On Sat, 12 Sep 1998 14:29:04 +0000 Dave_K9NX <n7ex@athenet.net> writes:
>
>At 11:39 PM 9/11/98 -0600, T A RUSSELL wrote:
>>
>>Hi Bill,
>>
>>Why use a thrust bearing at all?
>>
>>Most rotors can carry several hundred pounds of dead weight
>>which helps keep their bearings in their races. If a single
>>thrust bearing is used at the top of the tower and it is tightened
>>to carry the weight of the mast and antennas, then the side load
>>actually increases on the rotor, increasing wear on the races in
>>the rotor. NOT a good plan.
>
>Tom
>Hmmmm..........
>
>Explain how you would calculate the side loads on the rotator in both
>cases below.
>
>First case: The weight of the mast supported by the thrust bearing,
>
>Second case: Weight of the mast supported entirely by the rotator,
>Assume
>the mast has minimal (few thousandths) of play where it goes through
>the top of the tower.
>
>
>Dave
>K9NX
>
>>
>>de Tom N4KG
Hi Dave,
Perhaps I over simplified.
The side load will be the same in both cases, pivoting at
thrust bearing, with the antenna load above, stabilized
by the rotor at the bottom.
The important DIFFERENCE is that when the rotor
bears all of the weight, that weight tends to keep the
48 ball bearings in the upper and lower rotor races
inside the rotor centered in their races.
When the rotor bears ZERO weight, there is ONLY a
side load applied to the rotor (when the wind blows)
which tends to wear the rotors out, or so I am told by
people who have used a single bearing at the top
of their tower to carry the weight.
If I remember correctly, the HAM series rotors are
rated for around 900 lbs of vertical load. Why
spend all those $$$ for thrust bearings which have
relatively few ball bearings to carry the load when
the rotors have 96 ball bearings which are designed
to carry the load?
de Tom N4KG
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