Stump Grinder Build

[J_J]

Look at the specs for hyd stump cutter SG-26H .

Uses a gear box.

If you don't have the torque on every sweep of the cutter head, the rpm will probably drop off to stall speed. At the end of the sweep, the rpm will try and recover.

I am thinking you are on the very low end for torque and HP with your selection.

You can probably cut slow and get the job done, but is that what you want?


Yahoo! - 301 Moved Permanently

 

[hddnis]

BaumaLight - S14 Skid Steer Stump Blaster Model - Stump Grinder



Mr. HE

 

[woodlandfarms]

HDDNIS. You own this one? I am basically doing a S18 rip

 

[hddnis]

HDDNIS. You own this one? I am basically doing a S18 rip

No, don't own one, just posted because it had an easy to read specifications list that showed your design was on track with a commercial unit.




Mr. HE

 

[Renze]

Anyways, the surge valve is a good idea. At my previous employer we allways put a surge valve in the hydrauic fan drive, because the inertia winds it up to way past system pressure, lots of these motors burst when we first started hydrostatic fan drives. When the inertia is built up (hydraulic valve is engaged) the system is connected to the pump relief valve to blow off some while bringing the mass up to speed. When you shut it off, the system has to do the same thing but with the relief valve on the other side of the valve block, so the pressure is limited only by the integrity of the components themself.

 

[oldnslo]

Agree with the spinning mass theory but it takes torque / HP to keep the mass spinning under load.

If using quick disconnect on both pressure and tank lines I would suggest measuring your tank line pressure. As you most likely know, hydraulic motor torque is a function of the pressure drop across the motor. Since your machine is designed to be hydraulic drive the OEM hopefully sized everything to reduce system losses.

 

[J_J]

Your pump takes about 37 HP to develop the 18 GPM at 3000 psi, so the hyd motor HP at about 85% efficiency will develop about 31.45 HP. Torque developed will about 183 ft lbs.

I still think that is low torque as I see other stump grinders at 800 ft lbs and up.

More torque means more work being done.

 

[woodlandfarms]

JJ. Do you have a link to these? What I understand is that stump grinder designers tried and failed a bunch of times to make step up stump grinders (Meaning the hyd motor drives a gear box or belt to the wheel) and that in the end direct drive proved to be the best method.

 

[J_J]

WOSG-25H Skid Steer Loader Mounted Stump Grinder

STUMP GRINDER - SKID STEER MOUNT

40 gpm in a 30 cu in hyd motor has an rpm of 308 if driven directly.

Torque developed by the motor at 3000 psi = 1194 ft lbs

A gearbox will provide increased rpm, but lower torque.

a 2:1 gearbox would give you 616 rpm and 597 ft lbs or torque.

In order to get the 900 rpm, you need a combination of GPM to cu in.

More GPM more speed, or smaller cu in.

You then have to consider the HP required to run the pump.

In your situation, you have an 18 GPM fixed pump, and a potential of 3000 psi.

As I said above, you hyd motor can develop about 31 HP with a torque of 183 ft lbs.

I have a small stump driven by a 13 HP engine and has 4 teeth on the cutter wheel.

The wheel is spinning at about 1800 rpm, and takes a long time to cut stumps.

I also have the stump grinder/trencher by PT . It will slowly grind stumps, but does not have enough torque.

With what you have, you can grind stumps, but. It just might be what you want, who knows.

 

[woodlandfarms]

So JJ. Great stuff.

But looking at the first stump grinder, the WOSG. essentially it is a conventional PTO driven stump grinder with a pump motor that runs at 540RPM. The gear box is a gives the wheel an uptick of 1.5 so the top speed is 800 RPM.

Granted a 540RPM motor is going to have a bit more HP, but when gearing it up, aren't you loosing that energy? The most energy you can make from a motor is from direct drive. You an increase torque by gearing a motor to but...

What I am getting at is that why Hydraulics, either direct driving a motor that creates 800 RPM or getting one to make 800 RPM by running it through a step up gear still creates the same amount of HP and Torque.
Or am I missing something

Also, 8K for these stump grinders. But that is not really part of our conversation.

 

[woodlandfarms]

Just got off the phone with my Tractor Manufacturer....

He informs me that my hydrualic circuit has a relief valve built into it so no need for a relief valve across the motor (This assumes that my motor is rated at the full PSI which it is, if I had a 1000PSI motor then I would put a relief valve in).

 

[PapaPerk]

Subscribed. Interesting project. You need to have a good safety plan for when stuff fails. That wheel at 800 rpm will have tons of kinetic energy!

 

[woodlandfarms]

Nope, no safety plan in place other than jump out of the way... It is spinning sideways to me, not that that means anything but I have examined ways of failure and it does not appear it will hit the tractor (well, it would take a lot).

Oh, got my wheel from the machine shop.

 

[PapaPerk]

Nope, no safety plan in place other than jump out of the way... It is spinning sideways to me, not that that means anything but I have examined ways of failure and it does not appear it will hit the tractor (well, it would take a lot).

Oh, got my wheel from the machine shop.

What steel did you use for cutter wheel? Looks nice.

 

[woodlandfarms]

Just regular soft. I was on the phone with the teeth manufacturer thinking this wheel needed to be 1" thick and blah blah blah. He said "Nope, normal steel, 1/2" is overkill for 35HP"

Again, we will see. I am stealing from other designs so who the heck knows.

 

[tkappeler]

How are you going to balance the wheel of death before running it up to speed? Or is it not necessary?

 

[woodlandfarms]

As I understand it, it you should be pretty close. Some people don't do it at all. I had the guys at the machine shop run it and it was pretty true (they laser cut it and then honed it).

 

[J_J]

Just got off the phone with my Tractor Manufacturer....

He informs me that my hydrualic circuit has a relief valve built into it so no need for a relief valve across the motor (This assumes that my motor is rated at the full PSI which it is, if I had a 1000PSI motor then I would put a relief valve in).

You might ask Terry this.

Is your PTO relief valve designed to protect the pump or the motor circuit when you shut the solenoid off?

If your PTO valve is a motor spool valve, then no problem.

 

[woodlandfarms]

According to Terry, both. In looking at the control block, there is 2 pressure relief valves and the PTO solenoid.

 

[PapaPerk]

Just regular soft. I was on the phone with the teeth manufacturer thinking this wheel needed to be 1" thick and blah blah blah. He said "Nope, normal steel, 1/2" is overkill for 35HP"

Again, we will see. I am stealing from other designs so who the heck knows.

It looks like cold roll... Maybe 1045? Doesn't look like hot roll structural steel.