks during braking or coasting down on incline.
3. No need of separate pedal or lever to operate.
4. The driving member acts as a flywheel on the crankshaft. Thus. it is smoothened out the torque variation.
5. There is no wear on moving parts.
6. No need of adjustment is required.
7. No maintenance is necessary. except maintaining the required oil level.
3. It is simple in design.
9. There is no jerk on transmission when the gear engages. It damps all shocks and strains.
10. No skill is required for operating.
11. Car can be stopped in gear and moved off just by pressing the accelerator pedal itself.

Disadvantages Of Fluid Flywheel :

1. There is a drag on the gear box-shaft even the slip is 100%.
2. It has the gear changing difficult with the ordinary crash type gearbox. So. the fluid flywheel is generally used with an epicyclic gearbox which avoids this difficulty.

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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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