Don S wrote:

> Is the 3:1 ratio set by the distance from the start of the cross
> beam to the down tube and from the down tube to where the weight
> is suspended, B/A in the below:

No, it's like this:

A B C

O----------O-------------------------------O
Hinge Platen Weight
shaft

The distance for the "platen lever" is A-B, and the distance for the
distance for the "weight lever" is A-C. The mechanical advantage would
be A-C divided by A-B. (This is called a 2nd class lever. A seesaw is a
1st class lever.)

> I was considering a single 2x4 for the cross beam but perhaps
> two would be better, something like this when viewed from the top:
>
> |--------------------------------
> hinge | O weight
> |--------------------------------
>
I would use a pair of 2X6's, _on edge_, about 8' long.

Don, I have to agree with Tom and Darwin on this, that it is a lot of
work & expense (& design effort) to make a practical press from scratch.
Over the years, I've built two. While each worked (works!) well, it
was probably more hassle than it was worth. I now have a shiney new
bladder press (although this year's crop was too meager to warrant
getting it dirty :-( )
It's certainly a doable project, but not everyone would want to
undertake it. Someone who's very handy with tools & design can have a
fun time doing it, but but someone who isn't handy might well be
frustrated with the result.

HTH, Mike MTM