Stump Grinder Build

woodlandfarms · Jul 9, 2014

So I have been playing with the idea of a stump grinder for a number of years. The issues are cost for a new one (3 to 7K depending on how you go) or getting lucky with a used one. My tractor is fully hydraulic (like a skid steer) so it limits me on where to purchase one.

This all said, I finally had enough saved up to build my own. I am no engineer, and this has the wife in complete fits. the spinning wheel of death is her assumption.

Anyway, so this is the start of it. I am happy to take notes, but pretty set in my design. I think will compete the project in the next two weeks.

The implement is based on 6" C channel and Ship Channel. The wheel is custom made 20" with Green Teeth cutters. It is driven by a 4.6 cu motor turning at 800RPM based on my 18 GPM/3000PSI PTO circuit. The wheel runs sideways. Meaning you roll forward and back for the cut, you do not turn.

Costs to date
120 for the C Channel - Attach plate already exists but if you bought, add another $50.
160 for the motor (Surplus Center)
60 for the shaft (Ebay)
70 for the pillow blocks (Ebay)
350 for the green teeth (Kinda Ebay)
320 for the spinning wheel of death (This is being machined for me)
70 for the Love Joys (Ebay)
30 for the hub (Ebay)
250 for hoses and connectors (OUCH) I never budget correctly for these. (Local Hydraulic store)
50 for odds and ends so far (bolts, drill bits).
75 for poorly purchased parts (motor mount and hub for wheel)

Not included is the new plasma cutter and welder

J_J · Jul 9, 2014

Are you going to do yours like this video, or off the side of the bucket?

https://www.youtube.com/watch?v=GlA-NKNzmLc

I would suggest to use joystick tilt also with front and back movement.

oldnslo · Jul 9, 2014

No mechanical engineer either but hope your pillow block bearings will take the radial thrust load of shoving the wheel of death into the stump.

Be sure to allow some form of safety run down protection for the wheel of death when you shut it off. I don't have a clue on if there is some "standard" time in which it is supposed to stop but a 20" wheel at 800 RPM has some serious inertia.

best wishes on getting this build and in operation

J_J · Jul 9, 2014

His PTO solenoid is an on off setup.

I would suggest a relief valve across the motor.

MossRoad · Jul 9, 2014

I take it the spinning wheel of death will go on the shaft between the pillow blocks inside the rectangular box at the right end and the motor to the left bhy the lovejoy?

To echo the concerns of the above.... I would have put the shaft THROUGH the steel and used bearings on each side rather than pillow blocks. If the pillow block casting fails, there's nothing to contain the shaft other than the other pillow block. At least if its through steel, that MAY contain it a bit longer should the bearing or bearing holder fail. I'm not an engineer, but I did sleep at a Holiday Inn one night a few weeks ago. :laughing:

Good luck with your project. Scary scary project.

downsizingnow48 · Jul 9, 2014

I'm not an engineer either. Pillow blocks are rated by the manufacturer for dynamic load and RPM so an appropriate version can be selected for a specific application. Most are for relatively tame applications (eg blower fan), but some are designed to handle severe shock loads and heavy vibration. The 20" wheel of death will have plenty of that. Will the grinding motion be up and down or sideways? Pillow blocks will not be happy with much in the way of bending or axial forces.

woodlandfarms · Jul 10, 2014

J_J said:
Are you going to do yours like this video, or off the side of the bucket?

https://www.youtube.com/watch?v=GlA-NKNzmLc

I would suggest to use joystick tilt also with front and back movement.

Yeah, saw this a couple of years ago. Yes, like his.

woodlandfarms · Jul 10, 2014

J_J said:
His PTO solenoid is an on off setup.

I would suggest a relief valve across the motor.

JJ. I have considered the relief on the motor, but I don't think I need one. The PTO Circuit should cover this as Power Trac has designed. My mower does not have a relief valve on it. What am I missing?

woodlandfarms · Jul 10, 2014

So..... The Pillow Blocks. I don't disagree with any of your concerns. But pretty much every design I see uses Pillow Blocks. I asked the manufacturer when I bought them and they pointed me to these, with thick webs and the legs are fully cast. In looking at other versions, the part that goes around the bearing was thinner, especially toward the foot (the part that connects to the steel bars). Also, the foot is solid. The thinner version the feet are open to save on steel cost.

Does this mean I got the right ones? Nope. Does this scare me, given I am a filmmaker and not an engineer, and have no clue about Hydraulics? Eyup.

Keep it coming guys.

Oh, if I feel the Pillow Blocks are not going to survive, I planned for the use of blocked bearings. It would take a new motor mount, but I have enough room on the 6" C Channel to fit a new bearing in if it needs to happen.

