 Pressure generates force 2
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For a slightly larger gasoline engine, assume a maximum load of 5 tons. This is why, with the appropriate test setup, a heavy truck can be parked on four car pistons, which clearly demonstrates the stability of pistons.
What seems to be even more troublesome, however, are pressure oscillations.
These are usually a sure sign that something is wrong. Knocking combustion, for example, seems to hit the piston the hardest. This can even cause maximum permissible temperatures to be exceeded locally.
Temperatures well over 2000°C are possible for brief periods. Since the greatest heat always hits the piston crown, it is more likely to be dissipated through the top piston rings than the piston skirt.
These are usually a sure sign that something is wrong. Knocking combustion, for example, seems to hit the piston the hardest. This may even lead to the maximum permissible temperatures being exceeded in some
places. Temperatures well over 2000°C are possible for brief periods. Since the greatest heat always hits the piston crown, it is more likely to be dissipated through the top piston rings than the piston skirt.
We're dealing with an oscillating (back-and-forth) and a rotating mass. The connecting rod is also mathematically divided accordingly, its mass distributed between the two connecting rod eyes. The small connecting rod
eye is then assigned to the piston, the large one to the crankshaft.
Now you have a clue as to how to size the weights attached to the opposite sides of the crank throws, which are sometimes even bolted on in larger engines. Simply put: Saw through the connecting rod approximately in
the middle and balance it on the crankshaft using appropriate counterweights, which can be finely tuned by drilling holes in it.
But there are also the oscillating masses of pistons, piston rings, piston pins and piston pin retainers, together with the smaller part of the connecting rod. To balance these, for example, at dead center, the counterweights
would have to be even larger. Even in single-cylinder engines without a balance shaft, this only occurs to about 50 percent.
You can't balance 100 percent because this additional mass builds up a lateral force up to the midpoint between BDC and TDC, which can only be somewhat picked up by multi-cylinder crankshafts. A single-cylinder
engine would actually need a balance shaft to reduce the missing 50 percent.
However, it would have to be positioned exactly where the crankshaft is. Since that's not possible, two are used, one on the left and one on the right of the crankshaft, each with a 25 percent offset. These then provide the
desired 100 percent balance at BDC and TDC. If they are also allowed to rotate against the direction of rotation of the crankshaft, they also compensate the lateral forces fairly perfectly.
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