Bush hog breaking shear pins

   / Bush hog breaking shear pins #1  
J

Jason280

Bronze Member
Joined
Apr 17, 2012
Messages
95
Location
Ga
Tractor
Kubota L4330
I'm trying to troubleshoot an odd problem with a Land Pride bush hog, which keeps breaking shear pins. The bush hog has clearly been abused, and based on some of the dents on the front, has definitely hit a few stumps, rocks, etc. Now, I've never used this bush hog before, so I have no idea how well it functioned prior to me working on it.

I pulled the gear box cover, and the pinion gear looks good...oil is clean, no debris, and no chipped teeth. I can rotate it fully by hand, and rotation is smooth with no binding. The blades swing out correctly under centrifugal force, with no wobbling I can tell. I replaced the shear pin with a grade 2 bolt, and tried behind a Ford 3930. The bush hog made a lot of racket, didn't seem balanced, and promptly sheared the pin. Back to the drawing board.

I went through everything I could think of again, and replaced the pin with another grade 2 bolt. Rotated everything by hand, inspected the blades to ensure one didn't appear unbalanced, and tried again. Made the same racket initially, but smoothed out with no excess vibration. I tried it cutting some grass, bottomed it out a little on a hill of dirt, and again sheared the pin. Now, I have two different bush hogs that I have used for years behind a couple Kubota tractors, and have never sheared a pin...and that's occasionally hitting stuff that would shake the whole tractor. Basically, I am not sure what's going on with this one.

One thing I am not familiar with, is the slip clutch assembly ahead of the gear box. How do these things work, is there any adjustment, and are they able to be rebuilt. Any suggestions on how to proceed? The difficult part is rotating everything by hand in no way translates to what happens once you engage the PTO, at least to find issues.

Thanks!
 
   / Bush hog breaking shear pins
  • Thread Starter
#2  
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   / Bush hog breaking shear pins #3  
Service the slip clutch so you know it will slip as designed. Then put a grade 5 or 8 bolt in place of the grade 2 you are using. You don't need shearbolt protection behind the slip clutch, certainly not one that fails that easily.
Unfortunately LandPride takes the cheap way out and uses the same gearbox input shaft for both shearbolt and slip clutch models. Bush Hog and other outfits will use splined or keyed input shafts on their slip clutch machines so there is a more positive drive between the clutch and blades.
 
   / Bush hog breaking shear pins
  • Thread Starter
#4  
What all is involved with servicing the slip clutch?
 
   / Bush hog breaking shear pins #5  
Jason280 said:
What all is involved with servicing the slip clutch?
Click to expand...
Take a measurement on the distance that the springs are compressed , loosen them up several turns and then put the PTO in gear and let the slip clutch break loose , that will knock all the rusty buildup off of it, do it several times then tighten the slip clutch bolts until the springs are compressed to the proper measurement and you should be good to go, this should be done yearly at the beginning of mowing season.
 
   / Bush hog breaking shear pins #6  
Scribe a line across all of the plates that make up the slip clutch so you can see for sure the discs can slip independently. You can probably download an op manual from the Landpride website, that should give you a baseline spring length dimension. Start out just a bit longer (1/16" or so) and monitor the clutch for slippage. Tighten as necessary for your hp and conditions. Don't get carried away, tightening each spring a little bit will make a substantial difference.
 
   / Bush hog breaking shear pins
  • Thread Starter
#7  
It looks like these are all tightened just about as much as possible already...
 
   / Bush hog breaking shear pins #8  
Do the above, but first mark the slip clutch plates with chalk or a grease pencil or something so that you can tell they have slipped with the loosened bolts.

Edited to add- No, LOOSEN the spring bolts to get the clutch to slip freely. then re-tighten them to the previous tension (distance between plates)
 
   / Bush hog breaking shear pins #10  
Schrodinger said:
Do the above, but first mark the slip clutch plates with chalk or a grease pencil or something so that you can tell they have slipped with the loosened bolts.

Edited to add- No, LOOSEN the spring bolts to get the clutch to slip freely. then re-tighten them to the previous tension (distance between plates)
Click to expand...
Pretty much what "scribe a line" means.
 
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