Seeking advice on material choice for awning bracket spacer

outback97

Adventurer
Hey, I'm hoping someone here has some suggestions for a small project I need to wrap up. We have an Xterra with a DIY roof rack consisting of low profile unistrut crossbars attached with vibration damping ubolts. It's great for attaching cargo boxes, gas cans, traction boards, etc.



Recently I acquired an ARB 2000 awning and I am using ARB's awning brackets to mount it. I had hoped it would line up perfectly on my rack but I had to raise it up to clear the back door. I used some short strut channel lengths as a temporary spacer solution before our last trip, as shown in the photo above and the detail below.



What I'm wondering is what type of material I should consider using as a spacer block between the awning bracket and the strut crossbar. I could just leave it as shown above, but I would prefer something that just comes off with the awning brackets when I unbolt it for storage. I don't want to leave the awning on between trips as the vehicle is parked outside 100% of the time.

I am thinking some strong plastic that could be cut into about a 1.75" W x 6" L x .75" H block. This would then be drilled with holes matching those on the awning bracket, and when I mount it up I'd just use spring nuts in the strut channel to attach to as I do right now. It'd just be longer bolts going through awning bracket, spacer, and spring nut. I could even cut a shallow rabbet in the bottom of the spacer to key it into the strut channel.

What about something like this? Other materials I should be looking at?
https://www.mcmaster.com/#8540k325/=192f1nw
 
Last edited:

Airmapper

High-Tech Redneck
If I understand the mounting right it doesn't seem you will be putting a ton of stress on anything, awnings are not that heavy and just sit there.

I think for your purpose the nylon would probably be just fine. I'd also consider UHMW or Aluminum. I'd stay far away from anything corrosive.
 

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outback97

Adventurer
If I understand the mounting right it doesn't seem you will be putting a ton of stress on anything, awnings are not that heavy and just sit there.

I think for your purpose the nylon would probably be just fine. I'd also consider UHMW or Aluminum. I'd stay far away from anything corrosive.
Thanks Airmapper. I agree that in this application I don't think it's being put under a lot of stress. It's just there to raise the bracket up about 3/4", and I think it mainly needs to resist being compressed.

Looks like UHMW you mentioned might be a better choice than the nylon material I linked above. Lower tensile strength, but better impact resistance and lower moisture absorption. Both of them say they're not for use outdoors, but for my purposes I cannot see why not. It won't be outside for long periods of time.

https://www.mcmaster.com/#4296a165/=192k23y

Delrin or aluminum would be my choice.
Thanks, Delrin looks like another good option.

https://www.mcmaster.com/#8575k145/=192k7dn

I also think aluminum would work well, but I don't have a good way to cut grooves into it, whereas plastic would be easier to work with.

Micarta !
Sounds like a lot more work!
 

rayra

Expedition Leader
delrin, nylon, aluminum. Hell renshape would work. So would wood, if you could. Or the recycled plastic deck boards. Any solid chunk of material you could trim to shape to use as a spacer block between the awning bracket and your rack crossbar. You could also use square tubular steel or aluminum, if you find a size that matches what you want..
 

outback97

Adventurer
I decided to go with delrin since it sounds like it'll be easier to work with than UHMW, and it was about the same price as the nylon.

I'll update this after it's finished, thanks again for the suggestions guys.
 

outback97

Adventurer
I found the Delrin to be easy to work with, and it seems like it should be plenty strong for this application.





Will try these out on our next trip coming up soon. Thanks again for the material suggestions.
 

v_man

Explorer
Was there a reason you didn't want to use square or rectangular steel tubing as a spacer? Out of curiosity , how much does Delrin cost?
 

outback97

Adventurer
Was there a reason you didn't want to use square or rectangular steel tubing as a spacer? Out of curiosity , how much does Delrin cost?
Great question. Square would have been too tall for my application, and to be honest I didn't really realize there were many options in rectangular tubing, as I have not done much metal working and I have better wood (or plastic) cutting tools at my disposal. I just looked on McMaster and there's some that might have worked, but they're not really any cheaper than what I ended up doing.

Delrin was about $21, so it's not exactly cheap but it had the following attributes that appealed to me. It was super easy to rip the Delrin with a radial arm saw. Also very easy to drill it with a drill press. It was also quick to notch out the Delrin to clear space for the welds on the ARB awning bracket. I could put rabbet grooves in the bottom to key it into the strut channel if I decide to. No worries about corrosion. And, it's black so no need to paint them to match*.

In hindsight I may have just been better off with some right angle steel L brackets to make my awning mounts from, but I had hoped that the ARB brackets (which are nice and well made) would be usable without any modifications to them or the crossbars. I think this solution will work well and gives me the 3/4" lift I need to clear the door.

*The Delrin did go milky looking on some cut faces, it'd be nice to get that looking a little nicer (maybe a black dye or something?) but it's not the end of the world.
 

rayra

Expedition Leader
fine / wet sand to a smooth finish on the surfaces you cut. You can even flame polish it WITH CARE not to scorch / bubble it.
 

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outback97

Adventurer
fine / wet sand to a smooth finish on the surfaces you cut. You can even flame polish it WITH CARE not to scorch / bubble it.
I probably should have sought clarification before I worked on this, but can you tell me more specifically what has worked for you? Honestly on this project it's not something I want to spend a ton of time with (it's a spacer for an awning bracket) but if I work with this stuff in the future it might be nice to know how to make it look decent.

On my lunch break I went down the street to a Fastenal store and got the finest grit wet / dry paper they had, 1000. After wet sanding for a while with my scrap piece, I could get the surface smooth to the touch, but it just looked like a brushed gray appearance and still quite whitish at a high angle of incidence.

Next I put a little tiny bit of clear finish on it and wiped it down, now that look I can live with, as it did get it closer to black.
 

Herbie

Rendezvous Conspirator
Regarding the pricing of Delrin and other plastics:

If you live in any sort of big city, check to see if you have an industrial plastic supply company nearby. Tap Plastics, RidOut, etc. They always have a scraps/cut-offs/rems bin that is pennies on the dollar, and usually sold by weight. For the size of the chunks outback97 used, I doubt I would have paid more than $4.00 out the door.
 
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