Log Splitter tonnage rating - are they on crack, or just lying?

BlueRidgeMark · Aug 11, 2006

In answer to a question on another thread, I did some calculations of various pressures and ram sizes to see what kind of tonnage each would put out.

But when I look at the manufacturer's claims for tons for their units, things don't seem to add up. They're claiming more tons than should be possible if they are typically running 2000, maybe 2500 PSI, which is what I've understood them to be running.

So how do the log splitter manufacturers justify their tonnage ratings? For example, Iron & Oak claims that one of their units has 26 tons of splitting force. It has a 4" diameter ram. To get 26 tons out of a 4" ram would require a fluid pressure of 4136 PSI. Are they really running that much pressure?

How'd I get that figure? Simple arithmetic. The AREA of a 4 inch ram is 12.57 square inches. (3.14*2^2) To put 26 tons of force on that requires enough pressure to exert, well, 26 tons. 26 tons is 52,000 pounds. So, to get the required pressure per square inch, simply divide 52,000 by 12.757, and you get 4,136.

The same kind of numbers hold for the other manufacturers.

Troybilt claiming 27 tons out of a 4.5 inch ram. They need 3395 PSI.

Timberwolf claiming 20 tons out of a 1.75 inch ram. They need a whopping 16,330 PSI!!!

So, either they are running that kind of pressure in all these splitters, or they are using some "creative" method of calculating their tonnage.

Anybody know?

mga · Aug 11, 2006

ha...i've often wondered the same thing. i've read those ads and looked at that they claim to offer.

i think they're relying on the ignorance of the general public. i also have ran the calculations and they don't seem to add up. maybe they use a different formula......who knows.

good post and good question!! it should be food for thought for those who are thinking of buying a splitter.

here's a link that does calculations....look at hydraulic calculator number 1...fill in the blanks:
http://www.baumhydraulics.com/calculators.htm

olyman · Aug 11, 2006

well--mines got a 6" dia bore--at 3000 psi--figures to at least 30 ton--sure will bow the 16" i beam when have big ones in--then deflects back-----

BlueRidgeMark · Aug 11, 2006

TreeCo said:
1.75 is the diameter of the rod, not the piston.

Ah! Good - that explains that one. Thanks for catching that.

Now they are down to needing 3138 PSI. Sound like a reasonable operating pressure?

BlueRidgeMark · Aug 11, 2006

olyman said:
well--mines got a 6" dia bore--at 3000 psi--figures to at least 30 ton--sure will bow the 16" i beam when have big ones in--then deflects back-----

Actually, with a 6" ram, you only need 2122 PSI to get 30 tons, so that's VERY believable. With 3000 PSI, you'd get 42 tons. Not too shabby!

BlueRidgeMark · Aug 11, 2006

mga said:
here's a link that does calculations....look at hydraulic calculator number 1...fill in the blanks:
http://www.baumhydraulics.com/calculators.htm

Great! Thanks for the link - their calcs agree with mine. It validates my approach, anyway. Since I haven't done any hydraulic engineering, I was operating from some basic understanding, so I would not have been surprised for a hydraulic expert to come along and show me where I had missed something basic. Guess I got it right.

So what about those pressures? 3000? 4000 in the ballpark?

BlueRidgeMark · Aug 11, 2006

TreeCo said:
What would it do to your calculations if the ram was pushing the log into a splitting edge of various surface areas? (i.e.,.5, .8, 1.2 sq inches)

That's the big question - how are they measuring tonnage? What the ram puts out? That's a very straigtforward multiplication problem, as above. Surface area of the piston times pressure. Nothing complicated, so there's no wiggle room.

OR are they claiming a certain tons per inch based on the surface area of the wedge? That could make a huge difference. It's very unlikely that you'd have a cutting surface area that is MORE than the piston's area. It's going to be less - probably much less, so you'd have a multiplying effect on the final number.

However, they never say that. There's no "tons per square inch" mentioned. I do often see the phrase, XX tons of splitting power", which is meaningless.

Rather like the all too common, "Compare at $29.95!" Sounds like they're saying something, but when you break it down according to rules of grammar, turns out they didn't even make a sentence. They SURE didn't say that you could compare their product to somebody else's, though most would get that impression.

So I guess we're back to, "Does anybody know how they measure the tonnage?"

CaseyForrest · Aug 11, 2006

I had that argument too once. When you do your calculations, and figure an advertised 26 ton splitter is actually 18 on the ram, you also need to take into account the fact the the contact area on your wedge is not as much as the ram, thereby multiplying the splitting force.

BlueRidgeMark · Aug 11, 2006

Yes, but what is the contact area? If the wedge is blunt - square on the end - it's easy enough to measure it and do the arithmetic. If it's SHARP, the contact area is (theoretically) zero, so your tonnage is infinite.

I don' theeen so, Lucy!

If the edge is not perfectly square, but not perfectly sharp, you've got a very complex calculation, and therefore LOTS of room for fudging the numbers!

That's why lawyers love complex contracts! :laugh:

CaseyForrest · Aug 11, 2006

Well, if you want to get pissy about it!!

Just kidding.

Your sharp edge does have a contact area, it has too, you can see it, feel it, and when it come in contact with something, it moves it. Not to mention as your wedge pushes in, the contact area increases which is why your pressure goes up. Thats why a sharp knife takes less effort than a dull one, the same pressure on less contact area.

