Function of hydraulic clutch

The hydraulics with the master cylinder (in the picture on the right) and the slave cylinder (on the left) take the place of the Bowden cable. The brake fluid is taken from the reservoir (mounted high enough) of the brake system or from a separate container. This pipe leads to the master cylinder (in the picture, at the top). The amount of fluid sinks as the brake-pads wear down, therefore, in this situation the container should not be filled to the brim.

The pressure is distributed from the master cylinder and stays the same for the respective pedal pressure everywhere. By using various piston diameters, a manufacturer can set a transformation ratio, e.g., by using a smaller master cylinder diameter, the pedal force can be reduced. The spring in the slave cylinder presses the piston through the linkage, even when no activity is taking place, against the release bearing, which then lies on the tongue of the membrane spring and always rotates with it.

Earlier, only the hydraulic clutch operation was self-adjusting, nowadays it is also the standard in cable operated systems.

thermostat (wax-pellet)

The engine temperature is primarily controlled by a wax-pellet type of  thermostat, a valve which opens once the engine has reached its optimum operating temperature.

When the engine is cold, the thermostat is closed except for a small bypass flow so that the thermostat experiences changes to the coolant temperature as the engine warms up. Engine coolant is directed by the thermostat to the inlet of the circulating pump and is returned directly to the engine, bypassing the radiator. Directing water to circulate only through the engine allows the temperature to reach optimum operating temperature as quickly as possible whilst avoiding localised "hot spots." Once the coolant reaches the thermostat's activation temperature, it opens, allowing water to flow through the radiator to prevent the temperature rising higher.

Once at optimum temperature, the thermostat controls the flow of engine coolant to the radiator so that the engine continues to operate at optimum temperature. Under peak load conditions, such as driving slowly up a steep hill whilst heavily laden on a hot day, the thermostat will be approaching fully open because the engine will be producing near to maximum power while the velocity of air flow across the radiator is low. (The velocity of air flow across the radiator has a major effect on its ability to dissipate heat.) Conversely, when cruising fast downhill on a motorway on a cold night on a light throttle, the thermostat will be nearly closed because the engine is producing little power, and the radiator is able to dissipate much more heat than the engine is producing. Allowing too much flow of coolant to the radiator would result in the engine being over cooled and operating at lower than optimum temperature. A side effect of this would be that the passenger compartment heater would not be able to put out enough heat to keep the passengers warm. The fuel efficiency would also suffer.

The thermostat is therefore constantly moving throughout its range, responding to changes in vehicle operating load, speed and external temperature, to keep the engine at its optimum operating temperature.

Radiator construction

Automobile radiators are constructed of a pair of header tanks, linked by a core with many narrow passageways, giving a high surface area relative to volume. This core is usually made of stacked layers of metal sheet, pressed to form channels and soldered or brazed together. For many years radiators were made from brass or copper cores soldered to brass headers. Modern radiators save money and weight by using plastic headers and may use aluminium cores. This construction is less easily repaired than traditional materials.

Honeycomb radiator tubes

An earlier construction method was the honeycomb radiator. Round tubes were swaged into hexagons at their ends, then stacked together and soldered. As they only touched at their ends, this formed what became in effect a solid water tank with many air tubes through it.^[1]

Some vintage cars use radiator cores made from coiled tube, a less efficient but simpler construction.

Electromagnetic tooth clutches

Introduction – Of all the electromagnetic clutches, the tooth clutches provide the greatest amount of torque in the smallest overall size. Because torque is transmitted without any slippage, clutches are ideal for multi stage machines where timing is critical such as multi stage printing presses. Sometimes, exact timing needs to be kept, so tooth clutches can be made with a single position option which means that they will only engage at a specific degree mark. They can be used in dry or wet (oil bath) applications, so they are very well suited for gear box type drives.

They should not be used in high speed applications or applications that have engagement speeds over 50 rpm otherwise damage to the clutch teeth would occur when trying to engage the clutch.

