brush hog shaking

[coldstream]

I've got a 5' brush hog don't know the brand it's beat up and I bought it used for almost nothing. I've used it for 2 or 3 years and it's always shaken a little bit but when using it yesterday the shaking has really picked up. I crawled under and made sure the 'hinge' points on the blades are free and they are though it does take some effort to 'swing' each blade. Should I lube the blade 'hinge' points? The gearbox does leak but I'm pretty good at keeping 90wt in it. Any suggestions? Thanks - Coldstream

 

[psj12]

take the blades off and check to see if they actually weigh the same. Sometimes when one is damaged it will be replaced with a similar aftermarket blade od a different weight. Also check to make sure your drive shaft is not bent.

 

[HarryN]

When you take the blades off, do sharpen them and like psj12 said, make sure they weigh very close to the same. Not quite as critical as a lawn mower blade but need to be pretty close.
And, YES, lube up the pivots good. Which allows the blades the ability to easily straighten out during rotation.
If that does not solve the vibration problem then I'd be looking at the gear housing, shaft, etc next.....

 

[Bird]

As psj12 said, the weight of each blade should be the same or very close, but to answer your other question, those blades should swing quite freely, so I'd want to know why they don't.

 

[ssls6]

I've got a 5' brush hog don't know the brand it's beat up and I bought it used for almost nothing. I've used it for 2 or 3 years and it's always shaken a little bit but when using it yesterday the shaking has really picked up. I crawled under and made sure the 'hinge' points on the blades are free and they are though it does take some effort to 'swing' each blade. Should I lube the blade 'hinge' points? The gearbox does leak but I'm pretty good at keeping 90wt in it. Any suggestions? Thanks - Coldstream

Something is out of balance…could be a blade, u-joint is bad, or the gearbox. Start with the easy stuff.

 

[Oaktree]

If it was a balance problem, why would it have gotten worse? Almost sounds like a bearing in the gearbox...of course not to say that an imbalance wasn't the cause of the bearing failure.

 

[Soundguy]

blades should swing freely.

don't lube the pivots. it will attract dirt and become a grinding compound. those bld bolts should be shouldered and only tighten to captur ehe blade. check for strings and grass int he blad pivot area.

also check that the stump jumpe ris not loose ont he output shaft. measure each blad and see if it is close in shape / size ( if you don't take them off and weight..e tc. )

stump jumper look bent?


if the gearbox leaks a lil.. when you top off with 90w.. try 85/140 instead and put in a few shots of #2 gun grease at each top up. makes it thicker and less likley to leak.

 

[ssls6]

If it was a balance problem, why would it have gotten worse? Almost sounds like a bearing in the gearbox...of course not to say that an imbalance wasn't the cause of the bearing failure.

A bad ujoint can throw a shaft out of balance. rpm*out of balance = shake. Like I said, could be ujoints, bearings, blades. I would also check the attachment points. The shake may be worse from a loose implement.

 

[coldstream]

Thanks guys for all of the input. I will check it out and report back.

 

[coldstream]

I wanted to wrap this issue up, might help somebody in the future. Based on the suggestions here I mounted the mower and got under it (with jack stands as a safety back up). The blades would pivot but they were rather stiff. A lot of old grass and debris had worked it's way into the pivots. After some scraping with a putty knife and screwdriver and a shot of knock er loose they were swinging very freely. I saw no noticeable damage to the stump jumper or the blades. I then topped off the gear case with 85/140 and lubricated the u-joints (which looked to be in good shape. This thing runs smooth as glass now. It's like having a new mower! Thanks guys! Coldstream