[TowerTalk] how much rust is too much?
matthew at matthew.at
Thu Oct 16 21:17:43 EDT 2014
On 10/14/2014 1:40 AM, Roger (K8RI) on TT wrote:
> On 10/13/2014 11:45 PM, Matthew Kaufman wrote:
>> On 10/13/2014 8:37 PM, Tim Duffy wrote:
>>> Hello Matthew:
>>> What is the center to center distance of the legs? It could be Rohn
>>> 25 - not
>>> model 45 from the photos.
>> If my notes are right, I measured it at about 17 inches, and the
>> joints are like Rohn 45 joints, not swaged joints.
> I installed 100' of 45GT. It used swedged joints, just like the 25G
> only larger. The solid leg 45Gs use a circular flat plate joint. It's
> about 3" in diameter IIRC, but it's been a long time since I saw one.
Went and re-measured. Almost certainly is Rohn 55. 17 inch faces, 1-1/2"
legs, welded sleeves and bolted.
> Look for pits after removing the rust. Be extra cautious if there are
> any pits large enough to notice. There are ultrasonic thickness
> gauges for measuring the tube thickness. I used to measure a lot of
> pipes and tanks, even with epoxy paint on them. If there are ANY pin
> holes in the tube or welds, you will need an auxiliary base to hold
> the tower, or a big crane.. A job for professionals.
It is starting to clean up pretty well, but there's a bit of pitting
where the worst of the rust was... no pinholes and nothing deeper than
this though. Photo of a mostly cleaned section here:
Except for the pitting, the diameter is within 0.2mm of the non-rusted
(and still galvanized) diameter after cleaning according to my caliper.
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