Mechanical Design Assignment

Institution of Afiliation

Hydraulic Clutch Actuator Device

Design of the Master Cylinder with Reservoir

Product design specification.

Over the years, clutches have been used in the automotive industry for the transmission of power. The major function being to engage or disengage the power drive from the engine flywheel to facilitate change of gears. The clutches are mostly actuated by hydraulic systems comprising of a master cylinder where the force is applied by the operator, a hydraulic oil reservoir, transmission lines and the slave cylinder whose motion operates the clutch. The principle of operation is based on the fact that force applied at any point in a confined fluid is transferred undiminished to all points in the fluid. This principle only holds for incompressible fluids mainly liquids. In the existing designs used in the automotive industry, the hydraulic clutch system is foot operated through a clutch pedal in the driver’s cabin, in this preliminary design the objective was to come up with light duty master cylinder and hydraulic oil reservoir to be operated by hand from the steering wheel.

Performance, quality and reliability.

The design of the master cylinder should be such that it can be operated with ease and minimal force from the driver’s hand. This requires that the amount of hydraulic fluid displaced by the piston should be of sufficient quantity to actuate the slave piston. In addition to this, the design should be user friendly in all steering conditions, any power loses in the master cylinder due to leakages in the seals or insufficient hydraulic oil supply from the reservoir can lead to loss of precision in the actuator (slave cylinder). This might be catastrophic in case of an emergency. The effectiveness of the design in facilitating the operation by hand is therefore of key interest.

Life in service.

The master cylinder and reservoir design were also evaluated for the lifespan. It is desirable that the two function efficiently for a period of eight years with minimal break downs. Break down of the two leads to high operational costs due to purchase of spares and replacements. A good design therefore will be the one that serve for longer periods with less maintenance.


It is desired that the final product does not impact the driver or the vehicle occupants negatively. The design should therefore enhance the comfort of the driver during all driving and steering conditions. Additional features to the designs should enable it to be operated by the physically handicap and be inclusive for all operators.

The clutch being a very sensitive part of the power transmission in vehicles, the safety of the driver, the vehicle occupants and the cargo on board entirely depends on how effective the design is. The master cylinder push rod should be displaced a distance long enough to displace sufficient hydraulic oil that can cause total disengagement of the clutch once acted upon by the slave cylinder push rod.

Size and weight.

The size of the master cylinder and the hydraulic oil reservoir are made to be small in size to ensure they fit well into the vehicle dash board. The desirable materials for the manufacture of the master cylinder were metals that could withstand the high pressures of hydraulic oil while at the same time offer the advantage of light weight. The inner cylinder bore was ground smooth to facilitate a smooth piston travel, good sealing and minimal wear.

Design concept sketches.