Hydraulic Press Build

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I know some folks may not be a fan, but I noticed he made his main
uprights out of 1/4" steel plate welded up into a box.
I just made a deal on a small quantity of 4x8x1/4 A36 plate for about
half local metal yard retail. I'm going to use one piece as the top for
my welding table until I run across a good deal on something thicker. I
decided to buy some extra just because the price was good enough to be
worth sitting on it for a while.
I've been want a little better hydraulic press for a while. I have
pulled my 12 ton partially apart. I can still use it, but only above
the torn metal. LOL. My 20 ton now has a bow on the top beam. That's
what happens when you try to press a prop hub out in the wrong direction.
Anyway, I was wondering if 1/4 plate really was adequate for the
uprights on something like that. I have no need to make one as tall as
stretch built his in the video. I won't have a joint in the pieces like
he does, and I wasn't planning on going 50 ton. I've got a pretty beefy
30 ton cylinder and power unit off of a log splitter I was thinking
about using for the hydraulic part. My 20 ton has been adequate for
anything I needed to press except for the fact that I managed to bend
it. I've also got some heavier stock for things like the top and table.
Ok, tell me how stupid the idea of using 1/4 plate and making my own
upright tube is.
Reply to
Bob La Londe
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If you can match the frame members to this table you can calculate the tension and bending stresses, then give your modifications a larger margin.
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-jsw
Reply to
Jim Wilkins
The frame "uprights" of a press (hydraulic press) are in pure tension. Very rare engineering loading case. Abnormally easy to treat. Opposite of instability - the load "assists" pulling them straight. Load bearing in this very special case is totally simply to calculate on-paper: multiply the cross-sectional-area (width*thickness) by the yield stress divided a safety-factor (say 5?) and there you have it.
Typical other cases: In a beam you have to consider buckling instability, etc. Likewise a column (it looks the same as a "tie" but is in compression). The engineering design is much more complex and you have to work out which effect comes to the fore in most limiting the load-bearing capacity.
Hope this is helpful comment... Regards, Rich S
Reply to
Richard Smith
What he wrote is true only if the connections to the horizontal members that withstand the pressing force are somewhat free to rotate at their ends as they deflect, ie they are bolted along the centerline of the uprights instead of being welded.
A bolted or pinned joint with some give leaves the tension evenly distributed across the uprights, while a solid welded joint concentrates the stress on the inner corner as the top crosspiece flexes upward.. Look closely at the design of commercial presses. -jsw
Reply to
Jim Wilkins
What he wrote is true only if the connections to the horizontal members that withstand the pressing force are somewhat free to rotate at their ends as they deflect, ie they are bolted along the centerline of the uprights instead of being welded.
A bolted or pinned joint with some give leaves the tension evenly distributed across the uprights, while a solid welded joint concentrates the stress on the inner corner as the top crosspiece flexes upward.. Look closely at the design of commercial presses. -jsw ***************
Thanks. Being a boat fan (welded and molded) I am somewhat familiar with the stresses at what we call hard points. I have experienced various degrees of failure at hard points from broken welds in aluminum to stress fractures in gel coat even in name brand commercial products. Its good to think about this in a different application. I'd note that I've also seem failures on two hydraulic presses. Neither was instant or catastrophic. Both were Harbor Freight presses. The column on a 12 ton literally pulled apart with a 12 ton jack, and the top beam bent on a 20 ton using a 20 ton jack. They are both still moderately useable. I had certainly intended to study their modes of failure as I approach the new build.
Reply to
Bob La Londe
What he wrote is true only if the connections to the horizontal members that withstand the pressing force are somewhat free to rotate at their ends as they deflect, ie they are bolted along the centerline of the uprights instead of being welded.
A bolted or pinned joint with some give leaves the tension evenly distributed across the uprights, while a solid welded joint concentrates the stress on the inner corner as the top crosspiece flexes upward.. Look closely at the design of commercial presses. -jsw ***************
Thanks. Being a boat fan (welded and molded) I am somewhat familiar with the stresses at what we call hard points. I have experienced various degrees of failure at hard points from broken welds in aluminum to stress fractures in gel coat even in name brand commercial products. Its good to think about this in a different application. I'd note that I've also seem failures on two hydraulic presses. Neither was instant or catastrophic. Both were Harbor Freight presses. The column on a 12 ton literally pulled apart with a 12 ton jack, and the top beam bent on a 20 ton using a 20 ton jack. They are both still moderately useable. I had certainly intended to study their modes of failure as I approach the new build. *
***************
Hmmmmm.... looks like if I use 1" pins and holes closely sized I'd get some minor hole deformation at high tonnage the first time I used a particular set of holes, but be below the yield strength on those holes afterwards (full engagement of pins after first deformation.) If I used larger pins the upto under 50% of the column width my strength just goes up. As to the column itself I'd be an order of magnitude below what a 30 ton ram could dish out. After that it?s a matter or making sure the table and top beam are good for the stresses involved. I have time to think about this though. Its not tomorrows project. I'm still finishing up my welding table.
Reply to
Bob La Londe
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You can increase the bearing strength of the column holes by welding on doubler plates.
I have a similar bolt strength problem to solve for the splice plate(s) joining 8' channels into the the 16' track of a gantry hoist. -jsw
Reply to
Jim Wilkins
If instead of pins, you used structural tube, the tube (though having high yield strength) could elastically deform to the holes, which would minimize their yield (because of high contact area). Our old (?75) ton press used tube for the height-adjust pins.
Reply to
whit3rd
Some tubes have sliding fit inserts of smaller tubes and making up two or three tubes inside makes for a strong tube looking device. Often times layers are stronger than solid.
Martin
Reply to
Martin Eastburn
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"Of particular interest is the unusual construction of the Spitfire's main wing spar booms. Each spar boom is built up from five square-section concentric tubes made of 11 SWG aluminium alloy and one square section central plug. The tubes are made to fine tolerances and fit tightly into each other. Using specially commissioned photographs and original working drawings we show how at the wing root the spar booms are made up of five thicknesses of tube, but as the loads on the spar decrease progressively towards the wing tip, so the inner tubes terminate one by one, until at the wing tip only the two outer thicknesses of tube remain."
I have the book. It's a good effort but this is its weakness: "Scope for an in-depth technical manual is necessarily restricted by our self-imposed limit to 160 pages "
Reply to
Jim Wilkins

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