Buying a log splitter project?

[KTurner]

I've been watching craigslist for a log splitter for a while now, and the pickings are very slim. I'm going to look at a project tonight. The guy bought the parts to build his own splitter, but never got around to the assembly stage. The frame is a used towable lickety splitter brand frame with a fixed wedge. Includes, all new, 40ton ram, 8hp motor, hydrualic pump, control unit, hoses. His asking price is less than what the new parts cost him.

I've never built or worked on a splitter, but it seems pretty straightforward. I have done some research online. Does anyone have any tips on what to look for?

Keith

 

[J_J]

You have to look at what a 40 ton cost new, and what you are paying for a complete unit in pieces. Might be a great deal. Is the engine a Honda? Is the control valve a single lever or a double leaver valve? How about the tank and filter?

 

[LD1]

A couple of other things to think about is look at the parts selection.

40 ton is going to need to be at LEAST a 5.5" cylinder and probabally a 6" cylinder. If it is smaller than that, just understand that it is NOT going to be 40T.

Also look at the pump size. Because an 8HP motor is only going to run up to a 16GPM 2-stage. And if it is INDEED a 6" cylinder, that will make for some really slow cycle times and you will probabally be dissapointed. If it is an 11gpm pump, that is even worse.

So look at the specs of the components carefully. There are good online calculators that will compute the tonnage and cycle times. Most units for sale run ~16seconds give or take for a complete cycle. If it is a 6", you are looking at ~20secons with 16gpm and and close to 30 sec if it is 11gpm.

And one more thing, look at the cylinder stroke length. Most commercial models have a 24" cylinder. I have seen FAR too many homemade jobs with only 12-16" cylinders. This either limits you to very short peices, or the wedge not travelling far enough to split stringy stuff, depends on how it is designed.

 

[KTurner]

There are good online calculators that will compute the tonnage and cycle times.

Google isn't helping... AH!, scratch that. search for hydraulic calculator instead of log splitter calculator and all sorts of stuff appears.

Looks like I'll be printing a cheat sheet of formulas and taking my calculator with me.

Keith

 

[LD1]

Google isn't helping... AH!, scratch that. search for hydraulic calculator instead of log splitter calculator and all sorts of stuff appears.

Looks like I'll be printing a cheat sheet of formulas and taking my calculator with me.

Keith

Unless you are good at math, and probabally take a notepad, you might want to jsut take a look, and make some mental notes as to cylinder size, stroke length, and pump GPM, and then go home and do your calculations. As well as post back here. This will give you a little time for what you saw to sink in.

But when I mention that ~16 second cycle time being average, keep in mind that it is ALL the way extend AND retract added together. And the Retract of a cylinder is always faster because there is less volume due to the rod, so make note of rod diameter as well.

But if you ARE good at math, you basically just figure the volume which is pi*r(squared) times length. If you do this all in inches, divide that volume by 231 and you have the volume in gallons. Then figure the volume of the rod and subtract that from what you just did. That will be the volume on the rod side in gallons.

If you can make it that far, I am sure you can figure out how many seconds it will take to fill that volume given the GPM of the pump.:thumbsup:

But you may have to make notes and go home anyway, Because the specs might not be listed for the pump and you may have to look them up.
If you

 

[KTurner]

The info I'm seeing pretty much makes sense, except one thing. I keep seeing this rule of thumb for sizing the powerplant : 1hp = 1gpm@1500psi. That would mean that an 8hp engine would only be good for 4gpm @ 3000psi. I'm guessing this is where two stage pumps come into play. For splitting force, you get the much lower flowrate at high pressure (4gpm@3000psi), and then much higher flowrate at lower pressure to retract the cylinder (16gpm@750psi).

This seems to agree with specs of commercial log splitters, though they neglect to mention that you don't get the specified pressure at the specified flowrate.

When doing my calculations, I have to do them twice - once with stage1 for splitting force and time, then with stage2 for retract time. Am I on the right track with this?

Keith

 

[LD1]

The info I'm seeing pretty much makes sense, except one thing. I keep seeing this rule of thumb for sizing the powerplant : 1hp = 1gpm@1500psi. That would mean that an 8hp engine would only be good for 4gpm @ 3000psi. I'm guessing this is where two stage pumps come into play. For splitting force, you get the much lower flowrate at high pressure (4gpm@3000psi), and then much higher flowrate at lower pressure to retract the cylinder (16gpm@750psi).That is pretty much correct. Allthough the 16gpm is usually closer to 600-650psi but the changeover point on some pumps is adjustable

This seems to agree with specs of commercial log splitters, though they neglect to mention that you don't get the specified pressure at the specified flowrate. They do if you actually read the pump specs. It will be something like 16gpm @ 600psi and 3.5gpm @ 3000psi

When doing my calculations, I have to do them twice - once with stage1 for splitting force and time, then with stage2 for retract time. Am I on the right track with this? NO

Keith

You ONLY calculate the cycle times using the higher GPM. Because that is the way they are rated...NO load.

It would be inaccurate to try to calculate the extend based on the lower gpm. Because the point at which it has to "shift" onto the second stage depends on a number of factors, like log length, wood species, knotty peices, etc.

Some peices that split super easy like red oak and ash sometimes dont even go to the second stage. And some peices only drop to the second stage for a few inches and then kick back up to high speed. Our logsplitter switches @ 650psi and is a 4.5" cylinder. That means it develops just a tad over 5 tons even at 650psi and without having to change to low speed. That will split a LOT of wood.

And if by chance it is a 6" cylinder you are looking at....thats 9-tons @ 650PSI.

 

[KTurner]

I went to look at the project this afternoon, and the craigslist ad was, uummm.. how shall we say..., not accurate. While the "40 ton hydraulic ram" didn't have paperwork or identifying marks to find the actual rating, the OD was only about 3.5", so it may have been 10 ton. The new/unused 8hp engine "most likely has some bad gas" in it and "could be started with a few minutes work on the carb." The frame, which is what I was most interested in, was looking weak.

But, not a total loss. I learned a bunch of stuff today, thanks to you guys.

Thinking about a couple other options now.

Keith