Snowblower Shear Bolts failing

[andre53]

I have a GR2120 tractor with a GR2728 46" snowblower on it. I have done about 4 hours worth of snowblowing with it. All is good, except that I keep having the shear bolts on the blower fan (second stage) fail. I have gone through 4 shear bolts so far this season (so about 1 per hour of use...) The last shear bolt failed under no load. The snowblower PTO was engaged for about 30 seconds and was warming up before starting to blow snow and "bang" the shear bolt popped.

Now, I do have a gravel drive but I never had this issue with my old tractor/snowblower that I used on the drive for the last 20 years (I probably only sheared 4-5 bolts in all that time and those were always auger bolts (first stage)).

Any suggestions or ideas?

Thanks

 

[gssixgun]

I assume you have checked all the obvious stuff (grease, bearings, chain, gears,) and turned the Blower by hand to check for binding anywhere..

Chain tension is something to double check, too loose or too tight can cause issues...

When you changed the Tractor you also changed the Blower ??? did I read that right... So this is a fully "new" setup

 

[bosshogg]

Good advice from previous poster and if those items are not the issue do not replace shear bolts with higher grade pins or bolts. It is far better to "break" an inexpensive shear bolt then damage the blower or your tractor. Does sound like something is binding based on your statements. A bolt shouldn't shear without any load unless it had a severe flaw to begin with.

 

[Wild and Free]

I find that they tend to come loose during blowing. I stop and check and retighten the blower sheer bolt before during and after blowing, I use lock nuts but they seem to work loose as well over time and once they work loose it only takes a short period to break. I went from 5/16 sheer bolts and drill out things and now run 3/8 grade 8 and still break about 1 an hour. Everything else is A OK.
Part of my issue is the fact that I run mine on the 780 speed idled down to around 2000-2100 engine rpm versus the 540 speed wide open, it blows way better this way, on 540 it barely dribbles the snow out the chute.

 

[hodge]

I second checking everything for binding. Also, because it is a different setup than what you previously had, it could be that there are less tolerences in this blower than the old one, by design or by wear, and gravel are jamming things up. Once or twice is one thing; routine points to an issue. I also second that it would be better to find the problem than to try to force it by putting in harder bolts.
How are the feet adjusted? Is it low enough to pick up gravel?

 

[bosshogg]

I find that they tend to come loose during blowing. I stop and check and retighten the blower sheer bolt before during and after blowing, I use lock nuts but they seem to work loose as well over time and once they work loose it only takes a short period to break. I went from 5/16 sheer bolts and drill out things and now run 3/8 grade 8 and still break about 1 an hour. Everything else is A OK.
Part of my issue is the fact that I run mine on the 780 speed idled down to around 2000-2100 engine rpm versus the 540 speed wide open, it blows way better this way, on 540 it barely dribbles the snow out the chute.

You should be using Grade 2 at the maximum and by drilling it out you changed everything for the worse. Something is definitely wrong with your blower...do not use Grade 8 bolts.

 

[Wild and Free]

Something is definitely wrong with your blower...do not use Grade 8 bolts.

Yep something is wrong.................with me that is for buying a piece of chit Chinese built blower.

Mine is a 2 stage and the one sheer bolt drives the entire blower, both stages. it is the primary sheer bolt where the input shaft flange bolts to the discharge fan shaft flange which is also keyed and is a through shaft into the gear box which drives the augers which each have their own sheer bolts as well.

 

[meanjean]

Hopefully the problem is as simple as the shear bolt constantly working it's was loose. Add a lock washer, double nut, and lock tight.
Try again.

 

[hodge]

Yep something is wrong.................with me that is for buying a piece of chit Chinese built blower.

Mine is a 2 stage and the one sheer bolt drives the entire blower, both stages. it is the primary sheer bolt where the input shaft flange bolts to the discharge fan shaft flange which is also keyed and is a through shaft into the gear box which drives the augers which each have their own sheer bolts as well.

It sounds like it may not be designed to handle the task of heavy snow. The design of the impellers, gear ratios, etc.

 

[bosshogg]

Grade 8 bolts have much too high tensile strength to be used as shear bolts. Only Grade 2 or no-grade bolts should ever be used if you do not want to severely damage something else.

