BX2750 Shearing Pins

[Dyer retired]

My neighbor has a B2620 with a front mounted BX2750D snow blower . He has a paved driveway and lawn on both sides of it. There are no obstructions or rocks in his path, just fresh snow. He tells me that he has sheared 40 auger pins so far this winter. He had the same problem last year under the same circumstances. I had a BX2750 on my last tractor and experienced nothing like that...and I have a gravel driveway. When I broke a pin, I always knew why when I found a big branch that was under the snow, or a rock jammed in there, but that's what it was designed to do. He is not finding anything as a cause when he shears his pins. He is using the recommended Kubota shear pin and gets them from the dealer. He says that he doesn't overtighten them and he kicks the PTO in a low rpm's and throttles up once engaged. He took his skid shoes off and uses the scraper blade of the blower to get down to pavement, but says he doesn't put down pressure on the blower. I always left my skid shoes on and see this as about the only difference between his blower and my old one. 40 sheared pins during normal snow blowing is completely out of the question in my mind and I wondered if anyone else is experiencing this problem with the BX2750? He is going to reinstall the skid shoes and see if it makes a difference. There have no signs that he is bumping the augers on the pavement and it appears that there is plenty of clearance, even with no skids attached. Looking for thoughts on this. Dyer, retired

 

[Evil the Weasel]

This is the 2nd Winter with my setup and I still am on the factory shear pins. I have the heavy duty blower B2781A and not the BX one. I wanted the side mounted shoes and not the L shaped brackets used on the 2750. Still, I can't fathom going through that many pins. I suppose small stones could be doing it, but I'm surmising that there is something wrong with the unit itself.

 

[kevinj]

Does he have the augers properly phased????

 

[Snoho3]

I've broken a few pins tgus year from ice chunks trying to go through the blower. We've had some freeze/thaw cycles here and the road plow throws chunks onto my drive. If I don't get after it right away it can freeze hard.

40 is a big number though. Aren't Kubota shear pins expensive? And perhaps softer than those from a big box store?

 

[escavader]

DYER,
Gotta be something with the blower.Bad link in a drive chain,bad bearing somewhere.
He might try engaging at a low rpm,its hard on shear pins to snap the blower to life at full throttle.
If a gear box was defective ,and had a binding spot in it it would break pins.
Gonna have to go over that blower with a fine tooth comb.
Is he breaking most near the street?Fine rocks will fetch up my blower quicker than a big one,they get wedge in the tight spot between the blower fan and housing[lless than 1/4 inch.Ive snap pins at the street not knowing it til i was well down the drive.
I read on here your not suppose to tighten a shear bolt super tight cause theyll break easier.Iuse cheap grade bolts with lock nuts,they are cheaper and shear just fine.
ALAN

 

[radioman]

perhaps he is overtightening the shear bolts?

 

[Dyer retired]

Does he have the augers properly phased????

Yes he does. When he first got the blower and sheared his first pin, he asked me about the auger placement, so he's had that correct since the beginning.

 

[Dyer retired]

I've broken a few pins tgus year from ice chunks trying to go through the blower. We've had some freeze/thaw cycles here and the road plow throws chunks onto my drive. If I don't get after it right away it can freeze hard.

40 is a big number though. Aren't Kubota shear pins expensive? And perhaps softer than those from a big box store?

I've done the same thing and busted a few on my old one running into frozen banks, but I knew I was risking it when I did it. The neighbor is clearing his yard while the snow is fresh and fluffy, which is more puzzling with this problem.

 

[Dyer retired]

DYER,
Gotta be something with the blower.Bad link in a drive chain,bad bearing somewhere.
He might try engaging at a low rpm,its hard on shear pins to snap the blower to life at full throttle.
If a gear box was defective ,and had a binding spot in it it would break pins.
Gonna have to go over that blower with a fine tooth comb.
Is he breaking most near the street?Fine rocks will fetch up my blower quicker than a big one,they get wedge in the tight spot between the blower fan and housing[lless than 1/4 inch.Ive snap pins at the street not knowing it til i was well down the drive.
I read on here your not suppose to tighten a shear bolt super tight cause theyll break easier.Iuse cheap grade bolts with lock nuts,they are cheaper and shear just fine.
ALAN

The side support panels on that blower are thin and if you hit an ice bank and the auger jumped before it sheared the pin, the panels would actually distort out up to a 1/4". When it did it to mine, it didn't seem to shear more bolts, it just made the sheared bolt harder to find because there was a lot more movement in the auger rotationally and side to side. I fixed that, but again...it didn't seem to impact the bolts, just made them easier to find when I broke them. He's called the Dealer (Hammond Tractor) and they don't have any answers for him over the phone. I'm with you Alan and think they need to take the thing apart and check the entire unit. If he keeps up at this rate, he'll have spent as much for shear bolts as he did the unit!

 

[kevinj]

perhaps he is overtightening the shear bolts?

You may be on to something. Those are grooved bolts. Over torque could snap them off.

It would be nice to see the broken bolts to see if they sheared or broke in tension.

The augers are not bearing dependent nor do the touch anything but the snow unless you hit banks or pick up a stick.

