Diecast car collecting is a hobby children and adults have enjoyed decades. Dedicated diecast fans often keep this hobby throughout their life and collect and trade cars feverishly. Many avid collectors often want to design their own diecast cars, whether to replicate a design they can't find, to improve upon an existing design or simply to create something original. If you have a design idea for a diecast car you'd like to see, there's no need to wait for someone else to make the design.
Decide what scale your car will be (see Resources). Scale is the ratio of the size of your diecast car to the real thing. The scale model you work from will depend upon the size you want your diecast car to be. Early Hot Wheels were at a 1/64 scale and later models (in the 1970s) were 1/43. Use a scale conversion chart as you work through the design process (see resources).
Take measurements from your real-life model if one is available. Measure it with the doors, trunk and hood open and closed. Measure the width, height and length of your real-life model. Take detailed measurements of the open parts of the vehicle as well. Take as many photographs of your real-life model as you can, especially of the engine and the underside.
Rough out the design of your car. Start with the body of the car first. If you're working from photographs of a real-life model, lay the photos out or pin them to a cork board so you can see them as you develop your rough sketch. Sketch your design from every angle, taking care to add notes on dimension. Use a separate sheet of paper for each angle.
Sketch the detailed parts of your diecast model, which includes the engine and the underside of the car.
Work from your original rough sketches and do a polished sketch, this time putting the car together in one sketch. Draw every angle of the car both with doors, hood and trunk open as well as closed.
Color your car with colored pencils. Add any emblem details. The finished set of sketches, complete with dimension and design notes written in the upper left-hand corner of each sketch, is the final design model for your diecast car.