QA42A snowthrower sheers pin

[bob f]

I have a qa42a snowthrower on a cub 125, I have a problem sheering the pin in the chain pulley that is on the drive shaft for the blower. This happens quite often. It has to be driven in with a hammer, seems tight. Everything turns with ease and am not hitting anything hidden in the snow. Any ideas why?

[Graflex45]

You are using a sheer pin in it? they had a spirol or regular roll pin in the toothed gear from my understanding. Its quite a massive impeller to get going, I'd think sheer pins would break from just the torque of engaging the clutch.

[bob f]

Yes I am using a roll pin, I called it a sheer pin becaus it sheers

[bob f]

I remember my dad had one just like this in the late 60s and never had a bit of problems sheering the roll pin.

[spndncash]

are you using a spirol roll pin or a spring roll pin?

[bob f]

spring roll pin

[spndncash]

I think most of these were originally a spirol roll pins - they are much stronger then a spring roll pins. Please dont go by my word- I dont have a snow blower of this type.
But the roll pin in my creeper gear on my 106 is a spirol type by design, anything else breaks in about an hour. Cub Cadet Specialties has (or did have them).

[bob f]

do I use a stainless steel or a carbon steel pin Thanks

[ol'George]

Originally Posted by bob f

do I use a stainless steel or a carbon steel pin Thanks

Just use COILED pins and they do make heavy duty coiled pins that have more coils.
If you are not familiar with coiled pins, they are not solid,
------- or split like roll pins.
they are like a coil inside.
if you took the paper tube from a roll of toilet paper and cut it lengthways and coiled it tighter making it smaller in diameter, that is how a coiled pin looks inside.
Coiled pins are much more resistant to shearing.
Mc Master-Carr has them, also most case/IH and John Deere AG dealers
if you are in a rural area.

[Graflex45]

I'm amazed that the roll pin is shearing though. I just rebuilt the same model snowthrower and tried it out for the first time. The snow we had was way too wet and dense and I had to switch to the plow because it packed in completely and just plugged the chute. I even stalled the engine completely on a 1450 because it clogged when I pushed it in a show pile, and no damage to anything on the thrower.
Does the impeller spin freely without the chain attached? are the toothed wheels and the chain in good condition or worn out with a lot of wiggle?