I've got a "third eye" type bike mirror attached to my helmet. It has two points of articulation: one near where it mounts to the helmet, which controls how far it swings up, and the other near the mirror which adjusts the mirror angle. When I first got it, there was some resistance to adjusting it either way, so once it was adjusted it just stayed in place. However, over time this resistance has decreased, to the point where the movement of air past me down a steep hill, or turning my head suddenly causes the mirror to move or the whole thing to swing out away from me. In either case the result is I suddenly cannot see behind me until I have time to safely move my hand up to adjust it back into place. As it usually happens at a time when it is not safe for me to do this, my ability to use the third eye goes away at times when I might need it most.

I have tried using hot glue to fix both ends in place, and this works for a while, but over time it keeps working its way loose, especially the side closest to the helmet. At the same time, hot glue is not particularly flexible, so if I don't get it adjusted just right I wind up on my bike having to turn my head one way or another to hit the sweet spot where I can see directly behind me.

What it seems like would be useful is if there was some kind of fluid that I could run over the contact points which would increase the amount of friction enough that either end would stay put when I'm not trying to adjust it, but not enough to prevent me from adjusting it whenever I need to. Kind of like the opposite of oil, and ideally something nothing sticky to the point of attracting too much dust and grime or otherwise making a mess of my hands whenever I try to adjust the mirror, yet long lasting enough that I don't have to apply it more than maybe every month or to.

Does something like this exist? Or is there some other solution that can be recommended?

Update: Here is a photo of the mirror attached to my helmet: enter image description here

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    Could you add some pictures, ideally close-ups of the pivots? I have a couple of ideas depending on how they're constructed. – Chris H Oct 4 '18 at 21:10
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    I tried the blackburn version of a helmet mirror, and I found them both useless and dangerous. Useless because they move easily and even a fast turn of the head was enough to un-adjust them. Road vibrations also made the image hard to see. Dangerous because I lost sight of a sector, big enough to hide a car. I ended up using a bar-end mirror for a motorcycle and its been brilliant - much better than a plasticky bicycle barend mirror. – Criggie Oct 4 '18 at 22:40
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    Do you have access to carbon assembly paste? Could it be dabbed lightly into the ball-joints? – Criggie Oct 4 '18 at 22:41
  • Those things are useless, better have a look over your shoulder. They are dangerous as well because they are helmet modifications and additionally they may poke into your eye in the case of an accident. – Carel Oct 5 '18 at 6:59
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    @Carel: True, but some cyclists are afraid to look over their shoulder. For them this might be better than nothing. – Michael Oct 5 '18 at 7:52

Chewing gum, or putty. You do not need to put the friction-increasing substance inside the joints - you can put it outside. Easier to remove later. You can also wrap sticky tape around the joints (if it's not supposed to move, but does, use duct tape; if it's supposed to move, but doesn't, use WD40 :) ).

  • "Sugru" would be another choice. – Criggie Oct 5 '18 at 10:39
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    @Criggie Sugru sets up over time though... in fact, I had an extra packet I was saving for when I needed it for something and when the time came and I needed it I discovered it doesn't last more than a few months in the packet before setting up and becoming useless. – Michael Oct 5 '18 at 16:45

I've managed to make the joints on a headtorch (that I use on the bike sometimes) much stiffer by wedging a rubber band in the hinge. If you can disassemble it, a bit of inner tube might do the trick, or a smear of hot glue. But if the joint can't be disassmebled it's much harder. There may still be a possiblity of wrapping a rubber band (or slice of inner tube) over the joint many times until it's tight.

A trick I've used in a very different situation (to make a sort of poor-man's self-locking bolt) is to put a fairly viscous but not too permanent threadlocker in there. When it's dried, deliberately break the threadlocker free. It will stil increase friction dramatically.

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