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Author Topic: DIY bypass grapple  (Read 10074 times)

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Offline northforker

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DIY bypass grapple
« on: June 26, 2013, 01:51:47 am »
Thought I'd share a couple of pics of a 48" bypass grapple I'm building. It's tacked together just to be sure that the mechanism is working...there's funky geometry involved in these things. It's made of 1/2" and 3/8" T1 plate and 1-7/16" chrome moly pins. When complete, I'll dangle it from the boom of a hoe attachment on my ASV loader. I'm planning to add a bar saw to it eventually.




Online barbender

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Re: DIY bypass grapple
« Reply #1 on: June 26, 2013, 06:39:12 am »
Man, you do some nice looking fab work! I built one for my skid steer about 5 years ago, it is one handy attachment. Mine looks like I built it with stone age tools compared to yours though :D All I had for tools at the time was a stick welder, side grinder, and a cutting torch, so things came out a little tough. And yes, there is some fun geometry involved :) I'm anxiously waiting to see your bar saw, that will make the grapple the cat's meow ;) I will then shamelessly copy your design ;D
Too many irons in the fire

Offline logman81

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Re: DIY bypass grapple
« Reply #2 on: June 26, 2013, 07:05:05 am »
Nice job looks awesome!
Precision Firewood & Logging

Offline thecfarm

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Re: DIY bypass grapple
« Reply #3 on: June 26, 2013, 03:23:02 pm »
WOW!!!!! I'm impressed.
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Offline Ernie

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Re: DIY bypass grapple
« Reply #4 on: June 26, 2013, 04:22:35 pm »
A true craftsman, I look forward to action pics when you've got it done.
A very wise man once told me . Grand children are great, we should have had them first

Offline northforker

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Re: DIY bypass grapple
« Reply #5 on: June 29, 2013, 12:47:07 am »
Thanks very much for your comments guys. Here's some more pics. I just pinned the grapple together for a dry run this evening. My thought was how have I done without such a useful tool for so long? It works very well. The next order of business will need to be a heel bar for sure. The repurposed Bobcat backhoe arm should work well. The hydraulics for the bucket cylinder now open/close the grapple. I left the swing operable and it's pretty handy for maneuvering in the timber or just flicking stuff out of your path. I'll get some action shots in a couple of days.



 

Online barbender

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Re: DIY bypass grapple
« Reply #6 on: June 29, 2013, 07:09:18 am »
Yep, that is one handy attachment, I use mine all the time. Does your hanger swivel? If not, you'll want it to. I was too cheap to spring for a $1000 rotator, so I just made mine swivel. I just use momentum or bang it off of stuff to turn it. You could use a spring to recenter it, I found that I prefer mine loose.
Too many irons in the fire

Offline redneck logger

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Re: DIY bypass grapple
« Reply #7 on: June 29, 2013, 07:13:58 am »
Great Northfolker im telling you your a wizard when it comes to cutting out raw steel and fabricating something and you always seem to blow our mines goodjob. 8) 8) :) :) :) :)
got to love working in the woods

Online mad murdock

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Re: DIY bypass grapple
« Reply #8 on: July 01, 2013, 12:29:48 pm »
Very nice work on the Grapple!!  Did you cut all the pieces with a plasma cutter or from templates with a torch?
'64 Garrett 15A, JD AMT 626, Turbosawmill M6 Warrior Ultra liteweight, Granberg Alaskan III, lots of saws-gas powered and human powered :D

Offline northforker

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Re: DIY bypass grapple
« Reply #9 on: July 01, 2013, 06:18:30 pm »
Thanks again for your comments guys. Barbender, I don't have a swivel but will add one. I'm kind of thinking toward the next step in that regard with adding the bar saw and all, and what kind of swivel/rotator will be best for that application. Murdock, I cut the pieces out on my plasma gantry and welded with my Lincoln stick welder. I can see the real value of a mig outfit though...one of these days.

Online barbender

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Re: DIY bypass grapple
« Reply #10 on: July 02, 2013, 12:18:21 am »
I just left mine on a swivel with no rotator cause I wasn't ready to spring $1000-$1500 for a 360 rotator, especially since you don't really have room to rotate more than 180 most of the time anyways if you have wood in the grapple (it's too close to the machine) I thought a hyd. motor mounted on the boom to a shaft that the hanger is mounted on, like some grapple skidders are set up. I'm eagerly waiting to see the bar saw ;)
Too many irons in the fire

Offline northforker

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Re: DIY bypass grapple
« Reply #11 on: July 03, 2013, 01:51:03 am »
I'm with you on the rotator barbender, 180 of rotation is about all you need. I installed a swivel today and having used it, I see it's pretty much essential. It's free swiveling with no spring center. I like your idea of a hydraulic motor drive mounted through the boom though. I'll think about that application when deciding how to set up the bar saw. I sort of want it to be a felling grapple as well, with the ability to dangle the jaws horizontally to grab a standing tree and saw it as well as vertically to grab/skid the trees after they are felled.

 

Offline Randy88

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Re: DIY bypass grapple
« Reply #12 on: July 04, 2013, 09:07:13 am »
Excellent job, I'm impressed, how are you planning on going about adding a bar saw to it?

