Can PT-425 handle Sabre Saw?

[SPYDERLK]

Are you referring to the info on the Sabre Samurai Saw. The manufacturer says the saw operates at 3.3 GPM at max 500 PSI.

Yes, I have that saw. 3.3 GPM is about right for correct oscillation speed of the sickle. I run the tractor at about 1000 RPM to get that low flow. In order for the sickle to be able to cut anything more than a twig the motor driving it is going to have to supply some torque. 500PSI is probably the pressure across the motor while it is just oscillating the sickle but not cutting. The company claim is that the cutter is good for stuf up to 1". As the motor supplies the torque necessary to push the sickle thru, the pressure across the motor rises -- up to as high as the relief pressure of your system. There, if it hasnt cut, the motor stalls. If you have talked to someone at the company that told you the pressure required by the product is 500psi while cutting they just dont understand the product. Ask for a tech person.
larry

 

[MossRoad]

A couple things should be mentioned, here...

The original poster has a Power Trac with an air cooled engine meant to run at 3500 RPM (approximately) for proper cooling and lubrication. Running it at lower RPMs for extended periods of time to reduce the hydraulic pressure will also slow the cooling fan, reduce internal lubrication and could overheat the engine. Especially when using a cutter type attachment.

 

[SPYDERLK]

You want to reduce flow to the motor if delivery is above the 3.5gpm range. You want to keep full system pressure available. If you cant safely slow the engine to give appropriate ~3.5 flow you will need a flow divider to accomplish it.
larry

 

[J_J]

When the hyd pump is running, it is providing potential pressure. The resistance of the hyd motor will develop the pressure, and I am guessing here, that at about 500 psi, the sickle bar mower is cutting avg soft stuff. If it should get into some hard wood, the pressure will increase, and the pressure will build to the pumps potential. Either the motor will take it or fail.

You need to relieve the pressure at whatever the manufacture suggested, especially for warranty.

An external relief valve should work.

I would call the manufacture and double check.

This is a divider valve, with relief, but it doesn't say the lowest relief pressure.

https://www.surpluscenter.com/item.asp?item=9-4158-4&catname=hydraulic

 

[J_J]

Here is the manual for the saw.

http://www.cutthat.com/pdf/SabreManual.pdf

It says that the saw will run normally at 500 psi. It doesn't say anything about regulating the pressure. What is the manufacturer on the hyd motor?

This is the relief valve, which you could probably modify the spring to relieve at a lower pressure.

https://www.surpluscenter.com/Instruct/I9-4158-4.pdf

Relief valve 500 to 1500 psi

https://www.surpluscenter.com/Instruct/I9-4158-4.pdf

 

[Clumber]

Here is the manual for the saw.

http://www.cutthat.com/pdf/SabreManual.pdf

It says that the saw will run normally at 500 psi. It doesn't say anything about regulating the pressure. What is the manufacturer on the hyd motor?

This is the relief valve, which you could probably modify the spring to relieve at a lower pressure.

https://www.surpluscenter.com/Instruct/I9-4158-4.pdf

Relief valve 500 to 1500 psi

https://www.surpluscenter.com/Instruct/I9-4158-4.pdf

From the Q&A page:
"We use the following:
Charlyn (H) Series - #101-1001
Or Dan Foss - #151-2121
Or Ross - #MK021310AAAB
The motors are interchangeable mount and capacity but if parts are required you should specify the make and the model to obtain the correct parts from any hydraulic repair depot."

 

[Marks481]

Ready for the irony? If those part numbers all sound familiar, try should.

Those are the same model numbers of hydraulic motors that PT uses on their brush hogs (and maybe their mower deck).

So the hydraulic motors should be able to handle PTO outlet pressure. You don't need a high quality pressure regulator valve plus reliefto keep from blowing it up.

But you do need a diverter valve (or cheap bypass pressure regulator) to keep the blades moving at the right speed. Full flow might be a little too fast... By a factor of 2-3 times.

 

[J_J]

This is a 2.8 cu in motor, and if 4 GPM are used, the shaft speed will be 330 rpm. Torque, using 2500 psi, will be 1,115 in lbs.

If you put 8 GPM to this motor, it will run at 660 rpm.

This motor is capable of 2500 psi.

The components in the saw may not not be able to take all the torque the motor can produce, and 500 psi may be a safe limit.

If you must limit this motor to 500 psi, then the torque will only be 223 in lbs, not very much.

That is about as much as a person can do with an anvil pruner.

 

[SPYDERLK]

The info you have about pressure is wrong or misleading. The hyd motor drive has no problem at 2500psi. Call the manufacturer.
larry

Yes, I have that saw. 3.3 GPM is about right for correct oscillation speed of the sickle. I run the tractor at about 1000 RPM to get that low flow. In order for the sickle to be able to cut anything more than a twig the motor driving it is going to have to supply some torque. 500PSI is probably the pressure across the motor while it is just oscillating the sickle but not cutting. The company claim is that the cutter is good for stuf up to 1". As the motor supplies the torque necessary to push the sickle thru, the pressure across the motor rises -- up to as high as the relief pressure of your system. There, if it hasnt cut, the motor stalls. If you have talked to someone at the company that told you the pressure required by the product is 500psi while cutting they just dont understand the product. Ask for a tech person.
larry

You want to reduce flow to the motor if delivery is above the 3.5gpm range. You want to keep full system pressure available. If you cant safely slow the engine to give appropriate ~3.5 flow you will need a flow divider to accomplish it.
larry

Ready for the irony? If those part numbers all sound familiar, try should.

Those are the same model numbers of hydraulic motors that PT uses on their brush hogs (and maybe their mower deck).

So the hydraulic motors should be able to handle PTO outlet pressure. You don't need a high quality pressure regulator valve plus reliefto keep from blowing it up.

But you do need a diverter valve (or cheap bypass pressure regulator) to keep the blades moving at the right speed. Full flow might be a little too fast... By a factor of 2-3 times.

This is a 2.8 cu in motor, and if 4 GPM are used, the shaft speed will be 330 rpm. Torque, using 2500 psi, will be 1,115 in lbs.

If you put 8 GPM to this motor, it will run at 660 rpm.

This motor is capable of 2500 psi.

The components in the saw may not not be able to take all the torque the motor can produce, and 500 psi may be a safe limit.

If you must limit this motor to 500 psi, then the torque will only be 223 in lbs, not very much.

That is about as much as a person can do with an anvil pruner.

Pertinent points consolidated. :thumbsup: In actual practice the product shows that 2500psi stall causes no damage. This will seldom happen on green wood, even a little above an inch. Seasoned trimmings can be a bit harder to cut.
larry

 

[Clumber]

Thanks to all who responded. Your responses was a great help in understanding the requirements.
I am going with using the PTO (8 GPMs) as the main drive circuit. Tim suggested that:
"So the hydraulic motors should be able to handle PTO outlet pressure. You don't need a high quality pressure regulator valve plus relief to keep from blowing it up. But you do need a diverter valve (or cheap bypass pressure regulator) to keep the blades moving at the right speed."
The nomenclature used here in the thread is somewhat different than product titles used in the catalogs. I am not confident of selecting the right "valve". I think that the thread concludes that all I need is a "flow regulator" that can reduce the PTO 8 GPM to 3.3 GPM. A separate or included "pressure regulator" is not needed.
Can anyone suggest a product that satisfies the requirement?