[ML-Hams] HARC Tour This Friday

[Kris Kirby]

On Wed, 13 Apr 2016, Jeff Cotten wrote:
> Hi Hams :) 
> 
> This Friday is the HARC tour of Makers Local 256.  They should arrive 
> around 8pm.
> 
> Here's an off the top of my head update:
> 
> * Darryl helped come up with a design for a tilting mast.  We have the 
> pole, we just need the base.  If anyone knows where we can get cheap 
> metal pipe fittings (the same kind used to run water or gas lines), it 
> would help cut down on cost.

There's no such thing as cheap when structural elements are involved. I 
would recommend scouring local surplus for structural titanium pipe. 
Surplus from NASA projects are a great source. Entirely possible to run 
across T6061 aluminum and Schedule 80 or greater steel tubing. Just 
don't compromise aluminum tubing by drilling it or welding to it (unless 
you're a certified structural welder). Clamps are the way things are 
done when it comes to antenna mounts. 

I recommend studying up on rigging and having a firm understanding of 
the dynamics involved before going vertical. What works at roof level in 
70 MPH winds won't cut it at 300 ft where the wind is almost always 5-35 
MPH.

It's pretty fascinating stuff when you look at how a gin pole is used, 
the history of such, and the development of the crane. Also load 
factors. 

http://training.bnl.gov/demo/BasicRiggingWorkbook.pdf
http://energy.gov/sites/prod/files/2014/01/f6/HoistingRigging_Fundamentals.pdf
http://www.globalsecurity.org/military/library/policy/army/fm/5-125/fm5-125.pdf
http://www.globalsecurity.org/military/library/policy/army/fm/5-125/

I would not recommend taking any guidance from HARC's previous use of a 
trailer-mounted tower as a crane for raising and lowering towers at 
Field Day. It's worth pointing out that HARC has had a number of 
engineers involved over the years, and specific safety factors may have 
been followed, compromised, or simply ignored during use of the rig. 

People can get killed, and that's why proper rigging is important. 

Elk River is a local manufacturer of safety equipment, and GME Supply 
distributes that gear. If you buy Elk River gear from GME Supply, the 
Elk River equipment ships directly from Cullman, the rest of the gear 
from GME Supply's warehouse in MO. 

> * Marshall Space Flight Centers (M) Amateure Radio Club (MARC) is 
> revitalizing on the arsenal.  I toured their ham shack \ building, 
> it's pretty awesome.

It's a great place to be in case of tornado warning. My first contact 
was from there, to Shuttle Discovery, around 1992/1993. 

Just remember to visit the bathroom before arrival. 

> * Lisa and I tried to call into the MARC (Marshall Space Flight 
> Centers) first ham net last night, but alas, there are no ham radios 
> on our ham shack.  It was held on a repeater hosted on Brindlee 
> Mountain ( 147.180 ).  I was eventually able to call in to the 145.330 
> repeater on Monte Sano , someone did some kind of magic that bridged 
> the two repeaters.  Fancy.

NARA has the ability to link 145.33 / 146.94 / 147.18 when the occasion 
arises. A yagi might have helped in this case. 

Also, steel is heavy and aluminum is "light". In outdoor installations, 
regular steel ("zinc plated") will corrode to the point you have to cut 
it to remove it. Galvanized steel ("heavy, hot dipped") can be removed 
in 20 years. Stainless steel can be removed and reused at 20 years, 
provided it's not galled. Stainless is expensive, but strong, and worth 
it almost every time. The only downside to stainless is that it can 
develop stress fractures over time. This has been noted particularly in 
rail cars, where an aluminum skin was used over a stainless steel frame. 

Also, never apply cold-galvanizing to copper. Always stack metals 
according to electronegativity; an easy way to remember is stainless 
between aluminum and copper. No-alox between aluminum antenna elements, 
aluminum junctions, etc. where ever aluminum meets another metal. 

--
Kris Kirby, KE4AHR
Disinformation Architect, Systems Mangler, & Network Mismanager