Hydraulic Clutch

Without knowing what size vehicle (if it is a vehicle) the application is for makes it a bit difficult to make suggestions.

Pneumatically assisted clutches are common place in heavy vehicles.

Vacuum assisted clutches are/were available in many vehicles including Toyota 60 series Landcruiser.

SAAB used annular hydraulic clutch actuation in its 99, and 900 (classic not the crappy GM cars) this system had a minimum of moving parts. Light but positive actuation, long wearing.

There's plenty of examples to be had, just visit your local scrap/junk/wreckers yard.

Must modern sistems go for mechanical friction clutches with only hydraulic actuation to improve performance and avoid mechanical losses. But I still believe that the future belongs to electricity. Take in account all the losses we have in gearboxes and differentials, not talking about energy recovering possibilities, and it starts to make sense.

I am not sure exactly what you are looking to do with the clutch. Are you looking for more holding power? There are many ways to improve a clutch, but it would help me to understand what you are looking for and to do this I would need to know what you have currently and what aspects of the clutch you are wishing to up grade.

In the most common usage, "hydraulic clutch" means a clutch that is disengaged hydraulically (but spring applied). This is very common in cars. The clutch is released hydraulically (with the hydraulics making the connection between the foot pedal and the clutch release lever at the engine). The systems are mechanically interchangeable with cable or lever actuated systems -- in other words all of the work done to release the clutch comes from the operator's leg muscles. To the operator, a very good cable system and a hydraulic system are almost indistinguishable. Pneumatic or vacuum assistance is possible for such hydraulic clutches. These clutches can also be operated from a small hydraulic pump and valve system, so the the operator does not do the work of releasing the clutch. (see Citroen's Citromatic, which had an automatically operated clutch.)

Then there are clutches that are hydraulically engaged, such as the clutches in a conventional automatic transmission.

There are also hydrodynamic clutches (or slip couplings) in which the hydraulic fluid is actually doing the work of engaging one piece with another. These are the only ones in which "efficiency" is often an issue (if by efficiency you mean [power out]/[power in]. Unlike a hydraulically-released clutch (which are 100% efficient when engaged) a hydrodynamic clutch varies in efficiency depending upon its design and how it is used.

I would guess this is homework assignment? Otherwise you would be coming here with a particular problem to solve, I'd think. Perhaps you can elaborate on what you have in mind.

How about a electrically variable torque converter?

All you would need is a stable ferro magnetic fluid

Thanks again to Rhabe for the additional links.

To add to your answer, and bring up another possibility, there are also hydraulic clutches referred to as wet clutches. In this instance, the friction material is saturated in a fluid. (commonly a type of oil) The oil is constantly sprayed onto the clutch pack to remove the heat and allow prolonged slipping with out harm or wear.

Please send more information.

Fill the system with 80 weight gear oil. This will take care of most small leaks or bypass. Making the clutch work better. Dont expect it to work right in cold weather, though. The gear oil may also soften the rubber seals,meant to be used with brake fluid. Replace with nyton seals, if you can find them.

i agree withe the other posters we need more information.

is this clutch automotive, heavy equipment, or for some other power transmission.

when you state hydraulic clutch and can pneumatics assisted clutch for the same. we need to know if hydraulics and pneumatics assist is for clutch release or lock up.