I have a hydraulic brush cutter that I use on the front of my telehandler. The spec for the cutter motor is 15-20gpm and my machine claims 20gpm. But when I go up a hill, the engine starts to labor and doesn't have enough power. My question is whether there is a way to reduce the demand of the brush cutter by some amount, say 5gpm, and see if it allows the engine to maintain speed uphill. For example if I were to add a flow restrictor so 5gpm less flow can go to the brush cutter, does that reduce the hydraulic load on the engine or does it keep the load the same and just send less flow to the brush cutter. I mostly mow pasture grass so I don't care about cutting heavy grass, I just want to be able to maintain speed going up hills.
Hydraulic bush hog and engine power
Richard
Super Member
- Joined
- Apr 6, 2000
- Messages
- 5,082
- Location
- Knoxville, TN
- Tractor
- International 1066 Full sized JCB Loader/Backhoe and a John Deere 430 to mow with
I don't know the answer to your question but, have a hydraulically powered rear 15' flexwing ('Terrain King' but is now made by Alamo)
Couldn't you simply turn power to blades off or, are you trying to work while driving up the hill?
Me not knowing how yours is setup, do you have a speed increaser on it? I've got a 4x speed increaser that takes my 540 to 2,160 RPM's and my hydraulic pump hangs off the increaser. I once almost stalled the engine then thought about it and presumed if it's a 4x increaser to make it work, then when blades get bogged down, that works 4x in reverse stressing the drivetrain/engine. I don't know that to be fact, just presuming.
Hope you figure it out.
Couldn't you simply turn power to blades off or, are you trying to work while driving up the hill?
Me not knowing how yours is setup, do you have a speed increaser on it? I've got a 4x speed increaser that takes my 540 to 2,160 RPM's and my hydraulic pump hangs off the increaser. I once almost stalled the engine then thought about it and presumed if it's a 4x increaser to make it work, then when blades get bogged down, that works 4x in reverse stressing the drivetrain/engine. I don't know that to be fact, just presuming.
Hope you figure it out.
I need to mow going up the "hill". This is Illinois, so hills here are different than in most places. It's really just the leftover natural contours of what used to be the natural drainages for the crop fields.
I don't have a speed increaser, this isn't a pump running off the PTO, it's running off the hydraulic pump for the machine which also powers the wheels. It's setup just like a skid steer where the front hydraulic attachment line runs the bush hog. I think the problem is they measure the 20gpm while stationary because they assume the kind of attachment being used on a telehandler will be things like an accumulator grapple for hay bundles, or hydraulic forks. With those kinds of attachments you're going to be moving slowly over relatively short distances, so all you care about is if you can operate the jaws or forks on the attachment.
oldnslo
Super Member
What type of pump is on your telehandler? If a gear pump you cannot reduce HP by using a flow control. Reason being a gear pump is fixed displacement so always produces full flow while in operation. Slowing input pump speed will reduce flow and HP requirements.
If variable volume piston pump with load sense control you can reduce flow and HP demand.
If variable volume piston pump with load sense control you can reduce flow and HP demand.
anomad
Gold Member
I have a hydraulic bush hog for my excavator. I use the momentary activation almost all of the time. So when I am tracking or doing other hydraulic functions I can let off the bush hog. It has plenty of momentum to keep mowing unless I'm chopping down trees. Holding down the momentary activation for long periods doesn't bother me. But it drives some people crazy. Do you have momentary activation capability?
It is a similar issue with mulchers on CTLs. It takes hydraulic flow for both and since you are asking for flow to both when moving then the flow gets reduced to both as the pump has a fixed flow to deliver. Unless there is a separate pump for travel and for high/low flow to the implement operators have issues.
It's variable displacement.
So does that mean if I reduce flow to the attachment, there will be additional HP available for the wheel motors?
I have momentary and continuous. I normally run the mower in continuous mode, but as soon as I let off the flow to hydraulic attachment the mower stops almost instantly. Maybe you have some kind of float position on yours that allows the fluid to continue circulating freely while the blades spin the motor?
I have run my mower on a Kubota CTL and it can go straight up a wall without anything slowing down. But that was a somewhat bigger machine than mine, I think it was 75hp. I have a 56hp Kubota Engine in my telehandler.
oldnslo
Super Member
How is flow directed or controlled going to the implement? Is there a solenoid operated or manual operated direction control? If yes is there a small pilot line going from the valve to a control on the pump?
anomad
Gold Member
Our combinations must be a little different. I can let off the flow to my bush hog and it just spins free to a stop. I can mow grass for a minute or two before it stops depending on the density of vegetation.
anomad
Gold Member
Maybe its something built into your bush hog? Mine spins free after you let off hydraulic pressure. Sorry I'm not much help.
Yes but totally different hydraulic setup. I have a ASV mulcher that is a complete animal but it is designed to do it and thus the hydraulic motors are spec'ed to do it. Talk to folks that have a head on a Cat 305/306 or earlier 308 excavator and they can't track move with the head running without losing power. Just not designed to do that job. A telehandler would have a similar issue. Great for what it is designed to do but running a mower head, not what it was spec'ed to do.
Will it do it, yes but................... You got to give up something.
I have a toggle switch on the joystick operated with my thumb that directs the hydraulic flow in either direction to the attachment. I also have a separate switch to lock that flow on continuously so I don't have to hold it with my finger. It's very similar to how a skid steer is setup.
Yes I think you're getting at the heart of the problem. Although I know a guy who has a hydraulic snowblower on the front of the same telehandler and it works great. I would have thought the hydraulic demand for a snowblower would be greater than a bush hog. I'd be very interested in trying mine on a lower flow bush hog, say 10gpm, and see if it would work with that. Like I said, I'm only mowing pasture grass so there really isn't much power required.
Do you have a case drain?
ptsg
Super Member
This being a telehandler, should have a closed circuit hydrostatic pump and motor for the travel that only shares the fluid with the rest of the system.
So the only affect that running the cutter should have in the machine is eating up the engine HP.
What machine is this exactly? Usually telehandlers aren't really setup for attachments requiring high flows and pressures.
Don't know what pressure the system runs but 20GPM at 3000PSI is already using about 41HP. So there isn't much left for the hydrostatic transmission that also sucks lots of power.
So the only affect that running the cutter should have in the machine is eating up the engine HP.
What machine is this exactly? Usually telehandlers aren't really setup for attachments requiring high flows and pressures.
Don't know what pressure the system runs but 20GPM at 3000PSI is already using about 41HP. So there isn't much left for the hydrostatic transmission that also sucks lots of power.
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oldnslo
Super Member
Can you vary the flow with the toggle or is it strictly on - off? Suspect on - off and if that is true then limiting flow to the cutter head will create heat. Reason for this is that I suspect you have a pressure compensated control which keeps the pump at full flow until pressure setting is met and then starts to de-stroke the pump while maintaining pressure. In this type of system it is harder to regulate flow to function since pressure is at max on one side of control and load dictates pressure on other side of the control. Pressure difference is burning HP and creating heat.
Do you have a hydraulic schematic for the telehandler?
anomad
Gold Member
No I do not.
That is exactly what happens, going up a hill the engine starts to labor and the ground speed goes down.
Gehl RS4-14. It's the same machine as a Manitou MT420 (Manitou owns Gehl)
I never looked at it like that, obvious there isn't enough power. It runs at 3400psi.
So I'm back to my original interest in finding a way to make the brush cutter draw less flow. If I put a flow restrictor in the line would that do it?
