[TowerTalk] Thrust Bearing Concerns

[Paul F. Merrill]

Kurt told me that the PP is fine taking the weight and discouraged me from
having the thrust bearing take it all.

Paul / W7IV

On Sun, Jun 22, 2025 at 08:03 <towertalk-request at contesting.com> wrote:

>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 22 Jun 2025 06:00:30 -0600
> From: Tom Hellem <tom.hellem at gmail.com>
> To: towertalk <towertalk at contesting.com>
> Subject: [TowerTalk] Thrust Bearing Concerns
> Message-ID:
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> CANyX0AqQ2w2hqpUzeLx_kTvfwPrZ5FVtbEYrtCiLj0dpwSk3uw at mail.gmail.com>
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> Looking for some input on the DX Engineering TB-400 thrust bearing.
>
> Here is the scenario:
> Rohn 55 tower supporting a large 6 meter EME array, in an "H"
> configuration.
> 4 yagis , each with 50' boom, and the main boom is also 50 '.
> The total weight is approx. 700 lbs.
> The rotor is one of Kurt's prop pitches, the small version (9,000:1).
> I believe the max thrust that can be handled by this rotor is 500 lbs. or
> so.
>
> We have purchased the DXE-TB400 thrust bearing to be installed on the
> BPL55G
> flat top. The hope is that this bearing can be used to support the entire
> weight
> of the array, thereby eliminating any thrust load on the rotor.
>
> Problem is, the documentation that comes with the bearing does not specify
> a max
> thrust load for it, nor does it give a torque specification for the  three
> set screws
> that tighten against the mast. Furthermore, the upper half of the bearing
> is cast aluminum,
> so the threads for the 3   3/8" stainless set screws are aluminum. My gut
> feeling is that
> the aluminum threads are going to strip out  before we can get enough
> torque on them
> to prevent the mast from slipping down and putting the entire weight of the
> array
> onto the prop pitch rotor.
>
> I am in no way suggesting that the bearing is not a good quality part.
> But I am concerned that we are asking too much of it.
> Another concern is that the bearing doesn't come with a grease fitting.
> This setup is located near the coast of Oregon, they get a lot of rain
> there.
>
> Anybody have suggestions how we can improve this setup?
>
> All input is appreciated.
>
> Tom Hellem
> K0SN
>
>
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