A puzzler, and it's solution

[mutantmoose]

So, at the academy, we have two strips wired with bungee cords, and two with reels. I rewired the bungee ones recently, using equipment as it was given to me.

Recently, a fellow fencer who fences epee was having problems on one strip. He could not get a touch at all. We fixed a few things, and he started getting touches, but not with all his weapons. Problem was, everything of his worked fine on the other strips.

So, I took a look at his body cords. They were quite old, and there was a lot of corrosion on the wires. Hmm, perhaps a resistance problem? No, a borrowed cord produced the same results.

I started testing his epees, and sure enough, one had a problem - the middle socket was grounded, so he would get a yellow light as well as a touch when the button was pressed.

But why did it work on all but one strip?

Turns out that the wires on that bungee cord strip were hooked up to XLR (or Cannon) microphone connectors to a wall plate, with both green and red wires on the same plate. The plate was metal, so the grounds for both wires ended up being shared, completely unnoticable until a bad epee was hooked up. I'll be tearing that apart in a couple of days, and isolating the wires from each other.

Lessons learned -

1. Use a test box on your weapon and body cord. Don't just blame the reels and scoring apparatus.
2. When wiring and testing a bungee system, test for continuity between any and all possible contacts. Make sure it's only where it needs to be.
3. Building a fencing academy next to a brew pub is a really good thing after a day like this.

[fencerbill]

3. Building a fencing academy next to a brew pub is a really good thing after a day like this.

Maybe that's where the problem originated?

[Fechter1]

I started testing his epees, and sure enough, one had a problem - the middle socket was grounded, so he would get a yellow light as well as a touch when the button was pressed.

But why did it work on all but one strip?

The better question might be: Why did the weapon work on all the other strips? If your B plug is grounded, the weapon should not register touches at all. Might be limited to a certain type of machine, but that's been my experience.

[mutantmoose]

All the machines are Eigerteks with the DOHO 1.3 chip. The yellow light would come on for a touch, but the touch would still come up.

I'll have to take another look now and see if the grounded wires are accidentally grounded to the floor. I'm pretty sure I checked for that, but not so sure that I won't check again.

[DHCJr]

Maybe that's where the problem originated?

Bill, as a great Armorer you should know there should be a requirement to have all fencing salles next to a good brew pub.

The better question might be: Why did the weapon work on all the other strips? If your B plug is grounded, the weapon should not register touches at all. Might be limited to a certain type of machine, but that's been my experience.

The Eigertech as well as the St. George are designed to work in Epee even with a grounding problem. It is a modification of the anti-fraud in Foil.

[Fechter1]

The Eigertech as well as the St. George are designed to work in Epee even with a grounding problem. It is a modification of the anti-fraud in Foil.

I stand corrected (educated).

Thanks

[mutantmoose]

The Eigertech as well as the St. George are designed to work in Epee even with a grounding problem. It is a modification of the anti-fraud in Foil.

So, if I was to hook up our old pre-cambrian Prier scoring machine, we would have not seen any touches? Interesting...

[DHCJr]

So, if I was to hook up our old pre-cambrian Prier scoring machine, we would have not seen any touches? Interesting...

Even with a modern Favero the Epee would not work. I was at a tournament with mixed Favero and St. George. A fencer had been using the same weapon through the pools and preliminary DE's. Suddenly against someone good they no longer could use their favorite weapon. I don't need to tell you what happened to them in the DE. They had been fencing on St. George machines the whole day until then. I asked them if they noticed any yellow lights. They had but hadn't worried about it since the weapon was working.

They are watching for yellow lights now, even when their weapon is working.

As illustrated, your weapons should be set up in such a way that you never have a 'favorite weapon'.

[Fechter1]

So, if I was to hook up our old pre-cambrian Prier scoring machine, we would have not seen any touches? Interesting...

I don't know scoring machine brands/models, but yes, some machines will not register a touch if there is a short to ground within the weapon or bodycord. Seems almost like they share the ground... (as in your specific case)

Let me tell you, it's frustrating trying to troubleshoot these cases. Weapon tests perfectly, but under bout conditions the A line shorts to ground either in the tip or just inside the guard, preventing some touches from scoring.

[DHCJr]

Some may ask why don't all machines work like this. First this gives an advantage to first St. George and then Eigertech and to what advantage would it be to tell how they did it to the other manufacturers.

The second reason is these machines do not follow the letter of the law (M.31); they follow the spirit of the law. Part of how they do it is they do not use a common ground between the 3 grounding circuits as required.

This is what makes the rules interesting to apply. This is not the only time where innovation has exceded the letter of the law.

[DJ Apostrophe]

Also... if you are fencing and you have a ground light on, and you hit your opponent with your blades engaged, you're quite likely to have your weapon not go off... Electrically, your tip is now connected to their weapon, and the hit will ground out...

DON'T FENCE WITH A GROUNDING LIGHT ON.

-w

[mutantmoose]

Some may ask why don't all machines work like this. First this gives an advantage to first St. George and then Eigertech and to what advantage would it be to tell how they did it to the other manufacturers.

The second reason is these machines do not follow the letter of the law (M.31); they follow the spirit of the law. Part of how they do it is they do not use a common ground between the 3 grounding circuits as required.

So, when I accidentally connected the grounds, they operated like any other machine - no touch. With the grounds separate, touch and yellow light. And me getting dirty looks from fencers because their equipment works on all the strips except one. (No, they didn't give me dirty looks, but they were exasperated!)

More and more interesting.

[Fechter1]

And me getting dirty looks from fencers because their equipment works on all the strips except one. (No, they didn't give me dirty looks, but they were exasperated!)

More and more interesting.

Good thing they didn't give you the looks, since it's their fault...

DJ - I'd completely forgotten about the possibility of shorting to the opponent's ground by connecting C lines (blade/guard contact). Thanks for mentioning that.
Yes, grounding shorts anywhere are a baaaaad thing.

[mutantmoose]

Good thing they didn't give you the looks, since it's their fault...

But of course, it didn't look like it was their fault. Now, if all our machines were Faveros or something like that, their stuff would not have worked and that would have been that. But, since their stuff worked on three out of four strips, and the one strip had been installed by the newbie wanna-be armourer, well, it's really easy to draw conclusions.

I'm actually considering just leaving the one strip the way it is, so that people will find problems before going to another club and having equipment that worked yesterday not work today. (Nah - I'll fix it up.)