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CrestonM 
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Joined: 08 Sep 2014
Location: Oklahoma
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 Topic: How to Choose a Hydraulic Cylinder?
Posted: 10 Mar 2022 at 9:21am |
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I’m in the planning stage of building a cultivator with folding wings (3-30” rows on each wing) and figure there has to be a rule of thumb or formula to determine what size cylinder should be used. I’m planning to make the wings fold similar to how some folding planters work, where the cylinder is inside the frame tube. I’ll probably be pulling it with my 7080, and I don’t know the hydraulic PSI and flow rate off the top of my head but I could look it up this evening.
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Edited by CrestonM - 10 Mar 2022 at 9:21am
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Tbone95
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Joined: 31 Aug 2012
Location: Michigan
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Posted: 10 Mar 2022 at 11:07am |
I don't know about a rule of thumb, since there is a lot going on, a lot to consider. Such as, total weight, how it's leveraged, stroke required for full range of motion.
I would design for pressure around 2000 PSI, any "modern" tractor should be able to supply that. I would then mock up your mechanism as close as I could and determine the stroke length you need. Diameter of bore you'll have to calculate by how much weight you're lifting and allowing for the leverage ratio, usually such that the force required by the cylinder is more than the weight, because the load is usually on the longer side of the lever......lots to consider, but one step at a time not too bad.
A relatively small cylinder can supply a LOT of force. At 2000 psi, a 4 inch cylinder exerts 25,132 pounds.
Edited by Tbone95 - 10 Mar 2022 at 11:11am
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DrAllis
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Posted: 10 Mar 2022 at 12:17pm |
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As many hydraulic fold tool bars/planter frames/cultivators that have been built in the last 50 years, you need to just look at one and figure out what size they are using for a comparable weight/length wing.
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steve(ill)
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Posted: 10 Mar 2022 at 12:25pm |
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YEP... looking would be a good plan... Also searching the internet and post a PHOTO of what your trying to build and some guys can help... I would guess that someone here has something similar to what your thinking.
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Like them all, but love the "B"s.
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Tbone95
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Posted: 10 Mar 2022 at 12:54pm |
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I was more of the line of thinking that.......knowing Creston,. . . . . . he's already looked, quite a lot, and therefore had the idea, but now wants to get a little more nitty gritty.
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steve(ill)
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Posted: 10 Mar 2022 at 1:06pm |
the BIG thing with cylinders is where they are mounted... If you mount a cylinder 8 inches from the PIVOT POINT then it has a specific mechanical advantage... If you move that 3/4 inch and make it 8.8 inches from the PIVOT, then you have added 10% MORE pulling power ( or pushing)..... Thats kind of what Tbone was saying.. You can move your anchor points an inch or two one way or another to get a lot more PULL if needed.
and i agree Tbone... Creston probably knows more than he is saying at this point.
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Like them all, but love the "B"s.
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Stan R
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Posted: 10 Mar 2022 at 2:51pm |
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If you put the piston lift at 12" from the pivot point (overall length is 30"), and with a hydraulic pressure of 1000 psi, you would need a 2" piston. The piston would provide about 3000+ lbf lift, and you need about 2,500 lbf lift.
I'm assuming this beast weighs 2,000 lbs.
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CrestonM
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Location: Oklahoma
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Posted: 10 Mar 2022 at 3:20pm |
Since I’m using my cell phone right now and am not very good at posting photos from it, here’s a link to a photo album showing what I’m thinking of. It’s a Deere tactic to do this, but I’m thinking of copying the way this planter folds up. I believe the cylinders it uses are 3x8, but I’ve not verified that. There’s also a photo of one of the cultivators in the album. I have another nearly identical that I’m going to cut in half, and attach each half to the ends of this one pictured. It’s not an overly heavy implement, so I didn’t know if I’d need the same size cylinder as what lifts those heavier planter wings. But, just like in the planter toolbar, leverage isn’t very good on the cylinder side of the pivot point. So it may need a 3” diameter cylinder to lift the wing, with basically no leverage. The link: https://photos.app.goo.gl/DXJkqVJM5ukFY2Rj6
Edited by CrestonM - 10 Mar 2022 at 3:23pm
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jaybmiller
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Posted: 10 Mar 2022 at 3:29pm |
yeah, I'd 'cheat'..find one that someone sells, look at their exploded view/parts list, might shed light as to what they used.
When 'mocking up'.... use 1/4" plywood for steel plates and 'cylinders'. a LOT easier to fabricate...THEN cut and weld.
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3 D-14s,A-C forklift, B-112
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steve(ill)
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Posted: 10 Mar 2022 at 3:39pm |
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your right Creston... they use a short stubby cylinder so the ARC it swings is very small.. You can get the same PUSH by using a 2 inch cylinder, but the pin would need to be moved out a couple inches, and that makes the ARC it swings longer... so it might need a 12 inch stroke instead of an 8.
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Like them all, but love the "B"s.
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DiyDave
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Posted: 10 Mar 2022 at 5:49pm |
Check out Surpluscenter.com's tech help. They have the calculators and data you may need. Prices and service ain't too bad, either...
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