Phenolic cutless bearing

[saltyrob]

Hi Folks,

I have noticed that there is a small amount of movement between the phenolic resign sleeved bearing and shaft. The bearing has replaced before last years season.I have read that this type of bearing swells slightly in water, therefore is it correct to assume that it may have dried out during the winter and on immersion will again swell and reduce the amount of movement.

Many thanks

Rob

 

[Fr J Hackett]

Its the phenolic case that swells to make a tight fit in the stern tube the play you describe is wear of the bearing material, the black grooved rubber compound inside the phenolic case. Depending on the amount of play it could indicate some eccentricty in the prop shaft, however a mm or so of play is not a problem. What was it like before launch last year?

 

[TigaWave]

We supply phenolic cutless composite bearings and yes there is some water absorption. However it is accurately known and the bearings are finished to run very close tolerances. The actual expansion is a factor of bearing wall thickness but as the bearing wall gets thicker it also has more strength to resist expansion so it's not a simple %.

For a 25.00mm shaft (35.00 carrier ID), if the bearing was supplied at the correct size I would expect to see less than 0.25mm radial clearance, or an inside diamater of between 25.12 to 25.22mm. This allows for the very small bearing closure due to moisture absorption.

However there are a range of makes of phenolic composites and some expand more than others.

What is the shaft and carrier size and what gap have you got? the calculator will let you know if this is normal, but any greater than 1% of shaft OD dry is getting to big for ours.

The calculator can be used on our website page for Maritex bearings, or you can download it.