Brush Cat Brake Question

[fishfactor]

Can anyone tell me where the braking action comes from on a Brush Cat (Bobcat) rotary mower when you shut off the flow? Is it something in the machine, or the mower?

 

[yellowdogsvc]

there is a valve block. When the lift arms are raised about a certain height, the valve is tripped by a lever and it shuts the flow off. It can be disconnected but I don't recommend it. Edit: The block is on the brushcat.

 

[fishfactor]

there is a valve block. When the lift arms are raised about a certain height, the valve is tripped by a lever and it shuts the flow off. It can be disconnected but I don't recommend it. Edit: The block is on the brushcat.

Yeah, that's been disconnected a long time ago. I was referring to the way the rotation stops a few seconds after you stop the flow, instead of free spinning until the momentum runs out.

 

[yellowdogsvc]

Sorry, I misread. Figured you curious about one.
I've had 3 since they first came out. All have braked pretty hard after flow is shut off and the blades clank together real hard.

I think it's still in that valve block. With a direct drive motor like I had on my davco, it would free spin. I think the valve block has some type of squash plate in it. I think I remember disconnecting the early version of the toolcat from the valve block and the blades would free spin after hydraulics were shut off. It's the only thing in-between the auxiliary hydraulics and hydraulic motor. It can't be in the machine because my other mowers free spin after hydraulics are shut off.

 

[fishfactor]

Thanks. That makes sence, but since I haven't ran another one I wanted to make sure.

 

[RINGPOWERTALLY]

there is a actual brake valve on the motor its self, it has a pilot activated check valve tied into a relief valve the connects the in and out of the motor causing a brake type action...... instead of a davco or other eaton type motor that just has the check valve that lets the oil recirc around and around until the mower stops

 

[fishfactor]

Thanks for the replies but it seems neither is correct. We built a mount so we can run this mower on our CAT excavator as well as the bobcat. We didn't want the brake when on the excavator. Bypassed the valve box, ran it on the excavator and all was good. No brake and the mower would spin until momentum ran out Put it back on the Bobcat and the brake was violent. Something would break violent. Switched the hoses back and it runs as normal on the bobcat with the brake. Put it on the excavator and there is no brake, free spins. So this braking must come from the bobcat?

 

[RINGPOWERTALLY]

thats interesting......... the hydraulics should work the same no matter what machine its on.......unless your EX is set up for a hammer and the return side hose is open to case drain, hence why it free spins instead of building pressure and stalling untill the relief opens like on your bobcat....

 

[SSdoxie]

thats interesting......... the hydraulics should work the same no matter what machine its on.......unless your EX is set up for a hammer and the return side hose is open to case drain, hence why it free spins instead of building pressure and stalling untill the relief opens like on your bobcat....

This is correct. The braking is in the valve, uses a cross port releif that allows the motor to coast until the pressure on the retrun side drops low enough to safely stop the blade without damage to the motor or gear box. Some brands may use a motor with internal by-pass circiut that allows coast down, but Bobcat does not. One benifit of the Bobcat motor is ability to use both sides of a double edged blade, if blades get too worn running in one direction, swap the hoses at the motor and motor will rotate opposite direction and cut with the other side of the blade. If running on an excavator as fishfactor described, it was with direct to tank return, in this case it will coast but the motor is spinning without oil flow through it and can eventually cause cavitation wear to the motor.

 

[fishfactor]

We run the aux on the ex on the foot pedal pilot control. Also have the tool control hydraulics so we adjust how many gpm go to the head. We can run the AFE mulcher in reverse to clear a jamb so I don't think the return hose is open to the case drain.

 

[fishfactor]

This is correct. The braking is in the valve, uses a cross port releif that allows the motor to coast until the pressure on the retrun side drops low enough to safely stop the blade without damage to the motor or gear box. Some brands may use a motor with internal by-pass circiut that allows coast down, but Bobcat does not. One benifit of the Bobcat motor is ability to use both sides of a double edged blade, if blades get too worn running in one direction, swap the hoses at the motor and motor will rotate opposite direction and cut with the other side of the blade. If running on an excavator as fishfactor described, it was with direct to tank return, in this case it will coast but the motor is spinning without oil flow through it and can eventually cause cavitation wear to the motor.

So should we bypass the valve box when running on the ex? Will this prevent the cavitation?

 

[SSdoxie]

So should we bypass the valve box when running on the ex? Will this prevent the cavitation?

The valve block works to prevent cavitation. It circulates the oil from the normal return side of the motor to inlet side keeping a flow of oil through the motor until it gets down to a pressure acceptable to stop the gear box without damage. The clunk noise that is heard is only the blades coming up against the stump jumper when it stops spinning. If your excavator has forward and reverse function, then I am guessing it has circuit port relief at the valve spool, these still stop the flow of oil going into motor inlet so cavitation can occur while it is dumping oil to tank in the valve unless the port relief(s) are on both ports of the valve circuit and ALSO include anti-cavitation valves in them.

 

[fishfactor]

Got the brush cat mounted up and running this week on the ex. Don't make fun of the JD yellow on the adapter. That's all they had. It'll get dirty and match soon enough.

 

[DIRTROAD]

That looks good dude!! That 6' cutter makes the 42" cutter that I had look very small. Let me know how the shear works on there.

 

[fishfactor]

That looks good dude!! That 6' cutter makes the 42" cutter that I had look very small. Let me know how the shear works on there.

Will do. We've got a logging job coming in a few weeks and will try it out. Got to go by CAT first and get programmed for it. The setting for the mulcher has very little reverse flow to clear a jamb and the mower has reverse blocked. The shear needs full reverse flow in case you get stuck half way through a tree.

 

[catdozer]

Could you show a few more up close pictures of your adapter? Would like to put one on a 320

 

[fishfactor]

Could you show a few more up close pictures of your adapter? Would like to put one on a 320

Give me some time. We're out of town on a 2 week job right now without it. May get to go home this weekend if the rain comes as forecasted.

 

[catdozer]

Give me some time. We're out of town on a 2 week job right now without it. May get to go home this weekend if the rain comes as forecasted.

Ok, we currently mow ditches with a Bobcat T190 and a T870. so it would work good to just track along side the ditch and not up and down all the time.