Hyd Press

[rdhem2]

Any of you guys out there have a good design for a cable lift system for the table on a hydralic press.  I have an idea for the crank and gearing but need some ideas for the routing of the cables.  Leaning towards using very flexable .125" or .1875" aircraft cable with crimp type fittings.

Always searching for better ideas.  I usually find them when I am about 75% finished on a project.           

[Lew_Merrick_PE]

RD,

How much does/will your "table" weight?  That is going to be one factor.

Take a look at an old cable-driven parallel beam drafting set-up.  The cables held the drafting beam "horizontal" to the table and assured that it moved in a (reasonably close to) parallel manner.  Many of them had the "equalizing" cable path cross behind the drawing board, but several of them had the cable run along the sides of the board which would be more to your liking for this application.  When I close my eyes and visualize it, I see six pulleys on the cable run and half-a-dozen or so "turns" on the capstan.

Does this help?

[DaveH]

Might be something here could help? http://www.metalworkingfun.com/showthread.php?tid=163
 
DaveH

[rdhem2]

Lew;
Thanks, I know what you are talking about but it has been years since I've seen one.  My drafting arm now has everything hidden in double tubes to each pivit so I know not what magic it contains.  If I get real desperate I may have to perform an autopsy!  Only difference here between me and a Doctor is mine has to work again after I put it back together. 
As far as weight probably in the 150 lb range, the press frame it's self is rated for 50 ton.

[rdhem2]

DaveH;
Thank you.  Cruised your offering and picked up an idea or two.  Hope I can explain my idea in a fashion that is comprehensable. 

If I make each side independent so to speak with a take up spool/reel on each side would the difference in diameter as the cable winds up to capacity be enough difference to be a problem?  Each side identical with a common drive connection so each turns the same.  After all some tilt would be OK as we are only lifting to clear the pins and then setting it back down.  Just so it does not jam or hang.  Little late for a redesign at that point.
Or
One take up spool with a pulley setup so all four corners lift the same.  Or so it says in the fine print.  The only down side to this idea is the cable crossing the opening of the press.

DaveH, not knowing all things pertenent I still have to ask.  I am a history buff from way back.  Reading a lot of Winston Churchill and his efforts early in life.  You being from S. Africa.  Are you what they refer to as a Boar?  One from Dutch decent?  One of those guys who used Mauser magazine rifles while the Brits tried to keep up with single shot Enfields.  They were saving the King money you know.  Just curious.       
Have a good day

[Lew_Merrick_PE]

RD,

The main parallel rule type of drafting board had a cable running "up" either side and crossing in the middle (making an "X").  The thing is that, were you to run the cables in a "U" shape such that each "edge" had a pair of cables (turned back on themselves with a pulley), you would have an "up" and a "down" at each (vertical) edge.  Most normally, you would make that an upside-down "U" to place things where you (most likely) want them.  This is the way the (1970's vintage, at least) EnerPac hydraulic presses had their tables move.

On the larger presses, there were two such cable runs.  They wrapped around an axle at one side of the main frame such that the runs avoided using more than the cable diameter where it passed the hydraulic cylinder.  I helped a friend of mine rebuild such a beastie back in the early-1990's and the hardest part was coming up with the maximum axle diameter that did not wear one out with the torque required to drive it.  If you table is 150 lbs and the axle is ø2 inches, then your "drive torque" will be 150 lb-in (12.5 lb-ft) and the table will move 6.28 inches/rev.  It seems to me that we ended up somewhere close to ø1.75 on the axle diameter, I just don't remember the weight of the table.

I hope this helps.

[DaveH]

Hi rdhem,

I was born, bred and educated in England (Leicester). I left in 1980 (emigrated) to live in South Africa mainly through the company I worked for at the time. I am a South African  by choice but not a Boer. The word boer (in Dutch and Afrikaans) means farmer - hence boerewors (farmer's sausage). Like you say they were Dutch settlers here. I always feel a little for them, they left Holland because they were persecuted and the same happened here. 

A little tilt shouldn't make much difference - mine tilts depending on how the cables overlap each other on the winding drum. I do get the feeling yours is a much larger table.?
 
DaveH

[duckman]

Get a small hand powered winch fasten it to one side of your table run cable over the top on some small pulleys, attach the cable to the other side crank up and down if the holes don't line up raise until the low side lines up put in pin and lower until other side lines up , make some slack in the cables.