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Crossbow Plunger Shaft Material?


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#1 SirTofu

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Posted 08 June 2006 - 02:50 PM

Ok, my coupler broke off (again) my xbow's plunger shaft. I need to know what material is the xbow plunger shaft made of? Is it polyethelene? And how can I make sure the coupler stays on?
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#2 Team Slaya

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Posted 08 June 2006 - 06:01 PM

Epoxy. Works every time. If you really wanna go nuts, roughen up the gluing surfaces with sandpaper or a file for better grip.

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#3 SirTofu

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Posted 08 June 2006 - 06:37 PM

Epoxy. Works every time. If you really wanna go nuts, roughen up the gluing surfaces with sandpaper or a file for better grip.

TS


I have tried epoxy and plumber's goop. Does not work every time.
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#4 TED

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Posted 08 June 2006 - 06:38 PM

I have found that epoxy is just too brittle and allows no movement. Plastic Welder is what you need it's very strong and will allow some bending without it breaking the seal. I have found it at walmarts and its in a silver tube in the hardware section.

Edited by Dark Shrimp, 08 June 2006 - 06:38 PM.

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#5 TimberwolfCY

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Posted 08 June 2006 - 10:56 PM

That's weird that Plumber's Goop didn't hold it. I created a sort of help article a while back about gluing, let's see how much I can rehash.

First, you have to make sure the surfaces to be glued are clean; wash and rinse them with hot soapy water, preferably with dish detergent. Make sure you rinse them thoroughly. The reason you wash and rinse the parts thoroughly is that if there is any excess machining grease, oil, dust, etc., you want to get it off, as it can severely interfere with the bond between parts. The second thing you can do, as others have suggested, is to sand and cut slashes in the parts to be bonded. This gives the glue something to "fill in" and grip to, further enhancing the bond (of course, make sure you wash the parts as mentioned above before gluing after doing this). Finally, put sufficient presure on the parts for a long period of time to all the parts to fully dry and bond. When I put together my chamber/coupler assembly for my Crossbow, I put four rubber bands longways on it, and then, while keeping it vertically balanced I put four college textbooks on top of it and let it sit still for two days to make sure it bonded properly.

None of the points can be overstated; they're all aimed at making the parts bond. This concept of "bonding" is very important to understand. Any good glue contains some kind of solvent; a solvent is something that actually melts the material it touches, so that when two parts are put together, they are sort of welded together; this is called "bonding." Everything you do in regards to gluing is focused on this one purpose. This is why its important to clean the parts, otherwise you're effectively attempting to bond oil and dust, neither of which are stationary, and thus the parts will eventually fall apart, because whatever true bonding does occur, is only superficial. This is why it's important to sand and slash the gluing surfaces, to increase the surface area for bonding. This is why it's important to press the materials together for a long period of time, to make sure that the parts bond properly. It's also important not to use too much glue, because the glue can get in the way of itself and interfere with the bonding. It's important that the glue bond, not just adhere (stick to).

Finally, external reinforcement never hurts; it serves to buffer and absorb some of the shock of firing, taking stress off of the actual bonding site; the reinforcement serves to absorb some of the force of the shock of firing. In addition to the Plumber's Goop on my Crossbow, I also used hot glue, a layer of duct tape, and foam to make sure that it stays steady and secure.

If you've done all the above, than I'm not sure what your problem is. I've only had my Crossbow for about a year now, and only fired it about 100 times, so I may well run into the problem you have. It could be that the plastic that the chamber is made out of doesn't work well (ie. doesn't bond with) Plumber's Goop or epoxy; I know Plumber's Goop bonds with PVC, because it says it on the package on the back, so your problem is not with the coupler. I'd suggest the steps I named above and try again with Plumber's Goop and see what happens, as you're not going to get a better plastic-to-plastic agent than Plumber's Goop.

Also, looking at your Crossbow ("stingy" I assume it is) it looks like you only have one coupler. This means that every time you pull the barrel out, all the stress is going to the bonding site. I'd suggest doing a double-coupler mod, like Rawray's here on NH, so that when you go to pull the barrel, you can grip the coupler assembly and pull; this will mean that no stress will go to the bonding site, greatly increasing its longevity. I wouldn't think this would be that much of a problem, considering you're going to be redoing it anyway.

Good Luck, and sorry if I wrote too much, I'm just trying to help.

Edited by TimberwolfCY, 08 June 2006 - 11:05 PM.

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