system
Given the following post, respond as if you're commenting on Reddit:
human
Why are rotary engines considered unreliable, or "bad" when compared to piston engines?
gpt
One of the main problems are the rotor tips. In a piston engine, the cylinder and piston have a rather large contact surface which is constantly lubricated and seals the combustion chamber against the crank case. In a rotary engine, the tips of the triangular rotor drive along the chamber walls to seperate the chambers. This means they have to be very precisely positioned and bear a lot of load, compared to a regular cylinder lining.
The tips have to be extremely abrasion resistant and hard, but function as tight seals as well. That's a difficult trick to pull of and makes the whole system somewhat less reliable.