Running a brush cutter off my thumb circuit.Cutter only requires about 2/3 the flow available and I have the cutter rigged up with a flow control valve that diverts excess flow back to tank. (Both the return flow and the excess flow go into the 1 inch dia return line that runs to end of stick for rock hammer return flow ) This all works ok but other functions are very weak as long as cutter is activated .Cutter stays at flow controlled rpm unless I raise boom when I can hear it slow down,which isn't a problem. Seems to me it'd all work better if I wasn't dumping all that unneeded flow back into tank. I'm thinking if I had a pilot pressure regulator? in the thumb pilot circuit I could dial back the thumb pilot pressure and hence thumb circuit flow to where I want it. Does this sound right? Better ideas?
Good day Your machine may have some kind of flow control, if you have a hydraulic schematic may be able to help out.I am sure you have just the two pumps & circuits on the machine, any flow - pressure used for the cutter will result in less available for the standard attachments. One possible solution may be a side sadle gear wheel pump. Kind regards Uffex
You are exactly correct it you will have to have flow meter hooked up to it to make sure your flow and pressures are correct. Before putting the attachment on.
Measuring flow is easy I just put an rpm counter on the mower.And I have the circuit pressure set at the valve bank. I wonder if I can use a pilot valve off my parts machine, hooked up in series with the electric thumb control,and set to the flow I want. Thinking of maybe the travel control valve with a screw to adjust pressure.
Any time I've set up a machine with aux hydraulics its just been a set of PRV's in the pilot lines to the aux spool. All they do is reduce the pilot pressure so the aux spool only moves far enough to provide the flow required.
I can see why you do it that way but you cannot see how inefficient your hydraulic motor actually is or how worn your pump is
So on investigating it is possible that my thumb solenoid valve has pressure regulating capability .there are a couple of knurled knobs that I cannot explain except they might regulate flow or pressure. Photo attached . Not a great photo but the knobs are underneath the solonoids.
The knurled knobs seem to be for flow not pressure so I'm looking for a pressure reducing valve .Reached out to Wainbee but no reply yet..Have this one I might try and refurbish.
Relief valves normally should be on the machine's main control valve.
The photo is a little strange as to the use, I could not figure out what it is for. Kind regards Uffex
The knurled knobs in the photo are just the nuts that hold the coils on the solenoid valves I think.
Below those. At first glance they look like pressure test ports but when you really look at them they don't.
I screwed the knobs all the way in and pressure on test gauge stayed same so I'm guessing they're for flow. The recent valve pictured is on an old hiab crane in my boneyard that I think is a pressure reducing valve. Not actually sure in that.
You say the mower requires 2/3 the machine flow, that only leaves 1/3 to operate the machine so it will run slow with the mower running. You're running a 35 year old machine that was designed for digging, not for running an attachment that is constantly running. Back when these machines were new I used to do some work for the Asplundh tree service and they were running Hitachi EX150s with D&M Slashbuster heads, (same machine other than the engine). If I remember correctly, these heads required 35-40 gpm and after all the extra valving and plumbing they did it never really work all that well.
Ive been running it for several seasons as is and its quite adequate ,Im just hoping to improve it a bit. When Im brushing the way it is,the only time i really have an issue is when Im on a hill and go to swing uphill with mower engaged;it wont really do it unless i disengage cutter for a few seconds. Other than that travel is slow etc but when brushing you arent looking for speedy moves really.All that being said Id like to divert some juice if possible.
What's the gpm rating on the mower head? D&M plumbed all the machines for Asplundh and if I remember right they used a Stanley V60 diverter which tied both pumps together for the head. That valve is no longer available. Several years ago I plumbed a Link-belt for the same thing and used a Lynch brand valve, made in Ontario, Canada. Lynch seemed very good at sales but not so much at tech support, we made it work but not to what I was satisfied with. Kobelco machines seemed to work with the D&M head better than any other brand, they used Daewoo, Hitachi, Link-belt along with Kobelco.
This is a flail mower I created out of a new Holland 918 mower.I calculated the volume of oil available in the thumb circuit by timing the cylinder and doing the math. Bought a hydraulic motor from princess auto that roughly met the calculated spec.Turns out there's more volume than I need in the thumb circuit so as originally posted I'm currently sending around a third back to tank .I think I'm using about 20 GPM from memory.As far as whether it's taking it from both pumps I really don't know. I believe it is,the book goes into gobbledygook about flow combining that's over my head.i do know the machine will walk straight with mower engaged so there must be some flow combining going on there somewhere I d think.
You're wasting a lot of efficiency doing it that way.
Slashbuster will be producing heads again here within the next 30 days. If anybody has any questions, concerns or needs product support please reach out.