Snow Going through second stage bolts

[Dave M7040]

I looked at the holes closer, and the back one was definitely elongated.

View attachment 499185

I filled it with my mig welder and redrilled it so that it is tight now. I also rebolted it with a new 1/4" grade 8 bolt with a longer shank so that the shear area is not where threads are. It looks like more snow this weekend, so I will try it out and see how it does. I also double bolted the shear bolt. Also the bolt that goes through the center shaft was damaged and gave it some play, so I changed this as well.

JR
I am puzzled by what I think I see in the fan flange hole. I have tried to draw a red line in what looks like a gap.


It looks like a bushing or something . What am I seeing? Sent you the material by email. Sorry for not seeing your pm sooner.

Dave M7040

 

[aczlan]

JR
I am puzzled by what I think I see in the fan flange hole. I have tried to draw a red line in what looks like a gap.


It looks like a bushing or something . What am I seeing? Sent you the material by email. Sorry for not seeing your pm sooner.

Dave M7040

If it is like the side we can see, it is a bushing that is welded in from the other side. The hole might be a little oversized so fitment is not quite as critical.
Given that it is egged out, I suspect that it was run for some time with a loose bolt and that let it chew up the side of the bushing. Now to make it perfectly good again, it will need to be drilled out and an oversized, lower spec bolt will need to be used or else the whole bushing need to be removed and replaced with a new one. Barring that, you could drill it out to maybe half of the outside diameter of the bushing and then weld in bushing to get the hole size back down to quarter inch


Aaron Z

 

[jrogers]

It seems like I have had some success. In addition to welding and re-drilling the hole in the back tab, I pulled the bolt that goes through the shaft (between the gearbox and the fan) and found that it was worn most of the way through causing additional play as the oversized shear bolt hole did as well. I replaced this bolt, put a new shear bolt in with a longer shank. With all of these changes, I went out and ran it for over an hour without issue. I even went over to a neighbors and ground up a big snowbank that had built up which worked it pretty hard.

When inspecting it after use, the shear bolt appeared tight, whereas in the past it would loosen up.

 

[Dave M7040]

It seems like I have had some success. In addition to welding and re-drilling the hole in the back tab, I pulled the bolt that goes through the shaft (between the gearbox and the fan) and found that it was worn most of the way through causing additional play as the oversized shear bolt hole did as well. I replaced this bolt, put a new shear bolt in with a longer shank. With all of these changes, I went out and ran it for over an hour without issue. I even went over to a neighbors and ground up a big snowbank that had built up which worked it pretty hard.

When inspecting it after use, the shear bolt appeared tight, whereas in the past it would loosen up.

JR

That is wonderful news after all your struggles with it.
I am certain others will benefit from your findings.

Looking back at this point what do you think was the origins of all the shear bolt breakage?
Being sold replacement shear bolts that were too short and thus the threads chewed out the holes leading to one issue after another.
Do you see something else that you would caution other owners about?

Did your blower have any labels on it spelling out which shear bolt to use?

I am still puzzled by the fact that you had grade 8 bolts when other owners of new blowers this Christmas had instructions to use grade two.

Dave M7040

 

[jrogers]

Not sure of the source of shearing the bolts, but I do chew through some gravel occasionally, and the legitimate failures may have caused the shear bolt hole to open up a bit.

As for the comments on the busing in there, I agree that these is some form of a bushing, but I am not sure why. It is definitely steel, since the hole welded up nicely. Maybe I should have cut the bushing out and welded a new one in, but I think the weld is pretty hard and hopefully will hold up.

I have not seen where it says what bolts to use, but I have about 50 data points that say it can shear a grade 8 bolt before damaging anything else. Also, I asked for shear bolts from both my local dealer and a mail order kubota place, and they both gave me the same bolts which I have pictures on here of the packaging and the bolt. Since then I have moved to a bolt with a longer shank, so maybe I should move back down to the one with the threads in the shear area, but this is a guess either way.

