Alright, I’m just thinking out loud here but I’m thinking about the strut plates and the the x axis and it occurs to me: instead of bolts what about pop riveting them on? Easy* lighter than nuts and bolts, good rigid connection. You can easily drill them out if needed. Are there mechanical, practical, ethical downsides I’m overlooking? What do you think?
*If you have the right size rivets and lazy tongs or a compressor powered riveting tool
One down side might be that rivits require expansion to work, I nave not tried using them in PLA. It may cause stress and cracking. I do like the the idea though, soft aluminum rivits might work with the right size hole
The neat thing is you should be able to more or less accurately ‘tune’ the compressive force by controlling the overall length of the hole in the PLA and match the wall thickness accordingly.
Have seen others glue captured nuts to help stay within the braces. Wish I’d known about that before burning time making 5 revisions of a M5 nut holder, shared on Printables. Created before buying dedicated socket wrench set.
Also, Doug mod’d the O.G. LR3 braces to have captured nuts, shared on Printables.
Well here’s the other thing - if you don’t need access to the back side to hold a nut then can the plates be extended to meet each other at the back and closer to the tubes at the front…
Might be able to have no gap for one or more edges (e.g. where back and bottom strut meet) using folded ACP, or thicker gauge sheet-metal to form 2 or 3 sides. Cutouts for brace-to-conduit mounts. Separate front Strut over the top. Think folk(s) bounced this idea around already, I don’t recall seeing actual build pics though.
Curious how rivets works out, I do like rivets but haven’t used much. Would you use adhesive/VHB-tape too to help dampen vibrations, or just use rivets?
Just my .02$ but pop rivets wouldn’t be the best.
They need quite a bit of force to get it to expand and they tend to crack the parent material a lot.
If you are going this route make sure to de burr the holes so you don’t have stress risers.
Also the pop rivets tend to loosen up over time. I believe there is some work around for depths like using orings but that would be a pita.
I use a set of forceps to hold my nuts so you can tighten them and that worked very well.
Do you have any clecos by chance ?
And also drilling them out can be a pita. Usually they will spin and create heat and if it’s plastic it will melt and deform holes.
I wonder about using larger plastic printed screws or the auto snaps like the ones with the middle insert.
Or plastic prrnted ones that have the threads in the supports.
Like @larryk said, I think the substrate has to be pretty strong in resisting expansion, and I would worry that the PLA wouldn’t be up to the task and as a result it would not generate much clamping. Or any clamping would be focused only on a small area on the inner edge of the hole. A washer might help with both expansion and spreading the load on the back side, but that perhaps defeats the purpose.
It got me thinking, hmm… toggle bolts would be hilarious and awful.
Maybe less terrible would be hammer nuts intended for use as T-slot nuts. The PLA could be printed to have a void that is just the right shape.
Yeah, hammer nuts are horrible for T-Slot, but are better captured nuts than hex in printed parts, providing threadlocker is used. Nylock hammer nuts would be nice.
I was thinking of washers on the backside too but it’s worth a test in just PLA to see what happens. I was also thinking, if you were using rivets, 3 fasteners in each location instead of 2. You could even have 4 and it’s still be lighter and cheaper than bolts.
I’ve not personally come across pop rivets ever loosening I have to admit. They’re used for holding the skin onto aircraft frames after all. But it’s worth thinking about thanks for bringing it up
I have drilled them out lots of times and it’s fine, you only need to shear the head flange off then tap out the shank. There’s even special drill bits with a shoulder for taking the heads off without scraping the material - aerospace again.
Another concern is in very hot weather could the PLA soften causing movement
Hey, I’ll do some prints and tests and the results could be: And this is why you don’t use rivets 
Generally no real airplanes use them for anything important. Cherry max rivets are what are used if you can’t get at the back side to put a solid river in.
Just adding my .02$ I say go for it!! And keep us posted. I also work in the aerospace sector. Oh the memories of being the small one and getting stuffed into a float with a bucking bar.
Also sorry I didn’t mean to come across as saying it’s a bad idea. I think it could work and might be a good idea.
Sorry I’m late. I’ve used pop rivets into PLA a few times in one specific instance!
Basically all the negatives outlined above are true.
In the project that worked - I made a stopper for a tube with a solid pla block which had a compression bolt through it lengthwise. Because the pla was constrained by the tube the cracking caused by the pop rivet was invisible, and added to the expansion of the block to hold it in place.
I wouldn’t use them in any other situation that I can think of. If this thread is still alive when I return home, I’ll post pics.
