Snow Going through second stage bolts

[Dave M7040]

Also, I am running my blower at PTO Speed (not a slower speed). I do throttle it down when I engage it, but them throttle up before blowing snow. Failure is happening at light load on the motor and not a heavy snow load or when blowing debris.

JR

Can I make certain I understand your info.

I understand you to say that you have the part shown in black on your blower except that it is painted orange. Correct?

It is not the one with the Green arrow pointing at it in the photo that is failing?

Is the bolt shown by the green arrow just a normal bolt with no grooves in it?

My friend had a new blower installed on his tractor in December. It has the style with the black hub but everything is orange so a factory blower not a dealer modified one.

The photo below is of the spare shear bolts the dealer gave him.

The bolts with the grooves are for the auger.

The shorter grade 2 bolts with no grooves are for the fan hub.

Can you advise if your fan hub shear bolts are the same as the shorter ones with no grooves and yet you are experiencing shear bolt failure.

The slip clutch you are asking about is a heavy thing with a clutch disc sandwiched between two steel disks. The two steel disks are clamped together by springs. the clamping effect transfers power through the clutch disk.
You can adjust the point at which the disk slips by increasing or decreasing the tension on the springs.

Where you see them is on pto's for a bush hog which is experiencing drive-line shock loads all the time so rather than having frequent shear bolt failures the clutch slips, you just carry on.

I have never seen one on a snow blower and never ever on a front mounted blower. The clutches require maintenance to ensure they slip when needed and are not frozen together because if they are frozen expensive things break.

In looking at the photo of the spare shear bolts my friend has. It looks like the short bolts have grade 5 marking on the bolt head. I am going to ask him to take a photo of the bolt head as these bolts were given to him with the new blower

Dave M7040

 

[jrogers]

The U joints appear to be in phase to me.


I did not see any other problems. The gear reduction seemed to be fine. There was one long bolt on the side that was loose which I tightened, but in general everything seems fine. There is a little play in the front U joint to the shaft, but not very much. Any suggestions from these photos?

 

[Dave M7040]

JR


My posting is going to be in reverse. After I wrote the material suggesting your blower was turning far too slow hence breaking shear bolts, I went to the Messicks site and looked around at exploded views of your blower.

The first big observation is it came with a 3 point hitch. I am not a small Kubota expert but most 3 pt hitch blowers are intended to run at the back of the tractor not the front.

There is a reduction gear assembly, actually sprockets and chains available which can be fitted to the blower assembly if its speedd needs to be slowed down because of a high speed pto which some small Kubotas do have.

The driveline on the Messicks site looks nothing like you have but exactly like a rear pto shaft would look.

I believe someone has seriously modified your blower to make it fit on the front and they did not have the knowledge to do it.

The blower could even be turning backwards which I would like you to check

Dave M7040



What is puzzling me is this. Your pto shaft turns a sprocket hidden behind the black plate but which appears to be much smaller than the sprocket which is visible with the chain wrapped around it.
This is slowing down the rotation of the shaft with the fan on it to perhaps 1/4 of the pto speed assuming your pto is coming from a mid pto on your tractor.

That shaft goes through the fan at the same time driving the fan at about 1/4 pto speed.

Next the shaft goes to the worm gear box between the two halves of your auger. This gear box is slowing down the augers again by a significant fraction.

If my interpretation is correct, the whole system is turning far slower than a normal design.

The end result of this slow turning is a great increase on the shearing force on the shear bolt(s).

By way of a comparison in the opposite speed direction, some large tractors have 1000 rpm rear ptos. The blowers they will drive have reduction gear boxes to lower the speed of the blower fan to around 540 rpm and the augers to about 140 rpm. The shear bolt in the pto shaft which is turning 1000 rpm

 

[olPete]

JR




I believe someone has seriously modified your blower to make it fit on the front and they did not have the knowledge to do it.


The end result of this slow turning is a great increase on the shearing force on the shear bolt(s).

