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

[woody]

So Slywoody, you just eyeball the cutter speed and don't control flow other than reducing RPMs till you have slight blur of cutters, is that correct? What maximum GPM does your tractor put out?
How many hours would you say you have on the cutter to date?


yes sir I just watch the blades till they look alright and start cutting, I have a B26 Kubota and the pump is rated at 11 gpm but since I am running my hydraulics connection from the back hoe I believe that has a flow of 7 gpm. the cutter does better with limbs and stuff than it does with grass, but if you are getting a new one you may not have that problem. it was used when I got it and I probably have 25 or 30 hours on it.

 

[J_J]

For some reason, the want the motor pressure limited to 500 psi.

I could find no reference to the lowest relief setting on the flow control valve. It comes set to 1500 psi.

The hyd motor is what develops the pressure due to the load imposed on the sickle bar cutter.

If you don't set it low, it can build up pressure greater than 500 psi, and perhaps damage some of the cutter parts.

Try it at idle and see if the cut and speed of operation is satisfactory, and if it is, just bypass the flow control valve.

 

[Coyote machine]

So Slywoody, you just eyeball the cutter speed and don't control flow other than reducing RPMs till you have slight blur of cutters, is that correct? What maximum GPM does your tractor put out?
How many hours would you say you have on the cutter to date?


yes sir I just watch the blades till they look alright and start cutting, I have a B26 Kubota and the pump is rated at 11 gpm but since I am running my hydraulics connection from the back hoe I believe that has a flow of 7 gpm. the cutter does better with limbs and stuff than it does with grass, but if you are getting a new one you may not have that problem. it was used when I got it and I probably have 25 or 30 hours on it.

Thanks for the reply. So I can guess that since you bought it used, and have added 25-30 hours since that the grass cut might be somewhat hampered by not so sharp cutters?

 

[Coyote machine]

For some reason, the want the motor pressure limited to 500 psi.

I could find no reference to the lowest relief setting on the flow control valve. It comes set to 1500 psi.

The hyd motor is what develops the pressure due to the load imposed on the sickle bar cutter.

If you don't set it low, it can build up pressure greater than 500 psi, and perhaps damage some of the cutter parts.

Try it at idle and see if the cut and speed of operation is satisfactory, and if it is, just bypass the flow control valve.

J_J,

Is the plumbing of the flow control valve I detailed most recently correct?
Wouldn't it make sense to try it without the valve first, and then if the flow control seems necessary, add it afterward?

 

[J_J]

Yes, for sure.

But, how are you going to relieve the pressure at 500 psi as suggested by the manufacturer?

 

[BukitCase]

JJ, from the actual owners manual -

"Hydraulic Pump requirements - minimum flow of 10
GPM @ 500 psi"

Their brochure is worded kinda funny, makes it sound like that's the MAXIMUM. The manual is a bit clearer, but still kinda fuzzy. They basically say to "set it by eye", more or less - quote - "if you can't see the blades going back and forth, it's too fast".

These use a standard Char-Lynn (or another name brand I don't recall ATM)

Mine is (eventually) going on my Case, and I bought one of the Prince constant flow valves - Because I will also use the motor circuit for another project (front mounting my 6' flail with a different hyd. motor) , and because the rest of my machine needs good flow, I went with the 30 gpm max model (my pump puts out 24 gpm @ around 2400 psi) and I'm plumbing it in AHEAD of the loader control -

Pump will go into the input of the RDR valve, CF goes thru 3/4" hard tubing up loader arms to 1" QD's (less restrictions) and return comes back to rear and tees into tank return. EF then goes into loader control.

The Samurai won't need that much flow, but according to my calculations the flail will need everything I can give it.

Plumbing it that way will (I hope) let me keep a SMALL flow to run the bucket if using the flail, and MOST flow to bucket circuits when using the Samurai.

