Snowblower shear pin mystery

[07wingnut]

I have a 2750D front mounted snowblower mounted to a BX23 tractor, that has performed well for the last couple of years. The only shear pins that have let go, did so because of encountering obstructions of some kind, the kind that does the pin in from physical shock. Lately, that has changed, and pins are shearing during normal blowing.
The shear pins are grooved grade 8 for the fan and grooved grade 5 for the augers. During the last snowfall, 20 inches of wet heavy snow, the snowblower went thru a dozen shear bolts for the fan only, and none for the augers. The sound of the blower changed as well, not a smooth sound, but more cyclic. Some of the bolts sheared when there was very little loading on the fan. My take on this was that there must be some vibration in the snowblower drive train that was causing fatigue in the shear bolts. So, the snowblower was partially dismantled in the garage for a bearing check, but they all were tight and smooth. The drive chain was not too loose, but on closer inspection, it was obvious that it was stretched or worn at the pins. The chain could be lifted from the top of the sprocket, even though it was tight. So, not seating properly on the sprocket teeth. I put on a new chain which did sit correctly on the sprockets, buttoned everything up, and spent 3 hours blowing snow with not a single breakage.
This apparently was the cause of all the shear bolt breaks. A worn chain causing repeated shocks to the drive train and inducing fatigue in the fan shear bolt. Who knew.
Hopefully this will help somebody from killing numerous shear bolts that were innocent of any crime.

 

[BoylermanCT]

Good to know and thanks for sharing!

 

[Hilbilly]

I have a 2750D front mounted snowblower mounted to a BX23 tractor, that has performed well for the last couple of years. The only shear pins that have let go, did so because of encountering obstructions of some kind, the kind that does the pin in from physical shock. Lately, that has changed, and pins are shearing during normal blowing.
The shear pins are grooved grade 8 for the fan and grooved grade 5 for the augers. During the last snowfall, 20 inches of wet heavy snow, the snowblower went thru a dozen shear bolts for the fan only, and none for the augers. The sound of the blower changed as well, not a smooth sound, but more cyclic. Some of the bolts sheared when there was very little loading on the fan. My take on this was that there must be some vibration in the snowblower drive train that was causing fatigue in the shear bolts. So, the snowblower was partially dismantled in the garage for a bearing check, but they all were tight and smooth. The drive chain was not too loose, but on closer inspection, it was obvious that it was stretched or worn at the pins. The chain could be lifted from the top of the sprocket, even though it was tight. So, not seating properly on the sprocket teeth. I put on a new chain which did sit correctly on the sprockets, buttoned everything up, and spent 3 hours blowing snow with not a single breakage.
This apparently was the cause of all the shear bolt breaks. A worn chain causing repeated shocks to the drive train and inducing fatigue in the fan shear bolt. Who knew.
Hopefully this will help somebody from killing numerous shear bolts that were innocent of any crime.

Hi neighbor and thanks for sharing.

You might also want to check the sprockets the chain rides on because they all wear together, so if the chain is worn, the sprockets are likely worn too. Check to see if the sprocket teeth are thin and sharp. If so, then the sprockets should be replaced at the same time. This stuff is cheap at Princess Auto.

 

[07wingnut]

Hi neighbor and thanks for sharing.

You might also want to check the sprockets the chain rides on because they all wear together, so if the chain is worn, the sprockets are likely worn too. Check to see if the sprocket teeth are thin and sharp. If so, then the sprockets should be replaced at the same time. This stuff is cheap at Princess Auto.

The sprockets are pretty well like new. I use generic roller chain that is cut to length from a roll of chain, these wear out fairly quickly compared to Oring chains. If the sprockets do wear out, I doubt if the stuff at Princess Auto could be mad to fit, probably have to order OE from Kubota in Kamloops. Enjoy your balmy temps in Barriere, here it is -37C and I hope that I don't need to start the tractor today.

 

[Hilbilly]

I blew out the outside bearing on the shaft that comes from the gear box to drive the auger shaft last year and the idler sprocket. Apparently snow blowers aren't meant to run through piles of gravel. PA had the bearing and the idler sprocket / bearing in stock. You're probably right about the other sprockets though.

It's not as cold here. -31C this morning and it's warmed up to -29C. Warm enough to put on shorts and go for jog.:laughing:

 

[metalbender]

Generic pa sprockets could be made to work, visit Bigbarn, he has the right stuff.

 

[07wingnut]

The chain in question had 2 seasons of use and if I recall, probably was not lubed often enough because you need to remove the cover. Not a big deal, but inconvenient in the winter. This mod makes it a lot easier and such, will be used more often.
Simply remove the plug, squirt in some chain oil, and let it trickle down the drop tube, directly onto the chain. The fly in the ointment is that the snowblower should be operating slowly, so the oil is distributed on the chain. My BX has a safety disable switch, which allows the pto to run while the operator is off the seat. Other options to do this may exist, depending on the tractor.

 

[Toyboy]

I've used motorcycle chain lube and Amsoil multi purpose synthetic spray grease on mine. I'll lube mine before snow season or when I remove blower in spring and clean it up. No need to drip oil on the chain all season.

 

[oosik]

I used motorcycle chain lube on mine, also. Spray it on - it turns to a whiteish, waxy goop and hangs onto the chain for dear life.

 

[MF RED in MT]

I used motorcycle chain lube on mine, also. Spray it on - it turns to a whiteish, waxy goop and hangs onto the chain for dear life.

+1

KC