Bush hog vs. stump

Denna

Member
While mowing with a 2 blade bush hog, I ran over a hidden stump that hadn't been cut flush to the ground.

There was a loud metal banging noise, so I immediately shut down the tractor.

I figured one blade was stopped abruptly and the second blade, forced to pivot, swung and hit it.

I checked the underside of the bush hog and didn't see any obvious structural or blade damage.

I understand the blades are pushed out by centripetal force and wouldn't contact under normal usage unless the clutch is suddenly disengaged.

Is there something to check for damage ? How much vertical play should there be in the blades ? Currently, the blade that rests on top can be pushed up about 3 inches.


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The pins that the blades turn on are going to wear, allowing the play that you have. It doesn't bother anything except when you hit something the forces the blade up to hit the housing. Eventually you will need to replace the blades and when you do you will replace the pins. They are usually designed so that you can get at the top of the pin through a covered opening in the deck. Hitting something is not a big deal so long as your slip clutch is working.
 
You might want to turn that shaft by hand and see if it is bent. It looks like it just might be from the pics, it also might just be the angle of the sic. If it is OK then I would pull the blade bolts and check for wear. Other than that, flip the blade around to where it's supposed to be and start it up & see if there is any problem. Just my thoughts, Keith
 
The blades are going to have some up/down movement, the holes in the blades that they pivot on are not precise so there is going to be slop in them. That mower since I assume you bought it used it probably was already like that, and had been run for quite awhile that way.

BushHog vs a 2" diameter solid steel rod
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Keith, showcrop, Tx Jim and ptfarmer,

Thank you for your quick and detailed responses.

A fair amount of contortion was involved in getting a clear picture, so the camera and the mowing deck were at an angle.

I'll take a look at the shaft.

If it is the shaft, how much do they cost and how difficult are they to replace ?

Yes, the deck was purchased used, but was in use for the last year without a problem.

The origin of this problem is credited to the utility company that came out this spring and cut down several trees on the fence line. After they were done, I drove down the fence line and picked up the logs they didn't haul away. What I hadn't counted on was the number of four inch stumps they left behind. The Bahia and brush had grown over and I couldn't see them.

Perhaps we need tractors with sonar ?
 
Your bolts holding the blades on are wore some, that is not unusual. Be nice to replace them but a lot of hogs are run a lot more wore out.

Shiny stuff is what worries a person. I see some of the share and collar is shiny. I would be concerneded about the gearbox. That shaft shouldn?t be able to move very much at all - measured in thousandths. To see that much shiny there on the shaft, I would be concerned about the gearbox, not the blades.

Paul
 
Well, my pic didn?t show up. See if it?s here, otherwise zoom in on your first pic, the shaft. The shiny bit of shaft looks like a lot of play there 1/4 inch or more, which is not good.

Paul
 
(quoted from post at 04:40:04 11/22/18) Well, my pic didn?t show up. See if it?s here, otherwise zoom in on your first pic, the shaft. The shiny bit of shaft looks like a lot of play there 1/4 inch or more, which is not good.

Paul

Paul, I see that shiny part and it is perfectly normal for it to be shiny. That is part of your shaft seal and it is getting constantly shined by pieces of grass that rub on it for a second or two and are then flung off by the centrifugal force. The seal is held stationary in the bottom of the gear housing. The seal is the weak point of all of these rotary mowers because when you run over and pick up some wire or twine, it wraps around the shaft and shines the rubber lip of the seal right away. Your seal is apparently still good. If the shaft were bent oil would be oozing out past the seal. Your blades look very good too. The end corners are not worn off they have nearly square corners at the ends. The blades have very little "droop" to them relative to what I have seen on others indicating little wear at the pivot pins. If you would like to give it some TLC, and there is an access hole in the deck as I referred to in my other post, open it up and remove the nuts from the pivot pins, drop the blades pins and put a little grease on the shoulders of the pins so that when you do need to remove the blades it will be way easier.
 
I am surprised that there isn?t a stump jumper on that mower. My machine, a Bush Hog brand, has a large dish shaped thing underneath. I also use a chain top link, it allows the mower to move up, lessening the shock to the machine.
 
(quoted from post at 11:46:59 11/22/18) I am surprised that there isn?t a stump jumper on that mower. My machine, a Bush Hog brand, has a large dish shaped thing underneath. I also use a chain top link, it allows the mower to move up, lessening the shock to the machine.

I have a Woods M5 rotary mower that came with an 8N that I bought. I used that mower for years before I finally found out that I could buy a stump jumper for it from Messicks. Here's a pic of the stump jumper. It's made of some very heavy steel.

StumpJumper.jpg
 
(quoted from post at 07:47:49 11/21/18) The blades are going to have some up/down movement, the holes in the blades that they pivot on are not precise so there is going to be slop in them. That mower since I assume you bought it used it probably was already like that, and had been run for quite awhile that way.

BushHog vs a 2" diameter solid steel rod
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I'm surprised that new Rhino mower didn't have a stump jumper on it. That test wasn't a very fair one. When using a mower, you're driving forward, not lowering the mower down onto something. I'd like to see that test where they drive forward over that bar and the blade carrier hits that steel rod as would more likely happen in real life. I don't think the mower would come through that as well.

Or they could have just lowered the mower so that the blade carrier hit the rod.
 

The distance from the stump jumper and the underside of the deck is about 1 5/8" all the way around. From that you can say it's sitting reasonably plumb.

After separating the blades and swinging them apart, I took the deck out for some mowing and it worked as expected.

Perhaps the blades were locked together and the centripetal force hadn't push them apart yet.

The blades probably became locked when I disengaged the clutch before the driveshaft spun down to a complete halt causing one blade to swing forward and on top of the other blade.

For now, it's mowing.

Thanks for all the helpful comments.
 
(quoted from post at 01:05:48 11/29/18)
The distance from the stump jumper and the underside of the deck is about 1 5/8" all the way around. From that you can say it's sitting reasonably plumb.

After separating the blades and swinging them apart, I took the deck out for some mowing and it worked as expected.

Perhaps the blades were locked together and the centripetal force hadn't push them apart yet.

The blades probably became locked when I disengaged the clutch before the driveshaft spun down to a complete halt causing one blade to swing forward and on top of the other blade.

For now, it's mowing.

Thanks for all the helpful comments.

Denna, I have had the two blades of my mower jam together a number of times. It is just part of using a mower. I always release them manually. Waiting for the CENTRIFUGAL force to do it could cause other problems due to the substantial out of balance.
 

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