broken stump grinder

[washita]

yesterday I was clearing out trees most averaging 4-6'' diameter when the grinder made a unusual sound pulled back and the grinding wheel/with motor shaft was leaning against the stump does anyone know the specifications on the motor? the shaft the hub was mounted to twisted off inside the motor, did not bend it, just glad it did not go freewheeling into the next county

 

[SimS]

Make? Model? This post needs pictures of the carnage.

SimS

 

[J_J]

yesterday I was clearing out trees most averaging 4-6'' diameter when the grinder made a unusual sound pulled back and the grinding wheel/with motor shaft was leaning against the stump does anyone know the specifications on the motor? the shaft the hub was mounted to twisted off inside the motor, did not bend it, just glad it did not go freewheeling into the next county

Did you perhaps stall out the hyd motor several times before that happened.

If the relief is not working in that circuit, and you were grinding real hard, and the wheel stopped suddenly, then it is possible that the motor could twist the shaft off.

Did the engine labor any more than mormal.

 

[washita]

I might have around 5-6 hours on the stump grinder I will have to look at the model but it is the one that was sized for the 425 tractor the motor did not stall anymore than typical actually it did not stall the motor it just simply twisted off the hollow pipe/tube that the hub and cutting disk was bolted to the break is at roughly 15-20 degree angle of a 90 degree shear typically seen when a shaft twists off I will take pictures and post them, now since the heat of the moment is over, and the thinking is a clearer, if powertrac does stand behind it I will rebuild it myself and make it so the cutting disk cannot escape and injure somone, I feel that the stump grinder is a indispensible tool to have

 

[J_J]

wa****a. Doesn't your hydraulic motor have solid taper shaft, and held on by a large nut and pin? I can't imagine a 1 1/4 in shaft twisting off. Pictures please. Does your stump grinder look like this, or does it have the bolt on blade? The second picture shows the wheel that can be turned around. Does anyone have a price on the wheel and hub?

 

[washita]

pictures looks like potmetal to me whats your opinion

 

[washita]

before any one asks the bolts on the teeth are not original I had problems with the bolts stretching and the nuts backing off so after a trip to my local bolt supplier I now have grade 8 bolts and metal locking nuts on the teeth only drawback is if I change teeth the bolts will have to be replaced they are not reusable I was informed that was a common upgrade locally the local sharpening center also claims to sharpen the top of the teeth also in a wedge shape I have not done that modification yet but might in the future but first to fix the motor issue 4 acres of stumps to grind

 

[J_J]

Well, that is a first for me. I haven't heard about or seen anything like this before. Do you think the wheel/teeth assemble might be out of balance. The only support for that shaft would be at the bearing, and the longevity would depend on how the stump grinder was used. Are you going to rebuild it or purchase a new motor? I didn't know those shafts were hollow either.

 

[washita]

my train of thought for now is 1 check to see if the wheel is balanced 2 replace motor with additional bearing support on shaft 3 move cutting wheel away from motor with bearing support on each side of it 4 make it belt drive/cogged like on a car motor 5 build it so wheel cannot escape if a bearing would fail 6 call terry at tazewell and see what they can do for me, good, bad, otherwise 7 research some other stump grinders to see what they have designed into their machines, bearing size, drive system, fpm of cutting wheel, etc. etc.

 

[washita]

most trees I grind out are either pine or 4-6'' saplings and muliflower rose, only removed one hardwood stump and it was a sugar maple, so I do not feel that I am overworking the grinder

 

[J_J]

When you get the new motor installed, just run it at maximum, and you will know by the vibration, if any.

IMHO, my observation is, that you have an unbalanced wheel. The nuts plus washer, gives more weight to that side.

 

[toy]

pictures looks like potmetal to me whats your opinion

Is it possible that the shaft that is on the hub of the grinder blade may have had a roll pin in it located just where it twisted off. The roll pin would have been driven in through that shaft and into the motor shaft to hold it on. If it wasn't put in or put in improperly that would have caused it to shear and as the blade worked itself off it egg shaped the the remainder of the blade shaft?

