Help with cylinder placement on grapple

[Stomper]

I am looking for help in trying to find the locations to mount a cylinder on my grapple. I have a 12” c to c closed cylinder with a 4” stroke. What is the best/easiest way to figure this out without using a computer.
The top cylinder mount and the grapple cross brace are only tack welded and can be moved easily if needed

 

[Stomper]

I have found this, specifically post #4 but I don’t fully understand what he is saying. If someone could help explain it that would be great

Grapple cylinder placement

Just built a grapple to bolt to the top of my bucket but not sure how to determine were to mount the cylinder as far as angles and distances from the pivot points of the arms, any help would be appreciated.

www.tractorbynet.com

 

[oldnslo]

Either you have to do a bunch of math to calculate open and closed positions or take a piece of wood with pin holes to simulate a fully extended and fully retracted cylinder and use those for your gauges.

 

[Stomper]

Either you have to do a bunch of math to calculate open and closed positions or take a piece of wood with pin holes to simulate a fully extended and fully retracted cylinder and use those for your gauges.

What’s the math way. Is there a formula for this

 

[4570Man]

That cylinder is way too short to give you a half decent opening height and still close all the way.

 

[oldnslo]

When I built my grapple or thumb for my loader I calculated the open and closed angles using sine, cosine, tangent formulas based on knowing two of the sides of the triangle.

You should have distance from lid hinge to cylinder mount pivot points. Now it becomes a matter of determining what positioning of the cylinder provides max opening movement and adequate clamping force.

After multiple calculations I got a rough idea on the amount of movement possible and then used two pieces or wood representing extended and retracted cylinder length to very my math was close.

The huge unknown for me was clamp force required.

Probably better ways to calculate but I do not what the formula would be.

 

[Renze]

Either you have to do a bunch of math to calculate open and closed positions or take a piece of wood with pin holes to simulate a fully extended and fully retracted cylinder and use those for your gauges.

Or you make a drawing to scale, and use a pair of compasses to determin where two radii meet at min and max stroke.

 

[Stomper]

Or you make a drawing to scale, and use a pair of compasses to determin where two radii meet at min and max stroke.

Can you please elaborate on this please. This sounds like what 3RRL was talking about in the link that I provided

 

[/pine]

There is the time tested trick of using a couple pieces of PVC that emulate a cylinder...just get similar sized pieces of PVC where one fits in the other and drill some holes...

HD sells 2' sections of PVC...

Good Luck...

 

[ddbackhoe]

What’s the math way. Is there a formula for this

Simplified Calculations for Choosing Actuator Parameters

There are electrical and mechanical considerations that must be taken into account when implementing a linear actuator. It can sometimes be difficult to choose the right size and force. For example, the actuator may be rated to handle twice the weight of a trapdoor in terms of force, but still...

www.progressiveautomations.com

 

[LD1]

I agree that the cylinder looks to short.

Mocking up with PVC, wood, etc is gonna be easier than all the math in the world. Because some things are easy to overlook in terms of clearances and binding angles.

For example.....with the cylinder base mount offset forward of the lid hinges.....the grapple lid wont ever be able to open much beyond just parallel with the floor. Otherwise the hinges will break over-center and the grapple wont close.....or will try to close backwards.

 

[Rustyiron]

Get some big pieces of cardboard. Mock up one grapple next to another mock up of the cylinder base mount, full size.
You'll find that 4" stroke isn't going to open enough from closed. That stroke might work on the the "other" side of your pivot but you've already made them and you'd need a cylinder for each side. (similar to the action of a 4/1 bucket) This does provide a better grip on oddly shaped loads.
What you have done looks very nice.

 

[Xfaxman]

I am looking for help in trying to find the locations to mount a cylinder on my grapple.

From the pictures I have looked at, your cylinder base pivot needs to be behind the lid pivots:

And you need a longer stroke cylinder.

Here is one that I have with a unique cylinder mount: Demolition Grapples - Features - Sidney Attachments

 

[Stomper]

Thanks for the help guys. I talked to a buddy at work who is a mechanical engineer in training and he is going to draw something up to see if it will work with the design i have. I am basically trying to copy this design for the grapple lid. 48″ Compact Tractor Root Rake Clam Grapple Attachment Fits Skid Steer Quick Attach – Skid Steer Attachment Depot

He also suggested adding another tine to the middle of the lid and extending it past the back of the top frame and lid pivot points and putting the cylinder on the back of the grapple. Similar to the below design but only one cylinder on the middle tine. Its only a 48" grapple so putting a cylinder on each outside tine on the back is not an option because of the SSQA. I may just go this route. If I did my math correct, with an attachment point of 8" past the pivot point, I should have just over 2000 pounds of clamping force, which should be plenty for its intended purpose.

72″ Root Rake Clam Grapple Attachment Fits Skid Steer Quick Attach – Skid Steer Attachment Depot

www.skidsteerattachmentdepot.com

 

[Stomper]

From the pictures I have looked at, your cylinder base pivot needs to be behind the lid pivots:

View attachment 790964

And you need a longer stroke cylinder.

Here is one that I have with a unique cylinder mount: Demolition Grapples - Features - Sidney Attachments

View attachment 790972View attachment 790973

View attachment 790974
View attachment 790983
View attachment 790976

I did some figuring using the explanation in the link i posted in my second post and it did placed the mount point behind the top frame

 

[4570Man]

I did some figuring using the explanation in the link i posted in my second post and it did placed the mount point behind the top frame

The rear cylinder pin needs to be higher than the lid pivot pins by at least a few inches. The more distance apart they are the more clamping force you would have. It looks like your cylinder pin and lid pin are almost the same height. The grapple lid pivots really should have been closer to the frame to make it more practical to make the cylinder pin higher. I’m 100 percent sure that the current cylinder is too short to provide a decent opening angle.Here’s a picture of my grapple and demolition bucket for reference. The grapple has a good opening angle but the demolition bucket would be better if it opened more.

 

[mikester]

If you are computer savvy a cad package like Fusion 360 can let you mock up the parts and take measurements for the assembly in open and closed positions

A scale cardboard model will work to take physical measurements

 

[jwmorris]

I am basically trying to copy this design for the grapple lid.

That doesn’t require any math. When you go to look at one, take a camera and tape measure.

 

[jb1390]

Thanks for the help guys. I talked to a buddy at work who is a mechanical engineer in training and he is going to draw something up to see if it will work with the design i have. I am basically trying to copy this design for the grapple lid. 48″ Compact Tractor Root Rake Clam Grapple Attachment Fits Skid Steer Quick Attach – Skid Steer Attachment Depot

He also suggested adding another tine to the middle of the lid and extending it past the back of the top frame and lid pivot points and putting the cylinder on the back of the grapple. Similar to the below design but only one cylinder on the middle tine. Its only a 48" grapple so putting a cylinder on each outside tine on the back is not an option because of the SSQA. I may just go this route. If I did my math correct, with an attachment point of 8" past the pivot point, I should have just over 2000 pounds of clamping force, which should be plenty for its intended purpose.

72″ Root Rake Clam Grapple Attachment Fits Skid Steer Quick Attach – Skid Steer Attachment Depot

www.skidsteerattachmentdepot.com

Let us know how this works out. I would recommend a computer for a couple reasons - one is to figure out the travel and make quick adjustments if needed. You can figure out whether you have the right piston, etc. The second is to calculate the clamping force. It's pretty easy to do in software.

Let me know if you get what you need from your buddy, if that doesn't work out and you can give me some more dimensions I can draw something up quickly for you.

 

[MTGreen]

Agree with others - use CAD: cardboard aided design