Does any Vex part exist that would allow a high strength shaft to be connected to a motor?
There is currently no easy way to directly connect a motor to a high strength shaft.
The high strength shaft was designed for use with high reduction gearboxes that can create more torque than the standard (0.125in) drive shaft can handle. The 393 motor by itself does not have enough output torque to damage a standard shaft.
That being said, there are cases where a high strength shaft may be desired because of it’s bending strength (like long intake rollers) not it’s torsional strength. In a case like this, a 1:1 gearbox can be made with high strength gears where the input gear uses high strength inserts to connect to a standard (0.125in) drive shaft and the output gear is connected to a high strength shaft.
Let me know if you have any further questions,