Will any glue stick bike plastics?

External Since: Aug 02, 2006 Posts: 80

On Tue, 19 Feb 2008 16:37:28 GMT, "Beav"
<beavis.original DeleteThis @ntlwoxorld.com> wrote:

<snip>
>> I imagined the plastic getting too hot generally and all
>> folding up (like welding thin ally)? Sad

>
>Thin ally generally just flops or bursts into flame at anything above 600
>degs. Plastic "flops" a lot sooner, but the heat still needs to be directed
>right at the job.

Understood.

> The speed of the passage of the gun is as important as the
>heat coming out of it and a rod guide/feed tube is a necessity (if you want
>an easier life).

Ah, and now I've seen that in action it makes much more sense. I was
thinking it was more like the metal brazing / silver soldering type of
welding where you apply heat, get a molten pool then apply filler rod
into that, whereas it's more like a packing tape dispenser. Wink

>>

>You need to get the original plastic molten and at the same time you need
>the rod to be molten. That way the rod flows into the joint and the result
>is a neat "line", but one made up wholly of plastic, not a mix of plastic
>and air pockets.

Understood and where a bit of experience / practice would come in. The
only issue with the (this) welding solution is I guess it's easier to
apply efficiently (especially for a n00b) on a nice flat open surface
than in and amongst lugs, brackets and nasty tight contours?
>
>It's not a bad idea to REALLY scuff up the inside of the panel and add a
>layer of either glass cloth, or carbon fibre cloth too. Obviously with a
>dribble or two of resin (fibreglass resin is better than polyester resin for
>fairings)

So is that the resin you get with those little 'David's' fiberglass
repair kits you get from Car Spares places?
>
>This tends to spread the fixing rather than have it concentrated in the
>joint.

Understood.
>
>> (I've got some woven cloth / carbon cloth
>> and tissue as well) over the broken area (a few inches either side
>> etc).
>
>Exactly that. Cloth rather than mat though, but another thing I've used very
>succespfully is a product aimed at the building/platerering trade. It's
>"sticky backed fibreglass cloth on a roll". It's designed to go across
>plasterboard joints just pror to skimming with the plaster, costs pennies
>and is available in various widths,.

Scrim [1]? I think I gave the remains of a roll to my builder
brother_in_law (so should be able to get a bit back) Wink

> Pull some off the roll and it sticks to
>the plastic panels with ease and it also accomodated compound curves. Dollop
>resin on after it's applied and Bob's shagging your Mam's sister again.

Hey, and is that as strong as the woven mat Beav (for it's thickness I
mean)? As you say, that would be very manageable and give a very fine
finish?

More good ideas thanks. Wink

All the best ..

T i m

[1] I think I remember that it doesn't tear itself but tears off one
sheet or the other when pulling down stud walls etc?

External Since: Oct 04, 2005 Posts: 13

T i m wrote:

> Yeah, I guess my question was really 'why ABS' (rather than any other
> type etc)?

TBH it is most popular, and came as standard in my kit.

> Luckily I was able to pop into my local bike shop today and not only
> do they have said Sealey plastic welding kit (and happy to lend it to
> me should I need) but he also showed me it in action on a bit of scrap
> fairing and the '> A B S < marking inside this particular panel.

Nice to know for sure.

> My thoughts are (and they may be way off) that any 'join' isn't going
> to be quite as strong as the original material so some reinforcement
> may be a good thing in any case to prevent it failing in the same
> place in the future <shrug>.

Normally, metal would actually be stronger on the weld (if the weld was
a goodun), and weaker on the HAZ (heat affected zone). On plastic, I
cannot think there would be no changes of properties, but IME welding
plastic leads to a stronger panel.

> With the joint currently securely re-made with good superglue (to hold
> everything in-line and in- place) clean the paint off the inside maybe
> 3" either side of the break and generally roughen up the surface.
>
> Drill through the prepared panel area with several evenly spaced (say)
> 6 mm diameter holes and countersink them to the thickness of the
> plastic from the other side. Cover the holes on the outside with tape.
>
> Apply fiberglass resin to the inside prepared area (especially into
> the holes) and a single layer of woven mat over the entire area, allow
> to go green.
>
> Lay some suitable strips of ally / wood / plastic over the break (at
> 90 degrees to and slightly shorter than the prepared area) and glass
> over with at least one layer of woven mat (the stiffness being from
> the section made by the glass rather than the inserts themselves).
>
> When cured, remove masking tape and fill the slightly opened crack and
> holes from the outside.
>
> Sand / prime / paint.
>
> The 'reasons' for the above solution for me would be:
>
> 1) I have the materials / tools already.
>
> 2) I am familiar with the processes (and they can be applied at my own
> pace).
>
> 3) I'm unlikely to make matters worse (or burn myself) and no
> distortion etc. The tapered holes should form resin 'rivets', even if
> the fiberglass doesn't adhere to the plastic (it may be considered
> overkill but it's easy and quick to apply).
>
> 4) It could potentially be stronger than anything else I could do?
>
> So, weld or glass, weld or glass ..?

Here's the thing,
1: do all of the above and take 2 weeks holiday, or
2: take the plunge and buy one or borrow one, and learn how to, saving
time in the future, and impressing your mates by fixing their prangs.

It took my apprentice around 1/2 an hour to learn it, and go on to weld
about 1m of plastic, saving ?300 on two replacements.
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