It started out of my own stupidity. The last time I used it, ranges suddenly dropped and I simply put it away without checking it out first. Two weeks later, I opened it up and discovered the plunger head had folded back on one side leaving a nasty crease and killing the seal.
Naturally, I wasn't going to leave it in its crippled state, so I started frantically trying to fix it. I tried flipping it inside out, then dipping it in hot water before flipping it inside out and neither laster for more than two shots. I tried wrapping it in e-tape, but it didn't help the range and made the creases worse. I moved on to rubber washer replacements (I couldn't find neoprene) but they were too big and cutting it down to a perfect circle was nearly impossible without say, using a lathe. Then I found this:
A rubber jar-opener. It was thin enough that I could cut it much easier than the rubber washer, so I stamped the bottom of the plunger tube on an ink pad and pressed it onto the jar-opener. Then cut out the circles very carefully. It will be slightly larger than the ID of the plunger tube, so you're not screwed if you slip up and the circle isn't perfect.
Next, position the old plunger head over your o-ring and mark the hole in the center. I used my rubber washer for this part.
Cut out the hole you just marked and stick it on the plunger rod. This is starting to look promising.
I consider this next step temporary as it isn't very efficient. To hold the new o-ring down, I drilled two tiny holes through the plunger rod and jammed two pins through them.
Cut them so they're smaller than the o-ring and hot glue the loose end in place and re-assemble your crossbow.
The end result was satisfactory- although it doesn't quite live up to its former glory. The needles don't do a great job of holding the O-ring down and the accuracy has suffered because of it.I intend to put a washer there instead, but it'll take some more planning because the cross section of the plunger tube is awkward. Also, because the o-ring is slightly larger than the plunger tube, it's a little frictiony. I added a little silicone lube to help that.
It's a little random, but most shots are over 100', and isn't half bad for an hour's work.
EDIT: This fix lasted a little more than a day. For better results, check out my other Crossbow fix.
Edited by BlackFox, 29 August 2008 - 06:02 PM.
