Logsplitter trouble shooting

[kered]

Hi all, i've got a small problem with my homemade log splitter. Its powered from the tractor PTO driving a 1:3.5 reduction box to the pump so as not to need to over rev the engine in order to get the pump speed and is working with a reasomable cycle on just over tickover. My problem is that on the return stroke it almost stops the engine so i have to centre the handle and let the engine recuperate. On the pressure/splitting cycle i have no problems at all with the engine slowing.

Previous to changing the pump from a 18 to 35lpm i had no problems and only changed to get a faster cycle time as it was a bit slow.

The cylinder is 90mm diameter with a 60mm rod and a stroke of 600mm
Hoses are 1 1/4" feed to pump and 1/2" out to control valve, 1/2" to cylinder on the split side and 3/8" on the return side. and 3/8" return to tank

Could it be the 3/8" hose is a bottleneck?

Does port A and port B on the control valve have the same output as they are not marked and could be the wrong way round although the pressure release valve is working ok on the splitting cycle.

Which is usually port A? the one closest to handle or furthest away( suppose it wouldn't make a difference if they are same output)

If you need any more info on the settup let me know

thanks in advance
Derek

 

[J_J]

Please give us the GPM, we don't do liters

18 lpm = 4.7 GPM

35 lpm = 9.246GPM

By increasing the lpm you doubled the HP requirement.

You may be running out of HP, and that will stall the engine.

Try running the engine at half speed and see if the engine will stall when splitting hardwood.

The return hose should be equal or larger so as to reduce back pressure.

Do you have a return filter and is it good.

If you used the Prince LSR 3060 fast log splitter valve, you could almost double the speed. It takes 4 GPM in and produces about 25 GPM.

Add on

Forget the Prince valve , as you have already changed out the pump.

 

[kered]

Sorry, here we don't use imperial other than pipe threads as i'm in Europe. The engine is a 30HP diesel so i don't think thats the problem especially as its ok on the power splitting stroke. It does seam better at 1500rpm which is the maximum torque speed for the engine but still slows down on the return.
No Filter in return line(as yet but its ordered)
I'll try upping the size on the return and see what that does.

Here we split mainly stringy Eucaliptus and some easier oak and chestnut, but as i say splitting is not the problem.

thanks for your input

Derek

 

[Stonehaller]

Your tank line is too small. On the return stroke, flow out of the cylinder is almost double the pump flow. Your tank line is getting pressurized because the 3/8 hose or more likely the fittings are too small for that flow. With a pressurized tank line your relief pressure will go up increasing the load on the pump to the point that the tractor cannot power it stalling the engine. You could be exceeding the working pressure of the pump, valve and the cylinder hose. Best not to use the splitter until you get the return line and fittings increased or if you must, run at a lower RPM as J.J. suggested.

 

[kered]

Thanks Stonehaller, thats where i'll start on the return to tank and see what happens. When i think about it its the logical answer as double the input volume is trying to get out the bigger volume end of the cylinder on the return and at double speed too so its probably a 4x flow rate in a smaller diameter hose.

Derek

 

[kered]

Is there a page i can lookup re balancing hose sizes as its basically been done by the fitting threads on pump, cylinder and valve outlets.
thanks
Derek

 

[kered]

Just a bit of update, first i increased the return to the tank from 3/8 to 1/2, i was gona go to 3/4" but the guy in the hydraulics shop said its stupid and far overkill.
Rechecked all the sizes of the hoses and i had made a mistake previously the output from pump to control valve is only 3/8 which i'm told is more than enough as i'm nowhere near the 35lt/m(9.25G/m)
Apparently from the pump speck max flow is reached at about 1600rpm and to get that i'll need to run the engine at about 2000rpm, never been there yet so i'm about 28lt/m(7.4g/m)

I have changed all the hoses from 3/8 to 1/2 other than the pump out which remains at 3/8, return to tank is also 1/2, pump suction is 1" ID
And the problen still remains the same, ok on the splitting stroke and slows engine on return. I also tried reversing the output ports A and B on the control valve(its a 1/2" valve) just in case the problem could have been a partail blockage on a port in the valve but no change.
So the question remains why is it taking more HP on the return stroke compared to the forward pressure stroke.

thank
Derek

 

[oldnslo]

Sounds like there is a restriction some place in the system. Can you install a gauge in the blind or cap end of the cylinder and also if possible the pressure port from the pump to the valve. This would let you know what the pressure difference is between these points. Would also show pressure required extending Vs retracting. I am wondering if there is some restriction in blind or cap end cylinder port.

 

[DarkBlack]

You already ruled out the spool, switching a and b.
Assuming you don't have a hidden check valve anywhere ( including in your cylinder assembly)
I would do a quick test: Make sure the tank is open/vented. Run the hydro pump/tractor at a slow speed.
In this case, does the engine still struggle on the return stroke?

 

[Leejohn]

Your pusher needs some grease on the under side of the beam it's digging in. Check the tilting of the pusher might have to drill another hole or just keep grease on it.