POWER BRAKES / VACCUM ASSIST BRAKES

 WORKING

ABOVE SHOWN TWO CHAMBERS (GREEN AND GREY COLOR) SEPARATED BY A DIAPHRAGM BOTH CHAMBERS ARE IN COMMUNICATION WHEN BRAKE PEDAL IS NOT PRESSED THROUGH A PASSAGE LINK.when pedal is not pressed both chamber is at vacuum WHEN PEDAL IS PRESSED PASSAGE LINK IS BLOCKED ATMOSPHERIC AIR RUSH IN NO MORE COMMUNICATION B/W CHAMBERS AND DIAPHRAGM IS PRESSED WHICH IS IN CONTACT TO PISTON CYLINDER ARRANGEMENT CONTAINING BRAKE FLUID .VACUUM IS CREATED BY INTAKE MANIFOLD.

HYBRID BEARING

When a stray current in an electrical machine uses a bearing as its path to ground, the resulting damage is referred to as “electric arc bearing damage”.

Electric arcing occurs if there is a difference in potential between the shaft and the bearing housing. Even a difference of a few volts in potential can produce the effect. Not only the motor or generator bearings can be affected — a stray current can damage bearings in the machinery directly coupled to the motor or generator. To prevent electric currents from arcing through the bearings, either the housing or bearings should be insulated.

Hybrid bearings have rings of bearing steel and rolling elements of bearing grade silicon nitride (Si3N4). Because silicon nitride has high resistivity, hybrid bearings provide insulation from electric currents in both AC and DC motors.
In addition to being an excellent insulator, hybrid bearings have a higher speed capacity and will provide longer service life than all-steel bearings in most applications.
The density of silicon nitride is only
40 % of the density of bearing steel. Because silicon nitride rolling elements weigh less they have lower inertia. This means less damage to the cage during rapid starts and stops and also significantly lower friction at high speeds. Lower friction means cooler running
and thus longer lubricant life. Hybrid bearings are thus suitable for operating at high speeds.
If the lubrication for some reason becomes insufficient, there is no risk of smearing between silicon nitride and steel. Also, the friction coefficient be- tween steel and silicon nitride is low. This enables hybrid bearings to run cooler and last longer in applications where there is inadequate lubrication. Silicon nitride has higher hardness and higher modulus of elasticity than steel. This means high wear resistance, increased bearing stiffness and longer bearing service life in contaminated environments.
Silicon nitride rolling elements have a lower thermal expansion than steel balls of similar size. This means less sensitivity to temperature gradients at high temperatures for better, more accurate Preloaded control.

Regenerative Braking

Introduction to Regenerative Braking 

A regenerative brake is a mechanism that reduces vehicle speed by converting some of its kinetic energy into another useful form of energy - electric current, compressed air.This captured energy is then stored for future use or fed back into a power system for use by other vehicles. For example, electrical regenerative brakes in electric railway vehicles feed the generated electricity back into the supply system.

Regenerative braking utilizes the fact that an electric motor can also act as a
generator.

The vehicle's electric traction motor is operated as a generator during braking and its output is supplied to an electrical load It is the transfer of energy to the load which provides the braking effect .

VTEC vs VVT-i

Working Principle

In an automobile engine the intake and exhaust valves move on a camshaft. The timing, lift and duration of the valve are determined by the shape of the lobes that make the shaft move. Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position and lift refers to how much the valve is opened.
i-VTEC uses not only timing but also the lift aspect of the valves, while VVTi uses only the timing aspect. The technology that uses timing and lift aspect developed by Toyota is called VVTL-i and can be equated with that of i-VTEC of Honda.
i-VTEC
Honda introduced i-VTEC technology in Honda's K-series four cylinder engine family in 2001. With this technology

• The intake camshaft is capable of advancing between 25 and 50 degrees when the engine is running.
• Phase changes are implemented by a computer controlled, oil driven adjustable cam gear.
• Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to somewhat advanced at full throttle and low RPM.
• The effect is further optimization of torque output, especially at low and midrange RPM.
• Valve lift and duration is still limited to distinct low- and high-RPM profiles.

