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Lbb Trigger Repair

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#1 Guest_Just Some Bob_*

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Posted 05 September 2008 - 02:43 AM

I'm positive LBB triggers have been repaired before, but I'll bet not quite like this.

Everyone who's taken apart LBBs (and BBBBs) can see that their triggers are a weak point. The LBB trigger is actually molded in two pieces and glued together, but the part with the "fork" in it is really too weak to last very long, especially if one plugs the pump.

My friend's broke just the other day:
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Here we see the trigger (now in 2 parts), the epoxy I ended up not even using, the repair material in its raw state (hanging folder) and the metal bits in several stages of evolution. I cut three short pieces out of the middle of one bar of a hanging folder, and ended up satisfied to use just two of them.

He had already drilled down the trigger base in two places for the first way we thought of repairing it - just insert two metal pins to take the place of the fork. But we didn't find good pins. Then he cut a lateral slot for an attempt that was made with a zip-tie. That slot is visible in the photo above.

I just used a cutoff wheel in my Dremel to turn the two vertical holes into a slot. I did not cut through all the way to the right side of the trigger, only as far as the "fork" needed to go. Then with the same cutoff wheel I shaped the notches in the metal pieces, and before completing it I decided to cut a slight relief in what would be the right edge - just so the slot didn't have to go deeper, saving more of the strength in the still-unbroken part of the trigger.

Here it is with the metal cut to shape and inserted:
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Initially I was planning to epoxy this all into one piece. After the photos, I roughed up the metal surfaces for epoxy. But then it occurred to me that flexibility is a virtue. So I cut a piece of scrap plastic to fit into the depression on the left side of the trigger where the two parts go together. Even without glue, the trigger pin will prevent the metal parts from extending out of the "socket" this forms. But when I glued on the flat piece, I also inserted the metal, I just didn't intentionally get any glue (Gorilla Glue - fast white formula) onto it on purpose. I'm pretty sure it got some anyway, but I just don't care. The strain is all transmitted through metal to plastic, the glue joint doesn't have to take any of it.

Here's the completed trigger (propped up by the cutters I used to get the metal to rough shape) showing the added bit of plastic and the relatively sloppy glue job:
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The whole trigger still flexes under load, but not nearly as much as before.

Not too hard; parts readily available, low cost. Anyone who can use a Dremel (or similar tool) could do it.
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#2 hereticorp



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Posted 05 September 2008 - 08:22 AM

Very nice, I'm going to try something like this on a BBBB and see if it helps with trigger pulls under high pump pressure.
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#3 BlackFox



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Posted 05 September 2008 - 11:37 AM

Sweet! It's kinda cool to see how many repair threads there are now. I think these will be very handy for answering all the help threads.

Very ingenious and precise. Full marks!
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"Until we meet in the place where there is no darkness"
-George Orwell, 1984

Think that piece is beyond repair? Think again!

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