I mixed my design from downloads taken from Baumalight and Rayco. Rayco loves pillow blocks.

Tor Arne · Jul 10, 2014

woodlandfarms said:
JJ. I have considered the relief on the motor, but I don't think I need one. The PTO Circuit should cover this as Power Trac has designed. My mower does not have a relief valve on it. What am I missing?

A lot of flywheel effect, I'd install a check valve between the hoses to the engine so it can freewheel down to stop.

J_J · Jul 10, 2014

woodlandfarms said:
JJ. I have considered the relief on the motor, but I don't think I need one. The PTO Circuit should cover this as Power Trac has designed. My mower does not have a relief valve on it. What am I missing?

Carl,

You may very well be right. It could have a motor spool valve on it, and if it does not, you will need a relief valve.

A hyd gage in a tee and plugged into the PTO circuit will tell.

Maybe your brush hog has a relief valve on it. How long does your brush hog take to spin down.

chopped · Jul 10, 2014

Not to derail but to simply show what can be done.
https://www.youtube.com/watch?v=hfdTe6VoThU

woodlandfarms · Jul 10, 2014

No derailment. I watched this. I don't have the guys tools so I had to farm mine out to the local machine shop. And his skill set with metal is so much higher than mine.

woodlandfarms · Jul 10, 2014

JJ. I will call Terry and inquire with him. Bush Hog takes a long time to wind down.

muddstopper · Jul 10, 2014

I believe your lovejoy couplings will fail before the bearing. Stump grinders experience a lot of shock loads, lovejoys dont absorb shock very well

whis · Jul 10, 2014

I agree on the lovejoy's and also don't think the pump is big enough. it might work but its gonna be slow

woodlandfarms · Jul 12, 2014

Lovejoys are standard with these hydraulic systems (I have been researching the heck out of them) I don't disagree with your assessment but I found no other alternative that would work.

The motor is suposedly correct based on other designs. 800 RPM with my 18gpm and 3000 PSI. It physically is very small. I thought it would be a lot bigger. I am prepared for failure and have set up the motor mount to adjust if need be. 800 RPM seems to be the hydraulic speed of choice.

I don't know if the motor has bypass, but I think my PTO circuit does. I mean my mower shuts off and winds down. I may be wrong, but can't call until tuesday.

Machine shop finished the wheel but I am in Canada until tuesday... :-(

J_J · Jul 12, 2014

Don't know why he said your pump was not big enough. 18 GPM at 3000 psi.

I think motor rpm is a bit high, and the torque is only only 183 ft lbs.

I would suggest going through a planetary converter of about 5 to 1, and that will drop the speed to about 160 rpm, but up the torque to about 915 ft lbs.

muddstopper · Jul 12, 2014

woodlandfarms said:
Lovejoys are standard with these hydraulic systems (I have been researching the heck out of them) I don't disagree with your assessment but I found no other alternative that would work.
-(

Your lovejoys look to be a size L, hard to say for sure with pics. The stumpgrinder attachment I own uses belts between a gear box and the grinding wheel. The belts absorb shock. I use a type L lovejoy to couple the hydraulic pump between my engine and pump on my wood splitter. Just a visual observation, but I dont believe a type L coupling will standup to the abuse of a stumpgrinder, if used to direct couple the hyd motor to the cutter wheel. There are other types of lovejoys that might handle the abuse. I dont know the type number, but there is a lovejoy spider coupling that uses two spiders encased inside a collar. The shaft ends look similar to the coupling that you are currently using, but the collar is made to accept a spider on each end and goes between the two shaft ends. There is also a chain type coupling that uses roller chain to connect the two halfs of the coupling that I believe would be a better choice to connect your hyd motor direct to the cutter wheel shaft. A collar is also available for the chain coupling to protect the roller chain from dirt and to contain grease for lubing the chain.
https://www.google.com/search?q=cha...tlanticbearings.co.uk%2Fcouplings.htm;357;358
KTR - ROTEX - Torsionally flexible coupling - Double flange design AFN

woodlandfarms · Jul 13, 2014

I love the opinions and insight, really. I copied my design from both Bauma and the other major manufacturers. This is basically my parts list (I ordered similar of everything, cobbled together off of craigslist). As you can see, L series. I don't argue your guys assessment. I have yet to find anyone who owns this Bauma (hydraulic). I do know that the Hydraulic versions are all direct drive. You loose too much through belts and gearing to make it work. According to green teeth, grinding is about spinning mass and HP is not as important.

This is the motor I got

4.75 cu in DYNAMIC BMRS80H4KS HYD MOTOR