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Chat Area => General Car Chat => Topic started by: VXL V6 on 19 September 2013, 20:06:03

Title: Repairing plastic bumpers
Post by: VXL V6 on 19 September 2013, 20:06:03
Anyone have any experience of this and can offer some advice?

The issue I have is that I have a bumper with two broken tabs (the large ones that clip to the underside of the car (front bumper) and i'm looking for a way to effect a strong repair. Never done any fibre glassing before but looking on the internet it appears that 3M do various repair solutions.
Title: Re: Repairing plastic bumpers
Post by: 05omegav6 on 19 September 2013, 20:26:26
For those I would do the following.

Find a suitable piece of stainless steel, say 0.75-1mm, sheet about 20cm by 45cm.
Position it so that it sits lengthways across the back edge of the bumper, with about 14cm overlap.

Drill and rivet it to the bumper. 10-15 broad headed rivets (like theses http://www.ebay.co.uk/itm/LARGE-FLANGE-HEAD-ALLOY-STEEL-BLIND-POP-RIVETS-x-100-/350559309296?pt=UK_DIY_Material_Nails_Fixing_MJ&var=&hash=item519ef68df0  (http://www.ebay.co.uk/itm/LARGE-FLANGE-HEAD-ALLOY-STEEL-BLIND-POP-RIVETS-x-100-/350559309296?pt=UK_DIY_Material_Nails_Fixing_MJ&var=&hash=item519ef68df0))spaced evenly should do it.

Then where the tabs are/were, mark the rectangular holes for the clips, and cut out with a Dremel or similar.

There are various things you could use to bond the plate to the bumper, but it will be completely out of sight anyway, and there's no saying how compatible or effective they'll be :-\
Title: Re: Repairing plastic bumpers
Post by: VXL V6 on 19 September 2013, 20:58:06
Sounds like a plan, I think most of the bumpers stability comes from the polystyrene pad on top of the crash bar, the rails on the wings and the assorted fixings at the wheel arch liners and the two on top by the headlamps.
Despite the size of the tabs underneath I don't think they actually do much apart from limiting the bumpers ability to flex and strain its fixings.
Title: Re: Repairing plastic bumpers
Post by: 05omegav6 on 19 September 2013, 21:15:28
They help keep some tension to it, which helps it keep its shape and make it a touch more rigid :y
Title: Re: Repairing plastic bumpers
Post by: Andy B on 19 September 2013, 21:17:57
If you have the tab, I've used a hot soldering iron to 'weld' a tab back on. You need a few bits of similar plastic too though to use as a 'filler rod' Seemed to work quite well.  :)
Title: Re: Repairing plastic bumpers
Post by: dbdb on 19 September 2013, 23:15:46
Welding plastic is quite straightforward IF you can get filler rod or strips of exactly the same plastic.  If the filler is different it is impossible (or looks fine and you congratulate yourself on a good job then the filler just drops out).  clean the joints, heat the rod gently with a gas soldering iron with the tip removed and feed it into the crack.   Or you can get expensive electric heaters.  Welding plastic without a filler at all is difficult and rarely gives a strong bond but can suffice if you don't need the strength and can lose some width.
Title: Re: Repairing plastic bumpers
Post by: dbug on 19 September 2013, 23:54:31
Most plastic bumpers today are made from injection moulded abs.  This material can be heat welded (abs rods readily available) or solvent welded (using acetone for example). ;)

Title: Re: Repairing plastic bumpers
Post by: Marks DTM Calib on 20 September 2013, 13:21:21
Plastic welding, and use a small section from else where on the back of the bumper as the filler.
Title: Re: Repairing plastic bumpers
Post by: Omegatoy on 20 September 2013, 19:38:45
as others have said,plastic weld using same material and a heat gun with a reasonably shaped tip,have a practice first on the old bit of damaged bumper you buy to repair yours,
its pretty easy as long as you remember not to actually melt the plastic you want it just before it melts then use the filler and work it in applying heat all the while,I have weld my quad plastics and headlamp units  ::)many times after falling off doing some wacky stunts,also welded around 11 or 12 plastic bumpers after one or two goes it becomes pretty easy but practice first!! i have also used cable ties as filler :y
Title: Re: Repairing plastic bumpers
Post by: symes on 20 September 2013, 22:30:34
you can buy sticks of plastic-like what you get for hot glue guns--which is for doing bumpers--saw set today in halfrauds :y