I strongly agree, a UV resistant plastic is a better way to go. I use
black UHMW which is UV resistant and is almost as slippery as teflon,
rulon, torlon or exotics like Vespel and < 1/10 the cost. I have a 6061
collar and stainless plate to ride on the UHMW 4" thick block (3" 22'
alloy mast) but it is set for the prop pitch to handle the axial load
(500#). The collar is there as backup and to facilitate work on the PP.
Every rotator or thrust bearing with steel balls on aluminum races I
have disassembled, resuscitated or trashed shows the results of
fretting. When parked the oil film breaks down and fretting digs a
divot for each ball. Very small rotation cyclic loads kill ball
bearings, even instrument grade ones in protected environments (eg disk
drive rotary actuators). Very expensive lubricants are often employed
to lengthen their life. White lithium grease is only slightly better
than Crisco for lubing your rotator. Check out DuPont Krytox lubricants
and others from Nye lubricants. More easily found are marine grade
fully synthetic greases with anti corrosion and high pressure additives.
Frequent rotation enough (~ 25-40 degrees depending on the race diameter
and ball size) to cause a full rotation of the balls brings a fresh oil
film into the ball-race contact area and is an excellent preventative
measure. Several times a week would be ideal. Parked for weeks is an
invitation for excessive wear.
Very few hams are "anal" about bearing lubrication, but I am when
replacing a $600 matched pair of ABEC9 angular contact bearings in a
machine spindle.
Grant KZ1W
On 12/9/2016 6:14 AM, charlie@thegallos.com wrote:
Looks really well made. I had the original Rohn counterpart for years and
it just kept on going.
I added a zerk fitting so I could grease it. They last a very long time
dry without lube, but I am anal
about lubing everything hihi.
Bob
K6UJ
Looks nice, but one thing I just have not been able to understand for years
Tower thrust bearings are a LOW rotation speed, high load application,
probably the WORST place to use ball bearings. I would expect either
tapered roller bearings, or today, do what most of industry does, and use
an engineering plastic bearing. I mean, we don't need a torlon bearing
there (the loads are NOT that high)
I mean, a glass reinforced nylon, or a PTFE (Teflon) (say a 25% glass
filled or molly filled) isn't going to cold flow at ALL under loads a 2"
mast could sustain, will NEVER need lubrication, will never corrode etc
You either get them molded for you (for some materials would be the
cheapest way - you do NOT want to know what torlon costs), or you slice it
from tube, or you even just use end on rods set around the circumference
I mean, today they run the pivot bearings and lower boom bearing on cranes
in plastic bearings, because they hold up better than metals in those low
rotation speed, intermittent rotation applications
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