Log Splitter Question(s)...Two Stage Pump and Situation Specific Questions

[mikehaugen]

That one is going to be a little tougher to answer. It is all going to depend on how it is designed. IE: you can use a long stroke and small bore cylinder or a short stroke large bore cylinder or anything inbetween.

What you need to do is sketch out some rough dimensions as to how big the log lift is going to be (from pivot to ground), and where you plan on attaching the cylinder to it at. Then you can get a rough Idea of what you need length wise (retracted and extended measurment). This will get you the stroke length you need. And then just depending on where its mounted (leverage), and the angle it is mounted on, and we can figure out the force needed. (bore diameter).

But it is going to me a MUCH smaller cylinder than the splitting ram. So unless you are wanting to build a firewood catapult, you may need to incorporate an adjustable flow valve in that circuit.

so what is a good figure for weight of a log... say you were wanting to split a 36" log 24" long?

 

[LD1]

A log that size is just under 10 cubic foot solid.

The heaviest woods around here are on the order of 45-50 lb per cubic foot when dry. So a peice that size would weigh in the order of 450-500lbs at the heaviest. But could be as light as 300-350 lbs if it is dry and a lighter-hardwood like ash or cherry.

But I'd figure on making it able to lift about double that, for the ocassioal rare big peice or green wood...since with a log-lift I assume you arent planning on vertical capability. AND...the more you make it "able" to lift, the easier it is on components cause they will run at a much lower pressure most of the time.

Would it be out of the realm of possibility to ever see something like a 32" diameter white oak or hickory chunk that is still green?
@ 36" long, that would be almost 17 cu ft of wood. And at a weight of 60+lbs per cf, thats a tad over 1000lbs there.

 

[MGH PA]

Again, thanks for all of the help on this guys.

I was researching possible cylinder sizes, and I think, based on JJ's recommendation, I'm going to go with a 4" bore. However, I'm having a little trouble understanding how cylinder size plays a role in cycle time. I've been using this calculator using various numbers, and it seems that cycle time does indeed get faster with increased rod diameter, but the extend time doesn't change. So, basically, your extend time is directly related to BORE size, and retract time is directly related to ROD DIAMETER? Is this because for extend time, you must calculate the volume of the cylinder (in cubic inches), conver to gallons, and then divide by pump capacity? Retract times factor in the rod diameter (area of rod is subtracted from area of cylinder, thus the higher the area of the rod, the less volume of fluid that needs to be moved), correct?

 

[LD1]

Extend time is related to ONLY bore size.(and of course length). Retract time is related to BOTH bore AND rod size.

Think of it this way:

The pump pumps a certain GPM of fluid. The cylinder holds a given amount of gallons. So the time it takes to "fill" the cylinder is the "cycle time". IF you have a larger diameter cylinder, it holds more gallons, and takes longer.

On the retract side, you are filling the "rod-side" of the cylinder. And since the rod occupies space in the cylinder on that side, the larger it is, the less fluid it takes and it will move quicker. BUT, thats not to say that a 2" rod is going to have the same cycle on a 4" and a 5" cylinder. While the rod occupies the same amount of space, the area for fluid around it is bigger with the 5" cylinder. So retract is BOTH the bore size AND rod diameter.

 

[Scooby074]

What LD said.

Some manufacturers use an abnormally large rod in an effort to speed up cycle times.

 

[brandoro]

I won't add anything to the technical side of this thread but I am curious how much wood you burn in a year at a camp. Sounds like this splitter will cost a significant amount even if built as a school project.

 

[J_J]

A two stage pump will start pumping at the high GPM in extend mode until the pressure builds to somewhere around 650 to 700 psi, and then will shift into low GPM if the load demands it, so times will vary.

The retract mode usually uses the high GPM to retract the cyl.

A single stage pump will pump at the max GPM if the engine is running at max rpm. When the pressure builds up, the GPM's slows down.

So the speed is not a hard set rule.

If you want speed, the rack and pinion log splitters are some of the fastest.

Super Split Splitter

Super Splitter - YouTube

 

[MGH PA]

Back again with some more questions about pressure limitations. If we go with a Prince valve, which as was indicated by another poster here that they are preset @~2200PSI, and the Haldex 22GPM pump we're looking at is rated at 3000PSI, but it producing 2500/6gpm on the high pressure side, what gives in first? When I'm making my HP calcs, what PSI figure do I need to account for? The highest theoretical rating, or that highest actual rating? What happens if the PSI generated exceeds the rating on the valve?

 

[J_J]

I believe the valve comes set at 2250 psi , but you can usually adjust the pressure to 100 psi below the max pump setting of 3000 psi.

However, Prince log splitter valve has a test pressure of 2750 psi. So set the valve relief at 2750 psi

Surplus Center - 11 GPM 2 STAGE HYD PUMP S21202-5292

 

[MGH PA]

Alright, here's another decision that has to be made, and we need a little advice (thanks for the last answer JJ). We are using a welded "T" style cylinder since it so happens we found the exact size we want (with a 2.5" rod diameter), at the best price, and that's the only style. Now we have two choices for the wedge/plate setup. We can push the wedge into the plate, or push the plate into the wedge. Because of the cylinder design and size, to mount a wedge to the cylinder and push into a stationary plate, the wedge would have to be quite wide and long, adding to the weight. It would be easier to have a plate pushed into a stationary wedge.

With that being said, what are the pro's/con's to each design?