Backhoe Need Max PSI Setting for LW-8 Backhoe Relief Valve

[3RRL]

Hello gang,
It's been a long time ...
Today, I finally added a pressure gauge to my LW-8 Backhoe. You may remember that I got one from a friend, then fixed it all up and made a custom sub-frame for it to fit my 55HP Kama.

This is the name of the thread about it: "Diamond Shape Sub-Frame for LW-8 Backhoe" with lots of photos.

http://www.tractorbynet.com/forums/customization/188249-diamond-shape-sub-frame-lw.html

Anyway, here is my question ...
Does anybody know what the max PSI I should set the pressure relief valve on the LW-8?
It has self contained hydraulic system with a PTO mounted pump.

After installing the gauge, I found out I was getting only about 1,700psi !!
Right now I've adjusted the pressure relief valve to 2,250psi (same as the tractor hydraulics). However, I thought I remembered reading that the LW-8 and other Jinma backhoes have a higher relief setting than that? Maybe I'm wrong, but it doesn't hurt to ask all you experts out there.

If you want to see some photos of the gauge mod, I can take some tomorrow and post them.
Thank you,
Rob-

 

[greg_g]

I don't have a technical figure for you Rob, but suggest you check the pressure rating that's marked on the hoses/cylinders/controller. It would seem logical to set the relief valve to at least 10% below the potentially weakest link.

//greg//

 

[RonMar]

Don't have specs for LW-8... FWIW, I believe my HW-03 is rated the same as my Jinma 284 tractor(looks like the same pump) at 16 MPa max, which converts to 2320 PSI... I think I set mine(loader and BH) around 2250 also...

Of course we want to see pics of your gauge mod... Your mods are always cool and very well done

 

[3RRL]

Hi Greg and Ron, thanks for the replies.
I guess I will stick with the 2250PSI I have it set to now. Just dug an 80' long trench and had plenty of power. Below are some photos showing the new gauge from front and back. I fastened it to the rear of the control housing with clamps and a shock absorbent hose liner. I cut the pressure line in to the valve and inserted a "T". All the fittings are re-usable hose fittings with JIC 1/2" for the pressure line, and 3/8" going to the gauge.

Thank you,
Rob-

 

[EE_Bota]

I set mine to 2350, so I think around 2300 is a good number.

 

[Bob Rooks]

Excellent work Rob.
My LW-6 was set at 2,250, as is my LiTW BH7600. And FWIW, My Mustang skid steer remote hydraulics are also 2,250.

Footnote: I'm running a Prince HC7-A PTO pump for the backhoe, and coincidentally, the dozer hydraulics are also set at 2,250 psig.

 

[J_J]

3RRL ,

Do you have a number or name on the pump .

I would think the pressure would be in the 2250 to 2500 psi range.

Is the pump like the Prince pumps or low profile PTO pump.

http://www.surpluscenter.com/images/p9-1047C.jpg



http://www.pegasus-industries.com/manuals/Backhoe.pdf

 

[3RRL]

Thanks guys,
Unfortunately, the riveted tag on the pump itself has been torn off so I was unable to identify the pump rating, which is why I posted the question. Anyway, the 2,250PSI setting seems to be comfortable for the hoe, so I will keep it there.
Thanks again,
Rob-

 

[psj12]

Didn't you originally have an Italian BH on that Mount?

 

[3RRL]

Didn't you originally have an Italian BH on that Mount?

Yes, but when I got this one, I moved the Nardi Backhoe over to Loretta's Jinma. Made a nice subframe similar to this one for that tractor.

 

[valley]

Rob, You always do the neatest things. Easy to smile reading your posts. Good to hear you!

Richard

 

[psj12]

How do you find the LW-8? I have a LW-7 and while it is serviceable the control valves are very jerky, especially the swing. This BH is several years old and things may have improved some. Also I modified mine to run off the tractor hydraulics.

When ordering a new narrow bucket for mine I found out that the LW series Backhoes are made by several factories in China and not all are the same. I ordered a bucket from Circle G and it did not fit and had to go back through Chip to have him order one from the original maker.

 

[3RRL]

The LW-8 works good ... lots of power and more reach than the smaller Nardi backhoe.
Although it lacks the refinements and rigidity of the Italian backhoe, it digs great. This one was purchased in 2007 by my friend Scott when he and I got together and bought his tractor and Loretta's tractor, plus a whole container full of implements for each of us. He sold his tractor and I ended up buying this backhoe from him along with a bunch of implements. So it is probably older or as old as your LW-7 maybe?

If you click on that link in my very first post in this thread, you can read more about the LW-8 and the Diamond shaped sub-frame I made for it to fit the 554 Kama.

 

[Bob Rooks]

I have a LW-7 and while it is serviceable the control valves are very jerky, especially the swing.

The hydraulics can be tamed just by adding restrictors in the circuit you want to control with no sacrifice to power.