Too much torque!

[mmarmino]

Guys,
I got done with the 420 upgrade and got it going.
So far though it's sheared off both rear tire plates where it mounts to the rim. And yesterday I was going to look at going from the #41 chain and sprockets back to the original #520. That's when I seen that the key in the Jack shaft was also sheared on the sprocket end. I know the sprocket that's on the 150s are splined because I took it off to see if I could put it on my jackshaft. I'll get some pics tonight of the situation.

 

[Bbqjoe]

What did you expect?

 

[mckutzy]

What was it mounted too???
If keys are sheared... Something else is awry...

 

[KartFab]

That shear sounds like fun. Ba dum tiss.

 

[mmarmino]

Not the best picture but you can see the setup.

 

[Bubba_Z]

Sounds like you are putting all the pressure on the key...
Key ways are only half of how you hold something on a shaft.
picture this...you clamp or tighten a thing to a shaft. Put torque to it and it slips.
The clamp was tight but the torque was more. So you add a key way. The two methods together, work like this. The Key keeps the slippage from starting and the clamp/nut (whatever) keeps the key from taking all the stress. Any slop and you are beating the key to death. When you turn a sprocket/wheel hub whatever and it moves but the axle does not
your key will fail sooner or later.

 

[mmarmino]

Well, I made the shaft and cut the keys for the sprocket myself on a mill. The shaft was made for that sprocket. All I can think that may be the key stock that was used wasnt a standard key material.

 

[mckutzy]

What was the size of the shaft?..

I have made dozens of keys all sorts of sizes, none have sheared in the manner you've described.. Also meant for far more powerful motors and machines...

Post a few pics of the keyway you milled and the hub it matches...