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Gadget Freak Case #232: Finding the Right Hydraulic Force
12/20/2012

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bob from maine
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Platinum
Re: A really practical gadget
bob from maine   12/21/2012 2:37:52 PM
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The one I built has a pressure gauge like the one shown. The pressure on the gauge directly correlates to the pressure applied to the component being bent/mangled/distressed. The gauge displays psig which can be fairly easily converted to lbs of force. If I was developing a process and had to train someone else to use this device, I think this display would be much more useful. Good idea.

RichardBradleySmith
User Rank
Bronze
More: Hydraulics in the AC72s.
RichardBradleySmith   12/21/2012 2:50:51 PM
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In case you missed it: "We have 38 hydraulic cylinders. We want to avoid running hydraulic piping to each of them, because that would be heavy, so we have electrovalves embedded in the wing to actuate the hydraulics. But if you had two wires, positive and negative, running to each electrovalve, your wing would look like a PG&E substation, and that's heavy too, so we use a CAN-bus [controlled area network] with far fewer wires. Still, it's incredibly complex.

"We wind up with lot of hydraulics," Cayard says, "and the America's Cup rules don't allow stored power, so two of our eleven guys—we think, two—will be grinding a primary winch all the race long.  Not to trim, but to maintain pressure in the hydraulic tank so that any time someone wants to open a hydraulic valve to trim the wing, there will be pressure to make that happen."

Full story:  http://blueplanettimes.com/?p=8022

enauman
User Rank
Iron
Re: who made the front panel?
enauman   12/22/2012 9:34:06 PM
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I made the front panel.  I used BobArt (from BobCAD) to generate the engraving artwork.  I have a 10x54 3 axis CNC vertical mill in my garage that I used to cut the panel and engrave it.  I also use the mill to make my own Printed Circuit Bords.

enauman
User Rank
Iron
Re: What am I missing?
enauman   12/23/2012 2:28:06 AM
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The comment about the number of pumps on the handle was editorial and has nothing to do with the calibration or operation of this system.  I was trying to relate how one goes about straightening something on a press that has no force indication or pressure gage.  In which case, the only way to crudely estimate the force applied between successive 'trys' is to count the pulls on the handle.

MYRONB
User Rank
Gold
Re: A really practical gadget
MYRONB   12/28/2012 12:41:39 PM
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If the only object is to straighten a piece of metal, then shouldn't we just apply enough force to "overbend" the workpiece to allow for springback and then measure the piece for straightness?   Then, if necessary, hit the piece again and re-measure as necessary.  It seems we just need a press with sufficient force to bend the metal. 

I had the damaged journals of of a race-engine crankshaft welded and the rebuild shop did just as I described above to straighten the shaft before machining and grinding the journals.  The press operation  was done by "eyeball",and precision measurements were made  with a dial indicator to check concentricity.  That crank lasted several seasons with many sprints up to 9.000 rpm with no problems.    Unless there is more to this story, I'm not sure why a force gauge is required.

Best regards,  Myron Boyajian

Tool_maker
User Rank
Platinum
Re: A really practical gadget
Tool_maker   1/3/2013 1:02:46 PM
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  I am with you Myron. In my years in the shop I straightened dozens of shafts, just as you describe. You put a block under the shaft/plate or whatever, at each end of the distortion, bent side up, and then apply pressure until it overbends. Measure with a straight edge and dial indicator, aplly that lesson and try again If there is a formula for how much over bend is required I have never seen it. This is also a problem I run into quite often in pressforming shallow bends. It may take many tries before you get to the right point of elastic deformation and it stays where you want it to be. 

  This device would have to be recalibrated everytime one of the points of contact has been changed. I can see where it would be usefull on a repetative operation (same shaft/same offset), but for just general arbor press bending, I think it would be a toy that would end up in a corner somewhere while work was being done.

Cadman-LT
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Platinum
Re: A really practical gadget
Cadman-LT   1/12/2013 11:00:13 AM
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I agree. Practicality vs functionality? or something like that

cookiejar
User Rank
Gold
Why bother?
cookiejar   1/13/2013 12:23:03 PM
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While designing electronics has been a career for me, when it comes to spare time, I don't cannot envisage spending the time and effort to build such a device when simple $15 old fashion dial pressure gauges are readily available in a wide variety of full scale ranges. 

To convert psi to pound force, you simple multiply the square inch area of your piston by the psi reading of the gauge.  Let's say you have a hydraulic cylinder with a 1.5" bore (1.77 sq. inches) rated at 10 tons (20,00 pounds).  The pressure at this rated load would be 11,299 psi.  In the stated application, all you want is repeatability, so the actual units don't matter. 

I've used a cheap 10,000 psi mechanical gauge on my press for over 30 years and it's still doing the job well.  I can guarantee you that in 30 years your creation probably won't be in service and the parts used definitely won't be available, while commodity pressure gauges will still be available cheap.  Such is the sad story of electronic devices.

However, if you have a need for automation, then electronics is king.

mrdon
User Rank
Gold
Re: who made the front panel?
mrdon   1/20/2013 10:36:02 PM
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enauman, What a nice analog and microcontroller application. I like the look of the front panel and I think it's impressive you made your pcbs by use of a milling operation. I definitely share this video with my Microprocessor & Microcontroller students at ITT Tech. Also, is there a clean circuit schematic diagram and software code available for this project?

enauman
User Rank
Iron
Re: who made the front panel?
enauman   1/21/2013 1:22:56 AM
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Hi mrdon,

The schematic was drawn in Sunstone's free design software "PCB123".  Since their software is free, it limits the type of file outputs available to their native format.  The schematic appears so poor because the only way to get an electronic copy is to do a screen capture and paste it into something that will allow saving to a different file type.  Not the best  way.  If you go to Sunstone's website and download the program, I will send you the file so you can open it.  I use PCB123 because it is a pretty good PCB design program and Sunstone's circuit board prices are reasonable.  When I mill a board myself, I use PCB123 to draw the schematic and layout the board.  But then I have to redraw it using my CADCAM program in order to get the tool paths.  It is a tedious process, but for me, it beats spending $10K for PCB design software.  And, for moderately populated boards,  I can go from the first "back of the napkin" schematic to an assembled prototype in a day.  Send me your email address and I will send you the schematic file and code listing.

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