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.

 

[J_J]

Just remove the sled from the cyl and manually move the sled back and forth to check binding, and also while the sled is disconnected, run the cyl in and out and check for loading.

 

[kered]

Thanks guys, i'll get onto what you have all suggested. The sled runs on a 10mm teflon/ptfe shim between the beam and the sled but it might be sticking. I also never thought of the breather in the tank, it only has a small hole in the cap. Don't have any guages but may be able to borrow for a test.
The strange thing is all i did was use a slightly bigger pump, before it was working great although slow.

This is a video with the old pump, First try, as you can see it was slow with the 10-12lt pump

I've also changed the blade

Derek

 

[J_J]

What kind of pump are you using that only runs at 1600 rpm.

What is the displacement and the rated GPM.

If you are coming off the PTO and through a 1.5 : 1, you are not close to the 1600 rpm for the pump you stated.

That means that your pump is running at 360 rpm.

 

[kered]

The reduction is reversed and its 3.5:1, maximum pump rotation is 2800rpm but you get almost maximum flow at 1600rmp, i'll check the make and model and let you know. Its a gear pump not piston.

Derek

 

[LD1]

I definataly got questions regarding the pump specs and actual flow. If the pump is rated for 2800RPM max, you are not going to be flowing nearly as much only running 1600rpm. So looking at a spec sheet would be helpful to us. As part of the formula for figuring out how much HP you need is GPM and PSI of the pump. And at this point, we know neither of those.

But "assuming" you are getting 9.25gpm and operating 2500PSI, that requires about 16HP. With a 30HP tractor, (probably around 24 at the PTO and a little less running through a gearbox) you should still have plenty of power for that flow and PSI.

So if you are stalling the engine (or nearly so), either you are making far more GPM than you think, or are generating more pressure than you think. Given that it is on the return stroke the only real pressure is when the cylinder reaches the end of the stroke. Most actual log splitter valves have a detent that kicks the valve to neutral one ~600psi is reached. It sounds like that isnt the case.

So aside from getting us more info on the pump specs, what is the make/model of the valve you are using? Is it spring return both ways? does it have the detent return? Does it stay in whatever position you put it in until you move it?

Some of the hose sizes are a little undersized as well, but shouldnt cause you to stall a 30hp tractor. Flowing 9.25 GPM 3/8" is a tad small. For pressure lines, 38" hose is good for 8-8.5gpm or so.

The return lines, when retracting the cylinder however, are trying to flow around 16GPM. which would want something in the 3/4" to 1" range.

But either way, regardless of hoses sizes, flow velocities, etc. If the pressure relief valve is set properly, there shouldnt be any stalling you your tractor. So whatever issue you have, is valve/pump related.

When splitting wood, it likely isnt taking as much pressure as you think. That is why you are only experiencing it when retracting and the cylinder bottoms out. Try extending the cylinder all the way till it bottoms out that direction and see if it is the same stalling situation.

 

[LD1]

I definataly got questions regarding the pump specs and actual flow. If the pump is rated for 2800RPM max, you are not going to be flowing nearly as much only running 1600rpm. So looking at a spec sheet would be helpful to us. As part of the formula for figuring out how much HP you need is GPM and PSI of the pump. And at this point, we know neither of those.

But "assuming" you are getting 9.25gpm and operating 2500PSI, that requires about 16HP. With a 30HP tractor, (probably around 24 at the PTO and a little less running through a gearbox) you should still have plenty of power for that flow and PSI.

So if you are stalling the engine (or nearly so), either you are making far more GPM than you think, or are generating more pressure than you think. Given that it is on the return stroke the only real pressure is when the cylinder reaches the end of the stroke. Most actual log splitter valves have a detent that kicks the valve to neutral one ~600psi is reached. It sounds like that isnt the case.

So aside from getting us more info on the pump specs, what is the make/model of the valve you are using? Is it spring return both ways? does it have the detent return? Does it stay in whatever position you put it in until you move it?

Some of the hose sizes are a little undersized as well, but shouldnt cause you to stall a 30hp tractor. Flowing 9.25 GPM 3/8" is a tad small. For pressure lines, 38" hose is good for 8-8.5gpm or so.

The return lines, when retracting the cylinder however, are trying to flow around 16GPM. which would want something in the 3/4" to 1" range.

But either way, regardless of hoses sizes, flow velocities, etc. If the pressure relief valve is set properly, there shouldnt be any stalling you your tractor. So whatever issue you have, is valve/pump related.

When splitting wood, it likely isnt taking as much pressure as you think. That is why you are only experiencing it when retracting and the cylinder bottoms out. Try extending the cylinder all the way till it bottoms out that direction and see if it is the same stalling situation.

 

[J_J]

The reduction is reversed and its 3.5:1, maximum pump rotation is 2800rpm but you get almost maximum flow at 1600rpm, i'll check the make and model and let you know. Its a gear pump not piston.

Derek

How did you figured the 2800 rpm pump would provide max flow at 1600 rpm

If the pump max flow is at 2800 rpm, why are you running it at 1600 rpm.

540 PTO rpm through the gear box increases the pump rpm to 1850.

Seems to me , you are running the pump at about 66%.

 

[kered]

I have 2 speeds on the pto, 545 and 760, I was told the pump data at the shop as they have the speck sheet in the cataloge which we consulted looking for the most appropriate pump, working pressure is 200bar(2900psi) with max at 250bar(3625psi) from 1600rpm up over the flow doesn't increase much, no idea about 66% but i don't believe running anything at 100%
I don't have any speck on the control valve only that it has 1/2" ports and is manual spring loaded both ways, no detents,i prefer it like that so that as soon as i let go everything stops and it was something i already had on the shelf.

I've opened the tank filler, oiled the sled with very little difference but i did try to stall the engine by not letting go of the lever as the engine slowed and it didn't stall, just dropped to tickover so maybe that has something to do things as a very slight movement on the hand throttle speeds the engine up quite a bit from tickover. I'm off to try and scrounge some pressure meters.

Derek

 

[kered]

OOps forgot, tractor is 28hp at pto
I don't expect to get the full 35lts- 9.25g/m hense the reasoning that going to 3/4 was overkill
Moving cylinder to full extention just opens the relief valve, no engine stall on the push stroke(i have it set pretty low)as soon as i pull the lever to return the revs drop, long before i hit the fully retracted but its not fully stalling the engine.
Maybe i'll do a short video as a picture paints a thousand words

Thanks to all for the input its really appreciated

 

[LD1]

So you are saying that going forward till the ram stalls and opens the relief and the tractor runs fine and dont bog, but on the return stroke, even with cylinder in mid stroke and a long way from bottoming out, the tractor bogs alot?

IF that is the case, where is the pressure relief? is it on the valve or pump? IF on the valve, it could have a different setting for each direction. IF on the pump I am unsure why it isnt operating the same as going forward. But in either case, the retrun lines are undersized. While it may or may not be causing the issue, it certainly isnt helping the cause.