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/c...-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.