Green Tractor Talk banner

1 - 20 of 49 Posts

·
Registered
Joined
·
150 Posts
Discussion Starter #1
Hey
I'm in the process of designing a grapple, i am trying to figure out what length of stroke I will need for my cylinder.
I have never built anything with a hydraulic cylinder before so not too sure exactly how it will work.

I am drawing the grapple in autocad, and based on my design I need a 3" stroke cylinder, which seems really short and not sure how I get so much movement out of the top jaw

I expected to need at least a 6"

Anyone with grapples, how much stroke do you have for full open to full closed?

does my drawing look like it should work just fine with the 3"?

thanks in advance for any help!

openclose.jpg
 
  • Like
Reactions: johnH123

·
Administrator
Joined
·
20,982 Posts
You're not giving that cylinder much leverage. Try moving the stationary cylinder mount up a few inches.
 

·
Registered
Joined
·
523 Posts
Couple of observations:

1. As Dieselshadow said. I would raise the fixed location away from the arm for more leverage.

2. I would also move the grapple attachment point to utilize the max range. No sense in using a 24" cylinder if you only need 3".

3. With a design with only 3" of travel, the flow is going to need to be valved way back. That grapple is going to FLY open or closed. You can also over size the cylinder bore, but that gets expensive.
 
  • Like
Reactions: mjncad

·
Registered
Joined
·
702 Posts
3x8x1 75 Double Acting Hydraulic Cylinder 9 5460 A | eBay

Looks like they are out of stock. 2 cylinders w/shipping was 123.00

I used 1" 4140 round stock for my pins, bought from a local machine shop. Used 2 plumb bobs and a magnetic torpedo level to insure the pin axis remained level and parallel to the axis of the square tubing frame. I left the 4140 long for this purpose and simply measured from the plumb strings to the frame and then to the pin to insure the distances were equal on both ends of the round stock. 100_7358.JPG

100_7551.JPG 100_7555.JPG

I tried to pick out pics that would best show the relationship between the grapple pivot point and the center of the cylinder pivot pins.

ETA: Bear in mind that my grapple is for a 55HP tractor but built to withstand probably one twice that size. It is 80" wide. I do not know what size tractor you have and you need to design accordingly.
 

·
Registered
Joined
·
150 Posts
Discussion Starter #5
thanks for the suggestions fellas!

I have moved the stationary mount up a couple of inches, and also moved the mobile one a bit, I now have a 6" stroke and the geometry looks a lot better.

as far as cylinder bore.....I was planning on using a 2" because they are on sale right now, but I see some of the grapples online that actually list their cylinders are using 3-4"

the 2" I am looking at has 10,000lbs of force, why would I need more than that?
or are the larger bores being used just to slow it down as fred suggested?

thanks again for the help


grapple1.jpg
 
  • Like
Reactions: johnH123

·
Registered
Joined
·
5,893 Posts
figure the down force

thanks for the suggestions fellas!

I have moved the stationary mount up a couple of inches, and also moved the mobile one a bit, I now have a 6" stroke and the geometry looks a lot better.

as far as cylinder bore.....I was planning on using a 2" because they are on sale right now, but I see some of the grapples online that actually list their cylinders are using 3-4"

the 2" I am looking at has 10,000lbs of force, why would I need more than that?
or are the larger bores being used just to slow it down as fred suggested?

thanks again for the help


View attachment 142841
I would figure the actual down force on the grapple, particularly the points or teeth. With a low angle, it might surprise you what the actual force at the tooth end is, particularly when almost closed. (Hmmm, is that the sine of 10 degrees or so. Dang, trig was a long time ago.)

At some point in my future, I will relocate the cylinder on my manufactured grapple as others have suggested. I'll move it higher and probably replace the cylinder with a longer stroke as mine doesn't quite close all the way. It's very workable the way it is, but could be improved. A higher mounting point and longer stroke will help both the closing force and the tooth to frame gap on mine. The downside might be that the grapple won't open quite as wide as it currently does. That's the other dimension you will want to look at, does the top arm open enough for your projected use.

