Flail Mower Circuit

[Waratah15]

I'm building a flail mower for my ASV Positrack, it has a hydraulic output of 16.3 gpm at 3000 psi and so far the best motor I have been able to find is this one:

Surplus Center - 1.80 cu in CROSS HYD MOTOR 40MH18DACSC

Will run the motor output through a belt drive to the main mower shaft. Even considered running the motor direct onto the mower shaft but I'm concerned that might put too much shock through the motor.

Here is an excavator boom flail mower that I'm pretty sure runs the motor on the end of the mower shaft. I'd welcome any thoughts on whether that seems feasible, would certainly make it simpler to eliminate belts and tensioners etc. I realize it would be wider overall but that's not really and issue for where I'll be working with it.

Mini Excavator 30" Mower - Raptor 30"


Looking for some advice on the hydraulic circuit, what I need to install to protect the motor.

Thanks,
Jonathan

 

[Willl]

I'm building a flail mower

Are you going to do the rotor yourself or sub it out ?

If yourself, thoughts on to how to balance ?

 

[Waratah15]

Are you going to do the rotor yourself or sub it out ?

If yourself, thoughts on to how to balance ?

I've found a local company that can dynamically balance the shaft with cutters on it. Realize that's crucial to making it work.

 

[J_J]

I have a hyd driven tiller that is direct driven.

I also have hyd flail mower that is belt driven.

I believe the belt driven system will take the shock load better. You can modify the rotor rpm's by selecting the belt and pulley arrangement.

You could also add a single relief/cushion valve across the motor for extra protection.

Surplus Center - 1/2" NPT 20 GPM 500-1500 PSI RELIEF VALVE RV-4L

 

[Waratah15]

Thanks for chiming in J_J was hoping you would!
Should the pressure relief valve be lower psi rated like the one you highlighted or was that just an example of the kind of valve? And when you say across the motor, do you mean in parallel with the motor or in series with it?

Can certainly see the advantages of having the belt drive for rpm tuning and for isolation. The high speed low torque motor only has an output shaft of 5/8", mounting that straight up to a big heavy mower shaft just doesn't seem right yet I believe that's what they do with the super heavy duty disk type slashers.

Also saw one of the flail mowers online had a bypass valve to let the mower shaft slow down independent of the motor.

The other thing I have seen is a case drain from the motor, is that a must have or dependent on the motor type?

Thanks for your interest!

 

[J_J]

Some hyd motors are built with case drains and some don't. I have 4 hyd wheel motors on my Power-Trac,and they have case drains.

This is the relief valve I should have posted.

Surplus Center - 1/2" NPT 20 GPM 1500-3000 PSI RELIEF VALVE RV-H4

It is used across the motor, paralleled.

If you think you will ever turn the motor in reverse, then this valve is the way to go.

Surplus Center - 1/2 NPT 30 GPM 1500-3000 PSI HYD CUSHION VALVE

Here is a pic of a relief valve across a hyd motor.

The controlling valve for the flail should have a motor spool valve to let the flail mower wind down.

 

[oldnslo]

Thanks for chiming in J_J was hoping you would!
Should the pressure relief valve be lower psi rated like the one you highlighted or was that just an example of the kind of valve? And when you say across the motor, do you mean in parallel with the motor or in series with it?

Relief valve should be in parallel circuit and normally set higher than operating for surge protection.

Can certainly see the advantages of having the belt drive for rpm tuning and for isolation. The high speed low torque motor only has an output shaft of 5/8", mounting that straight up to a big heavy mower shaft just doesn't seem right yet I believe that's what they do with the super heavy duty disk type slashers.

Also saw one of the flail mowers online had a bypass valve to let the mower shaft slow down independent of the motor.

Good idea to prevent over running the hydraulic motor

The other thing I have seen is a case drain from the motor, is that a must have or dependent on the motor type?

Thanks for your interest!

Motor with case drains depends on use and motor type.

Gear or geroler/geroter, vane style usually only have case drains when they are used in series to keep the shaft seal from being pressurized.

Piston style motors must have a case drain under all conditions and this line must be at low pressure usually less than 30 PSI.

Roy

 

[Waratah15]

Thank you gentlemen for your replies, what a great resource this forum is

J.J. you mentioned that the controlling valve should have a bypass valve to allow the flail to spool down - not quite sure whether you meant that my existing Control Valve that is part of the ASV circuit should have that installed already or that I should put one into the circuit. I checked through the Surplus Centre valves and couldn't find anything labelled as a bypass valve, is it called something else or do they not have them?

Here is a link to a shop in my city, near the airport district and interesting to see the things they balance. An over the phone quote for the balancing of the shaft with flails was $250, they said that they have done many similar shafts over the years. Nice to live in a city with a strong manufacturing history that has these resources.

Dynamic Balancing | Paul England Engineering

Thinking through the options of belt v direct drive.....

If I was to go belt I assume it would be advisable to have a bearing on the shaft coming from the motor outboard of the pulley? Because the motor shaft is only 5/8" I would turn up a shaft with a hole bored and keyed in one end that accepts the 5'8" motor shaft, runs through the bore of the pulley (maybe 1 3/8" ID) then runs through an appropriate bearing.

Sorry to be asking what may be dumb questions! I know a little about machinery, just not this particular style...

 

[J_J]

The aux valve for your attachments is probably a motor spool valve.

Is your aux valve a detent lever valve or a solenoid operated aux valve?

 

[Waratah15]

The aux valve for your attachments is probably a motor spool valve.

Is your aux valve a detent lever valve or a solenoid operated aux valve?

It's a switch on the dash in constant flow mode or a button on the joystick for intermittent for things like my auger. So solenoid operated aux valve.