Bush Hog 286 vibration

[aaluck]

Recently I have noticed my well used bush hog has a rough start (wobble) at start up at idle speed and a very noticeable vibration at mowing speed. I have looked underneath and cannot see anything that seems obviously wrong. Everything seems to look fine. No leaks of oil, no funny noises or anything else.

I purchased it used with the tractor and have no idea if the blades are original.

Any ideas of what could be causing it to wobble hard at start up and vibrate at full speed? Any suggestions would be appreciated.

 

[UpNorthMI]

You may want to check a number of items:
1. Is there any oil in the gearbox. They normally have a fill port and a full level drain port where oil will run out when at the full level.
2. Stand overnight with paper below to see if oil leaks.
3. Can you easily turn the blades manually, is the operation smooth.
4. Safely inspect the unit from underneath (jack stands). Any play or wobble in rotation of stump jumper / blade assembly.
5. If all looks good, maybe is time for new blades, bent blades?
6. Are bolts between gearbox and main metal frame tight.
7. Inspect PTO shaft, bent? U joints?

Good luck with it.

 

[SidecarFlip]

Blades not of equal weight? Pull the blades and weigh them on a scale. Should be equal in weight and the pivot pins / bolts not sloppy.

 

[re54drider]

Recently I have noticed my well used bush hog has a rough start (wobble) at start up at idle speed and a very noticeable vibration at mowing speed. I have looked underneath and cannot see anything that seems obviously wrong. Everything seems to look fine. No leaks of oil, no funny noises or anything else.

I purchased it used with the tractor and have no idea if the blades are original.

Any ideas of what could be causing it to wobble hard at start up and vibrate at full speed? Any suggestions would be appreciated.

That kind of thing is indicative of either a bent shaft, PTO issues or blade(s) not properly rotating on the head.

Recently I have noticed my well used bush hog has a rough start (wobble) at start up at idle speed and a very noticeable vibration at mowing speed. I have looked underneath and cannot see anything that seems obviously wrong. Everything seems to look fine. No leaks of oil, no funny noises or anything else.

I purchased it used with the tractor and have no idea if the blades are original.

Any ideas of what could be causing it to wobble hard at start up and vibrate at full speed? Any suggestions would be appreciated.

Personally I would check the u-joints as mentioned above by upnorth. Gearbox could be crapping out as well. You don't mention how many hours are on this unit.

 

[aaluck]

Thanks for the insight. I think I can rule out PTO shaft problems as the shaft easily slides in and out the entire length and I doubt it would if it were bent. I can also rule out the oil level as I check that about every 3rd use.

I will try to jack it up and see if I can rotate as suggested and from there take off the blades and weigh. Hopefully its not a gear box issue but when I changed the oil I didn't see any evidence of metal shavings or the like.

As far as the age I really don't know. It was part of a used "package" with the tractor. So on that note I don't know if these are the original blades or not.

 

[SidecarFlip]

Betting on either the blades or the pivot bolts or both.

 

[Dave_eng]

Is the real shaft of the pto shaft a profile which can only go together one way?

Since you don't know the age of the cutter, I wonder about the phasing of the shaft.

Old equipment with square cross section pto shafts had a ball bearing pressed into the end of the inner shaft so the two halves could only go together one way.

If the shaft was shortened, this ball bearing indexing feature was lost and the two halves could be put together out of phase resulting in severe vibration.

If not this, then try without blades to see if things are improved.

Dave

 

[SidecarFlip]

At 540 shaft rotation speed, I don't think rotational harmonics would be an impact or at least very little. If it's a square drive shaft, just set the crosses at 180 degrees to each other when sliding the sections together.

 

[i7win7]

pto shaft out of time? Good demo video.

 

[Dave_eng]

At 540 shaft rotation speed, I don't think rotational harmonics would be an impact or at least very little. If it's a square drive shaft, just set the crosses at 180 degrees to each other when sliding the sections together.

You are wrong!

If the shaft has any degree of an angle on the U joints, the phasing vibration is strong.

Of course the fix is simple if and I repeat if, you recognize the importance of phasing which, with modern pto shafts, improper phasing has been engineered out of existence, so younger owners have no knowledge of nor experience with it.

Dave

 

[SidecarFlip]

Whatever Dave, all my pto driven implements (I have a lot) have never had a vibration issue but then I always make sure the angle of the dangle is as straight as possible. I bet his issue is one blade is heavier than the other or the pivot bolts are worn and the blades are sloppy on the pivots. Unbalance blades and worn pivots will impart vibration.

