[Coco] Re: Loose plastic gears - CGP215 & PC2 Printers

[Andrew]

As noted, your best bet might be JB-Weld. Non-gel super glue may be 
problematic, as noted, because you have to spread the crack to let the 
glue seep in, then relax it, and hope. Most super-glues are based on 
cyanacrylate (sp?) formulas, and as such most cure via non-oxygen or 
non-moisture exposure (which is readily present in air, of course), 
which means you need to get the glue in, then press and hold it together 
to drive out all space and air from between the parts, and hold it that 
way until the glue cures completely (about 5 minutes or less). On a 
small part, this can be a near impossible task.

Other cyanacrylate glues (apart from super glue), formulated for various 
plastics, are available at hobby shops - one favorite of mine (though 
very pricey) is a brand called "PlastiZap" - comes in various forms for 
different model plastics. There is even a form hospitals use for surgery 
instead of stiches, which is available for home use under various names, 
though these escape me at the moment (great for cuts!).

JB-Weld, though, is a two-part epoxy, which cures via a chemical 
reaction. JB-Weld is *excellent* stuff - I have never come across a 
better two part epoxy. There may be some out there only available to the 
military and such, but I doubt it. My only gripe with it is that when 
you use it on something small, you still end up with extra that you 
could use, but you have to waste it. That, and you can't get large 
amounts of it (they make a "shop size" that you can get at auto parts 
stores which is a larger amount - but I wish you could get it in gallon 
sizes).

There are several forms of JB-Weld - but the two you are most likely to 
come across are the standard form (black and red tubes - sets up in 
about an hour, full strength in 24 hrs) and the quik-set form (tan and 
blue tubes - sets up in 5 minutes, full strength in 24 hours). One tube 
is the resin, the other is the hardener. Just squeeze out equal amounts 
next to each other (a plastic coffee can lid works well for this), then 
mix together with a toothpick or anything else you don't want again 
(once it hardens, and sticks, you will NEVER get it off - but it 
shouldn't stick to the plastic coffee can lid - which makes it the ideal 
place to mix it on). Once you have it fully mixed together (be very 
thorough on this step - unless it it mixed well, you won't get proper 
strength), apply it to the part.

The gears you are working with are likely nylon or delrin. I am not sure 
whether JB-Weld will stick to them or not, but it probably will. The one 
kind of plastic that I know for sure it won't stick to are PET (like 2 
liter bottles) and other polyethylene-based plastics. Just about 
anything else is fair game.

How good is JB-Weld? Well - I have it in a few places on my 1979 Bronco 
- one area is on the radiator, where it is holding a bracket in place 
where a weld failed. I bought the truck this way, so no clue how long it 
has been there, but it has yet to fail in the two years I have had the 
truck. Elsewhere, it is holding together an anti-backfire valve that 
broke when I removed it from another engine, and I couldn't find the 
right part elsewhere, so I figured "what the heck" - this part screws 
into the intake manifold (IIRC) on top of the engine. It has been this 
way for two years as well, no problems.

I have seen it used to fill cracks in the blower housing (alluminum - 
expensive to fix/weld) on a 1978 Detroit diesel engine - which held for 
about 10 years or so (my brother-in-law's dump truck - done so far back 
he couldn't remember when he did it). I have heard of crazier uses, even 
in places where you shouldn't use it, where it works and hasn't failed 
(like on exhaust manifolds - the temperatures at which it will fail is 
supposed to be something like 500-600 degrees F).

There are plenty of amusing and interesting testimonials at the JB-Weld 
website - take a look:

http://jbweld.net/index.php

Good luck, and I hope this information helps!

Andrew Ayers
Glendale (Phoenix), Arizona