Rotary engines aren't widely used, but are a valuable resource to those applications where they are used. They are becoming more and more common in cars today. Mazda motor company makes several cars with the rotary style engine in use.
Rotary engines are longer lasting than reciprocating engines. They have far less moving parts and are simpler to build. The fewer parts provide less movement and less chance for failure. Reciprocating engines have a violent up and down motion that causes failure. Rotary engines have a single rotor that spins perfectly centered.
Rotary engines are mainly used in airplanes where these engines are more reliable and have fewer moving parts to keep up. Most airplanes have a large rotary engine that moves at high speeds, these speeds are unachieveable with reciprocating engines.
