Snow Going through second stage bolts

[EdenKubotaDriver]

I had a similar problem. 2 different causes resulting in auger bolts shearing. Top sprocket

 

[EdenKubotaDriver]

I have been running a 5ft Agro-Trend 3pt mounted snowblower for 20 years. I don't use it many times per year but when I do it is usually rough and a workout in heavy snow. In mountains of WV. I can recall throwing large gravel accidentally for long distances, picking up chunks of ice that went through the blower sounding like a bush hog that just hit a 2x4. I drive it with a 24hp Kubota B2150. I have never replaced the original shear bolt. Never a problem (yet...) So I have to wonder what on earth is wrong with your rig. I've never owned a Kubota brand snowblower but I heard they are made in Quebec for Kubota by a company with a pretty solid reputation. What you describe is just not right -- something is haywire. The shear bolt must fit very snug/tight and cannot have any play in the hole. Go read the manual and don't count on the dealer to give you the right shear bolt. Does the rotor turn fairly easily by hand (when the tractor is shut off) and not seem to be catching on something or wobbling ? By the way, shear bolts are normally intended to break when excessive loads occur and are NOT normally high grade bolts. Plain old grade 2 usually. I would not go putting in a super strong bolt until I figure out what the problem is. The manual should tell you what grade bolt to use. Checked the lube in the gearbox ? ... Let us know what you find !

Had the same problem twice during my ownership, 2 different causes. 1st top sprocket set screws work loose allows the shafts to move forward enough for auger to contact housing. 2nd the chain has lost lubricant and there are stiff links developing they then ride up the sprocket and really engage, act like an impact hammer and the shear bolt shears

 

[jrogers]

Does the fan turn perfectly smooth and without rub by hand? My rear PTO shaft on my yanmar is completely freewheeling by hand when not engaged and engine off. I just finished a custom front mount JD snowblower that runs off a chain drive from the rear PTO. This driveline should have more friction than yours yet I can still turn the whole thing easily by hand. If you can't you need to figure out why. There's another thread currently where a guy clearly has water in his gearbox and he can't turn by hand. If there are any hard spots in the rotation you should investigate those hard spots, such as the chain sprocket being out of round and putting tension in the chain in one spot, or the fan rubbing the housing in one spot (Deere blowers have a tendency for both).

I notice that you have a lot of bright metal around your fan drum, and also behind. I've seen paint worn around the drum but behind is really interesting and I wonder if you are rubbing the fan against the rear of the housing. As has been said in my experience you can send some pretty good size gravel through these without breaking a bolt. The deer blowers use a 1/4" grade 5 bolt as a shear pin with a similar leverage on the fan so should be about the same.

Just another final thought. Set your shoes up a little bit more so you aren't getting any gravel through the blower at all. If you keep breaking pins when hitting absolutely nothing you know you need to investigate your blower some more.

When the shear pin is sheared, the fan turns smoothly without rubbing. I think all of the bright spots where there is no paint is from sand going through it. I tried pulling it front to rear, and I cannot make it drag. My driveway is paved, so the only sand I am getting is from my driveway when I send it, or from the road sander at the bottom. Generally this stuff is all 1/8" or less. Maybe there is a chance that the sand is just the right size to jam between the fan and it's housing, but others do not report this happening.

One other possibility that I am considering is that the last universal joint going into the snowblower seems to loosen up easily and has a bit of a wobble to it. There is a setscrew in this that seems to back out quickly, and I will try and keep it tight with locktite, and I may disassemble it and see if I can tighten it up with a new key, since I am running out of ideas.

 

[aczlan]

One other possibility that I am considering is that the last universal joint going into the snowblower seems to loosen up easily and has a bit of a wobble to it. There is a setscrew in this that seems to back out quickly, and I will try and keep it tight with locktite, and I may disassemble it and see if I can tighten it up with a new key, since I am running out of ideas.

Sounds like a logical reason for it to loosen up.

Aaron Z

 

[Dave M7040]

Instead of focusing on the setscrew, it might be worth considering the u joint fit that you are asking the set screw to deal with.

Look at some of the loctite products in this booklet designed to tighten up the fit of the parts themselves.

Start around page 16 up, http://www.loctite.ph/php/content_data/LT4680.pdf

Dave M7040

 

[olPete]

I am not familiar with snowblowers at all.. but pto and driveshafts yes.. would it be advisable, to the OP, if you are going to disassemble the UJ from the shaft?- I'd consider replacing set screws with roll pins. They will hold tight

 

[jrogers]

I am not familiar with snowblowers at all.. but pto and driveshafts yes.. would it be advisable, to the OP, if you are going to disassemble the UJ from the shaft?- I'd consider replacing set screws with roll pins. They will hold tight

Good Point. There are two things holding my U joint to the shaft. One is a bolt going though the shaft and U joint, and the other is the setscrew that pushes on the shaft that takes the wobble out of it. It seems like it would be better to replace the bolt with a roll pin, which would take more of the wobble out and make it tighter before the set screw is tightened. Do others have this bolt through the drive shaft, or is it a roll pin normally? A roll pin makes sense, since I never have to take this U joint out when changing attachments .

 

[olPete]

Good Point. There are two things holding my U joint to the shaft. One is a bolt going though the shaft and U joint, and the other is the setscrew that pushes on the shaft that takes the wobble out of it. It seems like it would be better to replace the bolt with a roll pin, which would take more of the wobble out and make it tighter before the set screw is tightened. Do others have this bolt through the drive shaft, or is it a roll pin normally? A roll pin makes sense, since I never have to take this U joint out when changing attachments .

Every UJ I have seen on a pto has had a double roll pin ie a little pin inside a bigger one. The only reasons I can think of that they've used that setup, is access, and low hp. Could be difficult to drift pins in and out if it is right in there? You will know the answer to whether it's do-able. Maybe the manufacturer used the bolt for that reason, if you damaged the UJ it may be easier to remove the bolt? Then again, designers draw things and engineers build what's on the sheet. Often little feedback back to the design team.. your problem intrigues me!

 

[PeterK]

Mine had a trouble with the drive gear loosening up and the shaft would move back and forth. I had to clean out the thread and use new loctite on them.

Also I've seen some over tighten sheer bolts. The type with self locking nut on the auger (with two cuts on the bolt) need to be snug tight. On my BX2750D the fan uses split lock washers and has one sheer cut on the bolt. I tighten these until the split washer is flat, no tighter. It's easy to "pre sheer" the bolts if you're not careful. Maybe? These bolts are not designed to tighten the assembly together, they're designed to sheer and protect the assembly.

Hope this helps you figure it out.

 

[olPete]

I have just been back tracking through the thread to find pictures and be sure I'm on the right one myself...
If that shaft is spinning at ~2500rpm then I would definitely not be running that bolt and setscrew setup. That could explain your "timebomb" that you described, the operating time being similar between failures of the shearbolt. Someone above suggested some type of locktite that may be of use to you, and it doesn't look like any issues access wise if you need to replace the bearing/UJ at any point in the future. You may even wish to keep the setscrew and locktite that in too, but a rollpin instead of that bolt would be my next step. You've certainly got to know your machine!!
Ps I'd have to agree with whoever suggested removing the chain and keeping it in oil over the off-season, sounds like a good idea to me.