I keep forgetting that being an engineer like you supposedly are and being a Canadian, you are always right. I digreess to your infinite wisdom hallowed one.

Of course most of my bigger PTO implements have constant velocity double Cardan joints too.

 

[aaluck]

So I spun it yesterday by hand. When I wasn't holding the camera and used both hands it spun for about 10 seconds by itself after I quit and let it go. I did record it spinning it with one hand and it still spun for about 5 seconds or more.

I am going to attach the video as I'm not sure which shaft I have as discussed above. I believe it has to be the blades. (The banging noise is the other end flopping as it turns).

Flip, not to show my ignorance but where are the pivot bolts? I'm assuming thats what attaches the blades.

https://youtu.be/DE4Xg-dQT8o

 

[freewheel3]

Whatever Dave, all my pto driven implements (I have a lot) have never had a vibration issue but then I always make sure the angle of the dangle is as straight as possible. I bet his issue is one blade is heavier than the other or the pivot bolts are worn and the blades are sloppy on the pivots. Unbalance blades and worn pivots will impart vibration.

I keep forgetting that being an engineer like you supposedly are and being a Canadian, you are always right. I digreess to your infinite wisdom hallowed one.

Of course most of my bigger PTO implements have constant velocity double Cardan joints too.

Wow. Either have less coffee or more sugar there flip, you seem kind of bitter today.

 

[Russell King]

Pivot bolts are under the mower deck where the blades attach to the rotating bar (stump jumper?) and allow the blades to fold if they hit something.

 

[beckmurph]

As mentioned above: check your gearbox mounting bolts.
My Woods 48” loosen up and I have to snug them up about once a year.

 

[SidecarFlip]

So I spun it yesterday by hand. When I wasn't holding the camera and used both hands it spun for about 10 seconds by itself after I quit and let it go. I did record it spinning it with one hand and it still spun for about 5 seconds or more.

I am going to attach the video as I'm not sure which shaft I have as discussed above. I believe it has to be the blades. (The banging noise is the other end flopping as it turns).

Flip, not to show my ignorance but where are the pivot bolts? I'm assuming thats what attaches the blades.

https://youtu.be/DE4Xg-dQT8o

They do. My Landpride bat wing has rubber plugs on the top of the deck to access the nuts, yours may not. Takes a stout impact wrench to break them, be apprised of that.

 

[SidecarFlip]

Wow. Either have less coffee or more sugar there flip, you seem kind of bitter today.

I find his technical dissertations at times to be tedious and the dude is never wrong. Gets old after a while. Same deal on TbyNet. Encyclopedia of cut and paste knowledge.

My coffee was fine this morning, just like every morning, Half-Caff. Maybe working on the round baler frayed my nerves a bit. I'd post the issue on there but old Dave would have a cut and paste solution I'm sure.

 

[notforhire]

Every now and then when I start up my 286 it vibrates really bad, even with new blades. After shutting it down I do an inspection. Everything seems tight, so I swing the blades on their pivots, leaving them at an angle. Baffled I restart the mower, now everything is fine, zero vibration.
This happens usually on my first startup of the season.
My only explanation is that one or both blades stick a little at the pivots and don't fly out straight.

 

[GeoHorn]

Whatever Dave, all my pto driven implements (I have a lot) have never had a vibration issue but then I always make sure the angle of the dangle is as straight as possible. I bet his issue is one blade is heavier than the other or the pivot bolts are worn and the blades are sloppy on the pivots. Unbalance blades and worn pivots will impart vibration.

I keep forgetting that being an engineer like you supposedly are and being a Canadian, you are always right. I digreess to your infinite wisdom hallowed one.

Of course most of my bigger PTO implements have constant velocity double Cardan joints too.

There’s no reason to be dismissive of another’s effort to help, IMO. It’s unfriendly and discourages helpful ideas. Don’t like what someone posts? Post factual info that proves your point. Politely.

 

[SidecarFlip]

George... I stated what I have to say. At 70, I don't mince words anymore. Nicey-Nicey isn't part of my vocabulary.

It's the blades, or sloppy pivot bolts, not the driveshaft anyway, not that the driveshaft in the picture is safe, far from it with no shielding whatsoever. That is an entanglement accident waiting to happen. Lots of people do that because shielding is a PITA until someone gets hurt or killed. No, non enclosed pto shafts on this farm