Looking for a filament for a very specific, outdoor, rugged application (antenna joiner). Recommendations welcome and more details inside.

[Poisson]

I am going to try and design a model for a replacement bracket that holds two sides an antenna to a mast for a amateur radio tower. Here are some pictures of the current bracket:

Close up of the current bracket (well this is the same design, but for a slightly smaller diameter antenna):

This has a lot of very specific requirements. The antennas on each side of the mast are about 5 pounds each, so it needs to be able to hold up that weight and have shearing strength to deal with being blown around by the wind.

It needs to be able to survive the elements, as well as hot season (up to around 110F) and cold season (down to around -10F).

It needs to be to survive UV from the sun.

It needs to not have to have maintenance done for 10 - 30 years as it will be up on a tower and not something can easily be replaced.

So far the potential filaments I've been seeing would be ASA or PC. Is ASA strong enough for this kind of application? Would it need to be something stronger like PC? Or something else I haven't considered?

Thank you for any advice.

Edited December 5, 2022 by Poisson

[smirk]

This is way beyond my area of expertise but Stefan from CNC Kitchen does a lot of testing for strength of printed parts and he has covered PC in one video. Guess the real question is what kind of (wind) forces and temperatures is that part likely to get up on a mast. I imagine there'll be a lot of bending and flexing.

[eugen360]

I know the right material for you: it's called aluminum.

Joke aside, PETG and ASA would be the best for outdoor use. Definitely with a different bracket design, NOT like the one in the picture. More robust and also printed with 20 perimeters

But do take in consideration some CNC work on aluminum ...

[Poisson]

12 minutes ago, eugen360 said:

I know the right material for you: it's called aluminum.

Joke aside, PETG and ASA would be the best for outdoor use. Definitely with a different bracket design, NOT like the one in the picture. More robust and also printed with 20 perimeters

But do take in consideration some CNC work on aluminum ...

Unfortunately this piece must be an insulator, so aluminum is not a good option.

PETG is good for outdoor use? I thought it was not UV resistant?

[eugen360]

3 minutes ago, Poisson said:

PETG is good for outdoor use? I thought it was not UV resistant?

It is very UV resistant if I can say so! I'm sure you are familiar with images like these:

PET bottles can "resist" the outside world for a very very long time... more than 500 years, or so they say!

[eugen360]

25 minutes ago, Poisson said:

Unfortunately this piece must be an insulator

Well, if you gonna choose a metal bracket you can use some rubber as an insulator. (like a piece of inner tube of a bicycle tire). That rubber WILL be affected by the weather but only the exposed part.

OR you can print only the insulation...

[smirk]

3 hours ago, eugen360 said:

more than 500 years, or so they say!

Sad but true, I think the reality is the plastic bottle/toy/chair/junk will still degrade (loose integrity) and fragment into zillions of incredibly long live parts.  It is probably the law of perversity going on. You want all the plastic waste to dissappear but it hangs around for hundreds if not thousands of years (granted as microplastics). 3D print something for outside use and it'll crumble faster than Dracula in sun light

Don't know if this link would help about UV resistance of various plastics  (clearly PEI is perhaps not cost effective).

I'd agree with @eugen360 regards the necessity for a robust print. Perhaps one of our resident engineers ( @Penatr8tor ) would have a view of designing something that is robust and suitable.

Although not my field it occurs to me that perhaps aluminium is the way to go (for strenght) just with some sort of UV-safe non-conductive [printed] sleeve to act as an insulator (I'm presuming we're not talk ultra-high voltages at play)? Although that sort of shimming could cause it's own issues.

[Penatr8tor]

This is probably your best bet... Carbon Fiber Filled Polycarbonate.

https://www.3dxtech.com/product/carbonx-pc-cf/

After that I would say PC (unfilled) then,  ASA... it's good but not as strong. CF filled Nylon maybe but nylon on it's own is not very UV resistant. Definitely stay away from Polypropylene it loses about 70% of it's strength when exposed for a week.

[Poisson]

13 minutes ago, Penatr8tor said:

This is probably your best bet... Carbon Fiber Filled Polycarbonate.

https://www.3dxtech.com/product/carbonx-pc-cf/

After that I would say PC (unfilled) then,  ASA... it's good but not as strong. CF filled Nylon maybe but nylon on it's own is not very UV resistant. Definitely stay away from Polypropylene it loses about 70% of it's strength when exposed for a week.

Thank you!

[claudermilk]

While I'm here still wrapping my head around the idea of that massive radio antenna being "amateur!" 

[smirk]

Wait till you see the small nuclear reactor  needed to run it!

[Poisson]

59 minutes ago, claudermilk said:

While I'm here still wrapping my head around the idea of that massive radio antenna being "amateur!" 

It's my father's, and he has a very serious setup. He has been a HAM operator for probably longer than I have been alive, and I am not a young man

Edited December 8, 2022 by Poisson

[eugen360]

1 hour ago, smirk said:

Wait till you see the small nuclear reactor  needed to run it!

