How does a 4 cycle internal combustion engine produce motion?

Question

I want to know how the energy from the piston turns the crankshaft. The connecting rod is not directly connected to the crank, there is a gap of a few 1000ths filled with oil. So why doesn't the rod just slip uselessly on the crank? Wouldn't a direct connection instead of the slipping connection produce more power?

Answer 1

think a little more. You need bearings or a smoothe surface with lots of oil so parts do not fail because of excess friction and heat. The end of the rod is pushing on the crankshaft. Look at a bicycle crankshaft and the pedals to get a better understanding. Your leg and the pedal are the piston rod, there is a bearing within the pedal, and then connected to that is the crank.

Where would the rod slip to. It has no other choice to push the crank down and have a connection that rotates about it. And remember when the spark ingnites and combustion happens the rod is not perpendicular to the crank, imagine if it was and the stress it would create, that's the only thing i don't like about the wikipedia video it shows spark occuring at top dead center, when the spark occurs before the piston hits top dead center.


here hope this helps

http://en.wikipedia.org/wiki/Image:4-Stroke-Engine.gif

Answer 2

If it was a direct connection it could not rotate. The rod journals are off center, during the power cycle, the fuel is ignited slightly after rotating past center, and actually five the crank a push which translates to rotation and rotary motion.

Answer 3

Weight called a flywheel keeps the crank in motion. Direct welded connecting rod to the crank shaft would produce no motion.

Answer 4

The piston is pushing on a crank. You need a crank to make things go around. Like the crank on a bicycle, where the pedal is.

what pushes the piston is pressure*volume of the burned gases. In engineering we call that PV work. When the gas expands, it does work on the piston, which transfers that work to the crank.

Answer 5

Just because there is oil between the parts doesn't mean there isn't friction consider the oil more of a cushion then rather an invisible force, between these parts there is still pressure. If you put a pillow against a door and pushed, the door would still close wouldn't it? Of coarse it would the same principle is in action here the oil is simply a buffer to prevent excess friction. In fact there are a lot of industrial tools that are designed to use oil alone to move parts such as hydrualic rams or a PHARS unit (Jaws of Life)

Answer 6

Linear motion needs to be converted to rotational motion.

You cant do that with a solid connection.

Answer 7

Are you kidding?