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Plastic Welding

The fairing is ABS, and you can chemically weld that with excellent results. The bottle I bought here in the UK (conveniently called Plastic Weld) cost a couple of our pounds. You can also buy ABS sheet,which can be used to reinforce parts.
Model shops sell it all.
 
hot air plastic welders (like the ebay listed item) would not be a good choice for your fairing IMO. They also require welding rod of matching material. For joining two surfaces the edges are chamfered and the rod melted into the opening. I think the smallest diameter rod is 1/8" so if the material is thin, you don't get much surface area to contact and you have a lot of excess rod to deal with. It does require a little skill as you have to get the rod and the material up to about the same temp without getting it too hot and scorching it. It might work but I certainly think you would need to practice with some scrap material before you attempted to do the fairing.

As far as I know, ABS can be epoxied and I think that would be easier, less expensive, and do a better job.
 
I found that epoxy did not stick so well to ABS.
The stuff I use is Methylene Chloride (Dichloromethane). Push the crack together and drop some onto it. It goes into the crack by capillary action, and melts the two parts together. Result can be almost invisible. You can then "weld" an extra sheet of ABS to the back to strengthen the join. I have not had a failure yet, and have repaired may ABS items, some with quite high stress loading too.
 
I had used Weld-on 3 previously and it seemed to work, although it is not specifically for ABS. Looks like their 2354 or 4707 might be better, but I'd still like to reinforce the area. Additionally, I've been told a product called Plastex is a good bet for fixing ABS. The crack I'm wanting to stop is on the left lower fairing at the top of the vent - right along the crease. I plan to do the work from the back side as the front does not show the crack much at all, given its position. Bizarre place for a crack. Also, I want to reattach a mounting tab on that same fairing that was previously "fixed" using Weld-on 3 and JB Weld.

Hmmm, I have a bottle of Plastic Weld (Dichloromethane) on the shelf from some other project. Maybe I'll give that a shot first and see what happens, then reinforce with the welding rod.

jdg
 
Though it can not fix a crack that has already started, i have reinforced plastics (including ABS) using the softer 5 minute cure epoxy mixed with chopped glass fiber. the 5 minute stuff is sticky, but never gets quite as hard as the 30 minute stuff, which allows for more flex before cracking. The chopped fiber adds strength, and together it works like mortar and aggregate.

Just scuff up the plastic first, using something like 60 grit sandpaper to give it something serious to stick to.

Just a thought for re-enforcing those crappy tabs.
 
In case somebody is interested; I had to fix 4 cracks in my Quota tank. Both front mounts, the rear mounting tab and the overflow hose barb. This is an Acerbis tank made out of Nylon-6(not the coloured stuff, but the white-ish paintable kind) which the local experts and forums told me could not be welded. I tried it anyway ofcourse and it did not work. The material feels greasy to the touch and I did not have much faith that anything would stick to it. Even the primer underneath the paint came loose where the tank had deformed.
The local automotive store sold epoxy for plastic radiator expansion tanks of which the product info looked ok, but was not garanteed for fuels. So I tried the 2 part fuel tank epoxy, made for metal fuel tanks. Supposedly you can even put it on a leaking tank, they even include a stick of wax to plug the hole, and some fiberglass to reinforce things. Anyway, the stuff gets really hot when mixed, gets really thin when applied but dries almost immediately. Since my tank was in rough shape I applied two layers for a total of $28 Canadian and two years later it still holds. I am a bit hesitant to take the bike offroad, but so far so good. Cheap fix.
JR
 
Also FWIW in the old days if ally got stress cracks a small hole drilled right at the root of the crack almost always stopped it spreading further. I tried it recently on an acrylic windscreen and it seems to have worked.
 
That's a trick that should work on almost any material, and that can be explained quite simply considering the distribution of shearing force at the "building-block" (molecular) level.

I have reinforced (preventively) the funnels through which the mounting screws of the Norge's lower fairing pass by filling them up with Patterson Repa(i)r Express. Seems to work, for the moment.
 
Now, I'm a simple person but what's a shed full of shearers (shearing force) got to do with plastic welding? Are you trying to pull the wool over my eyes?
 
No, I thought you were more a person to wear silk rather than wool :silly:
 
simple. Sharp corners are stress risers. you have a high concentration of force in a nearly infinitely small area. This creates a shearing force where the material comes apart.

Drilling a small hole creates a MUCH larger area for that force, though the force remains constant.

It kind of works like this.

It's really hard to rip plastic packing tape in half. But once you have a rip at one side, ripping the rest in half is a piece of cake. You have a large amount of force, centered in a really small area.
 
Yes, a hole drilled at the end of the fracture. What I've had good results with is using window screen,synthetic or metal as a base for epoxy over the repair. Sort of like fiberglass or on a large scale rebar. Just want to add, rough up the material that is being repaired, but you knew that.
 
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