Do you get what you pay for with cylinders?

[Groo]

The reason you don't find big hyd rods is the displacement ratio relates to increased return stroke volume in gpm...... For example,if the cyl displacement ratio is 2:1 then the return gpm that runs through the valve will be twice the output of the pump......if the valve core is not rated at the extreme gpm's then the two stage pump will sense the pressure drop and will cut back to the single stage or bog down the engine and will stall

On a typical installation of a log splitter with a large displacement ratio they usually use a single-pilot operated check valve mounted on a tee at a large port at the tail of the cylinder ( with a return line back to tank)..then they connect a pilot line to the retract port to sense the return pressure.......this method will allow most of the return oil to by-pass the main control valve instead of forcing it in through the valve core

2:1 is pretty easy to accomplish, and if you are pushing the valve and pump limits on the extend, without some sort of bypass, you will at least be running very high pressures during a retract. likely not enough to kaboom, but it certainly wouldn't be doing the machinery any good.

another thing to consider is that as return speed goes up, return strength goes down.

I was told by a Hydraulics engineer that a double acting cylinder needs at least 1/4" of clearance (1/2" bore to rod differential).

 

[the old grind]

I wonder if rod diameter gets overplayed at some point when it comes to log splitters. These are not fishing poles, and are rarely stressed in any direction other than how they are designed to be and installed. Operating pressure will have its bearing on the cyl diameter required to do work, but due to the greater area on the piston face isn't it most always doing its work on extension anyway?? If there are horror stories about bent rods there aren't many red flags popping up in recent splitter threads.

Extend/retract differences in flow and force are well discussed herein with no one is obviously recommending a particular advantage to rods more stout than we see on affordable off the shelf cylinders. Sure, there will be differences to consider for operating between say 2k vs 3k PSI, but being on the high end of that should be understood as part of matching up components for the splitting force desired and perhaps for efficiency.(?) IIRC, 'tonnage' obtained is a function of cyl ID and operating pressure, and a cylinder is a cylinder to a reasonable extent.

Am I totally missing that some 'Cadillac of splitters', whoever that may be, boasts of having a particularly large cyl rod and offers YouTube demos showing it's superiority? You want the biggest cyl rod? Get a single acting cyl, say 3" piston AND rod and you can brag like guys do as you winch it retracted or show 'em the clever return spring mechanism you designed ... and that it needs to cycle both ways. A x" cyl is what it is for piston size regardless. Yeah I "like to build stuff heavy duty" too, it's a guy thing, but it's perhaps a reason so many homebuilts I've seen are sloowww too.

I don't mean this to be a rant, or to belittle the OP's or anyone's leanings. Just to say that sometimes overkill is for naught, and that the desire for an 'x-treme duty' cylinder may be more a confidence or emotional decision than either practical or of necessity. btw: I suggest that something we can learn by scrutinizing factory mades might be which portions of the plan don't need to be out of sync with o'all design & intended use, and considering the possible limits of it's weakest point.

I say balance your components to work together. YMMV of course according to o'all size, but ultimately it's pressure that make the system work with required flow thus to be accommodated, and the bigger rounds one has to split the bigger dia cylinder they should plan for, plain & simple. (need one for the lifter too?) I'd expect rod size to be proportionally bigger as cyl dia goes up, and for the most part 'a cylinder' (gen) up to any task within its intended operating pressure intent. (flame suit on while I await reproach from rocket scientists)

 

[mikehaugen]

The advantage of a larger rod is more about taking up volume on the "unused" direction of cycle, thus speeding up retraction and reducing overall cycle time. The increased strength of the rod is just an added benefit, and like you said, probably not a necessity.

 

[LD1]

Yep. Increasing the rod diameter isnt for strength on a splitter. It is simply for return speed.

A 4" x 24" cylinder with a 1-3/4" rod will have ~1.05 gallons of volume on the rod side.

Same cylinder with an over sized rod @ 3", will have 0.56 gallons volume.

Lets say you are running a 11gpm pump for this 4" cylinder, retract time for the smaller rod would be 5.7 seconds. With the bigger rod, you could retract in 3.05 seconds. Almost twice as fast.

And assuming max pressure of 3000psi, the 1.75" rod would have about 30,000lbs of force in retract.

While the 3" rod cylinder would have 16,000lbs. But when do you even need that on a log splitter return??

I am actually in the design phases of a splitter I am going to build. Lots more research to do, but I am wanting FAST. 4" cylidner and 3" rod paired with a 22gpm or 28GPM pump fast. I know alot of heavy equipment uses some rather large rods in comparison to cylinder diameter. I I cannot find any used and affordable, I may be calling baileys to see how much one would cost to make. And if affordable, that will give me the chance to oversize the ports too:thumbsup:

 

[the old grind]

Mike, LD1, thanks guys, for the clarification! This is where I see the extra 'return' flow needing to be fully understood vs perhaps overlooked. (How do manufacturers account?), and my concern is that some may not fully understand/allow for it and NOT get the most from this discussion when 'balancing' the choice of components. ("I need a higher-flow valve & hoses ... can I return these for the 'right' ones?")

As I understand it, one or more pieces (valves, hoses, fittings) may need to be 'outsized' to best accommodate the higher return flow. (big help here for that) But, I'm assuming (too much so?) that using a 2-stage pump also figures into cycling rate somehow, say by higher pump flow/cyl volume ratio and less hydro 'churned' on return to cycle quickly and with the pressure boost of the 'stages' there for the heaviest loading. I guess if a guy had help to load logs he could really be held back by an awkwardly slow cyl return, but at some point the volume/rate of wood processed might still set a limit of output (home use vs hi-volume to be sold, etc). YMMV, right?

Guys I help with log splitting use from a 20 or more ton TSC down to 5 ton HFT portable electrics. Differences in capacity aren't obvious, even with 14" or 16" elm rounds ('twisty' grained headaches as a rule), but either type/size can wear out a duo of retirees as quickly as any chore we'd tackle. (old age begets teamwork/cooperation...)

Perhaps my BS-philosophical insight is just misplaced. btw: It was for 'hydraulics' info that I joined TBN, and for me this is an important 'class'/subject. I'm glad my naive questions are so well addressed, and hopefully the answers of benefit to others. Special thanks, as always, to J_J and WCHYD for sharing their knowledge & experience, say vs the supposed 'tacky faux pas' of asking a Doctor about one's sore elbow at a dinner party. It's guys like (all of) you that make TBN such a great place to learn. :cloud9:

 

[Industrial Toys]

Well, I just got an unpleasant education about cylinders. I needed a couple for a ten foot plow blade. I found some at Princess Auto on clearance, cheap. But a friend had to machine them so they fit. Shortly after using them, the one cylinder popped the dust seal partly out the end. A cylinder place, said this happens because the seals fail and then the back pressure does this. He said the seals of these Chinese cylinders, you can bite apart with your teeth they are so cheap. He wants $300.00 a piece to replace the seals. He said he once had forty guys building cylinders, now has six guys fixing Chinese ones!

Accounting for the machining of my cylinders to make them fit, I should have just replaced the seals in the original ones but the new ones looked so shiny and nice! Not sure if I still have the old ones

 

[wdchyd]

Sad to think of but "industrial toys" can be expensive

Repair/rebuild/replace is a tough call, but with fixing the old ones at least you know they were intended for that particular purpose and will fit....buying the cheaper cylinders is a gamble, sometimes successful sometimes not

I have not run into import cylinders with chinsey seals but have seen lousy fit and finish on their steel and cast iron housings, which will shorten their life significantly

A quality rebuild can be better but sometimes not less expensive