Hello! I'm completely lost trying to derive an equation that'll give me the driving force in a DAC, and I really need some help from you guys. The purpose of knowing this is to optimize the amount of air that is needed (24 litres are available, pressure up to 8 bar) to drive a radio-controlled car (60 kg), which needs 20 N to keep in linear motion. The connecting rod from the cylinder goes to a scotch yoke, and I guess this is where I get a bit lost because of the force that varies through the angles from 0 to 2π. And I don't quite know when the ideal gas law comes in the picture (it should be used with 1 atm being the ideal pressure at the cylinder bottom, right?). Data: * Car wheel radius: 0,1 m * Force needed to keep the car in motion: 20 N * Gearing between wheel and engine: 1:6 (that is, one rev for the wheel is 6 for the engine) * Efficiency is 10-20% * 24 litres of air available and the pressure is to be choosen between 1-8 bar * The volume of the cylinder is between 30-40 cm^3 (also to be decided) My technical english isn't flawless so if something is unclear I'll try to do a better explanation.