Need Hydraulic Motor Advice for Stump Grinder

[woodlandfarms]

So I need some advice...

I am going to try and build a stump grinder this spring. It will be a quasi direct drive (probably a lovejoy or mesh chain style connector). The disk will around 20 to 24"

My tractor is 18GPM at 3000PSI full tilt

I am looking at surplus center and I am getting very, very confused. I need a sturdy motor that is going to give me 1000RPM at 18GPM. I am figuring I won't be running my tractor full tilt, as 800 RPM seems to be the standard disk speed on a 24" disk.

If anyone can guide me, or help me figure out what i am looking for? I see motors that are 1500RPM at 30 gallons but, well, Help?

 

[J_J]

Carl,

A 5 cu in hyd motor will run at 832 rpm using your 18 GPM, and 3000 psi, will develop about 2,389 in lbs.

If you use a larger displacement hyd motor, like your wheel motor, it will run slower, but have more torque.

 

[woodlandfarms]

So continuing.

I am looking at the 4.5 cu series. None are rated to 3000 psi. Most ash ow peak at 2500.

Second. Why do the prices vary so widely?

Just saw this.... Intersted as it claims to be beefy but worried about speed

4.92 cu in CHAR-LYNN 104-1001 NP NICKEL PLATED HYDRAULIC MOTOR

 

[J_J]

That hyd motor looks to be close to what you want.

Prices vary due to the bidding surplus has to bid on the old stock from manufacturers.

They only have 1 left on this motor.

Are you going to drive it directly or belt/pulley. You could increase the speed using belt and pulley.

 

[oldnslo]

woodland,
I would suggest you look at factory made stump cutters to see what types of motors they are using. This is a very abusive high shock duty and your standard run of the mill motors may not survive very well. Most of the stump cutters I have seen on rental lots all use either a bent axis piston motor or a gear box and axial piston motor.

If you are planing to mount the cutter wheel direct to the motor shaft it will also have to be able to handle the side thrust from the cutter hitting the stump and then sweeping across the face.

 

[juddspaintballs]

Speed, sharp cutter teeth, and small bites are your friend when it comes to grinding stumps. Lots of cutter teeth are not ideal and slow down the recovery time of your cutter wheel. Hydraulic stump grinders usually cannot compete with an engine driven grinder for speed. There are stump grinder attachments for skid loaders that actually use a separate engine to drive the grinder as opposed to using hydraulics. I would seriously consider one of those before spending money on building a hydraulic unit with lackluster performance.

 

[J_J]

HP is HP, is that correct?

Then the HP developed by a hyd motor would be the same force generated by an engine.

How about electrical HP, is it the same force.

 

[juddspaintballs]

Horsepower is the same, sure. The hydraulic motor might even have torque on an engine, but recovery speed is another story. There's a reason commercial stump grinders are almost all engine driven until you get into the very large machinery and even they don't do as well as a purpose built machine.

For comparison, our small stump grinder spins it's 14" cutter wheel at 3000 RPM at full tilt and our larger tow behind with 24" cutter wheel spins it at 2000 RPM.

Speed is your friend.

 

[CJONE]

If you are going to direct drive it I would use a piston motor like was suggested or a vane type motor. Forestry equipment uses vane type on hotsaws all the time and they live a hard life. Obviously mount the head on a bearing supported shaft and couple the motor with a chain coupler. You have about 30 HP available at the motor once it is sized correctly for rpm.

 

[CJONE]

Horsepower is the same, sure. The hydraulic motor might even have torque on an engine, but recovery speed is another story. There's a reason commercial stump grinders are almost all engine driven until you get into the very large machinery and even they don't do as well as a purpose built machine.

For comparison, our small stump grinder spins it's 14" cutter wheel at 3000 RPM at full tilt and our larger tow behind with 24" cutter wheel spins it at 2000 RPM.

Speed is your friend.

They are engine driven usually with belts [to cushion shock and get desired rpm] because of cost, nothing more. If he has hydraulics already why would he spend the extra $$ for a engine package? The recovery speed would be the same or better with hydraulics because torque is always there unlike a gas engine when the rpms drop. With geroller motors he is talking about they have torque at very low rpms just like a vane motor. CJ