So far, my only concern is that "gray area" of what happens to the EF when you block the CF port - I won't know til I try, but I'm hoping that adjusting the CF down to zilch will still let the EF port use ALL the flow (they're not clear whether shutting the flow down with the LEVER will stop EF port, or just plugging the port causes EF to stop) - if not, my backup plan is a "bypass" needle valve between CF port and tank, adjusted to just enough flow to NOT stop the EF port.

This bypass will mount right at the output of the EF port so it's adjustable from the cab.

May not need it, but the way I'm routing hard lines and hoses it will be easy to implement if necessary.

I know my situation is a bit different, in that I can't impede normal flows or else other functions suffer, but I thought I'd throw my $.02 in just to confuse the issue ...Steve

 

[Coyote machine]

Yes, for sure.

But, how are you going to relieve the pressure at 500 psi as suggested by the manufacturer?

I have no idea how to do that part without the flow control valve, but as you said, the valve doesn't state how low it's relief pressure setting will go....

I'm going to see if I can find out more about the valve's specs....

I also don't get why some are running with no valve and theoretically no issues re flow, relief, etc.?

This situation makes no sense to me so far.

 

[Coyote machine]

Here is what I was told by Surplus Hydraulics tech dept.: The valve does not specify a lowest relief PSI, BUT other similar valves of theirs do have a 500 PSI low end setting, or lower number depending on how far the set screw is backed out.
So I was told to either get the flow control valve, and a needle valve and gauge to set the 500 PSI relief pressure, or to just get the flow control, set it up with the control lever to the speed I need the sickle to move at; just beginning to blur the cutters, then back off the set screw until the sickle stalls while cutting then turn the set screw in to bring the pressure up to where it doesn't stall while cutting approximately 1 1/2" branches.
The problem with the needle valve and gauge is I would also need to be able to restrict the sickle bar until it was at 500PSI at the relief, and I have no way of doing so to set the relief at the 500lbs setting at 10gpm.

Does this make sense?
I think, if I understood correctly, I would be best off installing the valve, setting the speed with the lever control on the valve then setting the relief pressure by trial and error to the point of having the sickle not stall when cutting 'green' vs. dead branches of around 1 1/2" in diameter.
Any thoughts on this approach?

 

[J_J]

If you talk to tech section of the company, ask them why the 500 psi limit on the motor.

My theory is that the motor will produce a certain amount of torque, but the parts used might not withstand the force exerted.

That 3 cu in hyd motor using 10 GPM, and 3000 psi, can can produce about 1,433 in lbs or 119 ft lbs, and that may be way too much for the sickle bar mower.

If they limit the pressure to 500, and 4 GPM, the torque would only be 239 in lbs, or 19 ft lbs.

If the valve feeding the hyd motor can not regulate the pressure to 500 psi, then something like this across the motor would.

1/2" NPT 30 GPM 500-1500 PSI RELIEF VALVE RV-4L

Logically a stronger force can cut better, so if the cutter is not performing as you like you could increase the torque by increasing the pressure.

 

[Coyote machine]

If you talk to tech section of the company, ask them why the 500 psi limit on the motor.

My theory is that the motor will produce a certain amount of torque, but the parts used might not withstand the force exerted.

That 3 cu in hyd motor using 10 GPM, and 3000 psi, can can produce about 1,433 in lbs or 119 ft lbs, and that may be way too much for the sickle bar mower.

If they limit the pressure to 500, and 4 GPM, the torque would only be 239 in lbs, or 19 ft lbs.



If the valve feeding the hyd motor can not regulate the pressure to 500 psi, then something like this across the motor would.

1/2" NPT 30 GPM 500-1500 PSI RELIEF VALVE RV-4L

Logically a stronger force can cut better, so if the cutter is not performing as you like yo could increade the torque by increasing the pressure.

Ok J_J, are we now considering just a PSI regulator instead of the flow control valve?
If so, plumbed one line, supply to valve and then output from regulator into sickle bar, then back to tank from other side of sickle?
The valve you show is set at 1000PSI; so how will I get it to 500? Will it need a gauge and needle valve for me to set it or some other method?

TIA,

CM