Some ****** at work hit my headlight and knocked it back more than an inch. This tore off the two mounting tabs that align the headlight unit. I have the tabs and have tried plastic cement, super glue, epoxy and now fiberglass resin. Nothing sticks to the plastic, seems to have a lot of nylon content. Does anyone KNOW of a glue that will work? Or is there an alternative? I could rig some sort of bracket and screw it into the light. Or, there is about an inch gap between the bottom of the headlight and a frame section. l'm thinking about putting a shot of the foam you spray around windows and doors in there and letting it expand. Obviously I'm adverse to spending a 1000+ for a headlight that has tabs still attached.

Cheers!

 

Sell the Jag and buy a Yugo if you are going to do that to it. You might find something cheaper on Ebay or a breakers yard.

 

Expando-foam absorbs moisture and also shrinks over time, so don't do that anyway.
Screwing into the housing will work along with making up some brackets, but make sure to seal around the housing hole/screw with a good silicone goop to keep out moisture.

 

I made brackets for my top inner ears. Both were broken off. Had to pull the lamp assembly out to lock nut the hardware. I wouldn't just wood screw the things together. Too much chance of a poor quality repair. I'd also take this time to install some flavor of dash cam that records all the time or if there's a disturbance.

 

Drill extremely tiny holes into the plastic. Then use 3M Polyolefin Adhesion Promoter. Use 3M Super Fast Plastic Repair (04247) to bond whatever plastic bracket you intend to use to the headlight. I repaired two tabs this way. I'm in a rush now but can respond to questions and provide more details later today.

 

Ironic you had your finger on it and went off course.
Familiarize yourself with Nylon Welding- it beats having to pay a grand.
Some use high quality zip ties as the raw material to melt, as it too is nylon.

Also if you are good with fabrication, you can do 2 other things
Drill some small holes and make that clip by twisting solid wire.
You could also drill carefully larger holes in the nylon and use small nylon zip ties to make that clip.

 

 

This is where plastic welding comes into play. Forget glues and adhesives, they won't cut it, needs to be welded.

I've welded a couple of busted headlights back together, call up a few crash repairers and ask if they have someone who can plastic weld.

 

Thank you for the replies, and I was kidding about the expanding foam. I did call a bit and plastic welding isn't very common. But my neighbors boat guy (I know) gave me a jar of mystery resin and a nearly empty tube that said "hardener" and "keep out of eyes". He also said the trick is to rough sand the plastic and leave deep scratches so the resin can bond to it. I decided to use fiberglass cloth as well. Hope to put it back together tonight. It looks like it will hold.

 

No mate, that is still gluing. (They cheat and call it welding)
Welding is melting two parts together. It bonds at a molecular level. Also the weld is stronger than the rest of the material.

 

I looked into a plastic welder and I agree when done well it probably is almost good as new. But how do you prevent ending up with a cold solder joint? What I saw you guessed at the temperature setting on the welder and how fast/long to apply heat. And I'm afraid you only get one try at it. If the fiberglass fails I'll drill holes and use lacing wire.
​​​​​​​thanks again!

 

You'll know when it works because the plastic will literally melt together at the seam. We use soldering irons with blade tips to melt belting together at work and it's a really neat simple process. You can do the same process, just use zip ties as filler rod like mentioned above.

Epoxy on plastic just doesn't work well for long, especially with temperature changes and any vibration. You'd be better off gumming a bunch of RTV silicone between the parts and using that versus an epoxy based product. The plastic will flex and the epoxy will peel away over time. BTDT.

 

Yes a cold solder is different with plastic, you have either melted it and joined them, or they are still like they were.

what you are trying to do is not just melt one to the other.
Think of it like mixing 2 paint colors, or melting and meshing.

Just practice by cutting a zip-tie in half and rejoining it.
I bet you are a plastic welding expert giving tutorials here after your second zip-tie......

It could be the start of a new life, where you are going around parking lots knocking off plastic parts and offering welding services.

 

Hey Ranch let me bounce something off you.
They make hot glue guns with precision tips that do 428F....they make nylon ties with melting temp of 425..
What's the problem?

 

I assume not enough of a temp difference to keep the cooler plastic at a melting temperature. It'll act like a heat sink and draw some of the rated temp out of the tip. Kind of like metal solder or Tig welding aluminum.