Weird epee grounding problem

[veeco]

Yesterday I came across something very weird while working on my epees:

One of my blades was grounding, but only when I depressed the tip. When the tip wasn't depressed, no lights on the test box would come up. When I pressed the tip, only the grounding light would come up.

I visually checked both wires at the junction between the tang and the blade, and they looked fine. As a matter of fact the spaghetti tubing clearly extends past the bell guard and into the blade, so I know that there can't be any grounding happening there.

Trying to troubleshoot the problem, I removed my tip screws, pulled the tip out, and was able to get a correct light when inserting a screwdriver to short the contacts in the cup.

Baffled by this, I put the tip back together, using THE EXACT SAME PARTS than what was in there before, and no grounding anymore, everything works fine!

I didn't change anything on the tip, all I did was to disassemble it and reassemble it. I didn't extend the contact spring, I didn't change the weight spring.

Do you have an idea what could be causing this?

[Zilverzmurfen]

Hey, you're the Fencing Expert!

But really, it sounds odd. Perhaps it was just a little dirt/dust?
I'm sure DHCJr will have a more sensible answer for you.

[daveappr]

When you removed the tip did you notice if the contact spring was seated properly or perhaps there may have been a small metal burr or shaving in the barrel? Possible causes I've seen in the past. If it hasn't recurred since you've removed the tip and cleaned the barrel, it seems to me that the problem occurred somewhere in said barrel. I'm sure DCH will be able to provide a better and more thorough answer though.

[telkanuru]

I'm pretty sure your contact spring was bent and touching the side of the barrel. Either that or something in the barrel, as daveappr said. Any other problem that would cause the symptoms you suggested would have re-manifested itself when the tip was reassembled.

[veeco]

I would have thought that if the contact spring was bent and touching the side of the barrel, there would not be any grounding, it would just not register at all, since the contact spring would not hit both contacts in the barrel (I have German wires, so there is a cup that holds the contact spring in place).

Also, if there was a metal shaving, I would have thought that the grounding would happen even when the tip wasn't fully depressed?

Hey even fencing experts can learn something new from time to time ;-). Besides, I am by no mean an expert armourer! You wouldn't want ME rewiring your blades!

[telkanuru]

It would depend on the location and/or orientation of the metal shaving. The german wires pretty much eliminate the bent spring problem. Did any parts of the tip seem out of alignment?

[veeco]

Not that much that I would have noticed it and thought about it... I mean I literally pulled the thing apart, and put it back together, all in the course of less and 5 minutes, so I didn't really have any time to fiddle with the contact spring or anything. After that it just worked.

Could it be something with my test box? I mean the weapon wasn't working, and there was a ground, but I'm thinking it might be showing only when I depress the tip on the test box, but be permanent on a regular box?

[DJ Apostrophe]

chances are, there was something (magically conductive dust, metal shaving, whatever) bridging a connection between the contact spring and the weight spring. the only time it manifested itself was when the tip was depressed because that would complete the circuit between the B & C lines, and when you took the tip out, whatever was causing this bridge got jarred loose and that is why you haven't seen it again.

-w

[acaba]

Another possibility is that one of the wires in the tip was grounding to the blade. When you disassembled the tip and stuck the small screw driver into the barrel, you might have turned the little plastic cup, and moved the offending wire away from the blade. I sometimes use this trick as a last resort to fix epees that are grounding in the tip. You use the screwdriver to rotate the plastic cup in the barrel until either the grounding stops or you break a wire. If the grounding stops I will put a tiny drop of super glue into the blade end of the barrel to try and insulate the wires.

The reason you were only getting the ground light when the tip was pressed is because only one of the two wires was grounding. The electricity had to go through the good wire, across the tip and back down the bad wire before it could ground into the blade. With the tip open there is no path from the hot (good) wire to the ground, so no light.

[veeco]

Originally Posted by acaba

The reason you were only getting the ground light when the tip was pressed is because only one of the two wires was grounding. The electricity had to go through the good wire, across the tip and back down the bad wire before it could ground into the blade. With the tip open there is no path from the hot (good) wire to the ground, so no light.

Aaah, yes of course, that explains it all!

Thanks

[remise]

I can second that. The same thing happened to me at tournament this weekend with my epee.