hydraulic splitter sizing

[marks]

I'm considering the purchase of a splitter, and independent of the tonnage rating, is there some other limiting factor that would impact the maximum diameter. Most of the wood is pine and eucalyptus and less than 24" in diameter, however there are some rounds up to 30".

 

[gordon21]

Your ability to lift the pieces of wood into place.

Does your splitter tilt to work vertically? If not, lifting a 24-30" round that is 20" or more long sounds like a lot of weight.

 

[WayneB]

I'm considering the purchase of a splitter, and independent of the tonnage rating, is there some other limiting factor that would impact the maximum diameter. Most of the wood is pine and eucalyptus and less than 24" in diameter, however there are some rounds up to 30".

Just wondering how much wood you are splitting annually? I split all hardwood here in New England and some of the big pieces can get to be pretty darn heavy to lift up onto the splitter. Usually end up building a stepping ramp to get the big ones up.

I think you also want to check the gpm of the pump and capacity of the reserve tank. My splitter has a 6.5 HP engine, 16 gpm pump and the oil tank is a little over 5 gallons and 10 sec cycle time. The cylinder is 4" diameter and has a 24" stroke and it is rated for 25" log.

It came with a four-way splitting wedge which is nice with the right size wood, but I hardly ever use it. Just don't like the pressure that it put onto the splitter. Guess I am a bit of a chicken to stand that close to this thing under that much force.

 

[Wayne County Hose]

When splitting large diameters, the cylinder rod is not pushing straight out, the wood is trying to force the rod off of the cylinders centerline. The most common repair I see on log splitter hydraulics is a bent rod. All things being equal, or close to it, buy the splitter with the larger diameter rod.

 

[Highbeam]

I have split the big 30"-36" plus rounds of cottonwood and other NW woods. Always using the typical 18-22 ton 4" cylinder hydraulic splitters with a single wedge that flip to vertical and the wedge travels on the ram.

The large large rounds never sit really square on the foot of the splitter but that's OK since there is a guide that keeps the ram tight to the beam. As long as I get a decent bite on the huge round with the wedge then the round will partially split. Then grab the maul and finish the split.

Even the largest 35 ton splitters are often rated for a round which is the same diameter as their wedge so the splitter's rating is meaningless. I've never known anyone who was limited by the 4" ram model splitters unless they wanted to use a 4 or 6 way wedge. A larger hydro pump will speed the ram up.

 

[turnkey4099]

When shopping for one, take their tonnage ratings with a large dose of salt.

The bypass on the hydraulics is normally set at around 2500 - 2700 psi. Therefore the only thing affecting the 'push power' is the size of the cylinder (as long as the motor has enough power). A bit of math will show that the quoted figures are considerably optimistic.

Another point is that the size of the motor or pump has nothing to do with the tonnage rating. A bigger pump will result in faster cycle time, a bigger motor will push longer before it stalls but keep in mind that limitation imposed by the bypass.

Most splitters are built with a 4" cylinder. A 4 1/2" could be better but IMO a 5" is overkill. Cylinder size also has an effect on cycle time: bigger=slower.

I infest a firwood/logger forum and the rage over there is to add hydraulic lift tables to handle the big rounds. Not a difficult project if you can weld.

Harry K

 

[turnkey4099]

Even the largest 35 ton splitters are often rated for a round which is the same diameter as their wedge so the splitter's rating is meaningless. I've never known anyone who was limited by the 4" ram model splitters unless they wanted to use a 4 or 6 way wedge. A larger hydro pump will speed the ram up.

Errm...no, the rating on the splitters is with the ram stalled, i.e., the max pressure the ram can exert. The size of the round has nothign to do with it.

Harry K

 

[SPYDERLK]

When splitting large diameters, the cylinder rod is not pushing straight out, the wood is trying to force the rod off of the cylinders centerline. The most common repair I see on log splitter hydraulics is a bent rod. All things being equal, or close to it, buy the splitter with the larger diameter rod.

Cylinder should have a swivel built into the fixed end and also on the ram end, so there should be no bending moment exerted on the rod - just the standard 'in line' column buckling forces. Forces on a splitter cylinder are much more predictable than those on a loader cylinder because there is no possibility of pressure higher than relief. Thus a rod rated for the cylinder nominal force will be fine if the cylinder is properly set up [floating] on the splitter. Splitters not designed this way would be abuse to the cylinder and should be avoided. I cant imagine a cyl manufacturer condoning usage in a design situation where the rod was going to see bending moments beyond incidental small ones caused by swivel alignment tolerances.
larry

 

[Richard]

Most of the wood is pine

Just curious (to you or anyone else) why split pine? are you using it in a fireplace? (I always thought pine was bad for a fireplace?)

 

[Wayne County Hose]

Cylinder should have a swivel built into the fixed end and also on the ram end, so there should be no bending moment exerted on the rod - just the standard 'in line' column buckling forces. Forces on a splitter cylinder are much more predictable than those on a loader cylinder because there is no possibility of pressure higher than relief. Thus a rod rated for the cylinder nominal force will be fine if the cylinder is properly set up [floating] on the splitter. Splitters not designed this way would be abuse to the cylinder and should be avoided. I cant imagine a cyl manufacturer condoning usage in a design situation where the rod was going to see bending moments beyond incidental small ones caused by swivel alignment tolerances.
larry

Nice try, but swivels have nothing to do with the rod bending. They bend on a splitter because the rod is extended far out of the cylinder housing and more force is placed on the rod than it can handle. So, it bends. Kind of like pressing a 2"x4" piece of lumber against a wall. It doesn't matter what you do to the ends, it will bend in the middle.

The further the rod is extended, the easier it is for a catastrophe. The closer the piston gets to the gland, the easier it is for everything to bend. Same principal as an extension ladder, collapsed, it's very strong. Extend them all the way and they get shaky.

Cylinder manufacturers rarely have any input as to the engineering of the equipment their cylinders are manufactured for.

As for no possibility of pressure higher than relief, you have got to be kidding me. When you have a gnarly piece of wood that builds pressure on the piston end approaching relief, then the wood pops, the piston goes flying forward, exerting all this force on the rod/gland end of the cylinder. I would bet that pressure spikes on the rod/gland end approach double the relief valve pressure.