Hydraulic Chainsaw

[hounddog74]

Can anyone tell me how to size a hydraulic motor to replace a 8.7 hp 191 cc gas engine? I want to convert a portable chainsaw sawmill to hydraulic power and drive the pump with a twin cylinder engine. Any discussion or help would be appreciated.

 

[kubotakid USA]

Can anyone tell me how to size a hydraulic motor to replace a 8.7 hp 191 cc gas engine? I want to convert a portable chainsaw sawmill to hydraulic power and drive the pump with a twin cylinder engine. Any discussion or help would be appreciated,.. GOOGLE, your (Best friend) will give you pages of imfo,.. type in (hydraulic chain saw motor), Eric

 

[Don87]

Can anyone tell me how to size a hydraulic motor to replace a 8.7 hp 191 cc gas engine? I want to convert a portable chainsaw sawmill to hydraulic power and drive the pump with a twin cylinder engine. Any discussion or help would be appreciated,.. GOOGLE, your (Best friend) will give you pages of imfo,.. type in (hydraulic chain saw motor), Eric

The 'hydraulics' forum here on TBN would give fast results also, and may be friendlier.

 

[jbooth]

This site might furnish some ideas or even parts for your build.


Basic Saw

 

[oldnslo]

Can anyone tell me how to size a hydraulic motor to replace a 8.7 hp 191 cc gas engine? I want to convert a portable chainsaw sawmill to hydraulic power and drive the pump with a twin cylinder engine. Any discussion or help would be appreciated.

A couple of things you will need to know to size of pump and motor is.

What speed do you want the saw motor to operate at and what torque?

Knowing this will provide a starting point for figuring motor size and then pump size, etc..

Roy

 

[hounddog74]

The specs on the original 8.7 hp motor say 9000 rpm and I assume thats with no load. I know they make bucksaws that are hydraulic but I haven't been able to find out what the rpm's are or what the torque is.

 

[oldnslo]

The only style of motor I can think of that might run close to 9000 RPM is bent axis piston. These are usually rated for high pressure (5000 PSI or higher) operation so they are fairly expensive. I do not know of any gear or vane type motors that will operate at that speed. Possibly AKKAMAN will chime in since I believe he used to work on and around logging equipment.

Roy

 

[hounddog74]

The gasoline motor runs 9000 rpm. I'm not sure what speed the hydraulic motor would have to run but I'm thinking it would have to be less than that.

 

[oldnslo]

If my math is correct:

8.7 HP at 9000 RPM is around 60 in-lbs of torque.

8.7 HP at 7000 RPM is 78 in-lbs of torque

To generate 78 in-lbs of torque at 2500 PSI requires the use of a 0.2 CIR (Cubic Inch Revolution) or 3.23 cc/rev hydraulic motor. This torque can be generated at speeds from min to max RPM rating of the motor.

If we figure the 0.2 CIR motor operating at 7000 RPM your theorectical inlet flow would be. 7000 RPM x 0.2 CIR / 231 = 6.06 GPM

6.06 GPM x 2500 PSI /1714 = 8.75 HP theorectical input HP to drive the pump.

Now throw in hydraulic inefficency.

Figure the hydraulic motor at 90% efficient which is a good motor so inlet flow becomes 6.06 x 1.1 = 6.7 GPM required to keep the motor running at full load conditions.

Figure the pump at 90 % efficient which again is a good pump and your pump size becomes 6.7 x 1.1 = 7.4 GPM

now 7.4 GPM x 2500 PSI / 1714 = 10.8 HP to drive the hydraulic pump.

Do these numbers make sense and help give you some idea of component sizing required?

Roy

 

[hounddog74]

That's wonderful! Thank you. That's what I have been trying to figure out.