This one?

[Poisson]

On 12/7/2022 at 1:39 PM, Penatr8tor said:

This is probably your best bet... Carbon Fiber Filled Polycarbonate.

https://www.3dxtech.com/product/carbonx-pc-cf/

After that I would say PC (unfilled) then,  ASA... it's good but not as strong. CF filled Nylon maybe but nylon on it's own is not very UV resistant. Definitely stay away from Polypropylene it loses about 70% of it's strength when exposed for a week.

As I plan on this part being outside for quite a long time without maintenance (10+ years) do you think the CF addition gives enough UV protection in the Carbon Fiber Filled Polycarbonate? Or should I also coat the outside in some kind of UV blocking / absorbing paint as an additional precaution?

Edited December 8, 2022 by Poisson

[smirk]

It probably would not do any harm (assuming the paint was not nasty solvent based stuff, PC is not resistant to acetone but is resistant to many acids and other things). By definition any external paint will be UV resistant.

It will be an interesting long-term performance test.

[Penatr8tor]

You could design and print a 2 pc. cover out of ASA. I have left ASA parts on the dashboard of my car in summer where the temps are 105F the inside of the car is probably >120F. I also have 3 ASA eagles attached to mine and my neighbors flag poles that have been outside for a good 6-7 months with no sign of deterioration.

But paint works too. People have been painting PVC pipe for decades.

[eugen360]

From my point of view a bigger concern is not the UV, that can be solved easily but the mechanical resistance of the bracket. 90% of your effort must be focused on that direction! 10+ years is quite a time... 

[claudermilk]

17 hours ago, Penatr8tor said:

You could design and print a 2 pc. cover out of ASA. I have left ASA parts on the dashboard of my car in summer where the temps are 105F the inside of the car is probably >120F. I also have 3 ASA eagles attached to mine and my neighbors flag poles that have been outside for a good 6-7 months with no sign of deterioration.

But paint works too. People have been painting PVC pipe for decades.

I believe I've seen car interior temps quoted as above 140F, especially with an ambient of 105F.

PLA would just be a puddle of goo.  

[Penatr8tor]

1 hour ago, claudermilk said:

PLA would just be a puddle of goo.  

Probably make for some really interesting "art". 

[eugen360]

Hi Poisson!

I'm curious, have you finished this project? What material have you used in the end?

[Poisson]

3 hours ago, eugen360 said:

Hi Poisson!

I'm curious, have you finished this project? What material have you used in the end?

Not yet. This project is slated for sometime in the spring if I recall. I've been slow to work on this and haven't even prototyped the bracket in PLA yet to make sure it fits.

[Wannabe]

Lets face some hard facts here, just because we have a 3D printer doesn't neccesarily mean we should be printing everything that needs replacement or repair with a 3D printed component.

Lets look at the bracket that the OP has shown, as mentioned it has to withstand a variety of load factors plus some harsh and variable climate conditions, not to mention where or how high its going to be in service. What happens when (not if) the 3d bracket fails...danger....liabilities?

There is just no FDM filament that would hold up to the conditions/load the OP has indicated, for certain not in a reliable and safe manner.

 

[eugen360]

Everyone who has a 3D printer is perfectly aware of this! But things CAN be designed in such manner to withstand some tough conditions! And if you design something and it fails you'll learn to improve your design and also your printing capabilities! And if it fails again, you'll try again and again... maybe at some point a wiser person in your life (as your wife for example) will tell you to stop. But even then you'll try again!

No, Wannabe, you shouldn't stop trying!

[G_T]

So what sorts of molded or machined plastics do you see used for this application in the size/load range you are looking at? If you aren't seeing it commercially in molded plastic, then don't bother with FDM which is generally quite a bit weaker. IMHO, and unless you have a printer where you can print stuff like CF-PEKK and see what you can do.

Gerald KE4ET

[chrisalbertson]

The BEST solution, other than CNC'd metal is glass/epoxy composite.   You can not print this but you can print a mold.  The strongest way is to hand layout glass fabric, place it in a mold and apply clamps  The easy way is to mix chopped glass fiber into the epoxy until you have a thick paste then put it in the mold and then apply clamping pressure.   The excess will come out of the holes you made for this purpose.  You must polish and wax the inside of the mold and design the part so it will come out, so make it smooth and rounded.

But I doubt you need glass/epoxy.   Plain old ABS would work if you design the part so it has two aluminum plates that are on both sides of the ABS.   Basically a sandwich with (maybe) 1/8 inch AL then a brick of ABS and then another AL plate.  The there are through-bolts that compress the AL plates.  I would also epoxy the AL plates to the ABS  Make the ABS a simple shape, a brick (actually two half-bricks) with holes through it.   ABS takes paint well, the paint will protect from UV light.  Or use ASA

 

 

 

Edited 10 hours ago by chrisalbertson