Backhoe Power Beyond for Backhoe

[jgbanshee]

OK, I bought a new hydraulic pump for my Ford 345C and also a new loader valve after breaking both in the process of adding a Bradco bh to this tractor. I replaced the pump and that is buttoned up. Now I am awaiting my new Cross 2-spool valve with power beyond to come in (I got TOP porting for IN/OUT). Since the original loader valve did not have a PB port, the valve split in two when I ran that loader and bh valves in series. Then I broke the hydraulic pump shaft when I hooked the backhoe valve only in the hydraulic circuit. I do not plan on trying anything else until the new valve comes in.

Couple questions.
1. Do I need to prime the gear pump at all before using it since it is new?

2. What should a hydraulic system diagram look like for a backhoe now that I will have PB on the loader valve?

 

[jgbanshee]

I took a picture of the backhoe valve. In the one picture the red circle is around a rusted six sided nut...maybe. It is on the SWING section for the valve bank. Is that a relief valve? It the only one that is rusted like that and I broke the loader valve exactly when I swung the boom to the right and now the pump broke when I swung the boom to the left. This could be coincidental but I have been thinking about that for a while now and today I took the covers off the backhoe and see this. The other picture is of the end section that I think the main relief of on.

 

[john_bud]

OK, I bought a new hydraulic pump for my Ford 345C and also a new loader valve after breaking both in the process of adding a Bradco bh to this tractor. I replaced the pump and that is buttoned up. Now I am awaiting my new Cross 2-spool valve with power beyond to come in (I got TOP porting for IN/OUT). Since the original loader valve did not have a PB port, the valve split in two when I ran that loader and bh valves in series. Then I broke the hydraulic pump shaft when I hooked the backhoe valve only in the hydraulic circuit. I do not plan on trying anything else until the new valve comes in.

Couple questions.
1. Do I need to prime the gear pump at all before using it since it is new?

2. What should a hydraulic system diagram look like for a backhoe now that I will have PB on the loader valve?

Every time I read your story I cringe. You have my luck with backhoes! (and that's not a good thing)

1) No you don't need to prime, the tank will gravity drain to the pump.

2) I can't draw, but imagine this

The output from the pump is going to the loader valve "in" port
The "out" port from the loader valve goes to a filter then to the reservoir.

The PB port from the loader valve goes to the hoe "in" port.
The "out" port from the hoe control Tee's to the "out" from the loader valve before the "in" to the filter. Some filters have two inlets to allow this to happen easily. The "out" from the filter goes to the reservour. Circuit complete.

(if you don't have a filter be sure to get one.)


With this setup, you have 2 pressure relief valves. One in the loader control and one in the hoe control. Either can dump fluid back to the reservoir. The loader relief is usually set 50 psi higher than the hoe relief. That takes into account the pressure drop from the loader to the hoe, so they are in reality at the same effective pressure.

jb

 

[john_bud]

jg,

On the second picture - take off the cover (2 bolts) and you may see the relief. It should be right around there.


On the rusted cap. I don't think so, but....(?)

Have you called bradco to get a schematic of the hydraulics for the hoe? They may be able to help.

 

[john_bud]

Ok, this may help. Found on the baumhydraulics.com web page.

 

[jgbanshee]

If my bh relief does not work will the loader valve relief work instead for now? Can my loader relief be set at say 3000psi and the backhoe at 2500psi, is there anything wrong with that?

 

[john_bud]

If my bh relief does not work will the loader valve relief work instead for now? Can my loader relief be set at say 3000psi and the backhoe at 2500psi, is there anything wrong with that?

Well, yes. Imagine a pipe with a "T" half way down. You put a relief at the T and one at the end of the pipe. When ever the relief with the lowest setting hits that pressure it starts to open.

You could set one to 3000 and the other to 2500, but it would be MUCH better to set the loader to 2550 and the hoe to 2500 (or what ever the specs call for). A 500 psi difference means that the high set one will NEVER open as the lower one will open first and bleed off system pressure.


You do have a pressure gage, right? It is not smart to guess at hydraulic pressures! That is a short cut back to the parts counter.

If you are even a little bit nervous about the hoe's relief valve, take it out and replace it. It will be in the $35-100 range. Not that big of a hit compared to a new pump ...

 

[jgbanshee]

Ok so my backhoe has a working pressure of 2400 PSI and my loader I am not sure. My new loader valve has an adjustable relief so I should set it to 2450 or 2500 PSI. Will this hurt my loader at all if the system before the backhoe addition was say 2000 PSI?

 

[Dirthog]

I believe that is a load check as you will see all the sections have them the relief valve will have a different style of cap with a screw of some type to adjust the pressure look on the section where the flow comes into the valve most likely just oppeset the line

 

[john_bud]

Ok so my backhoe has a working pressure of 2400 PSI and my loader I am not sure. My new loader valve has an adjustable relief so I should set it to 2450 or 2500 PSI. Will this hurt my loader at all if the system before the backhoe addition was say 2000 PSI?

LOL! You do like living on the edge, don't you? It's so much cheaper to set the relief valves to a low pressure, make sure it's all ok, then go higher. Maybe you could consider doing that?

To your question:
No, your backhoe has a MAXIMUM working pressure of 2400 psi. Find the lower spec pressure and use that for both. The hoe will operate fine at 2000 psi, just a bit less powerfully.

If you were at a tractor spec pressure of 2000 psi and you raise to 2500 psi what will happen? Well, it won't explode in a pyrotechnic fireball of sudden death and destruction, but it may make any leaking cylinders leak faster (internal bypass leaks). Faster flow erodes the seals exponentially quicker. Price out new seal kits for the 4 loader cylinders, it's probably around $50 per cylinder if you do it yourself. Won't have to do it right away, but sooner than you would have otherwise.