Offline northforker

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Re: DIY bypass grapple
« Reply #13 on: July 06, 2013, 12:53:49 pm »
Thanks Randy! I'm still scheming about the bar saw addition. I'd like to just have a separate saw assembly that would bolt on/off without too much difficulty. Many of the commercially available grapples (Valby, etc.) have some parts of the grapple jaws or struts mounted external to the grapple frame. I built mine with all the moving parts internal to the frame so I would have a large surface to bolt a saw assembly to without interference from other moving parts. Even before I start building the saw, I know the devil is in the details, particularly when it comes to modulating bar feed with saw speed. Ideally, I'd want a system of valves that would sense pressure to the saw motor and speed up/slow down the bar feed accordingly. I will have a look at Danzco's valve assembly and see how much it costs. He's obviously thought about this problem in great detail. Then there is the matter of oiling the chain. I tested an idea for an oiler that I think I'll use. I have a small 2-way pneumatic cylinder that has about an ounce of displacement. I'll turn it into a pump using 2 check valves. Using the extending/retracting motion of the bar, it behaves like a syringe of sorts. When the bar retracts, the cylinder sucks in and fills with oil. The oil is pumped to the bar as the bar extends. The oil will either come from a separate reservoir mounted on the grapple assembly, or will be drawn from the hydraulic system. I also thought about using grease as a lubricant...anybody here ever try that?

Excellent job, I'm impressed, how are you planning on going about adding a bar saw to it?

Offline blackfoot griz

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Re: DIY bypass grapple
« Reply #14 on: July 06, 2013, 01:30:11 pm »
I'm with you on the rotator barbender, 180 of rotation is about all you need. I installed a swivel today and having used it, I see it's pretty much essential. It's free swiveling with no spring center. I like your idea of a hydraulic motor drive mounted through the boom though. I'll think about that application when deciding how to set up the bar saw. I sort of want it to be a felling grapple as well, with the ability to dangle the jaws horizontally to grab a standing tree and saw it as well as vertically to grab/skid the trees after they are felled.

 (Image hidden from quote, click to view.)

Northforker-Nice job--I am impressed.  Is that a Unimog in the last picture?  Do you use it as a skidder?  A Unimog is definitely on my wish list!

Offline snowstorm

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Re: DIY bypass grapple
« Reply #15 on: July 07, 2013, 07:33:49 am »
somebody beat you to it on using grease on the bar an chain. i saw a factory built system a few years ago. quadco was selling it dont know who built it

Offline northforker

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Re: DIY bypass grapple
« Reply #16 on: July 08, 2013, 01:01:15 pm »
Thanks blackfoot_griz. Yes, that is a Unimog you see in the pic. I use it mainly as a snowblower and have never really used it as a skidder so far, but I also have a Case extendahoe attachment for it that I sometimes use. I've seen that lots of people use unimogs as skidders and even as skyline cranes.

Snowstorm: Thanks for the info on grease chain-lubricators. I see someone has a patent for a system here:http://www.google.com/patents/US8225907

Offline northforker

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Re: DIY bypass grapple
« Reply #17 on: July 08, 2013, 01:20:04 pm »
I "road-tested" the grapple over the weekend up at the cabin. I am pleased with how it worked. Pound for pound, I would say it's the most useful and productive attachment I have for working in the forest...so far.

When I test a piece of equipment I build, I always try and break it, and I always succeed! The only thing on the grapple that I succeeded in breaking was a weld holding a collar to the swivel pin, which carries the entire load of the grapple. I did this by trying to pull/jerk a stump loose. This time, I will machine a new pin and collar out of a single piece of steel instead. Luckily, I sort of guessed this might have happened, so I designed the hanger to mount without the swivel...just in case. Everything else held. I have to say that, after using T1 steel for the first time, I'll never go back to mild steel again for any demanding application. I'm so impressed with how the steel held up with no bends or breaks. I can say with some confidence that the workout I gave the grapple would likely have mangled mild steel.

Here's a short action video from yesterday. Note that I didn't have my lexan door up...kids, don't try this at home!

Offline beenthere

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Re: DIY bypass grapple
« Reply #18 on: July 08, 2013, 04:20:14 pm »
Looks good, and it works.
Mighty fast action, which seems would be too fast. But not for me to say.
The grapple does well, and can see where you might like to add a heel to the boom.
All should make cleanup easy and fun.
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Offline northforker

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Re: DIY bypass grapple
« Reply #19 on: July 10, 2013, 04:01:28 pm »
Thanks beenthere. Yeah, it is pretty fast action. This is what happens when you throw 15-18 gpm at a 2.5 x 8" cylinder. Couple that with the bang-bang solenoid valves and that's what you get. I'm going to split off some of the flow, and look into getting some soft-shift solenoids for the next round of modifications. You are definitely right about a heel bar. I'm building one as we speak.

Needs a heel bar:


Looks good, and it works.
Mighty fast action, which seems would be too fast. But not for me to say.
The grapple does well, and can see where you might like to add a heel to the boom.
All should make cleanup easy and fun.