Interesting...how long are they? In my area we have a lot of truss arms on wooden poles in a normal type mount (not a clamp mount) and they are 20 feet long (6.096 meters)
Most of the arm we have around here are 15-20 feet long..... my electrical company uses standards of 30 inch, 10 foot, (and i suspect they started using 12 foot), 15 foot and 20 foot for the wooden pole installation....
However for the Maryland State lighting, on a metal pole...they have the longest arms I know of...and they are 30 feet! But someone may have found a 40 footer up in Canada..I believe
Jace it was me that found that 40 foot arm, and it was in Michigan. Here we use 6, 8, and 10 foot tapered elliptical arms as standards but I have also seen 4 and 12 footers installed before too, not to mention the few other designs and sized installed formerly.
Joe....markings aren't always found....for example...the older 20 foot truss arms on wooden poles I have found in my area doesn't have any markings (I have seen one up close) and I have been trying for a long time to find out who made them...I already knew the newer ones were made buy Curlees....but the older ones, I recently found out! It's HAPCO!
That's true I have a feeling that this arm design MIGHT be a Powerlite design since Al-Struct bought a lot of Powerlite's designs but I can't find any more info.
However for the Maryland State lighting, on a metal pole...they have the longest arms I know of...and they are 30 feet! But someone may have found a 40 footer up in Canada..I believe