View Single Post
Old 03-11-2017, 10:35 PM   #7
Ski in NC
Technical Guru
Ski in NC's Avatar
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,452
That bearing is not appropriate to the application. Neither the lock collar nor the setscrew can hold the prop thrust load. Engine and gear are on flexible mounts so thrust will cause fwd/aft displacement of the shaft. Shaft will move in that bearing as a result. And the rather trivial restraints via collar or setscrew are not going to hold it.

I wonder why the bearing is there at all. How long is the shaft and what is the fwd/aft spacing of the rigid supports? And what diameter shaft and speed? Those are the criteria for the shaft whipping calc, which is why intermediate bearings get spec'd.

Without knowing all the details, I'd be tempted to recommend letting the bearing ride loose on the shaft, and hopefully inner race will spin with it and not act as a journal bearing. Or maybe put a split piece of hose on shaft and inner race and hose clamp it togther. That way you are assured race will spin with shaft yet thrust load will be taken by gear.

I've designed a bunch of shaft lines and would never use that bearing style unless it was the sole thrust carrying device, and shaft restrained accordingly.
Ski in NC is offline   Reply With Quote