And my 4 cylinder Toyota may be rated for 140 MPH. Yes, I know, there are plenty of log splitters rated for much more force.
But the 5” cylinder will go 36% slower, which is why they are not common on ordinary splitters. To compare, a 5″ bore cylinder can produce 49,000 lbs force with the same pump, over 1 1/2 times as much.
With 2500 PSI from the pump it can exert over 31,000 lbs of push force. The most common size for log splitters is “4 x 24″, 4″ bore by 24″ stroke. The larger the cylinder diameter the more force (tonnage) it puts out, but the slower it will go: it takes more oil to fill, and so takes longer. The cylinder is the “actuator” of the system: it converts the hydraulic pressure and flow into force to split the wood, and speed to make it efficient. You must provide it elsewhere in the system! Almost always within the directional valve. These pumps do not have a high pressure relief valve. They are usually quite slow unless a much bigger than normal engine is used. We sometimes see home made log splitters with single stage pumps, often reused from another type of machine. So 2-stage pumps give our log splitters the best of both: high pressure when we need it, and high speed the rest of the time. It’s so smooth it’s usually difficult to notice it is happening. The opening and closing of the bypass is automatic, activated by the oil pressure. This takes a lot less horsepower and allows the use of a reasonably small engine to develop the high pressure necessary to split wood, while giving the cylinder good speed when not under a heavy load (which is most of the time). So the only oil being forced out is from the small gear set. When the back pressure reaches 700 – 800 PSI, oil from the larger set of gears is allowed to pass back to the inlet side of the pump (at almost 0 PSI) rather than being forced out the pressure port. But when the log hits the wedge, the resistance increases, and pressure is backed up against the pump. When the valve is shifted it moves the cylinder quite quickly. That is, the combination of the outputs from both gear sets equals 16 GPM. With a “16 GPM” pump, they will pump 16 GPM when the pump shaft is rotated (by the engine) at 3400 RPM. When the valve is in neutral & system pressure is low, both gear sets are pumping oil into the system. One gear set is about 3 times the size (length) of the second. A 2-stage pump consists of 2 gear pumps in a single housing, and a bypass valve. Two stage pumps give splitters great performance using small engines. Without a relief, most hydraulic pumps will build pressure until something breaks, like a hose, or the cylinder, or the pump itself. It is usually located within the housing of the directional control valve. (Suction strainers in the inlet line are not a substitute for a return filter and are not recommended.)Ī hydraulic relief valve controls the maximum pressure which can be created by the pump, and is a safety valve. There is, or should be, a filter in the return line from the outlet of the valve to the reservoir. A simple air filter in it keeps dirt out.
There is a vented filler cap on the reservoir which allows air to “breathe” in and out. Most use AW32 viscosity (approx 10 wt.) hydraulic oil, which is of course an important part of any hydraulic system. The oil source is a hydraulic reservoir (tank) which is connected directly to the inlet port of the pump. The oil from the pump runs to a hydraulic valve, which provides control over the movement of the cylinder. An engine, or electric motor, drives the pump shaft, and supplies the power for the system. The cylinder is driven by hydraulic oil, under pressure, produced by a hydraulic pump. Most log splitters use a hydraulic cylinder ( like these) to push a cut piece of log into a sharpened wedge, which splits it. BASIC PARTS OF A LOG SPLITTER The Log Splitter Hydraulic Circuit
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