Treefarmer
 

·
Registered
Joined
·
2,965 Posts
I got a couple 3.5x8x1.5 or 1.75 (I forget which) from Surplus Center for $50 each plus postage that I was going to use for my grapple before buying a Woods out of expediency. The 2.5" on many commercial units are under sized to increase speed and they're still not all that quick with a 11gpm pump pushing them. The clamping force is marginal in my opinion. These having such a large range of motion reduces the effective gripping substantially. This isn't to say they're going to lose a grip on something reasonable, but the leveraged forces involved in clamping a large log are greater than the force capable on the lever with the cylinder bore provided. These jaws take a remarkable amount of pressure when you factor in all the geometry and physics involved in use. Everything's a compromise because weight becomes a limiting factor against strength - you cannot over build this tool, you can only make it too heavy to use with your machine; thus some medium must be accepted.

If we had more flow, it'd be cool to make a twin hinged lid. You could have a lot opening with a second hinge - think of your fingers, they have 3 joints.
 

·
Registered
Joined
·
4,440 Posts
thanks for the suggestions fellas!

I have moved the stationary mount up a couple of inches, and also moved the mobile one a bit, I now have a 6" stroke and the geometry looks a lot better.

as far as cylinder bore.....I was planning on using a 2" because they are on sale right now, but I see some of the grapples online that actually list their cylinders are using 3-4"

the 2" I am looking at has 10,000lbs of force, why would I need more than that?
or are the larger bores being used just to slow it down as fred suggested?

thanks again for the help


View attachment 142841
leney,

hope you dont mind, but i had time to kill so i looked at your drawings and put it into 3D. i dont have the clamp(s) done yet, but here is the rake:

grapple rake1.JPG

grapple rake2-jdqa.JPG

grapple rake3.JPG
grapple rake4.JPG


i tried to follow it as close a possible, but there are a few small variations. hope you like it!:thumbup1gif:
 

·
Registered
Joined
·
150 Posts
Discussion Starter #9
hey that's really cool, thanks john

my design will have 7 lower jaws and 4 uppers


anyone else have any input on cylinder size?
 
  • Like
Reactions: johnH123

·
Registered
Joined
·
4,440 Posts
if you have something that can open .SLDPRT and .SLDASM files i can send them to you if to want.:good2:
 

·
Registered
Joined
·
4,440 Posts
i just noticed something. from your drawing, it looks like the jaws will extend far past the rake when closed? is that planned or inadvertent?
 

·
Premium Member
Joined
·
8,085 Posts
leney,

hope you dont mind, but i had time to kill so i looked at your drawings and put it into 3D. i dont have the clamp(s) done yet, but here is the rake:

View attachment 143098

View attachment 143106

View attachment 143114
View attachment 143122


i tried to follow it as close a possible, but there are a few small variations. hope you like it!:thumbup1gif:
I was going to ask what CAD program you used; but I saw in a later post the SLDPRT & SLDASM told me SolidWorks.
 

·
Registered
Joined
·
150 Posts
Discussion Starter #14
i just noticed something. from your drawing, it looks like the jaws will extend far past the rake when closed? is that planned or inadvertent?

It wasn't originally planned, but is one of the ways I increased my stroke to 6"
Hopefully if all goes well, they will not run into my round bar support, or go lower than the bottom rake.
But I will test all that before welding cylinder mount on.
 

·
Banned
Joined
·
419 Posts
grapple

Remember one thing the heavier you make it the less weight you can lift. Or lift without damage to the tractor axle housing and seals. I know a hydraulic system on a loader is built to life more than you should. The other thing to consider is you have two clamps. Are you using two different valves to control them independently? If not they will not be in time much like the quick attach bucket cylinders on the loaders. Only will move faster than the other unless you use a proportioning valve to keep it in time.
 

·
Registered
Joined
·
150 Posts
Discussion Starter #16
3X8X1 DA HYD CYL

The thread sizes on both ends are goofy, but could be made to work pretty easily, or you could just weld on some cross tubes and run with it.

Jim, I have read, I believe, all your build threads so I certainly will not take your advice lightly. Are you suggesting I go with a 3" bore cylinder?
I'm pretty limited for where I can get my parts, being in canada I don't shop at the surplus hydraulic websites like the rest of you. By the time I pay conversion rate and shipping it just doesn't make sense.

You seem very knowledgable with hydraulics from what I have seen, do you really think for my little 1025r I will need more than 9000lb of force?

Thanks
 

·
Registered
Joined
·
2,965 Posts
The problem is the geometry and physics involved. You're applying that 9Klbs at a tangent of maybe 15 degrees at full close (why the guys are telling you to raise the back of the cylinder higher), and you just don't get the benefit of that force when you cripple it with that geometry. Sure, your cylinder is pushing out really hard, but the jaw isn't translating that into more than a few hundred pounds of squishing and it's really trying to pull it off the pivot pins instead. Now that's not a calculated statement (I haven't run any numbers), but the premise is grounded in truth. Maybe one of the Solids guys can run your numbers and tell you exactly how much squish you'll get?

