Hydraulics 101 for my Mini Backhoe Build

[NormL]

I recently resumed work on the Mini Backhoe I began building nearly ten years ago. To quote what has been said on these pages a number of times, "Life got in the way" and I had to set it aside for a while. Now that I have the time, I'm back at it and the hydraulic aspect of it is what's on the agenda. My knowledge of the rules and precautions related to getting this right without risk to life and limb is elementary at best so I'm here for the wise counsel I'm confident is available on this forum.

I have drawn up a crude diagram of two sets of spool valves, one is a BM40 - four spool and the other a BM30 - three spool. The BM40 will be the first after the pump followed by the BM30 via power beyond. I'll try attaching the diagram and my apologies in advance for the poor quality of the drawing and photography!! Please advise if I am making mistakes.

 

[NormL]

I'm sorry folks, that picture did not work. I'm going to have to work on getting a better one.

Try clicking on the one on the right.

 

[NormL]

View attachment backhoe hydraulics.jpg Hmm.... still trying to figure out how to navigate the recent upgrade of TBN.

I'll try my best to explain the drawing: The hydraulic fluid is sent from the pump to P1of the BM40 and P2 has a plug. From there the A and B ports are plumbed to the indicated cylinders. At T1 the fluid return is plumbed to the T1 port of the BM30. T2 has a Power Beyond adaptor installed and is plumbed to P1 of the BM30. T2 of the BM30 is plumbed as the tank return and in "theory" will also carry The return fluid of the BM40.

If anyone sees issues here, please advise because as I said earlier, I'm not well educated where hydraulic protocols are concerned. I am preparing to acquire the hoses for the various hookups so I need to know if I'm getting it right.

 

[ptsg]

I was checking some info on that valve to get a little bit familiar with it. I have similar valves on my homemade backhoe.

So I think you have it figured out. You're kinda saving some hoses and a T fitting by using both T ports of the BM30 as a T fitting.

 

[NormL]

I was checking some info on that valve to get a little bit familiar with it. I have similar valves on my homemade backhoe.

So I think you have it figured out. You're kinda saving some hoses and a T fitting by using both T ports of the BM30 as a T fitting.

Thanks ptsg, I was hoping I could get this right. The BM30 and BM 40 are manufactured in Italy so they could be more common in your market than here. I'm a S&PC (scrounger and proud cheapskate) so saving on hoses and fittings works for me!!

 

[ptsg]

We're on the same boat regarding the saving everywhere we can. Hydraulics can get expensive really fast.

My Badestnost valves look just like yours pretty much.

 

[Rich B1]

I would simply use a T at your 3 spool valve, with sufficient size hose to reduce back pressure. If I am reading your schematic correctly, you are using the valve as a T. IMO, that will create some back pressure on your primary valve (4 spool).

 

[NormL]

I would simply use a T at your 3 spool valve, with sufficient size hose to reduce back pressure. If I am reading your schematic correctly, you are using the valve as a T. IMO, that will create some back pressure on your primary valve (4 spool).

I wondered about that too but I'll try it first and if that is a problem I can make that change without much hassle because that area is easily accessible. Thanks for the heads-up.

 

[dfkrug]

Do you have written plans for the machine? I see you have a spool for a blade. Will the unit stand alone and be self-propelled?

Since you ask about the hydraulic valves, I do not see any particular issues, but you may consider a flow divider if you are set on using 2 different valve banks that are on the same pump circuit. Usually a single valve stack is used, with as many as 8 spools. A flow divider will make it easier to operate 2 valves at once.

 

[Rich B1]

He has the secondary functions on the 2nd valve (3 spool), primary functions on his primary 4 spool valve. A flow divider would just rob from his primary functions.