Backhoe Hydraulics for Backhoe

[KJM]

AARRGGHH!! My comiserations, that's a serious bit of damage.

I'm just trying to get my head around what you did - since the loader valve (was) working, it was able to deal with the pressure, flow etc. Since it split, this must mean the fluid had nowhere to go. Which sounds like you connected the output (neutral, PB) from the BH to the output (neutral, PB) of the loader valve? If I understood you, it sounded like you might have ended up with this config.

Apropos the flow rates - and bearing in mind that I'm not a hydraulics guru - two things spring to mind. The first is that the 26gpm will be "flat out". So you could perhaps throttle back a bit. The second is that you could engineer a flow loss in the system by using higher friction plumbing. Hose has considerably higher frictional loss than smoothwall steel. I'm not suggesting downsizing the diameter (necessarily), just the material change.

You might be able to phone your local University's Mechanical Engineering department and ask them about this too. Mechs are strange people, but they like problems like this.

/Kevin

 

[jgbanshee]

The configuration is:

Pump>Loader Valve In>Loader Valve Out> BH In>BH Out>Tank

I was under the impression that my loader valve was relieving at 2500psi while the BH valve was relieving at 2450psi. Making my setup okay. I NOW think my loader valve was lower than the BH. My biggest problem now is that I cannot find a valve with PB, flow of at least 26GPM, and pressures of 3000psi that will even come close to fitting my machine. I would like to get in contact with HUSCO the original valve maker, but I have to go through my Ford dealer and they dont want to help me. I call and they either dont know anything or dont return my phone calls when I ask for particular information.

 

[FULLPULL]

I wonder if you still had the return from the loader valve to the tank ?Our old 730 loader kept it's return line in addition to the return from the backhoe as stated in earlier post.And if your ford NH dealer wont help you i would try another dealer till you find a good one.

 

[KJM]

The configuration is:

Pump>Loader Valve In>Loader Valve Out> BH In>BH Out>Tank

I was under the impression that my loader valve was relieving at 2500psi while the BH valve was relieving at 2450psi. Making my setup okay. I NOW think my loader valve was lower than the BH. My biggest problem now is that I cannot find a valve with PB, flow of at least 26GPM, and pressures of 3000psi that will even come close to fitting my machine. I would like to get in contact with HUSCO the original valve maker, but I have to go through my Ford dealer and they dont want to help me. I call and they either dont know anything or dont return my phone calls when I ask for particular information.

Again, I'm not a hydraulics guru, but the flow rate difference would have been the issue, I'd bet. The outflow from the loader needs to go somewhere, and the BH passes 12GPM less. That sounds a large difference to me, with the resultant hydraulic fracture. Hmmm.

I'm not convinced you actuallly need PB. PB comes into play when you need simultaneous operation of both valves. Is there one without PB that fits? My tiny B7100 has the pump->FEL->3PL. No PB, it works just fine (except if you try to mess with both at the same time). I'd guess you can do a similar trick but with some kind of flow splitter after the FEL (as was mentioned by MadReferee earlier). Even if you have PB, you probably still need this because if you're not messing with the levers, the full flow will go out the PB outlet (minus overpressure flow) and thence to the BH. I wouldn't think replying on the overpressure flows to nicely split off 12GPM to give you a safe 14GPM via the PB connection.

I'm just putting in a BRAND joystick 2 spool valve on the B7100. It is significantly smaller than the existing valve. BUT - now that I have the "plumbing" adaptors screwed in, it is a "tight" fit. If you can find the original, I'd go for it. Re-jigging the hoses/pipes is painful!

Gee, life in the big tractor world is a lot tougher than with the Tonka-Toy sized ones. I have 3.1GPM and my BH needs a PTO pump!

Best of luck
/Kevin

 

[R W]

Had a similar problem with a D46u, when using a diverter valve to operate a scoop, the hydraulic hoses were too small resulting in restricted flow (D4 had a high flow rate), fortunatly the only damage was a blown oring, the solution was to fit larger hoses.