On Wed, 29 Aug 2012 08:17:01 -0500, Pete Keillor
wrote:

On Wed, 29 Aug 2012 05:55:46 -0700, Larry Jaques
wrote:

On Wed, 29 Aug 2012 10:50:09 +0000 (UTC), xpzzzz
wrote:

Thinking of making a pedal-powered boat, stainless shafts, suggestions
for bearing materiel please. And sources for suitable plastic mitre
gears in qty=2 pairs, smallparts has some but they may be too small.

I've seen ceramic bearings advertised and wonder if they'd be good in
a watery scenario. Ball bearings would be much better than bushings.

I've used ceramic bearings in hot corrosive service, but not
submerged. I think the difficulty in getting a complete seal and
particulates in the water would cause ball bearings to fail sooner and
more catastrophically than bushings.

Dad tried roller bearing pillow blocks on his rice field levee rollers
once(4500# concrete spool, mild steel axle). They failed in less than
a year. Big loads, lots of dirt, slow speed, side of the field
storage. The maple blocks we boiled in old oil usually lasted at
least a decade.

But would they have worked as well on a pedal-powered unit?
Anything you can do to reduce friction or inefficiencies on a
human-powered device is a real must.

--
Stay centered by accepting whatever you are doing.
This is the ultimate. -- Chuang-tzu