Woods uses a 2.75" cylinder and I honestly think it's not big enough. Yes, I'm using a tractor that can literally pick yours up with the FEL. But I've been disappointed with the performance of mine being able to crush down brush when it has some larger logs in the pile. Those logs hang up and it stalls out the available pressure. Hydraulic force is a product of pressure and surface area: no replacement for displacement is true here just like in big block vehicles = if you want torque (what your cylinder is doing to your jaws), you need surface area.

Since you can't get our cheap stuff up there, maybe the cost factor is a bigger consideration. I love the surplus cylinders I've been getting. SC is like a drug dealer selling cheap crack. :laugh: I'd also hate to see you spend so much time on a project and then be disappointed because it doesn't clamp well enough. Being able to lift isn't the problem, it's being able to break branches and crush a pile down into a smaller clump before lifting it up and carting it away. Larger cylinders will have slower cycle times too, so that's something to factor as well.
 

·
Registered
Joined
·
702 Posts
Remember one thing the heavier you make it the less weight you can lift. Or lift without damage to the tractor axle housing and seals. I know a hydraulic system on a loader is built to life more than you should. The other thing to consider is you have two clamps. Are you using two different valves to control them independently? If not they will not be in time much like the quick attach bucket cylinders on the loaders. Only will move faster than the other unless you use a proportioning valve to keep it in time.
Yes-too much weight will limit payload. I tend to over-build everything because I am apparently too rough on equipment. My grapple weighs over 750 lbs. It will squat my tractor at least an inch when I pick it up empty. I'm sure it limits the amount of weight I can lift, but with about 12-1300 lbs rear ballast I have no problem doing what I need to do. Again-too rough on my equipment I'm sure.

I have found that not keeping the cylinders timed is much better in my case for gripping things (almost everything) that are not evenly dimensioned. I just have to continue gripping until both jaws are closed, even if only 1 jaw is gripping anything.
The easiest to move cylinder will outrun the other one until it encounters an obstacle. Then the other cylinder will catch up. Only when the second cylinder encounters an obstacle will the grapple apply significant gripping force to whatever you're grabbing. If you stop closing the grapple before BOTH cylinders have stopped moving, the load will be able to push one arm open, losing what little gripping force it had, and will transfer fluid to the other cylinder causing the second cylinder to close until it meets resistance. In my usage this is a non-problem. Just close the grapple until I hear the hydraulics load up. YMMV
 

·
Banned
Joined
·
419 Posts
grapple

Yes-too much weight will limit payload. I tend to over-build everything because I am apparently too rough on equipment. My grapple weighs over 750 lbs. It will squat my tractor at least an inch when I pick it up empty. I'm sure it limits the amount of weight I can lift, but with about 12-1300 lbs rear ballast I have no problem doing what I need to do. Again-too rough on my equipment I'm sure.

I have found that not keeping the cylinders timed is much better in my case for gripping things (almost everything) that are not evenly dimensioned. I just have to continue gripping until both jaws are closed, even if only 1 jaw is gripping anything.
The easiest to move cylinder will outrun the other one until it encounters an obstacle. Then the other cylinder will catch up. Only when the second cylinder encounters an obstacle will the grapple apply significant gripping force to whatever you're grabbing. If you stop closing the grapple before BOTH cylinders have stopped moving, the load will be able to push one arm open, losing what little gripping force it had, and will transfer fluid to the other cylinder causing the second cylinder to close until it meets resistance. In my usage this is a non-problem. Just close the grapple until I hear the hydraulics load up. YMMV

I agree totally. You have thought everything out beforehand. Which is good. If a problem develops then you know what to correct. I am working on a design that will use the pallet forks and you drive into them with forks and use the square tube hitch adapter to hold everything in place. That way can use the forks alone or with the clamp. Will work for my needs.
 

·
Registered
Joined
·
4,440 Posts
and here is the finished product...
i cant see a top view of your drawing, so hopefully i got it right.

4tine grapple1.JPG

4tine grapple2.JPG

4tine grapple3.JPG

this particular one has 8 tines on the rake and four on top, 2 per clamp. i also added an equalizer (pics 1 and 2) to keep them in sync better. again, you dont have to use these, i just thought it would be interesting to see in 3d and i need practice anyway.
 
1 - 20 of 49 Posts
Top