Hydraulic pressure relief issue when running hydraulic mower off remotes

[Bugcatcher]

Hi all,

Just bought a Sabre Samurai hydraulic brush mower and when I try to cut anything larger than 3/8" the hydraulic pump seems to cut out.

I'm assuming this is a pressure relief or safety on the tractor to prevent pressure spikes from damaging the pump.

I'm not sure if I should try adjusting the pressure relief on the tractor (Kubota L4330) or if I should buy a pressure relief or a check valve for the mower.
I've already bought a flow control valve for the mower which actually seems to make it cut out somewhat more frequently.

I can't get anyone at the local tractor dealer to call me back and the mower manufacturer is uncertain so any thoughts would be much appreciated.

Thanks,

Dan

 

[RNeumann]

Before we decide where to put or adjust the pressure relief can you tell us where the hydraulics for the mower is coming from? 99% it’s regulated by the Kubota pressure relief but it would be nice to make sure.

Before I did much messing with pressures I’d put a tee and gauge in the mower circuit. It may be hard to tell exact pressures but you will get an idea if it’s pressure spikes or if the 3/8” material is simply seizing the motor without much of a spike.

That mower may need a big flywheel to tackle the thick stuff.

 

[oldnslo]

Hi all,

Just bought a Sabre Samurai hydraulic brush mower and when I try to cut anything larger than 3/8" the hydraulic pump seems to cut out.

I'm assuming this is a pressure relief or safety on the tractor to prevent pressure spikes from damaging the pump.

I'm not sure if I should try adjusting the pressure relief on the tractor (Kubota L4330) or if I should buy a pressure relief or a check valve for the mower.
I've already bought a flow control valve for the mower which actually seems to make it cut out somewhat more frequently.

I can't get anyone at the local tractor dealer to call me back and the mower manufacturer is uncertain so any thoughts would be much appreciated.

Thanks,

Dan

The flow control regulates flow via pressure drop this pressure drop robs power from your mower. Can you idle the tractor down and open the flow control to see if the mower works better?

 

[BukitCase]

This
3/3 GPM Prince Priority Flow Divider w/Relief | Prince Mfg | Brands | www.surpluscenter.com
is the flow control I use with the samurai, allows full pressure divided into a small priority flow and a larger adjustable flow. Mine actually didn't have the builtin relief, so I got to pay another $400 for a new (non-split) hydraulic pump - didn't know enough then NOT to put ANYTHING ahead of the loader valve with its builtin relief.

Only thing that's slowed my cutter down is near full size (1-1/2") old growth laurel hedge - that has caused me to add a directional control (in process as of now) - that'll let me REVERSE the hyd motor when it stalls out on a "big mouthful" - without that reversing option, once those teeth bite into something they either cut it or stick... Steve

 

[Bugcatcher]

I've tried it with the flow control wide open and it seems to make no difference in how often it cuts out/locks up. If I take the flow control valve off it seems to cut out slightly less often.
It often locks up just after cutting a larger bit so I don't think it's a power issue.

 

[Bugcatcher]

Good idea, I'll try the pressure gauge first.

 

[Bugcatcher]

This
3/3 GPM Prince Priority Flow Divider w/Relief | Prince Mfg | Brands | www.surpluscenter.com
is the flow control I use with the samurai, allows full pressure divided into a small priority flow and a larger adjustable flow. Mine actually didn't have the builtin relief, so I got to pay another $400 for a new (non-split) hydraulic pump - didn't know enough then NOT to put ANYTHING ahead of the loader valve with its builtin relief.

Only thing that's slowed my cutter down is near full size (1-1/2") old growth laurel hedge - that has caused me to add a directional control (in process as of now) - that'll let me REVERSE the hyd motor when it stalls out on a "big mouthful" - without that reversing option, once those teeth bite into something they either cut it or stick... Steve

Just to clarify, Bukitcase, you're using the Flow Divider instead of a Flow control valve? Also, are you running it off the front end loader hydraulics?

 

[BukitCase]

Yes, I'm using the NON-relief version of the one I linked right now - after I grenaded my pump, I added a separate relief ahead of the flow divider, it relieves direct to tank. I also found that these flow dividers do NOT like for the variable side to be completely shut off - if that's done, they tend to get weird and shut off ALL flow to BOTH ports.

I got around THAT problem by plumbing in a small (1/4 pipe) stainless ball valve that stays closed when I'm using the Samurai, then when I'm NOT using the Samurai I set the variable flow to zero - but it leaks a little bit, and if that builds up pressure that's when things get wonky. My workaround is to set the flow adjust to zero, but OPEN the small ball valve so any small leakage just gets dumped to tank. It's just a tiny amount, so no noticeable effect on loader hydraulics.

The directional flow valve i'm adding is a Prince single circuit;
1 Spool 2 GPM Prince RD-2575-M4-EDA1 Motor Valve | Prince Mfg | Brands | www.surpluscenter.com

I need to mill a little bit out of the linkage so I can reverse the included "dogleg" handle to a more comfortable position, then I can just relocate the 2 hoses to the front QD's without changing anything, and I'll need to make up 2 hard tubing lines for the flow divider to feed the in/out of the directional valve. Those changes should let me "wiggle my way out of trouble" when the cutter bogs down on a mature 1-1/2" laurel limb (maybe)

I know this all sounds confusing ('cause it IS) - I have a few pics somewhere, but not sure which card they're on. When I find 'em I'll post back... Steve

Forgot to add - yes, the flow path is pump pressure out/flow divider/priority flow to loader valve, adj. flow to Samurai (thru directional valve)- Samurai return dumps to tank. Loader is pretty sluggish when the Samurai is on, but moving fast is NOT a good idea with this cutter anyway.

The PB of the loader valve feeds the hoe (this is a 12,000 lb. machine, these are 3/4" hoses except for the ports that service the Samurai; those are 3/8", and as I said the "leakage" drain valve is 1/4 NPT.

As I said, this is still a work in progress; but I'm pretty sure this last round of changes will let everything work as I want it to...