Small-scale olive oil processing in Ancient Rome

The hinge point in behind the olive stack. You can see that there's a bundle of sticks tied to the support there holding the log in place. The other end with the rock and pulley had a guy twisting a log in order to wind and shorten the rope attached the the rock. This causes the rock to pull down on that end, creating pressure on the olive stack as the other end of the log is anchored.
I'm guessing the tree is mostly a guide but the Y of the tree also provides a stop.

Is that Y-shaped tree trunk meant to be there? It seems to me like it's just getting in the way of the press operating
- Engineer here. I'm guessing the Y-shaped log acts as a support to hold the lever-log while the olive sack stack is removed for refilling. I'd guess two or three guys lift the log while someone pulls the stack out, and then they rest it on the Y so that they don't have to lift it from ground level each time.
  And to answer some other questions from the thread: it may be useful to have the pulley attached to the boulder instead of the groubd so that they only ever apply a known force to the olives during the squishing phase. Otherwise, they could compress the olives until the skins squeeze through or the sacks burst. Once the rock begins to lift, the press is complete.
  
  I'm not sure it would work very well as a rest to make removing the bag easier, since the press would be at its maximum depression while resting on the trunk. You could release sone length of rope to reduce the force, but if the weight of the log is a significant obstacle to lift then you do still need to lift it to get the bag out. It would probably be better to remove much more of one of the two branches so that you can press down beyond the junction, release the rope to the wright, then raise it and push it sideways just a little to keep it elevated above the bag
  That said, I do think it being a limit on the amount of vertical travel the lever has to prevent bursting / otherwise over-pressing the bags makes sense
- Same question. It looks like a fulcrum, which would pull pressure off the press.
  However, maybe the illustration is just misleading, and it's a guide to stabilize horizontal movement of the lever, and the beam is only touching the sides. It could also be functioning as a limiter, a stop to prevent too much pressure damaging the press, or breaking the beam.
  I think it's not a fulcrum, and only looks like one in the drawing.
  (Not an engineer, either)
  
  You've interpreted it the same way I did at first. I went looking for real historical examples and the hinge point should actually be at the end of the log that's on our left, which makes a lot more sense mechanically. I have to assume that Eheran's suggestion that it's only a horizontal guide and doesn't impede the vertical travel of the lever is correct
- Without it, it would/could just fall off the otherwise tiny support. It has no other function, only touches the log at the sides.
  
  I think you must be right. I have no better ideas, anyway
- It supports the beam to allow more or less pressure to be applied to the press, I think.
  ... I think. I'm not, uh, very mechanically inclined.
- I also fail to understand how such press might work, the counterweight seems to be working against the press purpose.
  
  The hinge point should be at the end of the log on our left, not where the Y shaped trunk is. If you assume the Y shaped trunk doesn’t obstruct the vertical movement until after the point you want to move it to, that then works as a press
  
  What do you mean? What counter weight even? The big block on the right where the man is, is the actual weight that causes the press to compress the olives.