Badly warped rare bumper

Anything goes in the world of fiberglass and plastic



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PostPosted: Sat Dec 09, 2017 8:27 pm
Hello,

I know that I should sand this thing down before I paint it. I'm not looking to have this thing be 100% perfect since it's a used bumper. I can't go and buy another one of these bumpers since it's an aftermarket part that's considered rare. The previous owner abandoned the bumper in FL heat and it completely warped itself.

I actually got the bumper to look a bit better with some heat and towels stuffed in the vent holes.

It use to look like this:
Image
L sport line front bumper by t07n, on Flickr
Image
L sport line front bumper by t07n, on Flickr
Image
L sport line front bumper by t07n, on Flickr

But I was able to get it back to this:
Image
Sportline bumper by t07n, on Flickr

Here's what I wish it looked like LOL:
Image
2zsmgxi by t07n, on Flickr
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2im9vsg by t07n, on Flickr
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2l948e9 by t07n, on Flickr

I also made a video to show the light curving around warps on the "flat surfaces":


It looks a lot better but it's no where near 90% perfect. I'm hoping to be able to sand it down and use plastic filler (if possible) to layer the bumper down and then sand it smooth.

Well that's the idea I have in my head anyways. I'm no expert so many some of you could offer me some assistance. Much appreciated!

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PostPosted: Sun Dec 10, 2017 12:19 am
Well, first, welcome on board.... and to your bumper. Man, with a single casting of poly that thick I can see why those things would sag/distort in the sun over time. Bravo, on getting it straight as you have so far..... I think I would be taking some electrical conduit and building an inner support hoop that I could rivet into to control future distortion. I'd agree with sanding it down but you have to watch about "building" much stuff on these flexible bumpers. Most I'd do is level it up with USC's Pro-flex which is designed for flex applications like this. Do that....seal up with epoxy and move into your paint system. You might also want to get some direct advice from some guys who live and breathe plastics everyday....
Check out www.polyvance.com
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Sun Dec 10, 2017 12:38 am
Thanks for the reply bud! Yes, there is so much plastic on this bumper and it's so heavy.

I'm thinking I could even get it a bit straighter with some vice grips, wood and heat. I'm going to try it sometime this week and give it a shot.

I saw a couple videos from those Polyvance folks. I'm going to look more into them.

Any more advice is much appreciated.



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PostPosted: Sun Dec 10, 2017 7:42 am
Work it with a good heat gun and good luck. What is the cover for?

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PostPosted: Sun Dec 10, 2017 6:04 pm
The only thing about the poly bumpers is their "memory." If you are successful at moving the stuff back to shape.....a good hot day in the sun can cause it to go back, depending on just how long it was distorted. Again, maybe try to work up some framing support on the inside......
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Mon Dec 11, 2017 6:21 am
DarrelK wrote:The only thing about the poly bumpers is their "memory." If you are successful at moving the stuff back to shape.....a good hot day in the sun can cause it to go back, depending on just how long it was distorted. Again, maybe try to work up some framing support on the inside......


That's exactly what I'm afraid of. I don't want to fully paint this thing and spend all that effort only for it to warp back. There are grill meshes that I could use to hold the shape of the inlets when I'm completely done with the job, but I'm afraid of the high-low spots on the bumper itself and whether California summer heat will get it to distort in the future.

tommie b wrote:Work it with a good heat gun and good luck. What is the cover for?


A Lexus IS300.

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PostPosted: Mon Dec 11, 2017 1:48 pm
If you wanted something even stiffer you could get like some 11 gauge sheet metal cut to the size of your grid material. Then simply start drilling holes into it for the air flow. If you made the sheet material about 1 inch larger all around you could cut and bend that over as tabs for the rivets to grab through. You could also obviously just shop out some industrial quality diamond pattern grid stuff which would be plenty stiff enough as well. My only point here is I wouldn't use the regular ebay style cheap gridding that you normally see on a lot of ricer cars....it just won't stop the movement.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Thu Dec 14, 2017 10:45 am
Sorry to Butt in but?
Couldn't you just glue in the reinforcements i.e. sheet metal or mesh cut to fit on the back side to make it hold its shape once you get it into shape? instead of riveting? wouldn't glue be better? wouldn't it hold its shape better? Better yet couldn't you weld in the metal mesh on back side with Plastic filler rod? Just the way I would go about it...

I haven't had one this bad yet! but I have always just heated up bad spots and pushed it back into place without over heating the plastic, Tricky to do with a good Heat-gun.
I didn't know the sun would or could make it go back once straitened? didn't know plastic had a memory? Always thought it took Heat and some sort of force to push it out of shape? such as leaving it off the car laying in sun in a pile or back of truck OR Blunt force from accident lol
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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PostPosted: Fri Dec 15, 2017 12:12 am
Dennis, there's a lot of crazy things that happen with these really thick poly bumpers once they've been heated up this much. It's kind of like the oil can problem that you see with metal. I worked my way through college in a large plastics extrusion plant. We worked with every kind of plastic available. From Lexan to vinyls, polyurethanes to polypropylenes, etc. Some plastics that have exceeded their original creation temp.s will literally take a permanent set distortion and only require extreme heat again to start moving back to that distortion. Intense sun with a dark paint color can be enough to get it moving. As for welding and gluing I don't have a problem with that but again I've seen the welds and glue rip loose as the plastic distorts again. With these extreme distorted pieces I've had pretty good luck with a combo of discreetly place rivets and graphics and/or trim pieces. But, hey anything goes with plastics. Worse case you'll end up doing it again..... :flatten: Trust me, I have a lot of experience in doing it again..... :lol:
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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