Rohn 25 Questions

[K5TS]

I am 68 and getting back into ham radio after many years, and going to put up a TA-33 at 40'. This is the current plan; I will be using a tilt plate built by NormsFab, which I already have and its built really stout and mounts with a 3/4" anchor bolt in each corner. The derrick will be two sections of Rohn 25 set in the concrete pad (vertical and parallel to) about 3 inches from the 40' tower tilt plate with a cable pulley at the top of the derrick and a winch at about 5' up on the derrick tower. The derrick will be approximately 17 feet high, (3' in the concrete) and set behind the tower about 3 inches. When the tower is in the vertical position, I will be attaching the tower to the top of the derrick with angle iron and u-bolts.
Question 1; With the tower essentially bracketed at 17 feet, and aprox 6 square feet of wind load, does it need a set of guys at the top? (Antenna will be about 25' above the derrick brackets)
Question 2; As long as 6 or more sections of 1/2" rebar are used to tie the 3'x3'x3' concrete pad together, can it be poured in 2 sections? Will a cold seam matter as long as there is plenty of steel tying it all together? At 68, I'm not sure I can mix and pour 45 bags of concrete in one day. (possibly, but not excited about that)

Any and all suggestions or critique are welcome.

 

[mmckenna]

This is one of those questions that probably is not best answered on a hobby website.
Rohn would be the ones to ask since you are doing a non-standard installation.

They will self support up to 40 feet, but 6 square feet might be too much. Adding a support at 17 feet will likely change that, but if you want to do this right and be sure it's not going to topple over and land on your house, or a neighbors, then talking with Rohn would be the way to go.

There are very few people on this site that I'd even remotely trust to answer this accurately, and then there would be a ton of variables about your particular installation that would be unanswered.

 

[K5TS]

oh okay. I was searching the web for ideas that would support my design, and came across Tower Talk. I assumed....wrong I guess...lol

 

[n5ims]

The tilt plate may also factor into the equation since it will have a different support structure than a standard tower section in concrete mount would so this may reduce (or even increase) the tower load capacity. It sounds like you may be good, but without specific calculations on your exact installation it's hard to really give you a firm yes or no answer. I prefer to opt for over designing the tower support than trying to get by with what might work as a minimal install. Good luck!

 

[merlin]

At 40 foot, I guyed my Rohn tower just because. A 5 element beam and triband vertical above that.
My pad was 4'X4'X2' that Rohn said will easily self support.
I do Agree with mmckenna and if you can't locate commercial tower install documents then go with Rohn pros.
As for the concrete, having a truck or even pumper come in is not much more expensive than DIY.
Use a template to set your J bolts and the work is done.
My tower survived the 6.6 San Fernando earthquake so glad I went a bit overkill.
73s

 

[K5TS]

At 40 foot, I guyed my Rohn tower just because. A 5 element beam and triband vertical above that.
My pad was 4'X4'X2' that Rohn said will easily self support.
I do Agree with mmckenna and if you can't locate commercial tower install documents then go with Rohn pros.
As for the concrete, having a truck or even pumper come in is not much more expensive than DIY.
Use a template to set your J bolts and the work is done.
My tower survived the 6.6 San Fernando earthquake so glad I went a bit overkill.
73s

Your concrete pad was 2 foot deep?

 

[merlin]

Your concrete pad was 2 foot deep?

Yes, doesn't really need to be any deeper. a 4X4, it would take a tornado to take over the tower.
I check the pad after the quake and still solid in place.
2 Meter dish is on a 1 foot deep pad.

 

[buddrousa]

The Rohn Tower book calls for all Rohn 25 concrete bases to be 3X3X3 that is 3 foot deep 3 foot square that is 1 cubic yard of concrete.

 

[merlin]

The Rohn Tower book calls for all Rohn 25 concrete bases to be 3X3X3 that is 3 foot deep 3 foot square that is 1 cubic yard of concrete.

I didn't read the book, besides, different soil has different stress factors.

 

[buddrousa]

I have put up at least 50 ranging from 50 foot to 180 foot I trust the Engineers at Rohn as all of my towers are still standing from 1974 through present day.