High-Stress Plastic Parts: Made to Fail

[HBWW]

CPS triggers aren't the only one. In the attached photo is also a cracked/bent trigger assembly arm from my Tiger Shark. (Let me know if the image is too large.)

I think we need better solutions for these. The conventional repair is to epoxy a sheet metal strip to the broken parts to hold them together, but let's be honest; this doesn't work that well and chances are that you'll have to make the same repair within a few years anyway. Although if done right, that conventional repair can last quite a while.

I repaired a BBT spring catch from their dart shooting Rapid Fire Tek blaster earlier by stacking properly cut/shaped sheet metal pieces together so that there's thickness. (I had to also supplement the plunger's teeth with sheet metal because plastic against metal simply doesn't work.) This repair has gone remarkably well, but trigger pieces are a bit more complicated and arguably more difficult to cut out and make. Still, I think it's clear that we need an all-metal solution for a lot of these sorts of parts, although I'm open to using plastic if it's something durable.

I'd love to just CAD these parts out and run them off a 3D fabricator, but I don't know if any printing solutions that are within my budget are suitable for that. Lots of printed plastics are weak. However, I think it's clear that 3D fabrication will be the future of our repairs. Perhaps if I invested in it and provided a service here and to the NIC, I could offset the costs of getting a decent solution, but I don't have time for that.

In the meantime, I will just sit and ponder, I guess. I've found that cracked plastic is stubborn when trying to shape it, until you snap the thing apart by hand so that it can be connected straight.

Edit: Shrinked the pic.

made2fail.jpg (16.16 KiB) Viewed 1751 times

Old one is still here: http://www.waterwar.net/site_wwn/board/ ... php?id=349 , not sure how to delete old/unused/unneeded attachments from the server.

[soakinader]

The image is a little too large for my screen...
But anywho, that's too bad about the Tiger Shark trigger. Well, at least now it will be easy to trim that sucker down!
Have you tried solvent weld? It worked wonders on the hard PC's of several of my CPS tech guns. All you need is some patience and plastic shavings.

[Drenchenator]

These kind of trigger parts were never designed to last that long unfortunately, and because of this I don't think just rotely copying the existing design into a computer and fabricating a new one will fix the problem. In a few years, it will break again, and we're back at the same place.

What we need to do it come up with a better design that fails less easily and less often.

The reason this current kind of design fails is because the bar on the right can only move forward and backward. It's fixed and can't rotate, so force from the user's finger creates a moment that puts stress on the joint in the middle, ultimately causing the joint to fracture. A starting point for a better design would be to strengthen that joint, specifically by making it wider so that it can handle more stress.

[marauder]

I've repaired 2 broken triggers and neither one of them has broken since. Doesn't mean they won't, but if you use epoxy and a metal strip you should be good for at least a few more years.

Anyone thought of just making a metal version of this?

[HBWW]

@Drench: The idea was to remake the parts with durable materials. I cannot see metal versions of such parts breaking easily despite the fact that those parts were specifically designed to break. (Engineers know what they're doing, what forces have on the effects of the materials they use, and know you'll just buy another blaster when the part(s) break, so they don't mind some hard-to-repair piece being made to break after a few years of use.)

@marauder: In the OP, I mentioned cutting out sheet metal pieces to match the piece needed and then stacking the several cutouts together. I will be experimenting with this further with the 2700 trigger (which will completely replace the trigger piece) and see if I can get a fix working.

@soakinader: Apologies. I shrinked it now.

[thelaminator]

A 4'x10' sheet of polycarb I scored from school did the trick for me. I can make essentially any replacement trigger I need.

[HBWW]

I'm going to stick to the sheet metal method, and make triggers entirely out of it. I'll glue some extra plastic parts or use duct tape to make it so that pulling the trigger doesn't cause your fingers to bleed.

We talk about how homemades are impractical and never used in real wars, yet they're the only real way out of this durability snafu that nearly every stock blaster is plagued with these days. Even something like the CPS 1200 can have pull valve issues, though the rubber band fix has taken care of it for years. Still, I don't trust some of the parts which, even though they may be well designed, are still made out of horrible quality ABS plastic that'll eventually break.

I opened up my Vindicator yesterday; quite an ordeal if I do say so myself. (I had to split the pump cap with a sharp flathead screwdriver and hammer, and force the handle area to split as well) K-mod looks unfeasible due to how the bladder was designed. (I need balloons to cover the whole PC, not just part of it, and the shape isn't even correct. Plus the mesh that stops it from expanding also gets in the way.) Everything's working and I only really needed to lube the ball valve (which I did), but I noticed some hairline cracks forming in the trigger arm mechanism. Really nasty design here; if they at least used PVC or something stronger, it wouldn't be a problem. Instead, I have to reinforce this thing; I refuse to put back the Vindicator together when I know it's just going to break after the end of the summer.

I'm going to be honest though, I still slightly disagree with what Drench said earlier, provided that:
1. The 3D printed part is at least as strong as the original.
2. The 3D printed part is modified with any needed reinforcement.
3. The 3D printed part can be printed again and again easily and lasts a few years everytime.

I'd actually be somewhat happy with such a repair solution. A blaster lasts 2-4 years, the same part breaks, you print a new one, take the blaster apart, replace, assemble blaster, and you're good for another 2+ years. Instead, we need to cut up sheet metal or plastic manually and glue stuff together; it's a lot of work in the end.

Unfortunately, my "ideal solution" isn't so simple, because other parts of the blaster will find ways to break, and they may not be feasible to print even in the future. (i.e. parts that require precise seals, mix of metal or plastic, etc.) On the flip side, the tech is catching up fast.