hydraulic design review

[bdw9862]

Unless you are running a closed-center hydraulic system, you will need special valves to allow more than the one that is furthest upstream to get any of the flow.

So power beyond won't work for two of the outriggers?

 

[bdw9862]

Dave a question, it appears from what you sent that 1/2 line works for everything except the source from tank to pump and that should be 1/4?

 

[bdw9862]

Dave a question, it appears from what you sent that 1/2 line works for everything except the source from tank to pump and that should be 1/4?

I ment 1 1/4

 

[bdw9862]

A few pics

 

[BHD]

unless you already have the valves, why not use stacked valves, when I built mine I used the stacked valves, and put joy sticks on the 4 center units for the swing, boom, bucket, and curl, and the two outside for the outriggers, I made mine with a undercarriage and bolts up to the tractor,

I bought mine through surplus center, (I started out with the idea of the self powered back hoe but redesigned it to mount on the tractor and use the tractors hydraulics, even tho I had a pump and engine), I know without the weight of the tractor I would have never been able to dig in some soils I have had to dig in,

my two cents,

 

[CincyFlyer]

So power beyond won't work for two of the outriggers?

Yes. When you operate an open-center valve, you cut off flow to anything beyond it, but only while that valve is actuated. Some valve blocks can "cheat" this a little, but valves in series cannot. Usually not a big deal.

 

[Dave M7040]

I ment 1 1/4

Yes that is the correct way to interpret the nomograph.

Are you welding with a MIG?

The power beyond limitations are as stated by Cincy......

Another option, which I have never tried but know about, is a flow divider.

This link gets a bit too technical but is a good place to start in understanding what one could do for you. It would be like having two pumps each feeding a spool valve bank.
Hydraulic two-path flow divider - MATLAB
Another link that may be more in line with your application.

A Study of Rotary-Type Flow Dividers | Womack Machine

Here is a reasonably priced valve from a Canadian company. You need to select a valve based upon how much oil you are putting into it so in your case 10 usgpm or higher.
Having a valve like this one which is rated at 16 usgpm would not be a problem for your application but with some searching you can likely find one made of 10 usgpm
16 GPM Divider/Combiner Flow Control Valve | Princess Auto
Why do you want to outriggers on their own valve bank? It seems wasteful and unnecessary.

Dave M7040

 

[leonz]

Good afternoon: I am building a towable backhoe (I will post some pics) and am getting to the point I need to begin the attachment of hydraulic cylinders as well as motor, tank etc.... Most of the fab and welding (other than cylinder mounts, valves mounts, etc) including frame, boom, pivot, outriggers, wheels and tires is done.

I have attached the hydraulic design for your review and thoughts. I have already ordered and received the 4 outrigger cylinders as I want to weld the rear outriggers prior to the installation on the frame (they run straight down). The front outriggers are already on the frame.

One thing that has me puzzled is the source and return line sizes for the tank. I am looking at a 15 gallon tank online and the openings are 2 inch 1 1/2 inch and 3/4 inch NPT. I am not sure what size line to use to run to the gear pump and also the return lines. I would like to use 2 wire JIC hose. I am also not sure where to get fittings to move from these size NPT to smaller JIC and SAE.


Any constructive help would be appreciated.

============================================================================

Your design and the flow chart needs a bit of work.

A very small vane pump will do what you want to do.

The suction side of "A" pump is always larger than the pressure side.

The oil tank needs a baffle to help cool the oil and eliminate air bubbles.

The suction hose for the pump inlet need to be at the bottom of the tank on the smaller section of the 2 compartment tank
to allow any air bubbles to surface and to allow the cooler oil to sink.

A very small pilot operated back of valves will let you do all you want and prevent premature valve spool failure from excess external pressure from a hand hold on to the valve spool handle.

The pilot operated valve spools(most of them) also have check valves to hold the position of the cylinder as well.

you need one valve for each outrigger 4

one boom swing valve if you are not going to use a double rodded differential cylinder with roller chain to move the boom left and right.

One boom cylinder valve to raise and lower the boom

One dipper arm cylinder to crowd(push) against the excavation to dig

one bucket cylinder to control the bucket.

a bank of 8 pilot operated valves with a vane pump from a hydraulic repair shop DONE THE RIGHT WAY will stop your problems before they start.


If you really want to save a lot of headaches and grief you need to look at car wash pit cleaners to see simple, numb, dumb, and stupid hydraulics that have worked for many years and that are still working today.

www.ring-o-matic/carwash-pitcleaning.html

It would be well worth your while to buy a manual and learn how simple it is to work.

 

[bdw9862]

Thanks to all for the input, the tank I am considering is on Surplus and has an internal baffle. I intend the place the tank about 3 1/2 inches higher than the pump and motor and will use the lowest connection on the tank for the suction line into the gear pump.

The stacked valve set for six of the 8 cylinders is the following on Surplus

6 SPOOL HYD VALVE W/JOYSTICKS PRINCE SV

Item Number: 9-7502

It appears to be put together (by Surplus) for small backhoes with hydraulic stabilizers. The other two valves will be accessed via power beyond and will be the rear outriggers. I don't expect to use them much once they are extended prior to starting to dig. There is a load check in each section of the valve noted above. The swing cylinder will be fully retracted when the hoe is moved 90 degrees to the right of center and fulled extended when 90 degrees to the left of center.

Thanks for all the input.

Sincerely.

Doug

 

[IceStationZebra]

How long do you intend to run without stopping? Without a dedicated cooler you will eventually overheat as a reservoir can only reject a small amount of heat by convection. May just want to just plan for one and not install it at first, then if you find you do need one it won't be a big deal to add it later.

"The suction hose for the pump inlet need to be at the bottom of the tank" - There are two schools of thought on this. Flush with the bottom is preferred if the oil is always clean and water free. Otherwise if the suction protrudes up from the reservoir bottom it allows debris and water to settle out and not go into the pump. The only issue with a protruding inlet is that for a given size pipe the flow restriction is higher than a flush mount so it needs to be ~30% bigger OD, then necked down to the appropriate size for the pump. (I also like to add a good magnet as cheap insurance, but they only work on ferrous metal)

Rotary flow dividers work, but they are big and I don't think you really need it. How often are you going to move the machine vs. the expense and complexity? Plus if you plumb in a flow divider how do you operate one outrigger individually? If you want productivity focus on the boom, stick and bucket circuits as that is where the majority of the time is spent. It is possible to multi-funciton open center valves, but it depends on the pressure needs being similar and the operator's ability to feather the spool positions.

I was thinking you could try to find a junked mini-excavator and reuse the valves, but they will be pilot controlled and metric thread. Doable, but will take some work.

ISZ