Brush Hog Stump Jumper Fell Off

[Zippo1]

I was out brush hogging very tall and thick grass in my field when there was a "clunk" and lurch and then the vibration from the brush hog stopped. I looked back to see that the stump jumper, with blades attached had fallen off. I see that the stump jumper has a female spline but am not sure what normally holds it on to the brush jumper splined shaft. I brought the parts back from the field but thought I'd ask here before turning the brush hog over with an eye to fixing it. Thanks for any info. I believe the 5 foot brush hog was made by "Modern Mfg".

 

[M5farms]

the shaft is splined and it will have a castle nut and some washers. you could have just lost the cotter pin and it vibrated loose and hopefully didn't mess up your shaft splines

 

[Steave]

I'm not familiar with the "Modern Mfg" brand but the ones I've seen or repaired have some kind of bolt or nut with a thick washer holding the stump jumper onto the spline shaft. Maybe a castle nut with a cotter pin or some older woods brush hogs have a large washer with a hex cut out in it to fit over the bolt head then it is tacked in place with a welder. Simply grind the tack off then remove. This is the best design to me because after you remove the holder the bolt usually comes off easy since it's not beat on with a hammer or powerful torque wrench and it won't fall off during use.

More than likely you'll find the threads to be fine threads and can get them at fastenal or another store that deals in bolts and nuts.

After you get it secured in place where you can inspect it you should be able to see what holds yours together. If not take pictures of it and somebody on here will be able to help. Keep us informed of your progress as I and probably many more are curious as to why it fell off. You never hear of this happening much. Usually the other way around everybody is trying their best to get them off maybe you found a good way. I sort of meant that to be funny but wow that's a dangerous situation.

 

[Zippo1]

Thanks, Steave. It'll be a couple of days before I can get to it but I will post a picture when I get it flipped over. Maybe I should take my metal detector out into the field and see if I can locate the bolt or nut...

 

[M5farms]

Thanks, Steave. It'll be a couple of days before I can get to it but I will post a picture when I get it flipped over. Maybe I should take my metal detector out into the field and see if I can locate the bolt or nut...

it will be a few feet from where it fell off most likely . I have better luck with my rolling magnet finding things behind the bush hog

 

[Zippo1]

it will be a few feet from where it fell off most likely . I have better luck with my rolling magnet finding things behind the bush hog

Good idea.

 

[JWR]

I had the same thing happen with a JD MX6 cutter being used on a JD4700 tractor. Had about 8 or 9 years on the hog and tractor (probably using the hog 15 or 20 hours per year) when the stump jumper and blades flew loose and went sailing across the field.
View attachment 521465

I think (since your stump jumper has a female spline) that it has a threaded hole in the splined main gearbox shaft and uses a fine threaded bolt to hold it all together. Don't guess at it. Get out your manual/parts book.

Mine was held on by a fine threaded bolt and lock washer -- no certainty of keeping it on such as a castle nut and cotter pin. It was fine for several years before it flew loose and then did it twice in a short time before I found out the torque specs ! I had not tightened it nearly enough. Darn thing required huge torque -- I want to say 600 ft-lbs ?? Maybe 450? So the problem was I had nothing to begin to put that much torque on the bolt. Once I found out the torque specs I used a LONG cheater pipe and busted some socket set components. Finally got it right. BEST: Use a good air wrench with high torque rating. Read your manual. Comeback and check tightness after several hours use. In later years I am using a 7' Bush Hog 297 on a larger MF2660 tractor. Thankfully this 7' hog has a castle nut on a 30mm threaded shaft to hold on the stump jumper and blades. Dealers do not emphasize enough the need to retighten after some hours of usage.

 

[Zippo1]

Thank you all for the help. I turned it over and found that indeed that it was a splined shaft threaded on the end for a castle nut. I purchased the nut and a couple of washers and a cotter pin and got it all back together (with sharpened blades) and it is working great again. I do appreciate all of the info.

 

[JWR]

Good to hear. In going back to check for tightness of the blade carrier under that castle nut, I find I can rock the carrier or "stump jumper" by hand slightly if it has loosened. If it has not loosened I feel no play. Give it a few hours mowing and check. I've grown paranoid enough that I check it very frequently now.

 

[DieselBound]

Yes, folks eally should follow JWR's advice. I'd done that on my newly purchased, used, Bush Hog and found wobble. Some searching around on this subject I found others that ended up with messed up shafts. I consider myself lucky in that it was only the nut that was loose: I suspect the previous owner didn't tighten it properly- he'd installed new blades and I'm thinking that he dropped the stump jumper to do so.