Tapping off Hydraulic line for thumb

[AKKAMAAN]

This is true of all the valves on most hoe attachments: the only way
to use more than one valve simultaneously is by feathering the control
levers. But usually only one valve is working at a time. This is a
limitation of a one-pump system, surely, but you don't generally see
flow dividers here.

A separate monoblock valve before the stack valves will not cause any
problems....it would be just like any other valve in the stack.

The main reason for difficulty to operate open center, constant flow systems, is that the control valve varies the output pump pressure, while in a constant pressure, closed center system, the control valve varies the output pump flow.....

 

[dfkrug]

The main reason for difficulty to operate open center, constant flow systems, is that the control valve varies the output pump pressure, while in a constant pressure, closed center system, the control valve varies the output pump flow.....

OK, but in the compact tractor world, we essentially have single-pump
open center systems. Crude, perhaps, but effective.

 

[AKKAMAAN]

OK, but in the compact tractor world, we essentially have single-pump
open center systems. Crude, perhaps, but effective.

Cost effective maybe, on "hobby" applications or applications with low utilization
For sure a very "inexpensive" solution, but inefficient in competitive operation and fuel economy....
hydraulics will undergo big time challenges in the future... electric actuation-drives are already "knocking on the door....and "as fuel prizes increases, demand on more efficient hydraulic systems increases too.....here is on example on whats going on....instead of to throttle using control valves, the future is, directly pump controlled actuators, bi directional variable pumps in closed loop with the cylinder....tests has been going on for a while now...
here is an example

 

[racerboy832]

Just talked the Kelly Backhoe people. My Hoe is the B30F which is now their 851 Model. They offer a Kit for the PB for $90. Anyone out there have one already. I don't mind the $90 I just hope it isn't a couple fittings and some instructions.

 

[J_J]

It would be interesting to see what they call a kit. It is probably only a sleeve for the PB port. If it is a stack valve, they may just send out a new the end plate, with PB outlet, and sleeve. Maybe something like this.

Stack valve with different end plate. This one has PB.

.https://www.surpluscenter.com/item.asp?item=9SV-2-Y&catname=hydraulic

This is a PB sleeve. It doesn't cost $90

https://www.surpluscenter.com/item.asp?catname=hydraulic&item=9-4895-B

 

[racerboy832]

I'm assuming that I'll still have to get the lever to operate the thumb. I'll try to get some pics of what I have. I was hoping that someone on here would already have one and could chime in on what it includes.

 

[J_J]

Did you ask the dealer for a PB kit, or a new spool to operate the thumb. With a stacked valved, you can add valves, and longer bolts, to do what you want. Price would be the spool section and longer bolts. Probably would not need the PB. If you can not add to your current valve, then you need an additional valve, and since your dealer said a PB kit was available, the contents of the kit needs to be known, and where to place the new valve for the thumb.

 

[racerboy832]

I called the manufacture (Kelly) Direct. I saw on a ad that the PB kit is available so figured it was worth a phone call. They are gunna send me a copy of the Manual. I asked him to Fax me the part about the PB so I could get it ordered if I wanted it. He said he was going out and could do it in the Am. Nice guy but he didn't know much about the PB kit. I don't mind the $90 if it is a clean setup. This backhoe is on a older Deutz Allis 5220. When I mention it to most people they have no idea what it is.

 

[J_J]

Can you take some close up pictures of the valve, especially the outlet side?

 

[dfkrug]

Cost effective maybe, on "hobby" applications or applications with low utilization...

Interesting article. Our simple hyd systems make sense on compact
tractors, but you start to explore their limits with backhoe attachments.
To quote from the CCEFP article:
æ’¤ump-controlled technology is
best for machines that have multiple
actuators that work simultaneously,
like excavators, telehandlers, timber
harvesters, wheel loaders and so on,
Williamson explained. é„*ny cylinder
could be pump controlled, but there is
little advantage over traditional systems
for actuators that work infrequently
or a single actuator by itself "

I had a long discussion with a Kubota engineer about their move to dual
HST drives for their latest mini-excavators. Electrically-controlled mult-
pump systems make a lot of sense here.

Since our simple one-pump systems are a feature of our compact
tractors (rather than a bug), we make use of several work-arounds.

One is to put restrictors in the swing circuit. Some hoes have this, mainly
to slow down the swing. But it also helps the operator use another
valve simultaneously.

Parallel switchable work circuits, like I did for my thumb, also make sense.

Operating 2 valves at once also gives you a type of "load sensing". e.g.
if you set a hoe bkt on the ground and simultaneously operate BoomUP and
DipperIn, you can rake the ground with the bkt teeth, following the ground
contour. With the thumb, you can grapple objects better than with
independent operation.