Helmet Mirror: Mirror Modifications

Mirror shaft - 2-56 stud

Mirror shaft - 2-56 stud

This 2-56 stud will hold the mirror shaft into whatever helmet mount I eventually decide on. It’s a pan-head screw that miraculously fits snugly inside the cut-down shaft section, held in with a delicate epoxy dribble around the edge.

The head abuts the end of the smaller shaft section, so the two no longer slide. I think a length of heat-shrink tubing will stabilize them in rotation, although perhaps I should have just slobbered more epoxy into that joint.

After the epoxy cured, I sliced off all but 2 mm of the screw thread with an abrasive wheel and cleaned up the wreckage with a file. I actually remembered to spin on a nut before cutting, which ensured I finished the threads properly.

The business end of the mirror has far too many moving parts: two indented plates for the balls on the mirror and shaft, a screw, and a nut. That’s one too many ball joints, at least, and Wouldn’t It Be Nice If the mirror had a watertight seal around its perimeter?

Mirror ball joint clamp

Mirror ball joint clamp

For now, I just epoxied the nut in place after scuffing up the plate and nut with some sandpaper to give the epoxy something to grip:

Mirror ball joint - epoxied nut

Mirror ball joint - epoxied nut

You can’t see the new washer and rubber grommet under the screw head that provides a bit of compliance to hold the balls more securely, plus a dot of low-strength Loctite in the nut to discourage things from falling apart on the road.

  1. #1 by John Rehwinkel on 2011-06-26 - 09:15

    plus a dot of low-strength Loctite in the nut to discourage things from falling apart on the road.

    I like how you say that, in lieu of how some folks will say things like “I did this to prevent problems on the road”. As we well know, you can’t “prevent” much of anything, just try to improve the odds.

    My life became much easier when I learned how to use a file to clean up threads. I’ve done some perfectly horrible things to machine threads and was able to make them useable again with just a few passes with a file. External threads, that is. If I goober up a nut, it’s pretty much done for unless I have the right tap on hand.

    • #2 by Ed on 2011-06-26 - 11:33

      you can’t “prevent” much of anything

      Feels like I’m fighting a holding action against entropy…

      Went for a ride around the block yesterday and felt the seat shift slightly. It seems the double-nutted and Loctite-d nuts on the clamps holding the seat stays have loosened just enough to slip when enduring what passes for moderate acceleration…

    • #3 by smellsofbikes on 2011-06-26 - 14:01

      >My life became much easier when I learned how to use a file to clean up threads.

      Have you ever seen thread repair files?
      http://www.tapsndies.com/threadrepairfiles.html
      They do a great job.

  2. #4 by peter on 2011-06-26 - 18:28

    Looks very nice, am reading your story with interest. (though I don’t use a helmet-mounted mirror – hard to attach it if you don’t have or use a helmet :-) ). Hm – now that remark got me thinking… maybe a skull implant with M3 thread….? It could be used to attach many other things too!

    Back on topic – I have no doubt about the strength of the epoxy – especially its adhesion to metals – if the surfaces are prepared properly. First thoroughly degrease (acetone), then sand to roughen up the surfaces, then degrease once more. Once did shear-tests of epoxied magnets that were prepared like this and epoxied to steel, and the bond that failed was the nickel coating of the magnet substrate – the epoxy held on. What I thought to be an unexpectedly good result.

    It’s just that a blob of epoxy looks a bit…. amateurish? (no offence). Given the high quality of the rest of your work, I think I’d have brazed the joint. Then with a bit of filing you can get a very professional looking ‘thingy’ that will hold forever. Ok, so I’m nitpicking – the epoxy should be strong enough. (as long as it is epoxy, not *puke* polyester)

    • #5 by Ed on 2011-06-27 - 09:55

      a skull implant with M3 thread

      I’ve long thought that a true bikie would have a titanium socket just over the left eye socket for exactly that purpose.

      All three of us have caught ourselves looking up-and-left to see what’s behind when we’re walking: we’ve gotten used to a rear-view mirror in that spot and it’s downright unnatural to not have one!

      a blob of epoxy looks a bit…. amateurish

      Remember, the bigger the blob, the better the job!

      Just for that, I’ll try resistance soldering the next one: less excitement, easier fixturing, no flames.

      No filing, though: when it’s cool enough to touch, it’s ready to use!

      For what it’s worth, I’ve actually used a couple of helmets for their intended purpose over the decades, generally as part of a graceless zero-speed rollover. Contrary to popular impression, a helmet doesn’t protect you in a crash, because there’s more energy than the foam can absorb, but I have smacked my head on the ground and lived to tell the tale. What it does do is keep you from collecting a concussion for no good reason… and I appreciate that!

      • #6 by peter on 2011-06-27 - 18:09

        Hm. Resistance soldering – hadn’t considered that one yet! (and no, I still haven’t tried to use the failed spotwelder as resistance soldering tool – too many other projects have priority at the moment :-( )

        As to helmets… I just deleted a long reply about that. I’m sure you’ve seen plenty of those discussions, as I have. Have little new to add to the topic. However, I am at the moment experiencing a different kind of head injury: otoliths that come loose, probably caused by the combination of a (too stiff?) neckrest and rough roads. Hardly dangerous, but causes very unpleasant dizziness for a few days after riding, when suddenly moving my head around.

        • #7 by Ed on 2011-06-27 - 20:33

          otoliths that come loose

          My esteemed wife sometimes gets nasty dizzy spells from rapid head motions, so you two could probably swap notes. She suggests you obviously need a more upright ‘bent, like, say, a Tour Easy. Which would be a bit of a step down for you, IMO.

          plenty of those discussions

          Yeah, including the ones that suggest we helmet-wearers ride crazy because we know we’re protected. If that’s true, then my normal riding mode would be barely distinguishable from a stupor… [sigh]

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