Personally, I would eliminate the mid-span fulcrum, having the pivot all the way at the far end. The pivot end could then be secured quite simply between two timbers or a notch in a wall timber or so.

You could use a screw mechanism like shown in the video, or more simply just use a block and tackle. Although with a screw on the end you can gain more force.

As for dating press types, there are examples of the remains of screw-type presses, the type with a screw that pushes directly down on the fruit, to be found in the walls of Roman ruins.

Both screw and beam presses are very ancient, with the screw principle known well among ancient Greeks, and the beam principle very simple and straightforward.

I learned a simple trick from Swiss cheese makers and their presses -they call them Schwarpressen. If your beam by itself is not heavy enough, set a big boulder out toward the end of it.

The mid span pivot is actually the top of the press stack. As the fruit pulp compresses it begins to resist the beam making everything past the stack a cantilever beam. I'm not worried about the forces involved in the center span pivot as seen in the video because if the beam can handle the loads when used on the end pivot it will be fine when used on the mid pivot.

This picture really simplifies things:

http://2.bp.blogspot.com/-0AXOSJ1OcK8/ToX3fkUGaiI/AAAAAAAAAO4/KCYdx7XJu5Q/s1600/Lever+Press.jpg

All the examples that try and explain shear horizontal talk about lying a number of planks on top of each other and then subjecting them to a load and watching how they slide past each other.

I need a member/s to resist 17700lbs in a point load. If the member is a 16"(depth) by 8" then it seems to be fine from my new found understanding of shear but what about 2 8"x8" on top of each other?

In Timber Framing see

Miller, Joe and Ben Brungraber
Mechanically Laminated Beams, 93:14

I found lots of stuff of mechanically laminated beams which was interesting but not very useful at the moment.

I did find a formula for Fb for a two layer non laminated beam which basically seemed to deliver the same required Fb rating for two 8x8s stacked on top as each other as for one 8 (width) x 16 (depth). Which is odd but maybe not too surprising.

Would failure due to horizontal shear be less of a factor given that the two members in the stacked beam are free to slide past each other?

Today i comeback this community and i would like to ask something relating to your topic which is that I'm struggling like many others to get on the property ladder.......... I know as other know that timber frame houses are far cheaper, but I don't know how you go about finding a plot and building one which is one of best, do I need planning permission?what you think...?