I've been watching this topic with great interest because I am planning to
install the used HZRN 72 ft crank up rotating tower I purchased recently.
My tower doesn't have any 'J' bolts supplied, and the specs don't spell out
anything but their diameter (1/2 inch). From the drawing of the concrete
pad for the tower, it seems that these bolts are only six or eight inches
long because the bottom of the bolts are shown to be even with grade level
and the pad is to be six inches above grade level. No cage or anything other
than the J bolts is shown in the drawing.
To apply what I've been reading to my installation, I thought I would get
three 1/2" diameter 'J' bolts as long as possible and build a 'cage' of
rebar around the bolts. This way, the concrete pouring cannot possibly move
the bolts with respect to one another and all I should have to do is make
sure the horizontal bars show above the concrete and remain 'level' during
and after the pour.
In other words, I'd like to make my bolts part of a 'cage' structure like
Tri-Ex uses. So, my questions:
1) Is the above plan ok (welding doesn't weaken the bolts or anything)?
2) Where can I get 1/2" diameter 'J' bolts and what lengths are available?
3) Are there different 'grades' or characteristics of these bolts that I
should take into account due to the welding I will be having done by a local
4) I paid for a mounting cage for a Tri-Ex LM-470 and they don't seem too
anxious to talk about letting me return it for a refund. If I have to keep
this cage, is there a way I can get some good out of it by using it as the
skeleton of the cage I want to build? It is pretty big and saves me the
cost of quite a bit of rebar and welding.
Thanks, and 73
Frank T. Brady - W0ECS
>>> the act of pouring the concrete twisted and turned my anchor bolts in
>> A better way to do it is to tack weld the J-bolts into position with
>My simple and effective solution for securing the threaded j-bolts for use
>with my self-supporting tower:
>1. Make TWO identical templates.
>2. Buy extra nuts.
>3. Attach the first template with a nut above/below at the lowest point of
>the threaded portion.
>4. Attach the second template an inch or above the first set with the extra
>nut above and below.
>This keeps the tower bolts from skewing relative to each other. The entire
>template/bolt cage can still rotate as a unit, but this can be detected and
>corrected at pour time.
>Rob Hummel (WS1A)
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
>Administrative requests: towertalk-REQUEST@contesting.com
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