 

[Wild and Free]

It sounds like it may not be designed to handle the task of heavy snow. The design of the impellers, gear ratios, etc.

Yeah it is not the best designed blower, and we have not had any heavy snow to blow yet only 4-5 inches of dry light fluffy stuff a few times.

I will finish out this winter with it and then sell it or trade it in for a better product. Or maybe do a tear down an redisign the drive coupler flanges a bit.
Live and learn. This is the last piece of Chinese junk I will ever buy.

 

[Jim Jacobson]

I'm going to throw in my two cents, keep in mind my experience is limited. I have a L4730 w/front mount blower. Prior to purchase I talked to everyone I could about which tractor to buy, attachments, front or rear mount snowblower, etc. Also asked a zillion questions about snowblower operation including shear bolts. Here's the wisdom from my own limited experience and in talking to others with vastly more experience:

1) Do not use shear bolts of a higher grade than what is recommended.

2) You mentioned your drive was gravel. Do not blow the first snow. Drive on it to get a good base packed. This is because you really want to minimize the amount of gravel entering the blower.

3) Although I have not yet sheared a bolt (there are two on my front mount) the wisdom of those with experience tell me they will blow out rocks bigger than your fist for hours on end, then shear a bolt on a very small rock that gets wedged between the impeller and the housing. I have personally kicked out a rock weighing around 10 pounds (I checked). Fortunately it did not go through the impeller.

4) With a rear mount blower don't even attempt blowing until the snow is greater than 3-4 inches deep. At 540 RPM the snow will dribble out the chute and increase the opportunity for clogs, particularly with wet snow.

5) With small amounts of snow I've found the best way is to angle my rear blade (reverse it so it doesn't dig in), make two passes, piling the snow in the middle of the road and then blow the center pile. Works very well with snowfall amounts that are small.

Not sure any of the above even helps, just something to keep in mind. Good luck.

 

[meanjean]

5) With small amounts of snow I've found the best way is to angle my rear blade (reverse it so it doesn't dig in), make two passes, piling the snow in the middle of the road and then blow the center pile. Works very well with snowfall amounts that are small.

Great tip!
I would do this if I had a front mount blower.

 

[Snoopy]

I have this exact set up. GR2120 with a GR2728 snowblower and I am also shearing bolts after about an hour. There was a problem with my system and it was even shearing at idle after a few seconds. That unit went back to the shop to fix an issue and I got a loaner snow blower. Sheared a bolt on that unit also after an hour.

It is almost like the bolt is not big enough, there is too much horse power being sent to the blower, or the bolt is made of softer material than the unit is designed for.

I am clearing pavement. No gravel.

I don't know what the problem with shearing bolts on two different units, but it does appear that there might be a defect in the engineering of the bolt being used in the discharge blower with regards to how much power the tractor can supply to the blower assembly and how much power the bolt can withstand.

Peace,
Snoopy

 

[hodge]

I have this exact set up. GR2120 with a GR2728 snowblower and I am also shearing bolts after about an hour. There was a problem with my system and it was even shearing at idle after a few seconds. That unit went back to the shop to fix an issue and I got a loaner snow blower. Sheared a bolt on that unit also after an hour.

It is almost like the bolt is not big enough, there is too much horse power being sent to the blower, or the bolt is made of softer material than the unit is designed for.

I am clearing pavement. No gravel.

I don't know what the problem with shearing bolts on two different units, but it does appear that there might be a defect in the engineering of the bolt being used in the discharge blower with regards to how much power the tractor can supply to the blower assembly and how much power the bolt can withstand.

Peace,
Snoopy

Or, there is a design flaw in the blower, causing a bind that creates enough resistance to cause the bolt to shear. Maybe the bolt is the issue- but, if it were my equipment, I would make sure it wasn't the blower before putting a harder bolt in there. Once that weak link is eliminated, something else will take its place.

