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Repairing threaded bosses in fairing plastic.

Discussion in 'Technical Discussion' started by austin, Oct 8, 2017.

  1. austin

    austin Well-Known Member

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    So my son threw his bike at the scenery while we were away in Scandinavia in June & July. Damage was limited to most of the sticky out bits - indicators, exhaust, 'bars etc etc and crucially the little flyscreen his Triumph speed triple is fitted with. He repaired / replaced most of it before he left on his world wanderings again but left me a few things to do including trying to repair the flyscreen.

    Its a simple affair. A back plate bolts to the clocks bracket up front. This is cracked but has glued back together OKish. A small fairing fits onto the backplate secured by 4 small self tappers into 4 bosses on the fairing. 3 of these bosses have snapped off. A small screen bolts to the fairing. The whole lot weighs about 1-2kilos so not a huge about of weight or pressure on the 4 screws but enough as it hanging on them.

    Son tried to glue/epoxy the bosses back on but the glue didn't really want to stick very well to the plastic and it hasn't worked and in any case the bosses don't have much surface area to stick to - about 6-7mm diameter.

    Whats the best solution. I cant find a fairing for sale anywhere, even at triumph where it would £200+ anyway. I could try some different sort of glue/epoxy and make sure it has a good key, Any recommendations for glue/epoxy? I have some fibre glass stuff that I am sure would work if it will stick to the plastic. Is there anywhere anyone knows of who does a good plastic welding job?

    I will get some pics later.
     
  2. austin

    austin Well-Known Member

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    here you are - the little screen thing above the lights. IMG_3372.JPG IMG_3371.JPG
     
  3. austin

    austin Well-Known Member

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    this looks worth a go......



     
  4. Lutin

    Lutin Administrator Staff Member Forum Supporter

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  5. hotbulb

    hotbulb Active Member

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    I'm told that the plastic used for cable(zip) ties is good for welding fairing plastic ... use a soldering iron to melt it. (Oh! Just spotted the video :))
    Or how about drilling out the bosses and replacing them with Riv-nuts - and then using real bolts instead of self-tappers?
     
    Last edited: Oct 9, 2017
    austin likes this.
  6. austin

    austin Well-Known Member

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    I gave the Rivets a long hard think and then decided I fancied a go at the plastic welding with cable ties coz it was cheap, looked like a good thing to learn as well as being fun and really really satisfying if it works.

    As you might expect its not as easy as it looks, in particular getting the cable tie to melt and mix with the fairing plastic so it welds together properly. The cable ties melt easy enough but you have to keep going with the heat to melt some of the fairing and get it to mix. If you don't the cable tie just melts and sits on top of the fairing in a black lumpy mess. Also getting a neat finish is not easy either. My repairs are a right mess of lumpy molten plastic and whispy bits where I lifted the iron off and dragged molten plastic all over the job. But, the bosses seem to be quite secure and it all lines up when offered up and the screws go in but I have only lightly tightened for now. I will let it cool for an hour or so and set properly before fitting to the bike properly. If they break off again I reckon a bit of a re-weld and then some fibre glass should do the trick.

    And, I only burned myself the once. :thumbsup:

    (it was quite a productive afternoon actually, I also nearly replaced the LiPo battery in my Sena headset. I say nearly as I had to re-solder the old connector to the new battery only to discover the new battery was both thicker than the old one and has significantly thicker wires. This means the back of the device won't go on properly. I have left that job to one side for now while I work out a solution - longer thin wires soldered nearer the battery I reckon.
     
  7. austin

    austin Well-Known Member

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    Some pics.....

    The 2nd and 3rd attempts. (the 4th had held with the glue my son used)
    IMG_3746.JPG

    The 1st one (I dunno what the blue stuff is, I think its just camera as there's no blue stuff there in actuality)
    IMG_3747.JPG

    and the finished job all fitted and done....

    IMG_3748.JPG IMG_3749.JPG

    My son is in Korea at the moment with no real plans to come home anytime soon, so this bike may be for sale at some time. Interested?

    Its a bloody good bike and rides great but has a bit of history. It was a Cat C (is that the lightest?) write off for cosmetic damage after someone drove into the back it - the bike then belonged to a very old pal of mine. He is a proper apprenticed black country engineer and easily fixed it up before selling it to my son. My son then out-rode himself on Hartside Pass in the summer and missed a corner riding onto the fell side before managing to drop it on both sides. It was just sticky out bits and damaged all now replaced or repaired.
     
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  8. Philwhiskeydrinker

    Philwhiskeydrinker Well-Known Member

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    Nice work Austin.

    I saw this bike earlier in the year & it certainly looked right enough.

    Sent from my SM-A320FL using Tapatalk
     
  9. Flyfifer

    Flyfifer Member

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    I realise a repair has been made but I use Milliput epoxy putty for all sorts of jobs like that.
    £3 or so for a two part pack that lasts for ages.
    Drill it /Tap it once it is cured, if required.
     
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