So I have a TimberKing TK340 feller buncher. It is the same as a hydro-ax 470 except it has a Cat 3126 engine. I am just starting the research on doing this conversion so I have not gathered all the pertain-ate info on flow rates and such. These machines that were factory built as mulchers have a closed loop system operating the mulching rotor. Is it necessary to run the rotor closed loop? The skid steers with high flow are simply combining the flow of two gear pumps, at least the ones that I have dealt with. I have two a10 rexroth pumps, could I not just combine these two pumps in an open center valve that could handle the flow. ? A a sure additional oil cooling will be in order either way.
Usually the use of a closed loop system is for higher pressure and smaller hydraulic reservoir and plumbing, higher pressure allows for smaller pumps and motors. Closed loop systems also tend to be a bit more efficient as the charge pump keeps the loop full and essentially supercharges the drive pump inlet side. Anything is possible, so if you determine what flow and pressure you have from the two variable pumps combined you can probably find a mulcher head that has or can accept a correctly sized motor to match. You will probably want a closed center valve setup, but open loop, meaning there is no pump flow when the mulcher is off, but when it is on the oil flows through the motor and back to tank, almost certainly by way of a large oil cooler. Your valve should have a motor spool in it, and either built in port reliefs or an external crossport relief with anticavitation check. You may also want either a flow metering spool in the valve or an external pressure compensated flow control to regulate flow and possibly provide feedback to the pumps if they're set up for load sensing. What displacement are the pumps, and are they auxiliaries or are they also running all the track, boom, and swing functions? What's the horsepower rating of the engine? Are you willing to live with a mulcher head small enough that the engine will run it and all the normal functions at the same time? I see at least some of the excavator mounted mulcher heads with an auxiliary power unit mounted on the back of the counterweight.
The engine is rated at 175 at 2200rpms . It has a three pad pump gear box with a hydrostatic drive pump rated at 44gpm, main hydaulic is a piston pump at 40gpm and the saw pump at 30gpm. The saw pump pad is where the grinder pump(s) will be placed. The two rexroth pumps I have are from a john deere 643h feller . They are the main and saw pump in their original application . The one has a through drive so they mount in tandem. They are also 40 and 30gpm. The timber king has a closed center load sense system. The mulcher head I plan to install is a gyro trac head. I will get specs on it soon. I think pressure spikes would be a concern . Would the closed loop system absorb these better?
You'll need the model number of the pump drive, there's a limit on the torque throughput to each pad so you'll want to use the maximum torque you can input to your tandemed pumps and adjust pressure/flow accordingly. 70 GPM @ 3,000 psi is roughly 125 HP so I think you're okay engine wise, if the pump drive will handle it and if that's enough to keep your cutter head happy. May be better to do some replumbing and split the power load across two pads for the cutter flow. Pressure spikes will be a concern. No, closed loop has the same problem only at higher pressures. An accumulator on the pressure line going to the drive motor will help, actually mounted on the cutter head if possible.
We used to figure one horsepower per GPM at 1,000 PSI. so the need would likely be around 210 HP at that pressure range. It's a load sensing system so the GPM would be dropping somewhere in that area to keep from overloading the engine making for less horsepower. Total GPM possible would be around 104 with the travel circuits pulling the heavy HP and highest pressures. Since mulching for the most part requires travel and tool use at the same time I would assume the working pressure of the mulcher is going to have to be at a lower pressure range. The manufacturer of the mulcher head will have the specs needed and probably provide a drawing of the plumbing and components. I was thinking that a machine designed for a hot saw could make an easy switch. I wouldn't think there would be a lot of difference turning the mulching head over turning the cutting saw. I don't recall any hot saws running a closed loop system but then haven't done much work on them either. Interesting job to do.
No offense but those must have been some really inefficient pumps or really small ponies... I always used 1 HP for 1GPM at 1,500 psi. The rough formula is GPM X PSI divided by 1714 making no allowance for efficiency, but modern piston pumps will usually operate in the 95% area. 70 GPM X 3,000 PSI is 210,000 / 1714 = 122.52 /.95 = 128.97 so roughly 130 HP at the pump shaft. Of course that's using the pump flows as stated, if the engine rpm varies between the two machines and/or the pump drive ratio causes the pumps to turn slower or faster that will affect maximum flow. Model numbers? A10VO or A10VSO the next two or three digits will be maximum displacement in CC's per revolution.
No offense taken. We used the 1,000 PSI rating because performance is never static. A machine that can marginally operate an attachment with everything new, a year later is over heating and running slow. People tend to forget to also provide some margin for mechanical loss in driving the pumps and attachments. Another thing I've found is that while in this case the engine might be rated at 175 HP with everything perfect, it is not designed to run at 175 continuous HP output. Duty cycle is likely in the 60% range. The pumps might destroke and everything will slow down with the load but the output of the engine must raise to its set point to carry it. That's probably the biggest reason most of the big mulchers I've seen had separate engines and hydraulic systems to run them. I've worked on plenty of dangle head processors that only work at half their capacity because they were designed to run on new machines or the next larger size. You see it when the operators use the machine swing to drag the processor over the tree.
Agreed, it's usually a borderline deal running everything off one power unit, the intermittent loads if not being compensated for by some type of intelligent control system can pull the engine down below the torque peak and you're done. Other issues are ambient temperature, system heat, and altititude, all of which rob power and cause more heat, leading to a cascade of system failures.
This machine will be for personal use so slower production won't be an issue. Still have not found the flow requirements for the gyro trac head. This gyro track head is similar in size to a fecon bh120 . Flow rating on the bh120 if I recall correctly is a min of 45gpm and max 90 min. So.... How about I replace the saw pump with the larger piston pump I have and then installing a priority valve on the main pump . Then have a high flow switch. Please correct me if I am mistaken but in doing so I could partially combine the two pumps in high flow mode for heavy grinding . Then back to low flow to limit horsepower usage when moving through lighter bush material.
Easiest thing, if the pumps are similar, would be to put the piggyback set where the main pump is, use the front section as the main pump, and the rear section to augment the cutter pump. Depending on the controls, you could limit flow and also set the pressure on the smaller pump lower than the main pump so it will cut back first. What model Gyro trac head are you using, or which machine is it off of?
I can,t yet answer either of those questions . I have searched for a serial or model number. I have also contacted gyro trac and they told me where the serial number should be located and if not to send them a picture and they can help identify it. I have yet to follow up with that. A custom mount will be required to attach to the timber king.
Start with a lager unit, much bigger engine to provide far more torque and hp and don't look back is my advice, nobody ever complained yet when running one, they had excess hp and sure wish they'd have gone with a smaller unit to save fuel, money and time