Log splitter will only split at low engine RPM

[Ashful]

With it working for a short period, and now returning to its former state, I'd want to have another look at that filter. I'd bet it's clogged. Even water makes a pretty decent non-compressible hydraulic fluid, when it's not frozen, so I'd doubt it's just water in the system.

edit: hah, I see kevin j and I were thinking the same thing at the same time. Our posts went up simultaneously.

 

[nezwick]

Interesting point about the (lack of) breather vent. Something I can try to test that theory is to open the fill plug during operation and see if performance improves. Oddly enough, that thought passed through my mind even before I made my first post on this board, but I was afraid to do it because I thought the tank was under pressure and all the fluid would shoot out in my face.

It is "totally sealed and locked down" as you put it. As far as I can tell, the only way of admitting air into the tank is through the gaps between the tank and the various covers/panels attached to it. I already eliminated one "leak" by installing a new cork/rubber gasket where there wasn't one, so I may have unknowingly made the problem worse. There is one more spot needing a gasket that I hadn't got to yet. Perhaps that's where the air and water were being drawn in.

I also agree the filter may have become clogged again. This is pretty similar to what I have. The machine seemed to work really great after the initial fluid change and filter cleaning, and there was definitely a lot of trash in the tank.

 

[kevin j]

OK so you have a recleanable wire mesh return filter. the pluse they are re-cleanable. the downside is they are pretty coarse and usually don’t have a bypass valve although it could be hiding in there somewhere. this is a bunny trail but I would pitch the wiremesh element and put a standard screw on disposable cartridge filter outside the system somewhere but that’s a project for a later day

and yes, run it the next time with the filler plug unscrewed or taken out and see if that makes a difference. again I think we’re chasing several different problems but that would be an easy test for one of them.

 

[triptester]

The picture is a suction strainer but it looks to small for use with hydraulic fluids. What is the size?

 

[nezwick]

I think the filter is on the suction side, not the return side. It's under the cover on the top of the tank and fitted to the hose that comes out of it. That big hose runs over to the top/rear of the pump.

 

[nezwick]

I didn't record the part number of the filter, but by my rough estimations it's about 8-10 inches in length and 4 inches around. As far as microns go, I'd have to research the part number.

 

[triptester]

If the strainer is mounted vertically it might not be fully submerged all the time allowing air to be sucked in. In general there are several design problems with the tank. Suction line routing, suction and return to close, no vent.

 

[VirginiaIron]

I think the filter is on the suction side, not the return side. It's under the cover on the top of the tank and fitted to the hose that comes out of it. That big hose runs over to the top/rear of the pump.


View attachment 223408

What a beast!
What is the threaded plug on top of the sweeping 90 and short 90? If that is the filler pipe is, you could drill a hole in that plug to make a breather. There may be a hole in there already and unless you protect it from rain will be a point of minimal water infiltration/contamination. This can be corrected with a soup can during storage or wet weather use. Due to the level/height of your sight glass, it would appear too high to be effective for expansion, if needed due to volume/heat, since most expansion would end up inside the sweeping 90.

 

[VirginiaIron]

This tank unit looks like a storage tank from a steam condensate pump.

 

[VirginiaIron]

Make sure you have a similar breather hole in the cap of the fuel tank (assumed adjacent to the tank) or the engine will draw a vacuum and stall every so minutes/hours until the vacuum subsides. Don't forget the soup can.

 

[jetsam]

If the strainer is mounted vertically it might not be fully submerged all the time allowing air to be sucked in. In general there are several design problems with the tank. Suction line routing, suction and return to close, no vent.

I dunno about the strainer taking in air, unless it's mounted high in the tank. There's a 15g reservoir that dwarfs the fluid capacity of the cylinder and lines... the fluid level can't change that much when the cylinder extends.

Or maybe it's on a flexible line inside the tank and the intake height varies!

 

[nezwick]

The threaded plug on top of the sweeping 90 is supposedly the fill port for the hydraulic oil. However, it's nearly impossible to use for that because it's so small. I'm actually wondering if that's where a breather is supposed to go. Or, maybe it's supposed to be cracked open while in use to act as the breather. The guy didn't say anything about that. When I filled the 15 gallons, I did it via the big top plate.


The strainer is mounted horizontally, and it sits about 1" from the bottom of the tank. It is attached to a rigid piece of pipe and can't move around.

Regarding the sight glass, I can watch the level drop as I extend the cylinder and rise when it's retracted.

It's pouring rain today so I can't do much with the splitter this morning.

I think you're right about vacuum occurring in the fuel tank too. Every now and then the engine just about stalls and I have to quickly hit the choke/throttle to recover it. I thought it was the governor acting up, but it could be this too.

 

[kevin j]

so that’s a suction strainer, not a filter. It’ll be very coarse. I think Jerry’s onto something that if that strainer is not fully submerged all the time it will be sucking air. typically there would be a a pipe going straight down toward the bottom then a 90° elbow and the strainer should lay horizontally down in the bottom of the tank. it needs at least a couple inches of oil over the top of the stranger to prevent vortexing and sucking in air. there are ways to baffle box around and use the strainer vertically but it’s more complicated than you want to get into here.

edit: duh, you said in post above strainer is installed correctly near bottom. never mind........

