what he said.....
FORCE & HP
Tons is only pressure times cylinder area. You can get 100 tons with a porta power, but no speed, if the cylinder is big enough.
Closed side area is ( (bore diameter) x (bore diameter) x 3.14159) / 4
Rod side, same calcs for the rod steel area, then subtract for net area.
How they get the tons? The box store units often rate at 3000 psi, when the relief valve in the valve is set at 2500 psi, and the cylinder is rated for 2500 psi. To me, that either indicates gross ignorance, or gross dishonesty.
At 2500 psi, with no back pressure on rod side,
4 inch bore = 15.7 tons, 4.5 bore = 19.9 tons
5 inch bore 24.5 tons 6 inch bore = 35 tons.
at 3000 psi, of course everything is 3000/2500 or 20% more force.
Speed is flow (gpm) divided by area. Bigger cylinder moves slower.
Horsepower is flow times pressure. A small motor will move 100 gpm but no pressure, or 1 gpm at high pressure.
Hp is (gpm ) x (psi) / 1714 theoretical, or divide by 1500 to account for losses, plus its easier to remember.
So the two stage pump is high flow, low pressure = hp. Then large section unloads, and small section is low flow, high pressure = same hp.
I split pretty small wood, usually 24 inch maximum, and usually mobile, not at a wood lot. So my main complaint is always speed, not force. For my usage 4 inch is plenty big, and light enough to move easily. I want lots of hp not for tons, but to get fast speeds while pushing some good pressures.
So, you can have a 3.5 hp 50 ton unit, or a 20 hp 10 ton unit- Cylinder and pressure are force, while engine and pump are hp.
ELBOW
There are charts and formulas, but in most mobile equipment, the variables of temperature, viscosity, exact type of fittings, etc make it a moot point. Usually design for suction size of pump or larger. Pump mfr tend to be optimistic. Although rated pump at 3600 rpm, the suction may be high at that speed with cold oil.
A screwed in 90 fitting is much higher pressure drop than a ‘bent stem’ 90 where it makes a sweeping bend from tubing or hose end.
Given the choice, better to have a 90 at the tank, and straight into the pump, as the flow into the gearset is less turbulent, but at these flows and hours of use no big deal.
Your hose is good routing for flow. Even a bent stem 90 out of the tank will have more restriction than straight fittings and smooth hose. Bent stem maybe equal roughly 3 feet of hose, a sharp 90 maybe equal 5 -10 ft of hose. Just off top of my head.
If you need a 90 at pump, not the end of the world, but a bent piece of tubing would be better. Another option is upsizing the elbow and hose, but not really necessary.
These are ‘good practice’ things but not the kiss of death. Unless you have a half inch suction hose, etc.
BTW, restricted suction does not decrease pump flow unless it is truly into blockage or cavitation. Just high vacuum conditions does not decrease pump flow, it is positive displacement after all. With enough blockage and serious cavitation, yes, pump flow is reduced but it will be very noisy.
kcj
