Broad curves must be made within limits. Once you know the middle of a space you want to use, the radius measure can help you fit everything you need to into the space. The number represents half the distance across the area inside a circle.
The Distance From Center To Perimeter
The measure for the gap from the exact center of a space to the perimeter tells you how far you can span. You are free to use space as long as you avoid the extremes. On any side of the center, stay within the radial distance.
If you do not know the diameter of the circle that fits on the perimeter, which can be divided by 2 for the radius, you can figure out this gap by using pi, π. Divide the circumference measured around the entire perimeter by 2π.
Room To Control
Using the hands to turn a car, the most perfect turn around you can do is one on the car’s turning radius. A driver can turn around on a street twice the width of the curb-to-curb turning radius. Any wider turn will end with the wheels hitting the curb.
If the manufacturer does not tell you the curb-to-curb turning radius, you can calculate it with the distance between the front and rear tires, called the wheelbase, the greatest angle the wheel turns in its space, called the outside wheel cut, and a conversion ratio from the manufacturer. Just multiply the wheelbase by the conversion factor divided by the outside wheel cut.
There is even a formula, developed by Englishman Simon R. Blackburn, for the room needed to park between two cars on the side of the street. The formula uses the turning radius, r. The only other information you need is the full car length, the width of the parked car in front, w, the distance from the front wheel to the corner of the front bumper, f, and the wheelbase, b.
minimum space needed = car length + √(〖(r^2- b^2)+(b+f)〗^2 – 〖(√(r^2- b^2 )- w)〗^2 ) – b – f
Any smaller space does not give you enough room to park.
Room For Curves
Using the hands to master a curve with a drawing pencil, the most large sweep you can fit in the drawing space on the paper is the one with the radius that measures from the extreme opposite point to the farthest edge of the curve. The broader the sweep, the more space you need. The method works for any drawn contour, not only a circular arc. Use the radius of a circle that has the same tangent and curvature as the curve at the point the in the middle of the strongest part. At that place, the circle approximates the curve.
Flatter curves can be drawn, but will not come around at both ends. The drawn contour gradually bends towards where the area the center point is in, but never completes a half circle. Practice continuing along while moving around the center at the radial distance, or lesser or farther, not only keeps you from drawing outside the space, but also can help you make more pleasing forms and proportions.
Learning to control your curves is better when you experiment with using the radius. Driving and drawing are just two common endeavors that can improve. Anything that involves curves might be a little finer.
Wolfram’s Mathworld, Radius
Fire Chief, Turning Circles (April 1, 2004)
National Public Radio Website, The Formula For Perfect Parallel Parking (January 23, 2010)