How it works – Electromagnetic tooth clutches operate via an electric actuation but transmit torque mechanically. When current flows through the clutch coil, the coil becomes an electromagnet and produces magnetic lines of flux. This flux is then transferred through the small gap between the field and the rotor. The rotor portion of the clutch becomes magnetized and sets up a magnetic loop, which attracts the armature teeth to the rotor teeth. In most instances, the rotor is consistently rotating with the input (driver). As soon as the clutch armature and rotor are engaged, lock up is 100%.

When current is removed from the clutch field, the armature is free to turn with the shaft. Springs hold the armature away from the rotor surface when power is released, creating a small air gap and providing complete disengagement from input to output.

Hysteresis powered clutch

Electrical hysteresis units have an extremely high torque range. Since these units can be controlled remotely, they are ideal for testing applications where varying torque is required. Since drag torque is minimal, these units offer the widest available torque range of any electromagnetic product. Most applications involving powered hysteresis units are in test stand requirements. Since all torque is transmitted magnetically, there is no contact, so no wear occurs to any of the torque transfer components providing for extremely long life.

When the current is applied, it creates magnetic flux. This passes into the rotor portion of the field. The hysteresis disk physically passes through the rotor, without touching it. These disks have the ability to become magnetized depending upon the strength of the flux (this dissipates as flux is removed). This means, as the rotor rotates, magnetic drag between the rotor and the hysteresis disk takes place causing rotation. In a sense, the hysteresis disk is pulled after the rotor. Depending upon the output torque required, this pull eventually can match the input speed, giving a 100% lockup.

When current is removed from the clutch, the armature is free to turn and no relative force is transmitted between either member. Therefore, the only torque seen between the input and the output is bearing drag.

Basic principles of ignition coil

An ignition coil consists of a laminated iron core surrounded by two coils of copper wire. Unlike a power transformer, an ignition coil has an open magnetic circuit - the iron core does not form a closed loop around the windings. The energy that is stored in the magnetic field of the core is the energy that is transferred to the spark plug.

The primary winding has relatively few turns of heavy wire. The secondary winding consists of thousands of turns of smaller wire, insulated for the high voltage by enamel on the wires and layers of oiled paper insulation. The coil is usually inserted into a metal can or plastic case with insulated terminals for the high voltage and low voltage connections. When the contact breaker closes, it allows a current from the battery to build up in the primary winding of the ignition coil. The current does not flow instantly because of the inductance  of the coil. Current flowing in the coil produces a magnetic field in the core and in the air surrounding the core. The current must flow long enough to store enough energy in the field for the spark. Once the current has built up to its full level, the contact breaker opens. Since it has a capacitor connected across it, the primary winding and the capacitor form a tuned circuit, and as the stored energy oscillates between the inductor formed by the coil and the capacitor, the changing magnetic field in the core of the coil induces a much larger voltage in the secondary of the coil. More modern electronic ignition systems operate on exactly the same principle, but some rely on charging the capacitor to around 400 volts rather than charging the inductance of the coil. The timing of the opening of the contacts (or switching of the transistor) must be matched to the position of the piston in the cylinder. The spark must occur after the air/fuel mixture is compressed. The contacts are driven off a shaft that is driven by the engine crankshaft, or, if electronic ignition is used, a sensor on the engine shaft controls the timing of the pulses.

The amount of energy in the spark required to ignite the air-fuel mixture varies depending on the pressure and composition of the mixture, and on the speed of the engine. Under laboratory conditions as little as 1 millijoule is required in each spark, but practical coils must deliver much more energy than this to allow for higher pressure, rich or lean mixtures, losses in ignition wiring, and plug fouling and leakage. When gas velocity is high in the spark gap, the arc between the terminals is blown away from the terminals, making the arc longer and requiring more energy in each spark. Between 30 and 70 millijoules are delivered in each spark.

What Causes Piston Slap?

Piston slap is the sideways movement of a piston in a cylinder when it is intended to assume the up and down movement. The main causes of piston slap are over usage of oil without replacement and deformation of the cylinder.