Hydraulic cylinders joined side by side ?

[lennyzx11]

Have you guys any information on placing two double acting cylinders together side by side? I can't seem to find a reference on the Web.

I'm thinking of a concept where two cylinders welded together side by side with the rod ends at opposite ends.
This could in theory allow a shorter package when compressed that would extend double the normal length when pressurized out.

Using this in a top link configuration is my main reason for this so far.

Any information, tips, comments, or ideas are welcomed.

Thanks,
Lenny

 

[lennyzx11]

Have you guys any information on placing two double acting cylinders together side by side? I can't seem to find a reference on the Web.

I'm thinking of a concept where two cylinders welded together side by side with the rod ends at opposite ends.
This could in theory allow a shorter package when compressed that would extend double the normal length when pressurized out.

Using this in a top link configuration is my main reason for this so far.

Any information, tips, comments, or ideas are welcomed.

Thanks,
Lenny

I'm not the first to come up with this. here's a sketch from a thread on TBN in 2009!

 

[oldnslo]

Yes you can use opposing cylinders to gain stroke length.

 

[npalen]

Looks like that would put the rods in a bending moment. Interesting idea for a top link, though.

 

[lennyzx11]

I'm not the first to come up with this. here's a sketch from a thread on TBN in 2009!

View attachment 538855

As I've been armchair surfing looking for this thing, I've found the name for what I describe.
These are called piggyback cylinders.

 

[BrokenTrack]

You can also use a single hydraulic cylinder to push a rotating gear that rides on a FIXED rack. Another movable rack on top of the gear pushes forward, doubling the stroke of the single cylinder.

What you propose seems more logical though since it is simpler to build.

 

[teg]

...Using this in a top link configuration is my main reason...

I would say that one of my problems with the hydraulic toplink, is that it's heavy and sometimes awkward to handle. This would double that problem (if not more).

 

[jgriffin1720]

Why not just use a double rod cylinder or a telescoping cylinder? What your describing would be super simple to make if you can cut and weld.

 

[4570Man]

Why not just use a double rod cylinder or a telescoping cylinder? What your describing would be super simple to make if you can cut and weld.

Because that’s not in the capabilities of a home shop fabrication job. And it doesn’t have full strength the whole stroke where a piggy backed cylinder would. I’ve seen forklifts with piggy backed cylinders and telescoping cylinder. The piggy backed ones are small and in comparison cheap cylinders. I’d bet the 4 step telescoping cylinder in my Cat cost more than I’ve got in the whole forklift. Not to mention it’s a real PITA to work on.

 

[BLSXJ]

hydra-spread manure spreaders use that configuration to push the product out the back.

 

[jgriffin1720]

Because that’s not in the capabilities of a home shop fabrication job. And it doesn’t have full strength the whole stroke where a piggy backed cylinder would. I’ve seen forklifts with piggy backed cylinders and telescoping cylinder. The piggy backed ones are small and in comparison cheap cylinders. I’d bet the 4 step telescoping cylinder in my Cat cost more than I’ve got in the whole forklift. Not to mention it’s a real PITA to work on. View attachment 538939

It is well within the capabilities of my home shop and skills, but that is different from person to person. Perfectly functional cylinders in different configurations can be found for cheap if you do some looking at scrap yards and such. Was just trying to point out some other possibilities.

 

[4570Man]

It is well within the capabilities of my home shop and skills, but that is different from person to person. Perfectly functional cylinders in different configurations can be found for cheap if you do some looking at scrap yards and such. Was just trying to point out some other possibilities.

What kind of equipment do you have if you can make a functioning telescoping cylinder with any size to it?

 

[jgriffin1720]

What kind of equipment do you have if you can make a functioning telescoping cylinder with any size to it?

