When sketching machines, it is important to remember that the goal is to communicate with the sketch. When observing the machine before making the sketch, you should notice what the most obvious parts of the machine are, and reproduce them as simply as you can on paper. Select the perspective that will best communicate the machine, and observe the machine from that perspective. What you need to do then is look at the basic shapes in the machine, and translate the machine into triangles, rectangles, and circles as the foundation of your drawing. Take the largest shape and start there, and then add the other shapes in size order.
To make your sketch realistic, use different size or weight lines, capturing the lines that are heavier and thinner from your perspective. You may need to use different size pens or markers to vary the line weights. The thicker lines anchor your machine on the ground or floor, while thinner lines capture the grace and lightness of the machine.
The best strategy for exceptional machine drawings is to practice, practice, practice. Find drawings of machinery that you like and copy the elements that you notice as most powerful. You can incorporate effective elements from one machine or tool into another drawing with similar features. You may not like your first sketch of a machine, or any object, but do not give up. Draw it again and again. A professional artist at a major museum said that she will sketch an object sometimes 100 times before she is satisfied with it. Each discarded drawing is not a waste of her time, she maintains, but a step of growth to being a better artist. When you do not like a drawing that you have done, it is likely that there is some element in the drawing that did not look right to you, and you can work on that portion of the sketch and get it right, and then move on to another part that you want to improve on.
Remember that sketches of machines are not fine art, and serve another purpose than to be aesthetically pleasing. The audience and purpose of your sketch will dictate the quality of the sketch that is necessary for you to be “finished” with it. Even the best artist is not ever convinced that he or she has the “perfect” sketch. It’s progress that is important in the artistic interpretation of a machine or tool, not perfection that is the goal of the work. A picture could be used in place of a sketch if an exact replica is what was desired.
In sketching, as in any type of art, the selection of your tools is very important. Various weight writing instruments can make the work much easier. It is best to begin with the lightest lines, with pencils or ballpoint pens, and if those do not achieve what you are working for, then move to the heavier tools, such as wider tip pens or markers. Heavy markers can easily overwhelm a sketch, and should be used only for accents, rather than basic forms.