At 03:39 PM 2/10/97 -0800, Vince Greczanik <vince@isolab.com> wrote:
>I have an aluminum Universal tower which has splits in the lower leg
>sections. Has anyone had any success in repairing this anomaly? Or should
>I just leave well it alone - I fear that heat due to welding may change the
>current strength in this area.
Yes, I replaced my 30" base section with two new 30" sections (took out a
22" straight section further up) to increase the wind load capacity. I
brought the damaged section to a professional welder who ground V notches
into the splits. He then welded the V using an inert gas welder. This
guy must have been an artist because he had to show me which legs had been
repaired when I came to pick the section up. He did an absolutely beautiful
repair job.
>I recently removed this tower from service and the sections were fastened
>with carbon steel bolts. I was surprised to see that the bolts were in
>pretty good shape! ... must have been the good drainage! I too noticed
>the 'reduced' diameter of the bolts but not too bad. Rig was in service
>over 10 years.
A Heights aluminum tower had developed the 'cracked leg' syndrome a
number of years ago. When the ham called the mfgr (in the dead of winter),
they recommended he 'splint' the damaged area until he could replace the
section. The splint was made by using two lengths of angle aluminum and
sandwiched the tower leg. A half-dozen U-bolts held the splint in place.
This tower stood for several years before it was taken out of service when
the house was sold.
>Before it goes back up I want to repair the splits and will surely use SS
>fasteners. I will also utilize the 33+ at all the joints - excellent
>suggestion by Tom (N4KG).
ABSOLUTELY DO NOT USE STAINLESS STEEL BOLTS ON YOUR ALUMINUM SELF
SUPPORTING TOWER!! You MUST use GRADE 8 steel bolts. The shearing
stress on a self supporting tower is even greater than a guyed tower.
I had the same idea as you did, eliminate the potential rust problem.
Fortunately the fastener distributor asked me what I was going to use
the SS bolts for. (I had brought the old rusty bolts in as samples.)
He said the SS bolts were substantially weaker in shearing strength
compared to the original bolts. A call to Universal Mfgr verified this
fact. (The bolt distributor DID offer to special order some stainless
that would satisfy the Grade 8 specs, but he cautioned me they would
probably cost about $10 each!)
Also, you could replace all the Grade 8 hardware bolts on your tower
4 or 5 times over for the same cost as one set of stainless hardware.
>Keep up the good work!
>
>Vince WD8MIC
73 de Bob - K0RC
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