By way of a comparison in the opposite speed direction, some large tractors have 1000 rpm rear ptos. The blowers they will drive have reduction gear boxes to lower the speed of the blower fan to around 540 rpm and the augers to about 140 rpm. The shear bolt in the pto shaft which is turning 1000 rpm

Let me first say I have never even seen a snowblower until I went on TBN.
Do have a lot of PTO hours though, starting at the age of about 7. So 30 years on...
Very valid points made on UJ phasing etc etc.
I'm wondering what rpms those mid PTOs run at and also how many teeth on the sprockets on both the OPs machine, and your friend's one. Sounds like too much torque ie. it's geared too low.
( I broke a UJ yoke on a 1000rpm mower by running it for 20 minutes at 540rpm as the control in the tractor only changed the readout, the selector was on the rear end outside. Mowed OK but obviously nearly double the torque was being applied at nearly half the speed. ) Be interested just to know how the gearing is in relation to standard if it's been converted as you suspect.

 

[aczlan]

JR
My posting is going to be in reverse. After I wrote the material suggesting your blower was turning far too slow hence breaking shear bolts, I went to the Messicks site and looked around at exploded views of your blower.
The first big observation is it came with a 3 point hitch. I am not a small Kubota expert but most 3 pt hitch blowers are intended to run at the back of the tractor not the front.
There is a reduction gear assembly, actually sprockets and chains available which can be fitted to the blower assembly if its speedd needs to be slowed down because of a high speed pto which some small Kubotas do have.
The driveline on the Messicks site looks nothing like you have but exactly like a rear pto shaft would look.

Dave, the model you want to look at is the B2781A or B2782A, the difference in the "A" model is that they add the reduction chain drive (PN: 70060-03496) and replace the 3 point brackets with the female quick hitch (PN: 70001-00840).
The reduction chain drive slows the 2500RPM mid PTO down to 540RPM at the fan input shaft.

The reason they do this is that Kubota does not make the blower, they outsource it to RAD (as do Deere, NH, Massey, LS, etc). They all use the same RAD snowblower assembly (shell, auger, fan, etc). The brands just get different brackets to match their quick hitch and the correct color paint. They also use the same snowblower assembly for 3 point blowers with different brackets and no reduction chain drive.
Edit:
Here are some pictures of a B2781A: Used KUBOTA B2781A



Aaron Z

 

[JWR]

Aczlan is right about the PTO rpm. The mid PTO that runs this front snowblower (and the belly mowers, etc.) is higher rpm than the rear normal 540 rpm. The reduction gearing is necessary and is not causing the blower to run too slow.

Guys, I really think owners with these blowers need to focus on some key things: The blowers are all made by RAD. Numerous users among MF and Kubota & no doubt other brands of host tractors are breaking shear pins/bolts at FAR TOO GREAT A RATE. The common points are the single manufacturer, RAD, that all the units are front-mounted, and the discovery that RAD has changed their protective shear design at least once. Instead of chasing so many theories, this manufacturer should be forced to back the product via the dealers and those who sell them. They owe you a solution.

 

[jrogers]

Just to confirm what was already said, the blower in question is not adapted for this tractor, but was bought new with the tractor as a front mounted blower.

From post 61:

I understand you to say that you have the part shown in black on your blower except that it is painted orange. Correct?

Correct.

It is not the one with the Green arrow pointing at it in the photo that is failing?

Correct. The Green arrow bolt in post #54 is not failing, it is the Shear Bolt with the purple arrow failing. I am torquing approximately 10ft-lbs, but I have tried 5-20ft-lbs with the same results.

Is the bolt shown by the green arrow just a normal bolt with no grooves in it?

Yes, it is a normal bolt with no grooves in it. I bought about 20 of them at the Kubota dealer, and they looked up the part number for my blower, so I am pretty confident that this is correct.

 

[jrogers]

One more thing, the U joint at the gear box as a little loose and had a bit of wobble to it. I tightened down the set screw on the side and this quieted things down a bit, so I will see if this will help. I did one pass of some drifted snow this morning and no shear failure, but only about 10 minutes of use. I will look at it more tonight.

I don't really have anything to reference, but review the photo below to see if this all looks correct.



Does this look correct with where the spline is and how the U joint is attached to the spline shaft? I have never taken this part apart, but it looks kind of strange, almost like it should be all slid back and in the bearing housing to the rear.

 

[Bavarian]

I had a Farm King 74" which was rated for 40 - 70 HP. Ran it on a JD 4200 with 26 HP.
I couldn't put enough original shear bolts in there. They just broke. They even felt like they were made from aluminum when I tightened them.

I went to the hardwarestore and bought a hand full domestic bolts and it fixed the problem. They still broke, but did last 10x longer.

 

[JCByrd24]

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.