Delrin vs. Lexan vs. Fiberglass 2

[Scott231us]

Hi, I need some help/input on this.. I'm uncertain which material would be best for this purpose. This setup is a little unique. Basically I'm trying to produce a non-conductive solution for mounting a 22lb antenna 6' feet off the side a tower. I've chosen to use a 1.5" solid round rod for this horizontal arm, but I'm not sure which would be best.


This material will be outside in a windy environment and needs to be tough and survive the element. The rod will stick out 4-5 feet, then a heavy duty piece of aluminum tubing with a 1.54" I.D. will mate with it and provide the last 1-2 feet. I would also like to be able to drill holes through the material to install bolts/mounting hardware. I believe lexan is the strongest and UV doesn't weaken it like Delrin, but I also heard it scratches easily, which then weakens it quickly. Perhaps I could mate the aluminum in a way to prevent it from scratching Lexan, I'm not sure.. I would like for this to be built to last 5 years.

 

[Pud]

Fibreglass rod - easily available, cheaper and much, much stronger! Pultruded polyester and glass tubing would be better still if you can source it.

H

http://www.tynevalleyplastics.co.uk

 

[MikeHalloran]

I'd suggest pultruded fiberglass rounds; they will do better in sunlight.

Most antenna forms will interact with the airstream enough that one round bar cantilever won't be enough support. Note how whips are commonly cantilevered with two bars.

Once you have a design roughed out, you might want to check with a structural engineer about the antenna assembly's effect on the tower. Towers are not designed to have arbitrary random loads cantilevered from them.





Mike Halloran
Pembroke Pines, FL, USA

 

[Scott231us]

Thanks for the responses. Fiberglass is tough, but I'm worried about drilling through it.. DOesn't it crack easily, due to the glass fibers it's made out of? Would lexan and/or delrin be more resilient?

 

[MikeHalloran]

So don't drill it. At least don't drill a single huge cross-hole and expect good results. It won't split like wood, but you can compromise its strength - at far higher loads than acetal or polycarbonate can take with similar geometry.

Thread it into threaded ends. Use a split sleeve with pinch bolts. Bond it into a roughened socket. Use multiple small cross-bolts. There are a lot of ways to terminate a pultruded rod, but each of them needs to be engineered to be reliable and effective.

Maybe you need a mechanical engineer on your team to help with this stuff.




Mike Halloran
Pembroke Pines, FL, USA