Originally Posted by Chief Engineer
That's a new one for me.
I would be very suspicious of that.
Loosing 1/3 of the shaft size?
Sounds like somebody was too cheap
to buy the right coupling.
As the Chief Engineer
notes, the shaft has been reduced to 66% of it’s original diameter.
This results in a reduction of cross-sectional shaft area to 44% of the original area.
I “believe” that the result is about 44%* of the original shaft strength (tortional).
* Perhaps even less, due to stress concentration factors.