[TheForge] Upside down Press - oh what a tangled web we weave

[smith at blacksmithing.org]

Bruce wrote:
So, have you considered the possibility of a double-inversion?  [snip]
 --hmmm---he says well scratching his head:
If I understand the idea, the lower die is fixed in space, the cylinder is 
no longer inside the frame but attached to the base, and the frame moves up 
and down. The crush occurs during the retraction of the ram rather than on 
the extension.  For those versed in hydraulics, is the power generated on 
retraction equal to the extension? The pressure would be the same (same 
pump, etc.) but the surface area would be different (by the area of the 
actual ram-shaft).  The lower die would also have to be well supported since 
the force of the frame coming down to the crush point would be transferred 
to the lower die and whatever was keeping it from moving.  Also, the frame 
moving implies a significantly wider left-to-right dimension for the slide 
assembly (from inside the frame to outside the frame) and hence a greater 
lever arm to content with.  Sounds like a lot more fabrication to me but you 
would gain a real space saving when the cylinder is fully retracted and the 
frame telescopes into the base. 

The only fundamental problem I can see with the original design is the 
simple weirdness of having the work move up and nobody has volunteered 
actual experience with this yet.  I guess I'll be a guinea pig - though as 
James Binnion pointed out, they do exist commercially, i.e.,
http://www.carolinaknives.com/press/press.html. I do note in that design the 
cylinder is fixed like the one in my plans and there is no overt precaution 
about screwing the seals with slag.  I like Chuck's suggestion of flipping 
the cylinder and I had planned on making a shroud to protect it anyway.  By 
modifying the design to let the cylinder move through a felt-lined hole in a 
cover plate, there ought not to be any contamination.  The only problem 
might be oil seepage around the seals (gravity and time working together) 
but if that is significant, then I would probably be taking an oil bath 
anyway.  Ahh - the "pleasure' of engineering-by-the-seat-of-the-pants'.... 

Steve Bloom