 

[Kubota Newbie]

Ok, so a 5/16 shear bolt should handle a lot before breaking. You could almost stall our old 65 HP Farmall on our M-C Rotary Scythe mower and it just had a 5/16 shear bolt. A 3/8 should handle a bunch of power!
I would check two things (assuming you've already checked all the other driveline issues as previously noted). 1.) The bolt must fit snug in its hole, you all mention the use of SAE size bolts. Are you sure the hole is not metric????? 2.) Problems as described often come from the use of too short a bolt. Using too short a bolt places the shear point in the thread area of the bolt. Stress risers from the thread cutting/forming operation will cause the bolt to shear in the thread area much much easier than on the shank. Make sure that the bolt length you're using puts shear point somewhere on the shank of the bolt.
Oh yeah, a shear bolt should stay fairly tight. If it's coming loose, even with a lock nut, just double nut it. It will not loosen. If it is coming loose it's usually because of #1, which is allowing it to work back and forth in the hole.

I'm betting on issue 2 above. Let us know.

Our old New Holland Insilage blower didn't have any bigger than a 5/16 shear bolt on an impeller almost 4 ft in diameter. I can't ever remember breaking one, even all the times we plugged the pipe.

 

[Wild and Free]

Ok, so a 5/16 shear bolt should handle a lot before breaking. You could almost stall our old 65 HP Farmall on our M-C Rotary Scythe mower and it just had a 5/16 shear bolt. A 3/8 should handle a bunch of power!
I would check two things (assuming you've already checked all the other driveline issues as previously noted). 1.) The bolt must fit snug in its hole, you all mention the use of SAE size bolts. Are you sure the hole is not metric????? 2.) Problems as described often come from the use of too short a bolt. Using too short a bolt places the shear point in the thread area of the bolt. Stress risers from the thread cutting/forming operation will cause the bolt to shear in the thread area much much easier than on the shank. Make sure that the bolt length you're using puts shear point somewhere on the shank of the bolt.
Oh yeah, a shear bolt should stay fairly tight. If it's coming loose, even with a lock nut, just double nut it. It will not loosen. If it is coming loose it's usually because of #1, which is allowing it to work back and forth in the hole.

I'm betting on issue 2 above. Let us know.

Our old New Holland Insilage blower didn't have any bigger than a 5/16 shear bolt on an impeller almost 4 ft in diameter. I can't ever remember breaking one, even all the times we plugged the pipe.

There is a HUGE difference on where and how a shear bolt is used. If it goes directly through a pipe and shaft coupled together it is a LOT stronger than what my blower has which has a sheer bolt through 2 flanges that are bolted to the shafts which is not as strong, gives the bolt a lot less surface area to hold versus going through a shaft and pipe.

 

[Kubota Newbie]

Every piece of farm equipment I own or that we ever had on the farm at home uses the flange arrangement. All use/used single shear bolts, and none were over 5/16 dia. One 5/16 bolt in shear should handle aplenty. I think the flywheel shear bolt on my baler might be a grade 5 bolt, but it is an odd diameter, I think 9/32 with 1/4 threads, the shear flanges meet on the 9/32 shank.
One other thing to check is that your flanges should have a stub shaft, nose, bushing, center bolt, or something that keeps them centered on each other. If that arrangement, whatever it is, isn't in good condition you'll break a lot of bolts because the flanges are essentially trying to run in two different circles. Vibration is usually a problem if this is the case.

 

[andre53]

To all,
First I would like to thank everyone for all of their inputs. This is what makes this site so helpful.

As suggested, I went thru the snowblower drive carefully, removing the shear bolts and checking for binding, chain tension, mis-alignments, anything that could provide a clue. Everything seems in order. With the shear bolt removed the fan spins very freely.

The only thing that I did find that may be contributing to these failures is that during operation, a layer of ice builds up on the back surface(perpendicular to the driveshaft) of the blower housing behind the fan. When this happens, it completely closes the gap between the rear of the fan and the blower housing. You can feel where the fan is rubbing on the ice. (Note: there is no similar ice build up between the actual fan "blades" and the blower housing (parallel to the driveshaft). I am not sure how to eliminate this ice build up.

the next time I need to use the blower, I will spray that area with Pam to see if that helps. Any other ideas?

thanks

 

[hodge]

Pam is a good idea. I know that there is a spray made that you can coat the underside of a truck when offroading, and it keeps the mud from sticking. Any releasing agent like that should work.