I have chewed into some pretty good plow truck banks and only ever sheared one when I picked up a tree branch in the snow.

 

[kevinj]

Yes he does. When he first got the blower and sheared his first pin, he asked me about the auger placement, so he's had that correct since the beginning.

Just so everyone knows; the augers run out 180°, not matched,

 

[kevinj]

Dyer,

I had another thought. Are all the bearing screws tight???? and the mounting for the gear box???

Maybe the auger shaft is moving sideways under load and catching the augers on the gearbox.

When mine was new everything was loose, it did not shear pins however.

 

[Dyer retired]

You may be on to something. Those are grooved bolts. Over torque could snap them off.

It would be nice to see the broken bolts to see if they sheared or broke in tension.

The augers are not bearing dependent nor do the touch anything but the snow unless you hit banks or pick up a stick.

I have chewed into some pretty good plow truck banks and only ever sheared one when I picked up a tree branch in the snow.

Well, you and Radioman might have found part of the problem. My neighbor tells me that he tightens the bolts to the point he thinks he might strip them. Why he does that, I'm not sure, but I've suggested that he just tighten them enough so that they're snug...I don't recall ever having one of mine come loose. We'll have to wait and see what happens the next snow storm....hopefully not too soon.

 

[radioman]

Is he using the jam nuts to hold shear bolts in or using regular nuts ? Using a regular nut om a real shear bolt will need to be real tight just to prevent falling out. If he is using the supplied jam nut with the shear bolts, then put it on to a point where the bolt can slide very little up and down . It would be kinda like a 1/16 gap or hair more for bolt to slide. This would virutally eliminate all tension on shear bolt, allowing max strength before shear.

Another school of thought is that is the bolt too long? does holding jam nut run out of threads before tightening? The wrenching can add more shear forces weaking the bolt before use.

 

[Dyer retired]

Is he using the jam nuts to hold shear bolts in or using regular nuts ? Using a regular nut om a real shear bolt will need to be real tight just to prevent falling out. If he is using the supplied jam nut with the shear bolts, then put it on to a point where the bolt can slide very little up and down . It would be kinda like a 1/16 gap or hair more for bolt to slide. This would virutally eliminate all tension on shear bolt, allowing max strength before shear.

Another school of thought is that is the bolt too long? does holding jam nut run out of threads before tightening? The wrenching can add more shear forces weaking the bolt before use.

He's had both jam nuts and regular nuts with lockwashers. I've always had the bolts with the lockwashers and they work fine just snugging them up. I ordered a pile for him through Messicks when I order some new ones for my new blower and they are the nut and lockwasher combo. He'll need to tighten them a little, but certainly not to the point of thinking they are about to strip. I'll call him Ralph (because that's his name) is the type that if a little tightening is good, then overtightening is better. We'll see how this next storm does and I hope I'll be able to report good news. Dyer

 

[keyman1808]

I am assumming that he lubricated the auger and all related points. And checked the gear oil in the gear box. If the auger isnt greesed then maybe its binding as its spinning. I know it obvios but I thought I would ask

 

[DGS]

There is one other thing that I can think of and that is the shear bolt holes in the augers and the shaft. Are they perfectly round or do they have elongated holes from working against the metal. If that is the case then drilling out those holes to the next bolt size may fix your problem.
Good luck
DGS

 

[Dyer retired]

I am assumming that he lubricated the auger and all related points. And checked the gear oil in the gear box. If the auger isnt greesed then maybe its binding as its spinning. I know it obvios but I thought I would ask

He does grease it often and isn't getting any unusual noise out of it.

There is one other thing that I can think of and that is the shear bolt holes in the augers and the shaft. Are they perfectly round or do they have elongated holes from working against the metal. If that is the case then drilling out those holes to the next bolt size may fix your problem.
Good luck
DGS

The blower was new last year and doesn't show any signs of the shear bolt holes elongating. He's had the problem since it was new apparently and seemed to think it must be normal. He mentioned to me this year that he thought he was shearing a lot of them and I was surprised to hear the number. As mentioned earlier, he may have been "over" tightening the shear bolts. I think the next snow storm will provide some answers.

Thanks again for all the suggestions and I'll update you all when the next storm has given us some test material. I haven't heard of anyone else having major, unexplained, problems like this, so it appears to be something unique to how he's doing things? Dyer, retired

 

[art]

To be riding the clutch petal or the petal on the left would answer the shear bolt problem. Seen it before with bad PTO pressure in full hydraulic units and a unit like the Kubota if the left petal was being hit while under load would cause the shear pins to shear from engaging and disengaging the The PTO system.

 

[Toyboy]

I got some new 5/16 x 2 1/4 shear bolts from dealer(70060-01338) for my BX2750 blower, and the specs call for torque of 17 to 20.5 ft pounds. I set mine at 19 ft #
I also drained and refilled the worm gear box with 80-90W Mercury marine lower unit lube. The stuff that came out was nasty looking. Surprised me to see a pressure relief valve on gear box. Maybe thats how moisture got in I think I'll make that a yearly PM, easy enough to do.