Andy

This type of prop shaft is used when the motor is mounted to a nose mount on most motors. In this type of mount the mount is placed in front of the motor. The motor is mounted with bolts thru the mount and the motor shaft extends forwards thru the mount. The collet is then placed on the motor shaft and secured, with the allen screw in this types case. Unfortunately, many of us have not had much luck with set screw retained collets. They tend to spin off. A more secure type uses a pinch connection. When the prop is tightened the prop backplate which is tapered internally tightens down on usually 3 jaws that go over the motor shaft and secure the collet to the shaft. One caviat with these is that is one ever does spin loose it will not for some reason be reusable and a new one must be used. Once they spin off once the seem to keep doing it. Having said that while I have had many of the set screw ones loosen, even with multiple set screws and flats ground into the motor shaft, I have never had a clamp down one come loose. They must be sized by the way to the shaft. Pretty much all are metric sizing.

bob branch

Hello Andy,
On some motors, like the AXI ...
If you mean the oversized wheel collar, then that is used when firewall mounting the motor.
If the prop is mounted to the rotating bell, then it is actually possible to pull the bell and shaft out of the fixed portion of the motor unless the big collar and "C" ring are placed on the shaft that protrudes from the rear of the motor. The C-ring, if provided, is not enough on its own.
When front-mounting the motor this is not an issue.

I hope I understood your question properly,
   Dean