Derby Tech - August, 1989

by Bruce Finwall

Many contestants find it difficult to got the proper brake travel in senior division cars. It can be particularly hard when you build a car with a small nose or if you are a taller driver with larger foot. You may find that your feet are just about on top of the front axle, which makes designing a brake that will work that much more difficult. Sometimes there just isn't much room for your feet to move the brake pedal.

One way to get more brake travel is through a "Mechanical Advantage". You can design a brake system where the brake arm will go down 3 inches only 1 1/2 inches of brake pedal travel if you use a double action pulley system (Fig. 1). Or, you can get the 3 inch from l inch of pedal travel if you use a triple action pulley system (fig. 2). Remember though, that if you use a double action pulley system the brake spring will feel twice as powerful to the driver, and a triple action system will make the spring feel as if it's three times as strong. So, smaller drivers may not be able to exert the force necessary to make a mechanical advantage brake work well enough to stop their car.

The brake pedal angle also has an effect on the efficiency of your braking system. A driver can exert more power when the brake pedal is at 90 degrees to the floorboard. So, it doesn't hurt to design your brake so that when the brake pad is touching the ground the brake pedal is vertical to the floorboard (Fig. 3).

When using the junior drop arm brake you can make It it work a little better by switching the locations of the brake spring eyebolt and the brake cable eyebolt, locate the cable eyebolt at the top hole (Fig. 4). Also many people use bungee or elastic cord instead of the spring and attach it to the top of the car (Fig. 5). In the junior division the same thing goes for the brake pedal angle as in the senior division.

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