 

[jrogers]

If it is like the side we can see, it is a bushing that is welded in from the other side. The hole might be a little oversized so fitment is not quite as critical.
Given that it is egged out, I suspect that it was run for some time with a loose bolt and that let it chew up the side of the bushing. Now to make it perfectly good again, it will need to be drilled out and an oversized, lower spec bolt will need to be used or else the whole bushing need to be removed and replaced with a new one. Barring that, you could drill it out to maybe half of the outside diameter of the bushing and then weld in bushing to get the hole size back down to quarter inch


Aaron Z

I thought about going oversize and a lower grade bolt, but with welding it up (if it works long term) then there is nothing special to remember, and the right bolt is the one spec'ed by Kubota. Do you think that the welded up and redrilled hole will not hold up as well as the original hole in the bushing?

 

[Dave M7040]

I thought about going oversize and a lower grade bolt, but with welding it up (if it works long term) then there is nothing special to remember, and the right bolt is the one spec'ed by Kubota. Do you think that the welded up and redrilled hole will not hold up as well as the original hole in the bushing?

I wondered if the fan flange with what looks like a bushing was a rubber mounted bushing within the flange to absorb some shock loads and possibly not shear the bolt on that occasion.

I don't think what you have done is wrong, rather your work is a first positive finding and you are to be commended for sticking to it.

RE your thoughts of going back to the bolts with more thread and thread in the shear area.

In my first 8 years as an engineer, I worked for the Canadian equivalent of the National Transportation Safety Board and my job was to find the cause of the worst motor vehicle accidents.
What I took from that job was this: just because you got the same part from two different sources, did not make it the RIGHT part as determined by the engineer who designed the shear flanges or equivalent assembly.

Parts supply chains all over the world are corrupted. Non legit parts were even found on Obama's Air Force One plane.

Right now you have a working unit. In the beginning your initial thoughts had to do with sand gravel and small stones. Others like me said you should be able to blow sod.

Leave it as it is for now. When you get past winter, then stand in front of your running blower and throw shovel fulls of sand and small rocks into the blower. I will be very surprised if the shear bolt broke.

As far as the bushing in the fan flange is concerned, ask your dealer's parts guy to go back up the chain and send him a photo of a new fan to give to you Then you will be certain what was there originally and can decide if your repair needs to incorporate the bushing feature.

Dave M7040

 

[aczlan]

I thought about going oversize and a lower grade bolt, but with welding it up (if it works long term) then there is nothing special to remember, and the right bolt is the one spec'ed by Kubota. Do you think that the welded up and redrilled hole will not hold up as well as the original hole in the bushing?

I suggested that because I wasn't sure if you had a welder or were comfortable using it. More people are comfortable a drill than a welder. I think the welder (as you said) is a better idea but it's not for everyone.

Aaron Z

 

[jrogers]

I thought I would post an update. I have not sheared a bolt since I welded up the hole so it was not elongated and moved to a shear bolt with a shoulder that is long enough that there is no threads at the shear point. Today I was clearing the driveway from about 1.5 ft of heave spring snow. At the bottom I have to move some pea gravel they sand the road with and at this point it died. When I got it back in the garage I found that it was not the shear bolt like the previous 100 times, but that the master link on the chain had failed. I went to my Kubota dealer but they did not have a master link. A local bearing shop had a master link, but not for an O ring chain like the one I had, so they sold me a new 50 size regular chain. They said it would work the same, and were surprised that I had an O ring chain. So far so good. I want the blower for another 45 minutes without issue. It seems quieter and smoother with the new chain. The optimist in me hopes that the old chain was a part of the issue. Time will tell. Hopefully I have not moved from failing shear pins to breaking master links.

 

[FatTire]

That's interesting. I haven't heard of anyone using o-ring chain on a snow blower, although off hand I don't see why it would hurt. The only reason I've even ever heard of o-ring chain is that a guy I worked with at one time used it on his dirt bike.