I agree its hard to measure, but it can be done!!

JeffHK454 · Aug 11, 2006

Good topic!

I've got a 34 ton SpeeCo , has a 5" piston and I always thought about the PSI needed to get 68K pounds of push with a piston area like that!

I would say I could count on one hand how many times I've had it above half throttle, reduces fuel consumption and cuts way down on heat build up.

Hell, I'm overheated and out of gas way before the splitter is

!

Jeff

BlueRidgeMark · Aug 11, 2006

CaseyForrest said:
Well, if you want to get pissy about it!!

Just kidding.

Your sharp edge does have a contact area, it has too, you can see it, feel it, and when it come in contact with something, it moves it. Not to mention as your wedge pushes in, the contact area increases which is why your pressure goes up. Thats why a sharp knife takes less effort than a dull one, the same pressure on less contact area.

I agree its hard to measure, but it can be done!!

Yep to all of that. That's why I said "theoretically". Actually, it's in that "complex calculations" area.

CaseyForrest · Aug 11, 2006

I know you knew that, just wanted to make sure you knew I knew that you knew that too.

BlueRidgeMark · Aug 11, 2006

Uh, I knew that.

I think. :dizzy:

BlueRidgeMark · Aug 11, 2006

JeffHK454 said:
I've got a 34 ton SpeeCo , has a 5" piston and I always thought about the PSI needed to get 68K pounds of push with a piston area like that!

I make it out to be 3465 PSI. If we assume that Treeco's "2500 and up" is truly on the low end, as he suggests, then the tonnage ratings start to make sense. We seem to be running in the 3-4 thousand PSI range.

So what's with a relief valve set at 2250, as was mentioned in another thread?

That would cap your splitter at 22 tons.

CaseyForrest · Aug 11, 2006

If you are running over 3000, check your fittings, valve, and hoses. Most are rated at a running 2500 to 3000, with a burst of double that.

asb151 · Aug 11, 2006

BlueRidgeMark said:
In answer to a question on another thread, I did some calculations of various pressures and ram sizes to see what kind of tonnage each would put out.

But when I look at the manufacturer's claims for tons for their units, things don't seem to add up. They're claiming more tons than should be possible if they are typically running 2000, maybe 2500 PSI, which is what I've understood them to be running.

So how do the log splitter manufacturers justify their tonnage ratings? For example, Iron & Oak claims that one of their units has 26 tons of splitting force. It has a 4" diameter ram. To get 26 tons out of a 4" ram would require a fluid pressure of 4136 PSI. Are they really running that much pressure?

How'd I get that figure? Simple arithmetic. The AREA of a 4 inch ram is 12.57 square inches. (3.14*2^2) To put 26 tons of force on that requires enough pressure to exert, well, 26 tons. 26 tons is 52,000 pounds. So, to get the required pressure per square inch, simply divide 52,000 by 12.757, and you get 4,136.

The same kind of numbers hold for the other manufacturers.

Troybilt claiming 27 tons out of a 4.5 inch ram. They need 3395 PSI.

Timberwolf claiming 20 tons out of a 1.75 inch ram. They need a whopping 16,330 PSI!!!

So, either they are running that kind of pressure in all these splitters, or they are using some "creative" method of calculating their tonnage.

Anybody know?

Blueridge,

Just for the record the Iron and Oak 26 ton has a 4.5 inch cylinder. It is incorrectly listed on their site. It is correctly listed in some in their other literature.

Aaron

BlueRidgeMark · Aug 11, 2006

Thanks for the correction, Aaron. That drops the required pressure to 3270 PSI.

I take it you have one? How do you like it? If I had the money, I'd be hard pressed to buy another splitter, based on the looks of it. Of course, this is all academic, since I don't have the money!

I ordered their maul (big & little) today, and a sledge, and a couple of wedges. Seem like nice folks.

Big Woody · Aug 11, 2006

What would it do to your calculations if the ram was pushing the log into a splitting edge of various surface areas? (i.e.,.5, .8, 1.2 sq inches)

The measure given is tons which is a measure of force. Hence contact area has nothing to do with it. Contact area is only important if you are talking about pressure which log splitter specs clearly are not. I thought most splitters would run up t0 3500 psi max which should give close to the advertised values.

For example on my 22 ton Husky the force is 44,000 lbs. With a 4" diameter cylinder the area is 12.566 square inches. This gives a required pressure of 3501.5 psi as the manufactures of Husky told me when I called them before I bought mine. I checked into this and called the manufacturer before hand to verify what was up.

Tractor hydraulic pressure can/should also run up to 3200 to 3500 psi for the 3 point tractor mounted splitters. I almost made the mistake of getting the 22 ton tractor mount from TSC ($450) to save money but I realized my Ford 3000 only ran about 2250 or 2500 psi which would have only given me about 15 tons instead of 22 tons. Glad I went with the briggs model instead

dtw902 · Aug 12, 2006

BlueRidgeMark said:
Great! Thanks for the link - their calcs agree with mine. It validates my approach, anyway. Since I haven't done any hydraulic engineering, I was operating from some basic understanding, so I would not have been surprised for a hydraulic expert to come along and show me where I had missed something basic. Guess I got it right.

So what about those pressures? 3000? 4000 in the ballpark?

Here is another link for ya BlueRidgeMark.
http://www.surpluscenter.com/Hydraulic.htm

Log Splitter tonnage rating - are they on crack, or just lying?

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