VVTi
Toyota introduced VVT-i in 1996. With this technology

• The timing of the intake valves varies by adjusting the relationship between the camshaft drive (belt, scissor-gear or chain) and intake camshaft.
• Engine oil pressure is applied to an actuator to adjust the camshaft position.
• Adjustments in the overlap time between the exhaust valve closing and intake valve opening results in improved engine efficiency.

Common Pass Height adds Advantages

Common Pass Height adds Advantages

Operations varying from large automotive and tandem line dies, transfer press dies to small progressive dies should be set up to run at a common feed or pass height. Generally, this should be as high as possible for the following reasons:
 
1. Presses operated near their maximum shut height adjustment wherever possible maximize adjustment screw engagement, which avoids uneven screw wear.
 
2. A common pass height will avoid the need to make vertical adjustments to the feeders or loaders in both coil and cut blank fed presses.
 
3. Making the pass height as high as possible provides for steep scrap chutes to improve dependable scrap discharge.

OPERATING DIES AT A COMMON SHUT HEIGHT

Definition of Shut Height

Die shut height is defined as the height of the die in the shut or closed position. This height may be greater when measured on the shop floor than in the press because the die might not close completely because of die pressure systems. The press shut height for diesetting purposes is the distance from the top of the bolster to the bottom of the ram or slide at bottom dead center, (BDC). BDC is the 180° or six o’clock position of the press.
It is not necessary to use a common shut height throughout the pressroom. An example of how dies may be grouped follows:
 

1. The line dies used to make a family of similar parts on one or more press lines form a group for standard shut height analysis. 

2. In the same way, for double action presses, the draw die punch and blankholder
shut heights are the same on symmetrically opposite right and left-hand dies.
 

3. This procedure is a basic procedure for groups of dies that are similar.If it is not practical to use a common shut height for all dies, he jobs changed most often are the logical dies to modify to start your common shut height project.
Often, several groups of shut heights are required. For example, a series of small progressive dies may operate at a shut height 14-inches (355.6 mm).

Automotive fender dies might require 72- inches (1829 mm). A well thought-out common height strategy
can both speed up diesetting and help avoid die and press damage.

 

Acura's VTEC Engines

Normal Engines

In normal engines the valves that supply the engine with air and fuel open and close at the same rate, the same distance, and the same length of time at all rpm. The problem is that the car will need air quicker at high rpms. An overlap of exhaust valves closing and intake valves open also helps by providing a suction. This suction brings intake air in faster.

Cars that are designed for speed need to be most efficient at high rpms. At higher speeds more power is require to accelerate 1 mph then at lower speeds. This being said, a sporty car or race car needs more power at the high end rpms to increase its speed quicker. For example, Nascar cars do not run well when idling. The valves open too long and overlap(exhaust is still open when intake opens). The cams are designed so the engine performs its best in the high rpms of the race.

Trucks designed for strength(designed to have large amounts of torque at low rpm to tow large loads) have power at higher RPMs but do not perform well in those high rpms. Regular driving cars lack power at both high and low rpm but work efficiently at mid range rpm.

The Problem

There problem because the valves are designed to open and close at a rate and distance that will work the best for its application. And when that vehicle's rpm is out of that range it loses power and efficiency. This is because the vehicles valve specifications, meaning opening distance and time, do not work well for the RPM.

VTEC Engines

The VTEC(Variable Valve Timing and Lift Electronic Control) systems fixes these problems. It is a system that changes the properties of the valves to fit the RPM. When at a lower RPM it uses 2 smaller cams on the camshaft to push the valves open and closed. This allows for less overlapping of the exhaust and

intake valves. They open at a smaller height for a shorter time. When at around 6000 rpm, it switches to one large cam in the middle of the other 2, this single cam pushes both valves. The larger cam pushes the valves farther and for a longer time period, overlapping occurs between exhaust closing and intake opening, which allows more air to enter the cylinder creating more power at a higher RPM. This system makes it possible to get more power at all RPMs. The Vtec system also provides better fuel economy, and lower emissions.