[Ground-station] Open Rotator - mechanical engineering meeting notes and plan

[Wally Ritchie]

The wind loading data is generally available as part of the specifications
by the dish manufacturer. Dishes of 1.8M and 2.4M are common. Dishes
without such specifications are likely to not have been completely
categorized as to RF performance either. Full characterization is required
to have high confidence in the G/T numbers.

The wind load depends on the design requirements. In Florida here, we have
to engineer fixed microwave dishes to the state requirements based on the
zone which ranges from 100mph to 150mph.  It's not trivial at the high end
even for a garage door. Since square laws are involved, forget about
meeting them. It's probably best to engineer to a reasonable operating
limit and to a stowed configuration during storms as only the latter can
meet code in South Florida.  (During Andrew all the dishes blew off the
National Hurricane Center).

BTW, a PE is required to do a site specific calculations for any commercial
installation. So avoid fixed installations.

We should probably have characterizations for stowed, deployed but
not-operating, and operating.

Just my $0.02





On Sat, Dec 7, 2019 at 11:57 AM Michelle Thompson via Ground-Station
<ground-station at lists.openresearch.institute> wrote:

> I hired a local open source robotics designer to go over our JAMSAT
> collaboration. This is a heavy-duty automated AZ-EL tracking station
> capable of LEO to Gateway. We fully intend for integration with SatNOGs.
> The demonstration is expected to be at Tokyo Ham Fair 2020.
>
> Our engineering consultant’s name is James Newton. You may recognize him
> as 2018 Hackaday Superconference prize winner. He’s very active in the San
> Diego Maker Movement. I’ve volunteered with him at events for 7 years.
>
> All of his engineering solutions for motor control are open source and are
> ready to go. He anticipates no further charges for his time, and is ready
> to help integrate his work for our prototype. I paid him out of pocket. No
> ORI money was used.
>
> What do we need to do to get to the prototype for demonstration?
>
> The sequence proposed moving forward:
> - Collect as many as possible dish data sheets with weight and mounting
> pattern to try to find commonalities.
> - Purchase / "procure" a "2 meter" (6 foot) diameter dish for local
> development. If Doug Phelps can send me all the remaining 2m dishes, then I
> will take them for prototype stations.
> - Pay for mechanical design of mount for common dish support maximum scope
> of commonly available dishes
> - Fabrication / adjustment of mount locally. Hopefully it can be welded
> using alignment "tricks" to keep the bearings right.
> - Attachment of actuators to axis (steppers / DC motors). Possible further
> mechanical design.
> - Attachment of encoder system  (James to lead)
> - Drive / servo controller / motion control electronics (James to lead)
> - Interfacing with existing control system (This is us)
>
> the first step is to gather data on the mechanical aspects of the target
> antennas; weight and mounting bolt pattern. The consensus from the local
> microwave and EME people is a pipe will be best.
>
> The mechanical designer doing the CAD (recommended by James) needs to know
> how fast they needed to move and how much load they would take from the
> wind. That last one is probably tricky to find out, but maybe we can
> prototype a solid mount and attach some strain gages to a data logger if we
> can’t find out from existing sources.
>
> Got answers, questions, feedback? Let’s hear it!
>
> -Michelle W5NYV
>
>
> --
> -Michelle W5NYV
>
> "Potestatem obscuri lateris nescis."
>
>
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