Hydraulic Press Build


https://www.youtube.com/watch?time_continue
“0&vςxlAWytx9g
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.
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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. https://www.engineersedge.com/standard_material/Steel_channel_properties.htm
-jsw
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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
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writes:

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
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"Jim Wilkins" wrote in message writes:

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.
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"Bob La Londe" wrote in message writes:

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.
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writes:

https://www.egr.msu.edu/~harichan/classes/ce405/chap5.pdf
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
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On Saturday, September 1, 2018 at 11:12:10 AM UTC-7, Bob La Londe wrote:

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.
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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
On 9/2/2018 3:32 AM, whit3rd wrote:

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https://www.aero-mag.com/read-all-about-it/ "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 "
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