Hi, I am new to the forum, but I have an auxiliary hydraulics problem very similar to the one described in this thread: HeavyEquipmentForums I run a Terex PT70 with a brush cutter attachment on high flow. When I turn on the hydraulics, the motor on the cutter has a loud whine. As soon as I boom up or down, the whine stops and then starts back a few seconds later. Some history: I bought this cutter new, motor has 25 gpm max flow, I run the PT70 around 2200-2300 rpm on high flow so I am estimating 26-29 gpm (the salesman assured me that he checked with his team and this motor could handle a few extra gpm), the original hydraulic motor began to continuously whine and locked up with about 40 hours on it and the salesman sent me a new motor under warranty, this new motor has about 250-275 hours on it and has developed the same whine as before although it is intermittent. The whine starts when I turn the hydros on but stops when I touch the boom joy stick. Also, as of yesterday, when the hydros are turned in one direction and the joy stick is engaged, the cutter will free spin to a stop with the hydro lever still "on". This problem is very similar to the thread I posted above but I never saw a resolution. I am new to the skid steer mulching business (6 months) so any help would be greatly appreciated.
What cutter / mulcher are you using? Does the PT70 operate other hydraulic attachment OK? If the PT70 aux hydraulics seem OK I would take the QD off of the case drain line from the mulcher/ mower and have some one else hold the open end in a 5 gallon bucket. Run the attachment and see how much case drain oil you get in a measured amount of time. This should establish your case flow. It should be no more than 1 gallon in 1 min as a rule of thumb. After you run the test and get some more info as to what the attachment is we can go further into the whys and how to fix. Pictues are very helpful.
I am using a SkidPro open front industrial brush mower. It has a char-Lynn hydraulic motor (part # 104-4053-006). The mower does not have a case drain line (2 lines only). The hydraulic motor has some type of "crossover relief valve" (not sure exactly what it's called) or something similar. The only other attachment I have is a grapple bucket but I can't try it out right now. It almost seems like when all power/flow is going to the attachment, that relief "valve" is triggered and whining occurs. Then when hydraulic power/flow is needed to for the boom cylinders, the extra pressure/flow is taken off of the relief valve so it closes and the cutter operates with no whining.
The PT70 parts diagram shows a relief on one side only of the Auxilary valve section. Does your mower run in both directions? If so does it act the same in both directions? If it does not run in both directions try removing the QD from the hoses and swaping which line they go on. Do you idle the engine down and let the blade get to idle speed before you cut the hydraulics off?
When you turn thr mower hydrraulics off the blade continues to spin. This turns the motor into a pump. The still spinning motor trys to pressurerize one side and cavitate (create a vacuum) the other side. The cross port relief relives the pressurized side and the excess (relived oil) is fed to the low pressure side of the motor to prevent cavitation. View attachment Eaton Circuit maker.pdf View attachment Eaton Circuit maker.pdf See page K3 for schematic.
Yes, the mower does run in both directions. It was acting the same in both directions up until the a few days ago. Now one direction acts as I described above. The other direction, whines when I initially turn the hydros on. After engaging the boom joy stick, the cutter will free spin to a stop even with the auxiliary toggle switch still in the on position. It's like the flow is cut off by the joystick in one direction. I typically do not idle the engine down before turning the hydros off. Should I idle down prior to turning them off?
Don't know about your other issues with the hydraulics, but if the motor part number you posted is correct, you're going to keep grenading them. That part number crosses to a model code for an Eaton/ Charlynn 2000 series motor of 80cc displacement. The ABSOLUTE max flow for that motor is 20 GPM, and as a wise old Charlynn factory rep once admitted to me, both ends of the rating chart for these geroler motors is a bit "optimistic". I'm thinking you have some debris from motor one or motor two in the valves: relief poppets, check valves, etc. to start with that would explain the spin down, but it sounds like some other issues with the machine hydraulic system as well. Probably going to have to have the main valve unit removed, disassembled and cleaned for starters. I would check the motor, if it is an 80cc, raise hell with the place you bought the mower, and I would insist on getting it either replaced again or at least torn down and checked, as it may already be badly damaged. It would probably live okay on low flow after that. Model code will start with: M02080 I think what has happened here is you got a low flow mower when you should have had the high flow, and replacing the motor with the same size has just perpetuated the problem. HTH
Thanks for the responses. I really appreciate the help. The model code for this mower is "M02080..." is correct. I have looked at it several times online. As I have been told by everyone, this motor is too small to handle the flow, but how did you calculate the 20 gpm max flow for this motor? Is there a standard rpm that should be used in the calculation to go from displacement to gpm? Do you use the rpm from the engine? The mower and owners manual have 25 gpm max for this mower. But I can't find anywhere on Eaton website that gives max flow. This would also help me to size the proper motor to go on this cutter. Thanks
http://www.eaton.com/ecm/groups/public/@pub/@eaton/@hyd/documents/content/pll_1323.pdf Page C-1-2, it's page 119 in the PDF file. Their numbers are a bit off, if you use their max rpm of 908 * 80cc = 72,640 * .061 = 4,431 Cu inches/min /231 = 19.18 GPM max rated flow. Note that the larger motors are severely restricted on RPM. I think you need a piston motor to use high flow. If you know what the input speed is supposed to be or what speed the mower is supposed to turn, and calculate in any gear ratio in the gearbox if it's not 1:1, you can calculate how big a motor you need to match say 30GPM maximum flow. Since this motor maxes out at roughly 900, let's use 800 rpm. 30GPM * 231 = 6,930 cu. inches/minute /.061 = 113,606 cc /800 rpm = 142cc motor. Roughly. Of course the motor has to be rated for more than 800 rpm and whatever pressure the crossover relief needs to be set at so you don't grenade the gearbox. :my2c
Look at a CID X-treme piston motor brush cutter. 27-35 GPM or 30-48 GPM. or 17-27 GPM LOW FLOW
I will check it out. I can't thank y'all enough for the help. I will post an update on my situation in a day or so. Thanks again
In the future decelatate the carrier engine before switching off the cutter motor. It allows the cutter motor to slow to the lowest RPM's and stops motor damage no matter what breed of hydraulic motor is fitted