Hydraulic technology is often regarded as a large scale operation, powering cranes, diggers and other construction machinery. There are smaller applications of hydraulic technology that people use every day, mostly without even thinking about the science behind them. Brakes on bicycles, cars and motorcycles employ hydraulic principles to effect the action of stopping the wheels, and the general public take this entirely for granted, expecting that a push on the brake pedal will stop the vehicle. The first hydraulic brakes were developed in 1914, by Fred Duesenberg, who used them on racing cars first, later introducing the technology to passenger cars in 1921. Unfortunately for Duesenberg, he did not patent the hydraulic brake and the invention was later credited to Malcolm Lougheed (who later changed his name to Lockheed) who patented his own version of the hydraulic brake in 1918. These early brakes were developed further into the self-energizing hydraulic drum brake which is still in use today, although disc brakes are becoming the more popular choice. The basic principles of hydraulics form the basis of the brake action, with the brake level or pedal providing the human input; the output takes the form of the brake calipers pressing against the drum or disc component of the brake system. The human input component is linked to an actuating rod, which joins to the top piston of the master cylinder construction, a vital component that houses the pistons, hydraulic fluid and reservoir. The action of pressing or squeezing the pedal (or lever) exerts force on the top piston, with the hydraulic fluid transferring this pressure to the caliper pistons which exerts a larger force against the brake drum or disc. The fluid most commonly used in braking systems is a substance containing ethylene glycol, used for its high viscosity. Removing the pressure from the brake pedal or lever releases a spring inside the master cylinder assembly which returns the pistons and brake calipers to their normal position. The system is entirely closed, and fluid levels do not decrease with use or from leakage, unless there is a fault in the system. However, brake fluid does need to be replaced over time as small amounts of water can enter the system and cause the properties of the hydraulic fluid to degrade. Other braking systems are used nowadays, but the hydraulic brake system developed by Duesenberg and Lockheed are still the smallest, cheapest and most efficient for many uses.