I my town they are doing some road construction around the main
intersection. They have some temporary telephone poles in place and use
large concrete blocks with a loop on the top to guy the telephone
poles. I'd estimate the block to be about 3 X 3 feet X 4 feet long.
The loop is ~3/4"-1" steel cable.
The telephone poles are used to hold up traffic signals that span the
intersection so there is quite a bit of weight up there and also a lot
of wind load.
On 1/22/2016 11:06 AM, jimlux wrote:
On 1/22/16 7:31 AM, dw wrote:
For those familiar with the AB-621 military launcher mast units.
Lets say there was an interest in using this on a field day event, where
there is a concern that the ground is too soft to safely establish
anchors.
Is there a possibility of using concrete wall-barrier blocks bolted
together, as dead-weights to safely hold the anchors?
Sure..
The catering/party equipment rental places do this all the time, as do
riggers for theatrical/music performances. They have big concrete
blocks with a big loop sticking out of the top (rebar or a piece of
pipe bent in a U) that they connect their guys to. We've got a 90
foot-ish structure in a parking lot at JPL with a bunch of 5000 lb
blocks like this holding it in place.
I've also seen portable anchors that you fill with water. You're
basically relying on bulk mass to hold things in place. IN some
places, dragging a hose to fill a kiddie pool or trash cans or trash
bags is easier than dragging concrete blocks around.
You could also look into what are called FIBC (Flexible Intermediate
Bulk Carriers) which are those big fabric bags full of just about
everything you see on the back of a semi flatbed truck. They hold
about a cubic yard, they cost about a dollar (empty), and you might be
able to rent/borrow/buy things like a yard of gravel or dirt in a
FIBC. If you have something that can move a couple of tons around.
They're pretty nice because they have a strong fabric strap handle
(how you pick it up with a crane, forklift, etc.) that you can hook
your guy to. And, depending on what it's filled with, it will spread
out and conform to the ground surface.
I've not tried it, but I'll bet you could get one of these things,
line it with polyethylene sheet, and fill it with a ton of water
pretty easily. They're really strong, really cheap, and store very
compact when empty. (actually, just looking up prices, I see that
they actually make liners for these things so they can hold liquids).
Looks like they're about $15-20 each on amazon when you buy just one,
brand new.
You need to calculate what sort of loads you're going to see, and make
sure you have enough mass to hold it. You can probably figure
something like a friction coefficient of 0.3 or something for the
sliding motion/horizontal component.
https://www.nzta.govt.nz/assets/resources/surface-friction-conference-2005/8/docs/frictional-characteristics-roadside-grass-types.pdf
has a handy table of sliding friction of a concrete filled tyre (in
NZ) across grass and dirt. (It's all about locked wheel skids and
distances). As you might imagine, grass is slippery when wet.
For example, I think I can come up with a number of 60lbs cement
wall-barrier slabs that can be bolted together for each anchor point.
If this would be a viable option, how much weight on the anchor blocks
would guarantee a safe installation?
The intent is to put up a 40 meter 2 element yagi, without a rotor, at a
height of 50 feet.
Thanks in advance.
N1BBR
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
--
73,
Gary K9GS
Greater Milwaukee DX Association: http://www.gmdxa.org
Society of Midwest Contesters: http://www.w9smc.com
CW Ops #1032 http://www.cwops.org
************************************************
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|