The pictures really helpful

that tee at the top of the curved pipe if that’s a dead-end thing that would be a good place to put a breather or at the pipe stub sticking up at the back corner by the tail light.

 

[nezwick]

Strainer not filter, got it. I'll have to get a hydraulic shop make a new return hose with a filter adapter so I can spin on a good filter.

The way you describe how the strainer should be, is exactly how it is.

I'll definitely try to open up the plug at the top of the curved pipe to see if admitting air into the tank will help the issue.

 

[VirginiaIron]

You don't need a new return hose. I would plumb the filter assembly, 1- 90, 1 COUPLING, 1 nipple below the the "T" and put your return hose into filter assembly. I would change the location .of the present "T" so it faces up in a horizontal position with a verticle nipple to a breather, and clean up that pipework. This may also reduce turbulence at the present T location that might be adding these bubbles.

 

[nezwick]

That makes good sense. Thanks for the diagram. The fill pipe thing is definitely useless as it is, so I think that's a good plan to eliminate it and replace it with a filter. It was clearly an afterthought. I would definitely feel better with a proper filter and breather vent.

 

[kevin j]

maybe this was covered earlier but how does the return go into the tank just into the top above the fluid level?That would be a source of massive aeration also. or is there a standpipe that goes down halfway or a little more down towards the bottom under the fluid level?

 

[brenndatomu]

The fill pipe thing is definitely useless as it is, so I think that's a good plan to eliminate it and replace it with a filter

Theres no vent there? In the absence of a proper vent elsewhere, that "fill pipe" thingy is exactly where I'd expect to find a vent...in this case probably a small hole drilled into the side of one of the flats on the pipe plug

 

[nezwick]

kevin j, I'll check for the answer to your question tomorrow. I can't remember, but I'm leaning more toward there being no standpipe.

brenndatomu, just looked, no hole at all. So either the plug with the breather hole has been replaced with a solid one, or it just wasn't part of the original plan. Maybe they just cracked open the plug for the vent action.

 

[VirginiaIron]

I would think the only issue would be pressurization due to heat since everything leaving the tank is returning to the tank, with the caveat that once the tank starts to cool it could go into a vacuum and draw water moisture through poor gaskets, etc.. This could be indicated by the collapsing of the vibration damper/soft hose, if applicable, at the pump intake.

 

[kevin j]

There is a drawdown in the tank as the rod extends. Difference in volume out vs volume in is the steel volume of the rod. a quart goes into cylinder closed side extending rod, but only maybe 3/4 quart comes back out of the rod side.

motors are one to one. Systems with accumulators really draw the tank level down as tghe accumulator charges and discharges.

The tank vacuum by itself is not an issue, if there was no breather. But if it draws a slight vacuum, then pump shaft seal, or hose connections, can leak air into system.

I am really curious now on the return, standpipe or not......

 

[kevin j]

Aeration: Disclaimer: scare story, it won’t happen to you, different scenario.

We had a machine with 500 gal tank, I think 18 gear pumps and 5 piston pumps, about 600 gpm of gear pump continuous flow at high idle. New startup out of the shop went ok. Parked overnight on a rail siding 10 miles out and got to about 0F that night. Next morning started up sluggish but ok, engage pump drive, and low idle for a few minutes. All good, flip the switch to high idle. About 10 seconds later, the steel top of the hydr tank (4 ft x 6 ft) and about 200 lbs of engine air cleaners blew off and landed 70 ft away in the weeds. flash and smoke and excitement. Took weeks of testing and autopsy, (not my design,I got called into the autopsy phase to figure out what happened.). it was a combination of thick oil building up in one compartment, not enough open baffle areas, and SEVERE aeration in one compartment due to a big check valve issue. The thick oil built up pressure in one compartment, tore the bolts loose, which caused a spark that ignited the aerated/foam/foamed oil in another compartment and ignited like a bomb.

Lesson, combination of small changes not thought through, check valve aerating oil but ok when warm, baffle changes ok when warm, machine destined for India so it had ISO 68 oil in it, very thick, but testing in Minnesota cold weather, all converged. If had been tested in India, never would have had the issue, but still the baffle and aeration issues would have been hidden in the tank. Everything seems obvious in hindsight. Luckily, no one injured or killed.

 

[triptester]

Putting the vent on the same tee as the return line may cause more aeration problems. Using the capped nipple at the rear corner would be better for the vent.

 

[VirginiaIron]

Putting the vent on the same tee as the return line may cause more aeration problems. Using the capped nipple at the rear corner would be better for the vent.

I believe that is the only opening to the tank. The tank could easily be drilled and looks thick enough to be tapped without welding. The cap in the rear, I believe, is a separate chamber/tank and used for fuel storage. With these limited options I was thinking the best position would be to use the T (vent) in the verticle position so flow is straight through the fitting after the filter where pressure is likely to be minimal. Thoughts & comments?

 

[triptester]

A vent could be installed in the cover that holds the suction pipe. This would allow the install to be done without worry of metal shavings or welding sparks near the tank.