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Adding auxiliary hydraulics to my skidder, have ???

Started by barbender, September 18, 2019, 11:54:31 AM

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barbender

 I have a Pettibone 501 skidder, and going from the manual, I understand it has a dual circuit (for the steering and blade) hydraulic pump. Now since poor Mr. Skidder sits in the yard most of the time ("lawn ornament" my wife calls it😁) I had a crazy idea about putting auxiliary hook ups on it and running a monster log splitter with it. So my question is, is it possible to combine the flow of both circuits, or would I have to use just one?
Too many irons in the fire

kiko

Combining the two circuits after the priority of flow divider would be the only way to direct full pump flow to the splitter. I am assuming the two circuit system on your skidder has one common pump?

Riwaka

The off road race cars use 2 postion hand operated valves to change the circuit to switch between steering and onboard jack system

For the skidder chain up the blade and get the flow from a blade lift  ram (stucchi quick couplers etc) ? Tie back the blade valve handle to make the flow continuous. (to a log splitter valve ) if the rams double acting on dozer blade - return there etc

I would be more inclined to mount a drive shaft off the camshaft pulley to drive a separate hydraulic pump (usually zip tie a spare fan belt in place between bolting up the driveshaft. Mount an oil tank on the bonnet, hydraulic lines back to a valve near your seat etc.) The radiator might be in the way, the blade to close etc.

After doing all that - probably better to get a trailer with a powerpack hydraulic operated wood splitter and get the skidder to pull the trailer into the woods.

tractor front pto unit
AXION 800 Front PTO / 2014 - YouTube

barbender

Kiko, I haven't dug into this very far, but what I understood from the parts and operation manual is that it is a single pump, with 2 seperate sides- so it basically acts like 2 seperate pumps. I assume this is so you can run the blade and steering (the only hydraulic functions on it) at the same time, without robbing flow from the other function. I'll have to have a good look at the pump.

Riwaka, I'm not sure if the existing pump is coupled to the cam already, I'll have to get a better look. I'm sure I could drive another pump with the fan belt as well. I'm just trying to give this machine another use around the place, not to mention it would also be handy to have hydraulic remotes to operate the lift cylinders on farm implements as well. 
Too many irons in the fire

luap

I think what you want falls into pick any two features out of three category. Temporarily connect lines from either your blade lift or steering cylinder to the size cylinder you would use and test the speed of the ram and tee in a pressure gauge to see if it is even a feasible concept. As far as combining two different pump out puts into one would seem like it would work for increasing flow but what happens under pressure resistance might be something else. I have seen water systems with more than one pump combined but never hydraulic. The suggestions about adjustable flow dividers and possibly a circuit diverter valve are the practical choices.

Haleiwa

There's a reason for two pump chambers; probably because the requirements for each system are different.  If you combine them and the pump pressures are different, the stronger one will backfeed into the weaker one.  My guess is that the side that powers the blade is plenty adequate for your splitter.  You could put a tee into the line, and terminate it in a pioneer style coupler at a convenient location, then run the return line to the tank.  That assumes the pressure is less than the coupler can hold.  When it's all said and done, I think you will find it was more of an academic exercise than a practical use of the machine.  
Socialism is people pretending to work while the government pretends to pay them.  Mike Huckabee

Puffergas

If your skidder has a manual truck transmission it might be possible to install a PTO on the side of the transmission and run a pump with that.
Jeff
Somewhere 20 miles south of Lake Erie.

GEHL 5624 skid steer, Trojan 114, Timberjack 225D, D&L SB1020 mill, Steiger Bearcat II

mike_belben

Pumps only make flow.  Relief cartridges dictate the maximum pressure in a circuit when a load is applied by introducing a self resetting controlled leak to prevent further pressure rise.  Relief cartridges are usually inside a spool valve body.  

If you take the two pump outlets and combine them at a T fitting into your own valve, you will have full pump flow and whatever pressure your splitter valve relief is set at.  This means getting the pump flow upstream of the skidder valves, not after.  

