Plastic welding ATC fenders - what kind of plastic?

[webbch]

I just picked up my first ATC's - a blue '84 110, '84 200s, and '83 185s. Fixing 'em up for the kids for Christmas. I'm working on getting them all running properly right now (I've spent hours finding very useful info on this site). After that, I was planning to weld some of the cracks in the fenders, but I'm not sure what kind of plastic it is. Best I can tell, it's either polypropylene or polyethylene. Anyone know which one for sure?

I don't have any spare fenders to cut up for welding rods, but I can get PP or PE rods in blue or red easily enough (probably not a perfect match, but should be close enough for my purposes)

[kb0nly]

The fenders are HDPE, and i have welded a few cracks now using a hot air welder and PE rods. I find though that your better off using the clear rods then the colored ones. The colored rods just don't blend in that well, adding fresh color to 30 year old plsatic thats faded stands out pretty bad. But the clear PE rods melt in and take on the color of the plastic your welding to.

Get some good degreaser, i wipe the area with some acetone then i grab my dremmel tool with a chamfering bit in it to make a nice V groove along the crack. Then one or two layers of fill with the rods, overfilling it like welding metal, then i shave it down and sand and buff. It leaves a slightly different looking area, has a bit of a hot plastic rippled pattern to it after smoothing down, but it blends in pretty darn good and its strong.

I'm planning on sometime this winter taking a fender and showing the process. I have just been too darn busy to do so.

[webbch]

Thanks! I'll give the clear PE rods a try - which is nice because I alread have some :)
Just out of curiosity - do you grind your v groove on the backside of the plastic to minimize the amount of fill that is exposed? I've done a few plastic welds, but primarily on out-of-sight items.

[hitmeup760]

Where can these plastic rods be bought at?

[kb0nly]

Depending on the crack i usually do front and back. If its in an area that will take a lot of flex, as most of these fenders are, i just make the groove and weld the back first to give it support, then i make the groove and do the front side. It makes for a really strong repair. A small block plane with a freshly sharpened blade works good to shave it down a bit then go through a few grits of sandpaper and then buffing, just like working on paint.

You can sorta see where the repair was but its blended in really good.

The rods are available a ton of places online, i buy mine here..

http://www.usplastic.com/catalog/item.aspx?itemid=24504&catid=881

Its sold by the pound. The Oval shaped rods they have work great for this, depending on the width and depth of the groove i make to prep it sometimes a single layer of rod down the center does the trick.

[tri again]

IS the HDPE plastic for the 90-110 185 etc only?
Seems like the 84 and newer big reds are more 'dusty' dryer plastic (different at any rate) whereas the older trike plastics seems more 'waxy'.

[NeverLift]

I just did some welding on my ATC70 fenders thought I would share the before and after pics. I'm not going to sand and buff these they are in pretty rough shape lots of scratches. I just wanted to stop cracks from spreading. I will say cleaning and prepping the plastic is a must. I didn't clean them as much as I should have there was still some paint real close to the crack causing me to over heat them and it distorted a bit.

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[kb0nly]

Awesome job!

I have a similar hot air rework station, i did a few plastic repairs with it as well before i bought a dedicated hot air welder, nothing wrong with it i just wanted something that i could take outside and not worry about beating it around.

Its not hard to repair this plastic just time consuming.

tri again - they all seem to be the same plastic from what i have done, they all bond good to the PE rods, i think the later models though they used a slightly different formula. It seems to dry out and get that crust on it faster from UV then others. I don't honestly know for sure. I had one shop tell me that with 84 and up they started seeing a lot more sun fading issues on trikes and quads, i'm guessing a formulation change but doubt we can ever prove that.

[NeverLift]

Interesting it is a 85. I welded the top and bottom side. The bottom welded very nice and easy but the sun faded top was a lot different I needed more heat before the rods would melt into the fender.

[webbch]

Very nice work! What kind of rods did you use?

[NeverLift]

At work we have about 800 of these tubs/lids that are made of HDPE polyethylene same as fenders. The ones that cannot be saved I cut into little strips to welding with.
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[bryan84]

this is cool

[barnett468]

Hello webbch;


Are you trying to do a cosmetic or structural repair?

If you are doing a structural repair you can do the following, it is stronger than plastic welding:

1. buy some panel bonding adhesive and extra nozzles from an auto paint supply store and store it in the fridge or cool place at around 60 degrees until use. if it gets warm, your working time will be GREATLY reduced. if it gets colder than around 60 degrees it will be very thick and come out extremely slowly.

http://3mcollision.com/3m-panel-bonding-adhesive-38315.html

2. buy a thin piece of flat 12"x12" metal from the heating/ac duct dept at the hardware store.

3. cut it 1 1/2" longer and 2" wider than crack.

4. sand metal and plastic with 180.

5. shape metal to conform with area needing repair.

6. cut around 1/4 - 1/3rd off plastic applicator or adhesive will come out too slowly. Don't use the first 2" of adhesive that comes out of the nozzle because it will not be mixed well enough.

7. put thick lines of adhesive around 1/4" - 3/16" apart.

8. press metal lightly into adhesive. you do not want to squish it all out.

9. if necessary hold pieces in place for around 5 minutes until adhesive sets.

10. place in warm place at least 60 degrees and it will be fully cured after 1 hour. you can spped up the process by warming it SLIGHTLY with a blow dryer on LOW.


The adhesive gets moderately hard and is sort if sandable kinda, lol.

[think369]

Wow. This is so neat. Didn't even know u could do that