Thanks to everybody who responded to my thrust bearing mounting idea.
Many of you considered the idea very carefully and crafted thoughtful,
detailed responses.
Bottom Line: Don't mount the TB-3 thrust bearing upside-down.
The reasons mentioned were:
1. Upside-down position places the bearing in "tension" mode
versus "compression" mode in the normal mounting position. Not clear
whether the bearing is designed to handle operation in this manner.
2. In the inverted position, the bearing may be more likely to
collect water, accelerating water damage.
3. If all the mounting hardware were to fail [fall out], having
the bearing mounted on top of the top plate provides a better fail-safe
situation.
I also received a couple of good suggestions regarding mounting of the
thrust bearings:
1. Mount the lower thrust bearing further down inside the top
section, and mount the rotor on the top rung of the section below the
top section. Cut out one of the lowest horizontal rungs of the top
section for rotor servicing. This increases the distance between the
bearings, providing more leverage at the lower thrust bearing and
reducing the potential for mast/bearing/rotor alignment problems. A
tower joint appears to be the place where removing a horizontal rung
will have the smallest impact on strength.
2. Investigate the possibility of mounting the upper thrust
bearing on a plate near, but just below, the top plate to allow for
easier removal, if needed.
3. Forget about a top thrust bearing altogether, and use a
tube-type top section instead. It will never fail and it's cheaper.
Thanks for all the help. Concrete for the anchors and base goes into the
ground on Monday morning. We'll be firing RF at you in a few weeks!
73,
Jim Idelson, K1IR
jimi@designet.com
http://www.designet.com/k1ir
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