That is not what I said at all. You are putting words in my mouth. I mentioned making a piggyback cylinder. It would be pretty simple, with some basic fabrication/machine shop skills, to make a piggyback cylinder from two existing cylinders. As far as equipment goes I have pretty stout arsenal of welding and cutting equipment, bridgeport mill, and a jet 1640 large spindle bore lathe, both with dro, a decent size shear/brake/roller, tubeshark bender, a surface grinder, an edwards 50 ton ironworker, 45 ton air/hydraulic press decent size gas forge, and several anvils, band saw, belt sanders, grinders, drill press, dry cut saw, mechanics tools, etc etc. I do metal fabrication and blacksmithing as a side business, but that is my home shop. I could make a functional telescopic cylinder from scratch, within the limits of my lathe, but making a piggyback cylinder out of two existing cylinders would not be anywhere near that difficult or require anything fancy except maybe a welder, something to somewhat accurately cut steel with, a drill press, and some reasonably accurate measurements. I've even seen them with just mechanical means of connecting the two cylinders, but that wouldn't really be appropriate for a tractor top link.

 

[4570Man]

Making a piggy backed cylinder is easy. Well within the capability of most home shops. My post said a telescoping cylinder couldn’t be made be the average home fabricator. I’ve got a pretty big lathe but I’d have to upgrade tooling to bore more than about 6 inches deep.

 

[JCByrd24]

As has been mentioned the issue with that piggyback design is a potential for side loading the rods. You cannot simply pin the two rod end clevis as you would a normal cylinder. You must restrain the body in a way that keeps it parallel with the rods but allows it to slide, complicating the design a little bit. I've seen rods bend when the side forces were not properly accounted for, but at the very least the packing and rod would wear poorly.

 

[lennyzx11]

As has been mentioned the issue with that piggyback design is a potential for side loading the rods. You cannot simply pin the two rod end clevis as you would a normal cylinder. You must restrain the body in a way that keeps it parallel with the rods but allows it to slide, complicating the design a little bit. I've seen rods bend when the side forces were not properly accounted for, but at the very least the packing and rod would wear poorly.

Hmmm... something to think about.
My first thought is the cylinders would be more or less self aligning to the rods on each end in a piggy back configuration if they were placed vertically on top of each other.
And actually be stronger than a toplink. And we are told not to back up under power to dig, scoop, etc to avoid bending lift arms so this is for a pulling scenario mostly.

Lots of good information here. I had thought of a telescoping cylinder but as noted, they are heavy, expensive, and I didn't find one that would work in a toplink scenario.

I agree also with the fact that I can piggyback 2 cylinders in my shop fairly simply with welder and drill press being the major tools required.

I have thought of getting 2 cylinders.
Maybe 12" in length. With the square base ends on each end. Weld the ends together. Or possibly a plate that both would push against with a slot cut out for the one rod coming out on each end of the assembly.
If this worked, I'd get approximately 13-16" length that would extend to 32-36".
If I could find cylinders with bolt holes in each end plate perpendicular to the rod, I could stack the cylinders, drop bolts/all thread down through both and that would be four bolts to hold the side forces during extension.

Do you guys think a 1" rod would be enough? Or step up to 2"?
For a 30 hp tractor, the smallest that would work would keep the weight down of the assembly.
A class 1 toplink has a 1 1/8" threaded rod I believe.

 

[CincyFlyer]

One could always use two small cylinders that equal one larger cylinder, with the larger cylinder in the middle, and the two smaller ones hooked together at the rod ends. Sort of this configuration:

 

[4570Man]

Pulling with the tractor compression loads the top link. 1” rod is a lot heavier than the top link on the 30 hp tractors I’ve seen.

 

[bcp]

One could always use two small cylinders that equal one larger cylinder, with the larger cylinder in the middle, and the two smaller ones hooked together at the rod ends. Sort of this configuration:View attachment 538999

I think that would move too fast.

Bruce

 

[lennyzx11]

I think that would move too fast.

Bruce

So now I've spit beer on the keyboard!
Thanks guys!