hydraulics help needed

[jimmysisson]

Hi all. I have a homemade trailer woodsplitter with a 4" x 36" cylinder, a 7 hp Briggs engine and a 13 gpm Barnes pump. I added a 2x18" cylinder for a log lift/takeoff platform. I have two logsplitter detent valves, one for each cylinder, with return hoses teed, then through a filter and back to the tank. I also plumbed in an hydraulic proportioning valve so the lift cylinder would get the proper volume (it's 'way too fast with full 13 gpm).
My problem is this: slow cycle times. With cold oil, a forward/return stroke takes over a minute. With warm oil, it's still 25 seconds. At low idle, it's about 40 seconds. I'm hoping for about 12-15.
This splitter started in life as a trailer model with no power, using a 22 gpm or so PTO pump on my old Farmall A. That had better cycle times. I decided to self-power it when the Farmall and pump went away and I had this almost-new Briggs engine. I started with a new 11 gpm pump, and it was too slow. 11 gpm was the recommendation from the chart for the 7 hp engine. I bought the 13 gpm pump, and it got a little faster. I made a mechanical stroke limiter for the ram that I can set when I have shorter logs, so that speeds things up a bit.
Here's really the question. The 7 horse Briggs barely sounds like it's under load when I'm using it. When it goes into the second stage of the pump (slower volume/higher pressure) it sounds like it is under no load at all. A lot of splitting is easy and would stay on the higher speed of the pump.
So, I can get (from Northern, source of all this stuff) a 16 gpm pump in the same form factor so it'll bolt right in. That's 'way above the rating for the 7 hp engine, yet at 13 gpm the engine sounds like it barely labors.
Does anyone know whether this little engine would just be bogged down all the time with a faster pump? I hate to spend the $180 (again!) if it won't run, but the slow cycle makes splitting tedious.
I use regular hydraulic oil in this machine. It's only used in the winter, so would synthetic be any better, maybe when it's still getting warm (REAL slow when oil is cold)? I presume that would not change the stroke time.
Any advice? Is there another way to get more speed?
Sorry for the long post. I could probably take a photo of this beast if that would help.
Thank you, Jim

 

[rswyan]

</font><font color="blue" class="small">( Does anyone know whether this little engine would just be bogged down all the time with a faster pump? I hate to spend the $180 (again!) if it won't run, but the slow cycle makes splitting tedious. )</font>
No it wouldn't - when it's running under no load (resistance) it shouldn't bog down at all .... it's when it goes into the 2nd stage (high pressure/low volume) where you'll have a problem, if any.

I'd guess it would largely depend on what type of wood you are splitting - if it's stuff that has a tendency to "pop" open before it's completely split, like maple you may not have any problem. If it's something like oak which is real grainy and gnarly the engine could stall if it spending too much time working in the 2nd stage.

 

[RonMar]

Well if I do my math right, that 4X36 cylinder has an internal volume of around 452 CU/IN(12.56 SQ/IN X 36") which equates to around 1.95 Gallons. 60 seconds divided by 13 gallons = a gallon every 4.6 seconds so that cylinder should move full travel in under 10 seconds with no load.

From your description it almost sounds like you are not getting full flow tho the cylinder. What gives me this impression was your use of the word "T". You said "with return hoses teed, then through a filter and back to the tank". That tells me that you used a "T" on the inlet port of the valves as well, placing the valves in parallel. What is happening is that as you work a cylinder, some of the flow is going through the open center of the other valve and not moving the desired cylinder I am not quite sure where you placed the proportioner in this, a picture or drawing would be helpfull.

Open Center Hydraulics 101: The fluid should flow as follows.
1. Tank
2. Pump
3. Inlet port on the valve
4. Outlet port on the valve
5. Filter
6. Tank

With the lever in the center position, the working ports are blocked and the cylinder is locked in place. The inlet port is connected directly to the outlet port and the fluid flows through the system relitively unobstructed(high flow, low pressure). When you move the lever, the inlet port is connected to one of the working ports and the other working port is connected to the outlet port. This causes the cylinder to move and flow is restricted based on the load on the cylinder(splitting wood) and pressure builds to perform this work. If you add another valve to your system, it needs to be added in series with the other valve IE: outlet of the first valve needs to go to inlet of the second or by the numbers above, 1-2-3-4-3-4-5-6. The parallel valves would explain why the engine dosn't sound like it is under any real load as a good portion of the fluid is bypassing the work.

As a quick test, see what happens when you run the lift cylinder to it's limit and hold it's control valve there(blocking flow through that valve), then try to cycle the split cylinder and see what happens.

 

[kennyd]

I would agree with Ron, he said it well.
Your valves must be in series, NOT parallel for them to function properly.
It sounds like you have plenty of engine and GPM to do the job.

 

[MMM]

Not sure of plumbing sequence, but if it's splitting wood, you either have it plumbed correctly or flow divider is in wrong place ahead of both valves limiting flow to splitter cyl. You need to divide flow after splitter cyl valve.
Run splitter cyl valve with power beyond sleeve, plumbed to flow divider(excess to tank), plumbed to lift cyl valve.
If splitter is correctly plumbed. you can try a thinner oil (what ISO# is regular hyd oil?), or even ATF if mfg allows for it..

 

[Soundguy]

Ron.. I've got a question.. if he had the valves in parallel, and one was open.. ( open flow to tank ).to tank and the other was powering the splitter cyl.. as soon as the cyl loaded up.. wouldn't ALL the oil divert to the least resistance.. and simply flow to the tank via the other valve.. and not splitting the wood at all?

Soundguy

 

[Deerlope]

Is there any chance that we could see a pic of the setup?

 

[MadReferee]

</font><font color="blue" class="small">( Ron.. I've got a question.. if he had the valves in parallel, and one was open.. ( open flow to tank ).to tank and the other was powering the splitter cyl.. as soon as the cyl loaded up.. wouldn't ALL the oil divert to the least resistance.. and simply flow to the tank via the other valve.. and not splitting the wood at all?)</font>

I'll take a stab at this one. I just had a similar situation with my dozer and I can tell you the fluid will take the path of least resistance. On my dozer one of the springs on the spool relief broke. This caused the valve to go into relief as soon as a spool lever was actuated. The majority of fluid went back to tank via the relief but some small amount was available to the work port to sloooowwwly raise the loader.

The same will happen with the parallel setup. The fluid should take the path of least resistance, but depending on the flow some may be available to the other valve which will cause slow operation.

 

[jimmysisson]

Thanks to all. I am trying to attach a pic with labels that you can actually read. Pressure goes from pump to proportioning valve set 90% ram, 10% lift. (Ram was no faster before I added the proportioning valve.) From prop. valve 1 line to ram valve, 1 to lift valve. Return lines come from both valves to a tee then to the filter and tank. 3/4" lines to valves from prop. valve. 1/2" lines to cylinders.
I don't know if this has anything to do with it, but every once in a while (rare) the ram cylinder chatters a little while stroking and runs a little slower. Also, so that the engine can start without load, and for maintenance, I have a shutoff valve between the tank and the intake line to the pump.
Thanks again for any ideas, this is buggin me. Jim

 

[MMM]

You're ok, but not optimal with that setup due to fact
the splitter cylinder has to run slower than before with 10% less flow. As I stated earlier, there should be full flow to splitter cyl, out via PB sleeve, then to flow divider.
If a valve with adjustable spool travel for lift cyl is installed, you could even remove the flow divider, which heat up oil. I know as I use 2 adjustable pressure compensated dividers for remotes on my tractor