 

[J_J]

Toy,

He said that it broke/sheared off inside the motor, almost like something came to a sudden stop. What do you think would happen if some one flipped the switch on the PTO when the stump cutter blade was up to full rpm. That should be a motor spool valve.

 

[MossRoad]

Toy,

He said that it broke/sheared off inside the motor, almost like something came to a sudden stop. What do you think would happen if some one flipped the switch on the PTO when the stump cutter blade was up to full rpm. That should be a motor spool valve.

That would let the motor and blade freewheel when the valve was turned off, but would not prevent damage if the blade was stuck and the valve turned on, would it?

 

[J_J]

That would let the motor and blade freewheel when the valve was turned off, but would not prevent damage if the blade was stuck and the valve turned on, would it?

David, That is the way it is supposed to work, but if something did not function correctly, then maybe. I can see someone dropping the stump cutter suddenly and it twisting off. Maybe. With the heavier nuts on one side, the balance should have been off somewhat.

If the blade is down in the stump, and you started the motor, it should go to relief when the relief pressure rating is reached.

 

[washita]

checked balance of cutting wheel today, it is balanced equal amount of nuts on both sides of blade, short of putting it on a car style tire balancer all indications is that it is ok, not sure what inside the motor retains the broken shaft ( still a piece of hollow shaft in the motor), when the pto is shut off at full rpms the wheel normally makes a couple of revolutions before stopping, wheel was not jammed or stuck when the cutting wheel exited stage left, called terry this morning, he claimed to not seen that type of failure before and was wondering if it was a manufactures defect, will send motor and shaft to tazewell at next opportunity, he claimed that even when you stall a grinder the pressure relief normally protects the motor, train of thought now is to support cutting wheel on its own set of bearings with a belt drive, plus add another steel disk to increase the mass of the cutting wheel, plus a overrun clutch on the motor. I miss the old days a stick of dynamite =no stump

 

[J_J]

wa****a, not sure what inside the motor retains the broken shaft ( still a piece of hollow shaft in the motor),



I believe that there is a gear on the end of the shaft.

 

[ponytug]

Ahh.. the old days, the smell of dynamite, the stones and tree parts whistling through the air... Nothing quite like watching a three foot long hunk of solid oak frisbeeing through the air at breakneck speed. It was certainly fast. I think that I was always around amateurs, because it seemed like the charges tend to send stuff up and out, rather than down and in.

Then there was the time a distant relation tried to break up an ice dam on the river before the ice pushed the bridge piling down river. The family story goes as follows;
Picture the potbellied stove, the highway crew clustered around it drinking coffee warming up on a cold winter day. Someone comes running in and says "There's an ice dam out on county G and it looks like its going to take out the bridge!" They call their buddies at the neighboring highway crews, because this is going to be fun. Everyone drives out to the ice dam, caucuses for a bit and they decide to dynamite the ice dam. All according to plan.

Guy hikes on on the ice, plants a stick of dynamite at the down river center of the ice dam, lights the fuse and runs for shore. Just as he makes it to shore...
bang, water spouts, ice flying, but, ...ice dam still intact.
"Ahah" says someone "it's freezing out here, let's just put a case out there, and get it done."...Guys drag out a case, plant it on the ice, light the fuse, longer this time, and run for shore. Cue music, and then watch in horror as the ice starts shifting and moving and the case of dynamite slowly moves down river...How far?
You guessed it, right under the bridge. BOOM!!!

Neighbors who hadn't watched it happened wondered why highway crews from three counties were working on the repair...

Ahh, yes the good old days... Brings a smile to my face, just thinking about it.

Looking at your photos, and I am no expert, it looks to me like a manufacturing defect, do to the erratic nature and granulated look of the break. Good luck on the repair. I hope PT/the manufacturer come up with something.

All the best,

Peter

 

[RegL]

Think ya used enough dynamite there Butch?
TURNER CLASSIC MOVIES

 

[MossRoad]

Think ya used enough dynamite there Butch?
TURNER CLASSIC MOVIES

Ahahahhaaaaaahhahahahaaa!!!

Oh, man! I forgot about that. Thanks for the laugh.