Motor and relief valve selection

[Waratah15]

I'm converting a pto flail mower to hydraulic to use with my ASV RC-60 Skid Steer and would really appreciate some advice on motor and relief valve selection. Found a good, used Flail-King for a good price which I have bought.

I have 16.7 gpm at 3000psi available from my skid steer and thought this motor and relief valve may do the job. Maybe I need a cushion valve as well?

Surplus Center - 5.4 CU IN PARKER NICHOLS 050-4-AM HYD MOTOR

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

Any comments would be much appreciated before I place the order, realise I need the adaptor for the motor to allow hose connections.

A simple sketch of the ideal circuit would be great, does the relief valve simply work in parallel with the motor? Can't tell from the image whether it has three connections to allow it to run in series before the motor with a relief line back to low pressure.

Thanks, Jonathan

 

[oldnslo]

I'm converting a pto flail mower to hydraulic to use with my ASV RC-60 Skid Steer and would really appreciate some advice on motor and relief valve selection. Found a good, used Flail-King for a good price which I have bought.

I have 16.7 gpm at 3000psi available from my skid steer and thought this motor and relief/cushion valve may do the job

Surplus Center - 5.4 CU IN PARKER NICHOLS 050-4-AM HYD MOTOR

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

Any comments would be much appreciated before I place the order, realise I need the adaptor for the motor to allow hose connections.

Thanks, Jonathan

Motor should work fine, may be a little bit high on the RPM at no-load. My calculator show be around 700 RPM.

If this is going to be high usage you may want to check what your back pressure is on the return line from the motor. If pressure is above 200 - 300 PSI you might want to consider using different quick disconnects or possible will have to run a remote case drain line from the motor directly to your reservoir to prevent damage to the shaft seal.

Higher back pressure also means less power to your flail mower to do work.

Relief valve is part of your skid loader unless you want back-up protection right at the mower it probably is not needed.

Roy

 

[Waratah15]

If this is going to be high usage you may want to check what your back pressure is on the return line from the motor. If pressure is above 200 - 300 PSI you might want to consider using different quick disconnects or possible will have to run a remote case drain line from the motor directly to your reservoir to prevent damage to the shaft seal.



Roy

Thanks oldnslo, I don't understand (just add that to the list of things I don't understand!) how changing the quick disconnects will affect the pressure on the shaft seal. Is there an alternative to the regular 1/2" flat face couplers I would normally use?

I don't have a case drain return line on my Skid Steer so was hoping to avoid that, also looks like that motor doesn't have provision for the drain.

And you don't think I need anything in the hydraulic circuit other than the motor - that would make it real simple

Appreciate your help.

Jonathan

 

[J_J]

The data for your hyd motor doesn't say anything about a case drain, so it probably does not have or need one.

How much HP is necessary for your PTO flail to operate efficiently?

Your skid steer pump requires about 34 HP to develop that pressure and GPM, so the motor operating at 85 % efficiency will develop about 28 HP.

What is the size of your flail?

Your PTO flail is going through a gear box off the PTO. Is it a 1 : 1 ratio or something else. That will determine the flail rotor rpm.

You could control the rotor rpm by reducing the GPM's from the skidsteer.

On the QD's, the rule of thumb on QD's is to use one size larger that the hose .

You can put a hyd gage in the system to check the pressure and back pressure if necessary

 

[oldnslo]

Thanks oldnslo, I don't understand (just add that to the list of things I don't understand!) how changing the quick disconnects will affect the pressure on the shaft seal. Is there an alternative to the regular 1/2" flat face couplers I would normally use?

I don't have a case drain return line on my Skid Steer so was hoping to avoid that, also looks like that motor doesn't have provision for the drain.

And you don't think I need anything in the hydraulic circuit other than the motor - that would make it real simple

Appreciate your help.

Jonathan

Jonathan,

Larger quick disconnects allow higher flows. Try doing a search for Flat Face QD's and you should find a sight that shows pressure drop Vs flow. Parker Pioneer, Snap-tite, Eaton-Aeroquip are three companies that I know make these.

Item 2: Tank line or back pressure: If you can find or get the Parker model number of this motor and the corresponding spec sheet it should list maximum allowable pressure on the shaft seal.

Item 3: As long as the flail mower is rated for the input HP or torque that this motor will generate, I do not see a need for another relief valve. The exception to this would be if you are going to be using this as brush mulcher where there would be the potential for lots of pressure spikes. Then the addition of the relief would help protect your motor.

item 4: If the Gear box is 1:1 ration can you remove the gear box? Would save some torque loss.

Roy

 

[Waratah15]

Thanks for the details Roy,

I'm limited in size to the quick disconnects that are on my skid steer, have to match those with the accessory connections. Are you saying that different brands will allow different flow rates? Sorry to be dumb....

I was planning on removing the gear box and mounting the motor directly to the belt drive, agree, no point wasting power turning over the gearbox.

Think I'll go with a pressure relief valve, some pretty scrubby stuff I'll be running it through, better not to stress things more than I need to.

Appreciate all the responses.

 

[oldnslo]

Thanks for the details Roy,

I'm limited in size to the quick disconnects that are on my skid steer, have to match those with the accessory connections. Are you saying that different brands will allow different flow rates? Sorry to be dumb....

Appreciate all the responses.

Different brands will have slightly different flow rates but usually not a significant difference. This is more a size issue or put another way, the opening size and restriction through the QD. The link below is an example that shows flow Vs. pressure drop for the different sizes.

ISO 16028 Flush face, non-spill quick couplings - SafeWay Hydraulics

 

[Waratah15]

OK I'm about to order the motor, relief valve and hoses from Surplus Center. Just to be sure I have this right and order the right hoses, the relief valve runs in series with the high pressure side of the motor and it has an outlet that feeds back into low pressure. So I would need a T in the low pressure return line.

Hard to see from the photos of the Prince valve but I believe it has three 1/2" ports so what I described above seems to make sense.

I have the flail mower now, it's 5 feet wide, same as the ASV. Strange setup, 1:1.75 gearbox and belts that increase the speed by a factor of 1.6. So with a pto speed of 540 rpm the main shaft would be running at 1500rpm. But the blades are tip to tip only 9.5" so the blades are running at a speed of about 4600 fpm. The blades are the hammer type, but even so this seems like a very slow tip speed for a flail mower.

Running the motor I'm planning to buy which has a speed of approx 700rpm will result in a tip speed of approx 6000fpm if I use the gearbox. Removing the gearbox would result in a tip speed of only 2600fpm which I believe is too slow.

Utilizing the gearbox and the 700rpm motor will result in a main shaft speed of about 1940 rpm, which hopefully is fine for the shaft bearings. I'm going to replace the bearings to give it a fighting chance.

Any thoughts/comments most welcome. Main thing is to know if I have the relieve valve circuit correct. Thank you

 

[J_J]

Your relief valve circuit logic is correct. It will come set to a certain pressure, and you will need to set it for the motor protection pressure.

This relief valve has a 1500 to 3000 psi range and comes set to 2000 psi.

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

You can bump that up to about 100 psi below the pumps max pressure.

 

[J_J]

This particular flail mower has a blade tip speed of 8464 ft/min.

Hurricane H70 Series Tractor Mounted Flail Mowers

Model H70-072: 72 inch working width, overall width of 85 inches, weight is 955 lbs., shipping weight of 1145 lbs., 2080 rotor rpm, blade tip speed of 8464 ft./minute, 80 blades