Hydraulic thumb Mini EX

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I have a Kobelko Mini Excavator.  I have priced a thumb for them and the cheapest cost I have found is $2900 plus shipping, and I still need to weld the thumb to the machine and also plum the hydraulics.  The machine is about 7k lbs and I have a 12" and a 24" bucket for the machine.  I have some 3/8" plate that I am going to cut the mounting brackets out of and also the thumb it self.  My design is to have the thumb completely out of the way and flat against the boom when not in use. but still have 180deg of movement to be able to grab things. I will load pics of the thumb and machine when I get cylinder ordered.Millermatic 250 wire feed, Miller Syncrowave 300 old and Bigger than a refridgerator, Lincoln Pro Mig 135, Cutting Torch,
Reply:Using 3/8 plate for the thumb seems light, to me anyway. Using that thickness make sure you gussett it sufficiently.....Mike
Reply:Seems light to me also.  I'd go with 1/2" on the plate mount anyway, and perhaps 3/4" on the ears for the cylinder mount.  Even though it's a mini excavator, when actuating the thumb, hydraulics can tear stuff apart if it's too light.
Reply:3/8 thumb.  Not a thumb merely a pinky.Nothing less than 3/4.  I have repaired ones made from 11 /4.  And it was broken badly at that.Even if its a mini.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:I chose 3/8 based on the fact that the buckets reinforced cutting edge is only 3/8 and the bucket wall is 1/4.  I will have to go get some 1/2.  I am planning on having all the crossmembers on the "pinky" run through the plate so it can be welded on both sides.  Now I have to find bushings to weld in the plate for the pins to ride on. That is the one problem with fabricating parts you have to find all the necessary components and parts. I will post some pics as soon as I find my camera.Millermatic 250 wire feed, Miller Syncrowave 300 old and Bigger than a refridgerator, Lincoln Pro Mig 135, Cutting Torch,
Reply:The pressure and force on bucket is spread out over a wide area. Plus, the shape of the bucket helps with this too.  I saw a kubota backhoe bucket the other day ripped apart because it was too light.  The force on the thumb is concentrated.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:The force on the thumb is concentrated.
Reply:Yah but... Originally Posted by wiLlweLd4FoOd ...I am planning on having all the crossmembers on the "pinky" run through the plate so it can be welded on both sides....
Reply:another thing about putting thumb on is the thumb cylinder has to have some kind of relief so if you do forget to retract the thumb and (it will happen eventually) when you curl the bucket it doesnt bend or break the thumb cylinder. Maybe some local rental stores have minis with the thumbs on them you could check out and see how thick they need to be.
Reply:Originally Posted by idacalanother thing about putting thumb on is the thumb cylinder has to have some kind of relief so if you do forget to retract the thumb and (it will happen eventually) when you curl the bucket it doesnt bend or break the thumb cylinder. Maybe some local rental stores have minis with the thumbs on them you could check out and see how thick they need to be.
Reply:Finally found the camera and got some work done and pics.First was cutting test run on some 3/8The cut wasn't as good as I wanted and I used the 1" stock as a straight edge. I adjusted the gasses and it started to cut better.  Here is the 1/2 I am using for the grapples.Tell me what you think and why I am having so much to grind off. This is my first real time using the cutting torch.Millermatic 250 wire feed, Miller Syncrowave 300 old and Bigger than a refridgerator, Lincoln Pro Mig 135, Cutting Torch,
Reply:All in all,  not bad.  From your drag marks, you are going too fast for the amount of heat you are using.I would worry about cleaning up too much.  The jagged edges will wear smooth enough and besides it will give you extra "traction".Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:The 3/8 ths was kind of crappy I got better on the 1/2.  On the 3/8 I kept having areas where the cutting stopped. ( going too fast) and on the 1/2 I just went slower with a little more gas and all was kind of good.Here is the machine it is going onHere is where you can see where I had problems with the 3/8How the jaws line up after being cut free hand.[IMG][/IMG]Millermatic 250 wire feed, Miller Syncrowave 300 old and Bigger than a refridgerator, Lincoln Pro Mig 135, Cutting Torch,
Reply:Looks like you're using too small of a tip, and it needs a real good cleaning.  When cutting that thickness I run 10psi Acety, 60psi Oxy.  Use a 6 preheat hole tip.  Attempt to get your speed of travel consistant and angle the cutting oxy a little ahead of the top cutting area to "clean out ahead" of your cut line.Good Luck.
Reply:Any combination of things can cause difficulty cutting.  Travel speed, torch angle, proximity of the torch head to the work, tip size, gas adjustments....  I think you'll get a handle on it after some practise.  Don't be afraid to change techniques if it ain't workin'.  Sometimes tryin' to make the same thing work-don't work.  Try somethin' different.First off, lose the straightedge.  It interferes with the torch angle, and the drag caused by friction rubbin' against it messes up travel speed.  Your freehand cuts look a damn sight better because your hands were free to actually manipulate the torch.I think it's good that you're takin' the plunge and workin' on the actual project.  You can cut scrap all day long, and somehow it doesn't make you learn as fast as possibly f'n up a good piece of steel that you're actually gonna use.  Quality time spent with a grinder cleanin' up a bad cut makes ya a better torch dude next time aroundFor starters, determine the correct size tip for the thickness of the work.Second, get the gas pressure right.  5psi Acetylene, 30psi 02.Third, Watch your speed.  Look at the cut kerf and see if it's fillin' up with molten metal behind the cut, if it is you need to move a bit faster.  If the kerf isn't fillin' up, but you don't get a complete thru cut, slow it down.  There's sorta a "sweet" sound when it's cuttin' right.  I don't know how to explain it.  Also look to see if there's a steady stream of sparks hitting the ground as you cut(that's the steel you're blowin' out of the cut)Preheat to cutting transition-  Tilt the torch so the flame points into the steel as you preheat, start the cut, then tilt the torch almost vertical as you continue the cut.It's the pits, but the first time you get a clean drop cut, it's MILLER TIMEI had to learn all this sh#t on my own, and it was somethin' else  You'll wind up doin' good even before you realize it"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I guess I have become kind of lazy. I cut everything up to 1/2" with a 00 tip, 10# of acetylene, and 40# of oxygen. I feather the oxygen lever for the thinner stuff and just squeeze it all the way for 1/4" on up. I adjust the preheat flame with the torch valves for the thickness I'm cutting and adjust the travel speed of the cut for the thickness also. I lay the torch over almost flat for 16 thru 12 gauge and bring it a little more verticle as I come up in thickness. 3/8 and 1/2", I hold the torch at 90 degrees to the cut. If I'm cutting quite a bit of the thicker metal I'll go up in tip size and oxygen pressure so I can make a faster cut. When you get your preheat, cutting oxygen pressure, and travel speed right you can make a very smooth cut.You can't have your cutting tip too clean. The cleaner the tip, the better the cut. The best torch hand in the world can't make a smooth cut with a dirty tip.Another thing is get as steady as you can. I call it making a pile of bones. Muscles shake and wiggle but bones don't. Get as much body support as you can, especially your arms and hands.
Reply:Hey Oltimer-- Happy New Year.  Another yr under the bridge"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Thanks, Samm, and the same to you. Yep, another year gone and it went quick.Your sig line is pretty revelent to me. I have my "three score and ten" in so I'm working on "three score and twenty".  You young whippersnappers (whatever the hell that is) be careful now, ya hear.