Smaller than OEM Engine on Wood Splitter?

[Woodtroll]

Hello folks,

I'm looking for a decent used wood splitter and the search is frustrating locally. I'm going to look at one later this week that is in my price range but an hours' drive away. Right now I have only photos to go by since there are no labels/decals left on it, except for the engine which the seller says is a 5 HP. I'm certain this is an MTD manufactured splitter, and I think from the cylinder size and extra metal on top of the beam (the square tubing) that it's a 31-ton model.



This splitter should have a two-stage 16 GPM pump and 8 HP engine. I don't need/want something this big, but the price may be right if I offer cash. If the engine is indeed smaller than factory (5 HP vs. 8), am I correct that the cycle time in the pump's first stage will still be what it should be when it's not in the wood, but the splitting force and time spent in the second stage will be lower/slower? I can live with that for now, and can put an 8 HP Predator on it later if I need to as long as the no-load travel speed is still good for now.

Anyone recognize this engine, by chance, assuming it is a 5?

Thanks!

 

[wildwes]

IF it is a 5hp when it was supposed to have a 8hp, it should still work, as you said it might be a little weaker and/or slower in tough wood.

FWIW- my Dad has an old MTD splitter similar to that, he bought it new somewhere around 30 years ago, give or take a couple of years. I haven't paid it any attention in a couple of years, but it still has the original B&S engine, and I am almost certain it is a 5hp

 

[triptester]

Just because the splitter might be a 31 ton model does not mean it came with a 8 hp. engine and 16 gpm pump.
A 5hp. engine would have a difficult time powering a 16 gpm pump.

 

[Woodtroll]

Thanks, folks. Without documentation I'm just working off the few poor photos from the seller. Beam construction and cylinder size makes it look like a 31-ton, comparing to other online photos of labeled machines, and MTD lists that model as 8HP and 16GPM with a 5" cylinder. There could be other models that look similar with different specs, who knows?

I really appreciate your feedback, thank you!

 

[buzz sawyer]

Take a couple gnarly looking logs with you and see how it splits. A strong 5hp may be as good as a worn, weak 8hp.

 

[sean donato]

5hp, won't be very effective with a 16gpm pump in high pressure mode @3000psi. Which should actually be around 4gpm in high pressure mode.
Which takes 7hp @3000 psi @4gpm.
Which is why an 8hp engine is generally the smallest engine you'll see on a 16gpm pump.
Without knowing what the relief is set at its all just a guess anyway.
Anyway, a 5" cylinder @ 3000psi Is 58995 lbs of pressure or 29.45 tons of (extending) force. Box store log splitters are notorious for rounding up tonnage.
At any rate, don't get worked up about it till you see it and split some wood with it.

 

[Jules083]

There's reasons not to like that splitter and we could discuss them all day, but as far as the motor itself I wouldn't worry about it.

If the price is right I'd go for it. If it runs and splits good then great, like you said a predator motor isn't terribly expensive if you need to swap it out later.

It might bog the motor down and get slower on a tough split but it still should be sufficient. Looks like it was stored outside so it's hard to say what kind of shape the motor will be in anyways. Hydraulic hoses might be a bit dry rotted from the sun.

 

[Big_Eddy]

If the pump is the same, the splitter will be just as fast with a 5Hp, 8hp, or 24 hp engine. The cycle time is determined by fluid flow, which is directly related to pump size and engine speed. Small gas engines are almost all designed to run at ~3600 rpm.

Where a smaller engine does make a difference is in two cases.
Splitters have a two stage pump, and they run at high speed until the load (pressure) hits a certain level, then they step down to low speed. The cutoff load is usually adjustable, but only within a limited range. If the engine does not have sufficient torque to hit the original cutoff pressure in high speed mode, the engine will stall before the pump steps down. You can almost always lower the cutoff pressure enough with a low power engine so it won’t stall and in practical terms, lowering the step down pressure does not affect overall cycle time. The splitter will still retract and advance to the wood at the fast speed, and will still move at the same lower speed while the wood splits. The step down happens almost instantly when the wedge contacts you a tough block of wood.

The other impact is ultimate splitting force. Most splitter components are rated for 3000psi, but rarely are the relief valves set that high from the factory. 2250 psi is more usual. A lower hp engine can develop less overall force, as it can output a lower maximum torque. But you can turn down the pressure relief (in the splitter valve) below the engine stall torque and the splitter will split everything up to the lower maximum force needed.

So long story short, a lower horsepower engine is just as fast as a larger one, but cannot generate the same splitting force. But it’s rare that a splitter needs to generate its maximum force. Most blocks split at a much lower pressure.

 

[Woodtroll]

If the pump is the same, the splitter will be just as fast with a 5Hp, 8hp, or 24 hp engine. The cycle time is determined by fluid flow, which is directly related to pump size and engine speed. Small gas engines are almost all designed to run at ~3600 rpm.

Where a smaller engine does make a difference is in two cases.
Splitters have a two stage pump, and they run at high speed until the load (pressure) hits a certain level, then they step down to low speed. The cutoff load is usually adjustable, but only within a limited range. If the engine does not have sufficient torque to hit the original cutoff pressure in high speed mode, the engine will stall before the pump steps down. You can almost always lower the cutoff pressure enough with a low power engine so it won’t stall and in practical terms, lowering the step down pressure does not affect overall cycle time. The splitter will still retract and advance to the wood at the fast speed, and will still move at the same lower speed while the wood splits. The step down happens almost instantly when the wedge contacts you a tough block of wood.

The other impact is ultimate splitting force. Most splitter components are rated for 3000psi, but rarely are the relief valves set that high from the factory. 2250 psi is more usual. A lower hp engine can develop less overall force, as it can output a lower maximum torque. But you can turn down the pressure relief (in the splitter valve) below the engine stall torque and the splitter will split everything up to the lower maximum force needed.

So long story short, a lower horsepower engine is just as fast as a larger one, but cannot generate the same splitting force. But it’s rare that a splitter needs to generate its maximum force. Most blocks split at a much lower pressure.

Perfect explanation. That parallels the way I thought it should work but never could have explained it that well. Thank you for the thorough and complete response.

 

[Woodtroll]

There's reasons not to like that splitter and we could discuss them all day, but as far as the motor itself I wouldn't worry about it.

If the price is right I'd go for it. If it runs and splits good then great, like you said a predator motor isn't terribly expensive if you need to swap it out later.

It might bog the motor down and get slower on a tough split but it still should be sufficient. Looks like it was stored outside so it's hard to say what kind of shape the motor will be in anyways. Hydraulic hoses might be a bit dry rotted from the sun.

Thank you, I appreciate the reply! I've decided to pass on this one, as I have found a lightly-used Dirty Hands 22 ton at a very good price. I liked the one in the original post because it had the old-style design where the wedge plate clamps onto the beam. I'm skeptical of the trough-style design on most of the new ones, but I guess I'm getting ready to find out for myself.