I love these old hand drawn cutaway line drawings of engine and machinery that were mainly used in shop repair manuals and the like. Sometimes they were used in advertising as well.

Producing these illustrations is a vanishing skill in light of modern computer-driven technologies. Still, there are some alive today who can still do this kind of illustration work by hand.

Triumph-Bonneville-650-Cutaway

Triumph Bonneville 650 Twin Unit Construction engine cutaway line illustration