Bumper fix

Recently our lovely little Freelander was rudely assaulted by an old MR2, the un-insured hit and run driver must have taken most of the front corner off his red MOT failure (reg K531CBO, if found inform Bedfordshire police) before speeding off into the night.
This left our car with a ten inch gash in the rear bumper. Now normally the simplest fix is to buy a second hand item and bolt it on, but this car is still new enough for spares to be pricey, and also I really didn’t feel like spending another afternoon away from my family fitting the damn thing.
So it was time to try a spot of plastic welding, this may sound complicated but actually it is no more difficult than most other ‘normal’ DIY jobs.
Firstly I should point out this only works on thermoplastic bumpers, they are the more flexible ones. Harder glass filled nylon or fibre glass GRP bumpers need gluing instead.
Thermoplastics can be melted and reformed, so the basic principal is to get the damaged part of the bumper hot enough that it can be re shaped back into something approximating the original profile, then get the split hot enough to melt and flow back together again.
A word of warning; heat guns can melt more than just the bumper, it is vital to ensure that fuel lines and wiring etc. are not going to get hot during the operation. The second safety point is that the plastic will be scolding hot, so don’t touch it!
Back to our Landy, to do this job I used an ordinary DIY style heat gun, usually used for stripping paint of windowsills. Moving the heat gently across the whole damaged area softens the plastic enough for the creases to be eased out by running the rounded handle of a screwdriver along the inside, working each section a little at a time so as not to create further distortions.
Unfortunately the plastic has stretched in the collision, so some material has to be removed from the split area. I did this by heating a large flat blade screwdriver with the heat gun and running the tip through the split whilst waiving the heat gun over the plastic, its a bit like soldering or gas welding, the hot tip ensures the edges of the split melt and can then join together.
Once the joint is complete and the bulges and creases are smoothed out, there is a surplus of material around the joint. This has a smooth surface which does not fit in well with the textured surface of the original, to get a rough approximation I pressed a course weave cloth against the joint whilst it was still pliable.
In my case I just wanted the split strong and safe again so I only spent a few minuets on it, but if you take your time and gradually work the material into the original shape you can get an invisible mend, saving a fortune on parts and workshop time.

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About Ralph Hosier

I love exploring everything the world has to offer, the fabulous beauty and intricacies of nature, the stunning majesty and grandeur of the universe, and the fascinating range of chocolates available from the local sweety shop. I have led a charmed life, sure there has been extremes, but the highs far outweigh the lows. I get paid for arsing about in very fast cars, I get to write about them and amazingly get paid for this too. My days are usually filled by making prototype and concept cars for car companies, a dream job. I have lived many of my dreams, worked all over the world, raced cars built by my own hand (and hardly ever crashed really badly), seen things and done stuff. But nothing compares to the love of Diana and my son Peter, beyond my greatest hopes. I am a chartered engineer, a member of the Institute of the Motor Industry (IMI), and of the Institute of Engineering and Technology (IET) and I am a member of the Guild of Motoring Writers. A pleasing fact is that there are now more letters after my name than there are in it ;) R.Hosier B.Eng(Hons) C.Eng MIET MIMI MGoMW
This entry was posted in Ralphy News, Technology Explained. and tagged . Bookmark the permalink.

One Response to Bumper fix

  1. Hi Ralph,

    Have a look at the attached link, it might be of help for you… (although it appears to me you have the process nailed!)
    http://www.hotairtools.com/PDF/Plastic_Welding_with_TriacPID_20TriacS.pdf
    Have a great day!
    Dennis

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