Flow control or not, for sickle bar: Samuri/Sabre

[J_J]

If using a hyd motor on your sickle bar mower, what regulates the pressure when the sickle bar gets jammed.

What is your relief pressure.

The point here is that there are limits/.restrictions on most things hyd and they need to be designed correctly and not have people just hook things and go.

Some people say I just hooked the hoses up and everything works good, until it breaks.

Where is my warranty, I hope I did not screw up.

 

[SPYDERLK]

I don't think there will be any trouble running a sickle bar straight from your usual QDs. This is what I have been doing for several years with my hedge trimmer. I usually run it just above idle on my JD 3520. The only addition I had to make was a direct return to tank for the hydraulic motor.

OP has a 17gpm hyd delivery on his tractor. Im not sure if this is combined P/S and accessory flow or just accessory flow. -- If it is just accessory flow then, even at idle it will be delivering too much fluid for the cutter speed desired. ... To make matters worse his tractor is HST and needs to be a bit above idle to move effectively. ... If its a combined flow number tho the accessory flow will be only part of the 17 - maybe 12gpm, and idle might work. But still, HST doesnt work well at idle.
larry

 

[J_J]

I think some of these guys are pushing the limit, and taking chances.

 

[J_J]

Let me inject a problem with Flow Control valve in question. Few days ago I posted
Need an expert hydraulic opinion.



This is what I wrote to Surplus Center:
Very recently I purchased and installed the flow control valve RDRS150-16. The purpose was to run a sickle bar attachment to my tractor. The pressure line is connected to PB of a three spool Prince MB31BB5C1 DA valve. When connected, the sickle bar (10 GPM motor) works satisfactorily. When disconnected, however, the PRV was screaming with the flow control valve was shut off. So I increased the PRV to 2000 psi, which in the beginning appeared to function okay. But at some point later, it crated a resistance that almost bogged down the engine. Of course, when this occurred, the valve was always in the off position. My understanding is that when this valve is in the off position it should not allow any fluid to pass and any remaining flow should be bypassed to the EF. This is not happening. The only way that this valve does not create resistance when the attachment is disconnected, is when I put a jumper hose between the CF and The EF ports.
Is this valve defective?

Here is a description of my system and pics to show the hydraulic connections.
35 HP tractor, 7.2 GPM PTO pump, 3 spool Prince MB31BB5C1 DA valve set at 2000 psi, 10 gal hydraulic tank elevated about 4 inches above the valve.



That was few days ago. As of today I have not received an answer.

Which relief valve was screaming, the flow control relief or the three spool relief valve?

When you unplug the sickle bar mower, connect a jumper across the CF and the EF in a tee going to tank

 

[NCMau]

Flow Control was screaming when it came from SC. with setting of 1500 psi. Then you suggested to increase it, i did. But instead of screaming, at some point (not right away) created to much back pressure to overload the engine. I turned the PVC one turn CW, I think it is set around 2000 psi. At this point I have not done any more adjusting.
Yes I have the Jumper across CF and EF and it works great. I guess I can operate in this fashion if I can't find out why the Flow Control is acting this way.

 

[Coyote machine]

Here's what the Samuri company owner told me today in a phone conversation: that if I was the only person running the sickle bar I could just run it below the blur of the teeth and if needed bump up the speed as needed to cut through thicker or harder to cut items. That 1000PSI would function, and I would not need a flow control or other pressure device to run the sickle.

I hear what you TBN guys who are very familiar with hydraulics say too- what happens if my sickle breaks due to too much flow or too high relief pressure based on the outputs of my tractor, etc.

NCMau's issues with the pressurized relief valve are similar to my situation. Though I suspect if I were to go the route of a CF valve I would have it use ONLY when the sickle was being used, and would remove it and the sickle when not in use, thus eliminating any non use squeal, etc.

 

[NCMau]

Coyote machine, That is my problem, it squeals when I remove the sickle connection. At this point the flow should be stopped. When the sickle is connected it runs great. It would take more than my wimpy hydraulic knowledge to figure this thing out.

 

[SPYDERLK]

Here's what the Samuri company owner told me today in a phone conversation: that if I was the only person running the sickle bar I could just run it below the blur of the teeth and if needed bump up the speed as needed to cut through thicker or harder to cut items. That 1000PSI would function, and I would not need a flow control or other pressure device to run the sickle.

I hear what you TBN guys who are very familiar with hydraulics say too- what happens if my sickle breaks due to too much flow or too high relief pressure based on the outputs of my tractor, etc.

NCMau's issues with the pressurized relief valve are similar to my situation. Though I suspect if I were to go the route of a CF valve I would have it use ONLY when the sickle was being used, and would remove it and the sickle when not in use, thus eliminating any non use squeal, etc.

I had this same type of discussion when I bought mine. They dont know, or are unable to convey, how the system works. There is no flywheel so you get nothing from faster speed unless you can slow to zero speed and nibble thru while the branch bounces like crazy. Only pressure can give the force to swipe right thru a branch as intended. The lo pressure the sickle can run at gets confused with what happens when the sickle encounters a load. In order to cut thru resistance the pressure rises. Enuf resistance and the system relief cracks and the cutter stalls. I know that 2500 is required to cut thru stuf about an inch thick. A little bigger or harder stuf will stall it unless the relief is set higher. Finally, who knows how far above 2500psi, the motor will have enuf torque to overload and damage the cutter or oscillating mechanism. My guess is around 3000psi. The relief on the tractor we use it on is set at 2600. It stalls rarely, but its always a bad scene [even at 1or2mph] if the blade cant fold back while you notice and get stopped.

 

[J_J]

Seems to me that motor is only rated to about 1800 psi, so where are these high figures coming from?

The thing about hyd is that you have about the same torque from start to high rpm.

 

[SPYDERLK]

Those are continuous use pressures. Intermittent is quite a bit higher. On the cutter the motor only sees hi pressure for an instant. Duty cycle at appreciable pressure is probably less than 0.1% and only a small fraction of a second at a time.