Hi Guys Its been a while since I was on here. I have been playing around with my B50 yanmar excavator hydraulics trying to figure out where I could tie in a pressure and return line for some aux hydraulics. I tapped into the biggest pressure line that comes off the hyd pump ( there are 2 the same size -), and put a pressure gauge on there to see what it was. To my surprise there was only any pressure when I cycling one the excavator main functions ( boomup/down, bucket curl, etc). The pressure is low until the cylinder meets resistance and then pressure climbs. Like when I put the boom down and pick up the machine, the pressure spikes to about 1000psi during the lifting) Not what I was expecting n- I was expecting some baseline stable working pressure . Must be a compensated pump. Does anyone know how these systems work. I can seem to find and feedback wires or pressure lines that come from the valve body back to the pump that could send control signals. I am kind of stumped. I'm sure someone out there knows how it works - hope they can enlighten me. Thanks John
Kinda depends on the age of the machine? Not sure how they work, looks like on the older units the two main sections are a pair of piston blocks with a common swash plate controlled by an internal regulator. The rear section is a gear pump, so that's just a typical open center valve setup, oil flows through to tank until you activate a function and then pressure will rise until the load moves or the relief valve opens. I would guess you could splice in a valve as long as it was set up for power beyond to supply oil downstream to the stack valve, but when you actuate the aux valve you would lose all the functions downstream because the oil would be diverted to the aux function. What are you trying to run off this machine?
I had a B50 years ago and there was a provision already on the valve bank for auxiliary hydraulics. We plumed it to the stick and ordered the linkage for the pedal on the floor to activate it, we set it up for a thumb.
Thanks for the input guys I have been thinking about more since the last post and I think I agree Lantraxco. It behaves exactly the way he is describing. I am trying to run a wood processor and I am not sure I can do it with this configuration. I did find the extra slot in the valve bank with a linkage spool operator that Tags mentioned and is not being used. I am pretty sure I can hook into that and runs lines off to the attachment. I just need to figure out the linkage to make it move. this project might even be easier than I thought it was going to be. Tags - do you remember where you got the kit for the linkage Thanks again John