Glossary D
Differential gear is defined as a bevel gear that permits rotation of two shafts at different speeds.
Dyes are characterized as a synthetic or natural organic chemicals that are soluble in most common solvents. Characterized by good transparency, high tinctorial strength, and low specific gravity.
Derail is a verb that is described as "to leave the rails"; as a noun however, derail concerns a safety device placed on the track, usually on a siding, to prevent cars from rolling onto the main line. It may have a cast steel frog that diverts one Wheel up and over the rail to stop a car well short of the clearance point. Some derails consist of a single switch point that is normally left open to stop any moving car clear of the main track.