Colt Case Ingersoll Garden Tractors

I'm designing a new grapple for my bucket and I thought it might be interesting to show the process to find/locate the proper attachment pivot points.

I have two different hydraulic cylinders available to me. One that has a 10" travel and one that has 5" of travel.
I used a CAD program to decide which cylinder to use, and to calculate precisely where to locate the pivot point holes.

I'm using CAD to do the "what if" demonstrations to help me think it through. Some people use scale-accurate cardboard templates. I prefer CAD.

I started with a side view drawing of my bucket and drew a likely looking grapple arm shape, pivoted just above and behind the top edge of the bucket.

I then overlaid my extended shorter cylinder and it was instantly obvious that the 10" travel cylinder is way too long. The 5" travel is actually about right. The pivot centers on that cylinder are 20 5/8" apart when extended, 15 5/8" when retracted. I chose a likely looking upper pivot point and drew in the cylinder there, angled as far downward as possible to where the cylinder will nestle between the grapple tines. (To be honest, this drawing is after several iterations of doing the procedure I'm laying out here and then adjusting the pivot point as needed. So this pivot point is "known good" but this process is how I found the "known good" location.) The cylinder's lower pivot point is the common pivot point where both the cylinder ram and the grapple cage will be pinned together.

Next I drew a circle that represents the swing path of the cylinder eye when it's retracted. Then I drew a circle that represents the swing path of the grapple's pinning point. Then I mark the point where the two sweep arcs meet at their upper point. At this point the sweep of the retracted cylinder eye meets the sweep of the grapple pinning point. That's where the pinning point will be located when the grapple is fully open.
Now that I know this "open position" upper pin point, I can proceed to draw in the cylinder and grapple in their open positions.
This allows me to envision how things look both open and closed, and judge whether I'm happy with it.

In the earlier iterations of this process, the upper/retracted intersection point wasn't where I wanted it to be. Either the grapple wasn't far enough open at full cylinder retract, or the grapple sweep never intersected the cylinder sweep at all, which would mean that the cylinder would be attempting to bend/crumple the grapple structure itself at full retract.
So I moved the cylinder upper pivot point up/down/in/out until I found a location that the cylinder could fully retract, while simultaneously having an acceptable open grapple position.

With that knowledge in place I can proceed to call out dimensions and details that I'll use to bend/weld create the individual components.

The tines themselves, the 1/2" rebar diagonal reinforcements, the relative positions of the upper pivot points, and the grapple pinning point plate.

The total time invested was less than a couple hours, and it leaves you ready to begin fabrication.

To the degree that you can perfectly create what's drawn, you could fabricate the components 100% and just assemble them. In the real world for me, I'll fabricate the 6 tines, weld them into a single assembly, and then re-evaluate how close the drawing is to reality.

Bob

Now that would be handy to use with my forks , but like a thumb on an excavator . Wouldn't even need to be full width . I have a third (centre top ) receiver tube I can mount one when the forks are on .
Thanks Bob now I have another project I don't have time for .

Just kidding , it is a great idea . It is something I will incorporate when I build Frankie 2 .

Hi Bob, it's really nice to see how you reason and calculate this. What CAD program are you using, FreeCAD? One of the forum members here pointed me to the free version of Fusion 360 and since then I gave up FreeCAD.

In any case, back to your grapple. I'm not sure I understand the drawing properly, but does the cylinder sit right on top of the grapple claws? Wouldn't that interfere with operation?

I retract my question, it seems most grapples are this way. Just had to look around a bit. Like this one for instance:

@thebuildist , your work inspired me to look more seriously at the CAD program and will use it for designing the backhoe, when the time comes.

Tried coming up with a simple cylinder and joints roughly like a hook, was interested to see if I can use motion with pre-defined limits and joints. Because the CAD program will have exact measurements, it's very nice to see the range of motion for the various parts. In summary, thank you for posting this, it will make a big difference to how I do things in the future.

Here's what I came up with.

https://vimeo.com/754127515

I also came up with the intersecting circles method. I figured it out myself back when google and youtube wasn't the goto adviser. I've been using Solid Works for 8-9 years; so now it's my goto. The version I have is getting a bit old, and I will likely not get another one. The animation I've done is just manual on screen, not a movie.

FUTZ wrote: ↑Tue Sep 27, 2022 2:32 pm I also came up with the intersecting circles method. I figured it out myself back when google and youtube wasn't the goto adviser. I've been using Solid Works for 8-9 years; so now it's my goto. The version I have is getting a bit old, and I will likely not get another one. The animation I've done is just manual on screen, not a movie.

Having tried all the free CAD programs and some of the commercial ones, my go to was FreeCAD as it was free and fairly easy to use. Found it quite buggy and lacking at times. Then Ray @ras101 , who is a member here, said he created many CAD models for parts for our Case garden tractors using the free version of Autodesk Fusion 360, so I gave it a try. I was amazed how easy to use, intuitive interface, and fully featured it is. I thought I point it out to @thebuildist and maybe make his life easier. My post is not to point out any shortcomings of the circles method, in fact it might be faster and better to get things done than creating a more complete model of the assembly.

I've played with Autodesk a little bit. And free cad. And I'm in a classic old dog new tricks situation. I've been using this shareware 2D CAD program since about 2002. So my understanding of the fundamentals of what CAD is are based on my experience with this relatively awful program! But when I try other programs they don't work right. In my sense of how cad ought to be.

I know that I could go cold turkey and through a lot of strenuous effort and mind discipline acclimate myself to something more modern and much more powerful and ultimately easier to use.

But I haven't yet made myself do it. So I keep reaching for the less powerful stupid way that is by now 100% second nature to me.

But thanks for the tips. And thanks for showing me just how badly I'm missing out.

Bob

Bob, when you have a tool that you're very familiar with you're most likely not missing anything switching to a tool that's new and requires an investment of time. Anyway, good discussion! I will go revisit your loader building thread, there are details that I'm interested in again.

Looking forward to your building of the grapple!!!