Itll probably be a fast splitter if you take whole pump flow off a full size engine.   Going off a blade cylinder port or something like that will work but youre limited to whatever flow and pressure is available downstream of the skidders control valve.  If its 1500psi at 4gpm thats all yer gettin.  

Specs and how cramped stuff is would help make the decision for me. And how often am i gonna unhook every hose and pour out how much oil to switch back to skidder mode.  If it was often id mechanically couple a splitter pump with its own dedicated two speed valve.  Hell id build the splitter ontop the blade. 
Praise The Lord

luap

The steam turbine in our power plant had hydraulic controls provided by two identical pumps of only one, which was used at a time. When they switched pumps we would have to adjust the relief pressure to maintain system operating pressure though the load didn't change. My point being identical pumps were not equal. In your skidder application with outflow combined,  one of your two different pumps is going to open the relief valve before the other one will. What happens during the pressure differential, I could only guess. I would consider using a valve with power beyond and have that first in the circuit with skidder valve second via power beyond. I think the fuel efficiency will be disappointing for the work accomplished having seen large farm tractors used in the same scenario having to run at high rpm to get enough speed on the ram. Even with combined flow the size of hydraulic lines may be a limiting factor. If you enjoy the tinkering you can get it to work but depending on what you have to spend, it will have diminishing return.

mike_belben

If both sections go to one valve with on relief you wont have that issue.  If theres multiple reliefs in the circuit then yes youll be limited to the lowest valve pressure.  

Be very careful stacking differential poppet valves in series.. You cant use both handles at same time or stuff explodes.  A differential poppet doesnt pop at 2000psi absolute.. It cracks at 2000psi DIFFERENCE across it.  If youve already got 3000 in the circuit a differential poppet set at 2000 will then fail to open until theres  and extra 2000 above that.  5000 psi ..  Youll be lucky if it stalls the engine before you get perforated. 
Praise The Lord

kiko

Running two pumps in parallel to increarse flow is commoning done.  Each pump must have it own relief , the two flows would be combined after the reliefs. The super t bell saws required pulling two levers to generate the flow for saw motor.  Barko also used this method for saw buck flow.  I have used this for mulcher conversations where a piston pump and a gear pump of different flow rates were used in parallel.  I agree that all pumps are different.  In the steam turbine with identical pumps the necessity to reset the line relief was because of the flow rate differential of the two pumps.  Back to Barbender , does your petibone have a Jimmy? If so there is likely an open accessory drive on the rear of the engine for a dedicated  aux sytem instead of the belt drive.

barbender

Too many irons in the fire

mike_belben

Why would the pumps each need their own relief? If they tee together then go to a relief sized big enough for both pumps output wouldnt that protect both?  Just curious.. Never seen it in practice either way that i can recall. 
Praise The Lord

kiko

Mike,I am certainly not a hydraulic engineer ,  and my knowledge is only self taught from practical experience.  So , when trying  to increase flow rate by combining two pump flows at the same head, all restrictions need to be addressed, with larger hoses after the T. So two reliefs might not be technically necessary, but trying to run two pump flows through one spool valve section would reduce much of the flow capacity.  Unless a large enough single spool valve was sourced . Using what is already available, spool valves already flow rated for the specific pump capacity, make things easier and cheaper. So maybe instead of must having a relief for each pump , it will have a relief for each pump.

snowstorm

why not use a combiner valve? the 546 valmets used them

luap

This has been a very informative discussion. Back to Barbender- what is a monster splitter? Huge ram? Fast cycle Time? Multi wedge?. Other accessories?  Hydraulic functions are amazing for example when you compare a simple  splitter to a mini excavator and think about all the functions it can do at one time and the size of the pump they have.

mike_belben

Gotcha @kiko.  Same here, just self taught greasemonkey.  I am a cheapskate and usually work with what i got too.  im confident it could be safely built either way we have described. 
Praise The Lord

kiko

Just to clarify on my last post, with a relief for each pump there would also be two separate control valves each with a main relief . 

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