Leverage and Hydraulics

The pedal is designed in such a way that it can multiply the force from your leg several times before any force is even transmitted to the brake fluid.

­In the fi­gure below, a force F is being applied to the left end of the lever. The left end of the lever is twice as long (2X) as the right end (X). Therefore, on the right end of the lever a force of 2F is available, but it acts through half of the distance (Y) that the left end moves (2Y). Changing the relative lengths of the left and right ends of the lever changes the multipliers.
The basic idea behind any hydraulic system is very simple: Force applied at one point is transmitted to another point using an incompressible fluid, almost always an oil of some sort. Most brake systems also multiply the force in the process.

Simple hydraulic system

In the figure above, two pistons (shown in red) are fit into two glass cylinders filled with oil (shown in light blue) and connected to one another with an oil-filled pipe. If you apply a downward force to one piston (the left one, in this drawing), then the force is transmitted to the second piston through the oil in the pipe. Since oil is incompressible, the efficiency is very good -- almost all of the applied force appears at the second piston. The great thing about hydraulic systems is that the pipe connecting the two cylinders can be any length and shape, allowing it to snake through all sorts of things separating the two pistons. The pipe can also fork, so that one master cylinder can drive more than one slave cylinder if desired.

Master cylinder with two slaves

The other neat thing about a hydraulic system is that it makes force multiplication (or division) fairly easy. If you have read How a Block and Tackle Works or How Gear Ratios Work, then you know that trading force for distance is very common in mechanical systems. In a hydraulic system, all you have to do is change the size of one piston and cylinder relative to the other.

Hydraulic multiplication

To determine the multiplication factor in the figure above, start by looking at the size of the pistons. Assume that the piston on the left is 2 inches (5.08 cm) in diameter (1-inch / 2.54 cm radius), while the piston on the right is 6 inches (15.24 cm) in diameter (3-inch / 7.62 cm radius). The area of the two pistons is Pi * r². The area of the left piston is therefore 3.14, while the area of the piston on the right is 28.26. The piston on the right is nine times larger than the piston on the left. This means that any force applied to the left-hand piston will come out nine times greater on the right-hand piston. So, if you apply a 100-pound downward force to the left piston, a 900-pound upward force will appear on the right. The only catch is that you will have to depress the left piston 9 inches (22.86 cm) to raise the right piston 1 inch (2.54 cm).

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/brake1.htm

How Brakes Work

The layout of a typical brake system. See more pictures of brakes.

We all know that pushing down on the brake pedal slows a car to a stop. But how does this happen? How does your car transmit the force from your leg to its wheels? How does it multiply the force so that it is enough to stop something as big as a car?
When you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. Since the actual brakes require a much greater force than you could apply with your leg, your car must also multiply the force of your foot. It does this in two ways:

• Mechanical advantage (leverage)
• Hydraulic force multiplication

­The brakes transmit the force to the tires using friction, and the tires transmit that force to the road using friction also. Before we begin our discussion on the components of the brake system, we'll cover these three principles:

• Leverage
• Hydraulics
• Friction

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/brake.htm

 

How Anti-Lock Brakes Work

Location of anti-lock brake components. See more pictures of brakes.

Stopping a car in a hurry on a slippery road can be very challenging. Anti-lock braking systems (ABS) take a lot of the challenge out of this sometimes nerve-wracking event. In fact, on slippery surfaces, even professional drivers can't stop as quickly without ABS as an average driver can with ABS.

In this article, the last in a six-part series on brakes, we'll learn all about anti-lock braking systems -- why you need them, what's in them, how they work, some of the common types and some associated problems.

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/anti-lock-brake.htm

 

Could anti-lock brakes detect a flat?

An ABS (anti-lock braking system) is a system that helps a driver to avoid skids during panic stops. In a car with a normal braking system, all four wheels will lock and cause the car to skid if the driver jams on the brakes in a panic situation. The problems with skidding are:

1. The car will actually take longer to stop.
2. The driver loses all control of the vehicle.

An a­nti-lock braking system lets a computer monitor the wheels. If one of them locks, the computer can pulse the brake on that wheel so that the wheel keeps spinning. Because the wheels continue to spin, the driver can continue to control the car with the steering wheel.
­The computer senses rotation using a rotation sensor on each wheel. If the computer were programmed correctly and if there were a light on the dashboard, then the computer could detect a flat tire. What the computer could do is look at different rotational speeds for one out of the four wheels. A flat tire would spin faster than a properly inflated tire, so the computer would look for one tire spinning faster than the other three, on average, over the course of a period of time. Then it could warn the driver by activating the light on the dash.
There are several production cars that use this technique. Starting with 2006 models, the NHTSA (National Highway Transportation Safety Administration) requires that all cars have a tire pressure monitoring system.
For related articles on braking and other automotive topics, check out the links on the next page.

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/anti-lock-brake-detect-flat.htm

Change Oil and Oil Filter

Oil is the lifeblood of your car. It keeps hardworking engine parts running clean, smooth and cool. Most owner's manuals suggest that you change your oil and oil filter every 7,500 miles (12,070 kilometers). Oil change specialists suggest every 3,000 miles (4,828 kilometers) or three months. The fact is, most of us do a lot of heavy driving during the summer when an engine is more likely to overheat. So at least check your oil before you head out on that road trip with the family.

To check your oil, let your car run for a few minutes, then park it on a level surface and shut off the engine. Open the hood and locate the oil dipstick. You're looking for two things here: the level of oil and how the oil looks. If you're low on oil, you can either add another quart or simply change the oil completely. The oil should look brownish yellow and clean on the stick. If the oil is a dark color or there's a lot of dirt and grime in it, then you definitely need an oil change and oil filter replacement.

Touch up nicks sooner rather than later

Touch-up paint won’t adhere well to rust. So be sure to keep some matching touch-up paint on hand so you can touch up any minor nicks, often found around door edges, before rust has a chance to form.

Preserve your car during long-term storage

If you are not going to use your car for more than a month, store it properly to prevent unnecessary damage and repairs upon your return.

• Fill the gas tank to help prevent condensation from accumulating in the gas tank. Add a fuel stabilizer and drive the car around a bit to distribute the additive to engine parts.
• Wash and wax the car thoroughly to protect the finish.
• Place a vapor barrier on your garage floor. A 4-mil polyethylene drop cloth will do.
• Disengage the parking brake to help avoid brake corrosion.
• Put the car on jack stands to take the weight of the vehicle off the wheels and tires.
• Disconnect and remove the battery to keep it from draining. Place the battery on a trickletype charger. Or periodically drain the battery, using a small light bulb, and then recharge it with a low-volt charger.
• Plug the tailpipe with a rag to prevent moist air from infiltrating into it.