Model 50 snowthrower breaking shearpins

I have broken a pin twice in the rotor drive assembly and don't know why. Everything turns very easily and is loose.
Yesterday I had the tractor running about 1/2 throttle, turned on the PTO and it broke the pin through the small chain sprocket.
The pin is the 1/4" x 2" coiled spring (from the dealer) and this pin is taking the full torque of the PTO and transferring the force from the driveshaft to the sprocket. There isn't enough room to use a hardened steel bolt and nut. I took it all apart and there isn't a keyway or anything else engineered. I also noticed that the sprocket slides easily onto the shaft. Should this be a tight fit?

Has anyone else had difficulty with this?

Outdoors,
Because you have a 184, with an 'electric PTO Clutch', having that pin break while engaging that 18" to 24" x 56" long drum at 1/2 throttle would be considered 'normal'. Because of the instant 'wham' engagement of an electric clutch, you must throttle back to idle before trying to engage that type of 'rotating mass'. If you had a 'manual' PTO clutch, like the 154 or 185, you could 'feather in' the engagement - but not so with an electric clutch. As a point of 'good operator manners', no matter what type of clutch you have, you should always throttle back to the lowest throttle position available (that won't stall the engine) before engaging any clutch driven accessory. You wouldn't wind the engine on your truck up to half throttle and 'pop the clutch' to engage the transmission (unless you are 16 and don't have to pay for the new tires). - NJDale

Are you 100% sure the dealer sold you an OEM pin? Maybe they picked them up from an independent supplier to save a few bucks.

I know the driveshaft pins on a Cub Cadet can't be the standard hardware store brand.

Just sayin . .

Already learned the OEM vs. Aftermarket lesson. This is definitely the OEM (wound springsteel) not a cheap roll pin.
Wish I had a little more space. 1/16" more would allow for a hardened steel bolt and nut.

I am thinking about putting a bolt through it then welding a knob onto the other side of the bolt as a keeper. It would have to be cut off to replace, but it would probably withstand the heavy snowblowing better than the pin.

I have a big bag of stainless steel roll pins that are very strong. I wouldn't use one if it is supposed shear when running through something bad in the snow.

Tom

Bolts usually wear in two from the constant loading/unloading. I also found out the hard way that you can get too hard of a pin, (very brittle).

Hope you get it figured out.