Help finding thread on mocking up cylinders with PVC

[Scott65]

I remember seeing something somewhere instructing how to mock up a hydraulic cylinder using PVC pipe and fittings. I'm having to change up the design of my grapple for a different length of cylinder. Does someone possibly remember where the thread is talking about what size fittings and such? I've tried searching but I'm sure I'm not wording it correctly, I can't seem to find it again

 

[J_J]

Bore a hole in the ends of the pvc tubes

Slide one tube inside the other.

Insert pins into the tube ends and bracket.

With the grapple fully closed, measure the pin to pin length. = cyl length

Raise the grapple and the pin to pin length is the closed length of the cyl. = cyl length closed

Also mark how much PVC is inside the outer tube. The two marks on the tube = stroke length.

 

[Scott65]

Bore a hole in the ends of the pvc tubes

Slide one tube inside the other.

Insert pins into the tube ends and bracket.

With the grapple fully closed, measure the pin to pin length. = cyl length

Raise the grapple and the pin to pin length is the closed length of the cyl. = cyl length closed

Also mark how much PVC is inside the outer tube. The two marks on the tube = stroke length.

Thank you sir! I didn't even think of drilling the tube itself. I was envisioning using smaller pvc and putting T's on each end. I figured someone would already know what size PVC would accept a 3/4" pin through it so I didn't make multiple trips to a tractor thats 60 miles away. But this works just the same

 

[Xfaxman]

I remember seeing something somewhere instructing how to mock up a hydraulic cylinder using PVC pipe and fittings. I'm having to change up the design of my grapple for a different length of cylinder. Does someone possibly remember where the thread is talking about what size fittings and such? I've tried searching but I'm sure I'm not wording it correctly, I can't seem to find it again

Did you use the "Google Custom Search" box that is above the forum "Search" icon at the top of the page?

Here is a recent one: http://www.tractorbynet.com/forums/hydraulics/291399-question-sizing-hydraulic-cylinder-diy.html

 

[Scott65]

Did you use the "Google Custom Search" box that is above the forum "Search" icon at the top of the page?

Here is a recent one: http://www.tractorbynet.com/forums/hydraulics/291399-question-sizing-hydraulic-cylinder-diy.html

Ah ha, no sir I didn't. I always use the Search button on the top row of controls. Its results are usually confusing and irrelevant. Thanks for the tip!

 

[Xfaxman]

Ah ha, no sir I didn't. I always use the Search button on the top row of controls. Its results are usually confusing and irrelevant. Thanks for the tip!

Your'e welcome.

The "Google Custom Search" box only searches TBN. l try to use the least amount of words in the search.

 

[MtnViewRanch]

Unless you either want to start modifying cylinders yourself or paying for custom cylinders to be built, you might want to look at some hydraulic cylinder charts and copy down a bunch of standard working lengths and make those work one way or another. Probably by altering your mounts in some way. You still need to do the PVC thing, just have the std working lengths pre marked.

Good luck.

 

[kennyd]

Unless you either want to start modifying cylinders yourself or paying for custom cylinders to be built, you might want to look at some hydraulic cylinder charts and copy down a bunch of standard working lengths and make those work one way or another. Probably by altering your mounts in some way. You still need to do the PVC thing, just have the std working lengths pre marked.

Good luck.

^^^^^
This!

 

[Xfaxman]

I remember seeing something somewhere instructing how to mock up a hydraulic cylinder using PVC pipe and fittings. I'm having to change up the design of my grapple for a different length of cylinder. Does someone possibly remember where the thread is talking about what size fittings and such? I've tried searching but I'm sure I'm not wording it correctly, I can't seem to find it again

I think you can use the cylinder that you have.

Lengthen the top lid arms, where I added the curved arrow to your picture, at an angle that will keep the tips touching the front edge of the bucket.

Lower the cylinder base pivot to where it is slightly above and behind the lid pivot, with full extension.

The lower base pivot will let the lid open wider with full retraction.

You may have to make the rod end bracket a little longer or drill the hole in the top corner so the rod doesn't touch the lid.

Edit: I posted this in another thread and thought about your modification.

Look at the pivot points in the highest position, this is what you need.

 

[Colonel Monk]

Unless you either want to start modifying cylinders yourself or paying for custom cylinders to be built, you might want to look at some hydraulic cylinder charts and copy down a bunch of standard working lengths and make those work one way or another. Probably by altering your mounts in some way. You still need to do the PVC thing, just have the std working lengths pre marked.

Good luck.

Yeah, + 1 jillion.

When possible, you always want to start with a stock collapsed length. If you don't use all the stroke on extend that's fine.

Rough Estimate of standard lengths for 2-3" cylinders is 8" + Stroke. So a 24" stroke cylinder has a 32" collapsed length.

 

[Colonel Monk]

Another way that makes them simpler to figure out, is to use a 2D CAD software or sketch in 3D CAD to mock up your motion.

You don't need to draw your design, just some lines to represent your cylinder, and mechanism at stop and end point, pivots, etc.

What it does for you, is that it'll solve all the geometry formulas for you, and tell you where to put your pivots for a given length cyl, or vice versa.

Here's one that I did recently for a work-related project:



You're looking at the load in two different positions, horizontal and vertical. I've got the vertical fixed mast and angle brace which has the cyl mount on it. The dimensions in parentheses (x) are being solved by the sketcher, and I input the rest.

Basically, I ended up changing the geometry to spec a standard cylinder, but in that example I solved for the position of that lower pivot. I could have hard dimensioned that pivot and asked it to find the other one, or the angle of the brace, or basically anything ....

Without farting around in the shop making mockups, this is sure an easy way to do it. There's lots of free cad out there that should be able to do this simple problem.

CM

 

[dfkrug]

Basically, I ended up changing the geometry to spec a standard cylinder, but in that example I solved for
the position of that lower pivot. I could have hard dimensioned that pivot and asked it to find the other
one, or the angle of the brace, or basically anything ....

Whether you use CAD, a ruler and some trigonometry, or a mock-up, designing around a standard
cylinder is the most efficient way to go. This is true for a grapple, or the hydraulic backhoe thumbs
I have written about.

Since you have to cut your jaws and make pivots anyway, why not leave them as variables and fit
to the fixed open and closed lengths of a standard cylinder? Save a lot of time, effort, and cost, and
also make a damaged cylinder easily replaceable.

 

[Scott65]

Oh my, wonder what happened here. I stopped getting alerts on this thread for some reason. Thanks for all the helpful responses! I've got the grapple redone, and working pretty well. Its still not a pretty thing, but I've been using it quite a bit so I'm happy with it. I'll work on making a new thread over in the BIY section.

As for CAD, its a neat technology. Probably way over my head. But I'd love to take a look at it some day. My problem would likely be replicating whats on the screen into real steel products. But I can't say for sure since I've never used any of the software. I've been slowly (very) collecting up the material to make a front mounted hydraulic post hole digger. Perhaps I'll take some time and try to mock up the bracketry on some of that software

 

[Xfaxman]

Thanks for the update.

His new thread: http://www.tractorbynet.com/forums/build-yourself/327929-grapple-build-kubota-l3301.html#post3985592