[Mgs] Pistons

[Paul Hunt]

Thanks, that was the conclusion I had come to.  However since then I've seen
an even simpler description, which is that when half way down on the expansion
stroke the centre-line of the con-rod is pointing at the thrust face.

PaulH.
  ----- Original Message -----


  Picture a piston half-way down the cylinder, during the power stroke.
Pressure from the burning fuel pushes straight down on the piston.  The conrod
is reacting this force; however, the conrod is at an angle, so the
(compressive) load in the conrod is also pushing the side of the piston
against the cylinder wall.  This side of the piston is therefore the thrust
side.

  Looking from the front of an engine, it spins clockwise (apart from, I
think, some Japanese engines - but let's not go there!).  Therefore, during
the power stroke, the big end of the conrod is over to the right of the engine
centre.  Its compressive load is therefore pushing the piston over to the
left, so the left side of the piston is the thrust face.