Melting Twistlocks

[icewolf08]

Charcoal- first off, everyone is allowed to make mistakes. Even professionals do.

As for your wiring project, does your school have an electrical shop, or shop or tech/ed. program with a teacher who is knowledgeable in electrical work? If you do, talk to them to get some help. I doubt that people here on CB will tell you how to wire your gear for liability reasons. If your school doesn't have someone you can go to then call your local dealer/repair/rental shop, they might be able to donate some time for you to come in or for someone to come out to you and show you had to do what you need to do. In other words, get some professional help/supervision.

 

[Charc]

Charcoal- first off, everyone is allowed to make mistakes. Even professionals do.
As for your wiring project, does your school have an electrical shop, or shop or tech/ed. program with a teacher who is knowledgeable in electrical work? If you do, talk to them to get some help. I doubt that people here on CB will tell you how to wire your gear for liability reasons. If your school doesn't have someone you can go to then call your local dealer/repair/rental shop, they might be able to donate some time for you to come in or for someone to come out to you and show you had to do what you need to do. In other words, get some professional help/supervision.

Closest thing I've got is the maintenance department. I'll check 'em out soon. Otherwise I'll probably forget about it. Academic year is over in under two weeks.

 

[lightbyfire]

BenjaminD,

One other thing to keep in mind if you are going to work on the female connectors on the pig tails. You need to manually trip the breaker in the dimmer rack. This is always a good idea, but particularly in strand CD80s which have trickle current running through them, even when the channel is at 0.

Also, try making friends with the facilities people in your school, help them out and they will help you. You can also find out who is in charge of low voltage safety, they will understand your issue and likely help, theatres are just as much a part of your schools electrical infrastructure than any other outlets.

 

[BenjaminD]

When I'm working on the pigtails, I trip everything in the rack (and have my little voltage-sensor-beeper-pen-thing with me to check everything before I touch it). I have a tendency to be overcautious (if that's possible).

I know most of the school maintenance dept. They're very helpful and friendly when I need to borrow mops, drills, etc. But I'm rather afraid to let them near the dimmer racks. Even the district electrician didn't really know about them, and seemed very suprised/leery of cleaning them, which makes me worry about them touching them at all, I don't want them damaged by someone who knows nothing about them.

I'm very glad to discover that this isn't just something that happens randomly, thank you all very much!

 

[gaffer240]

One thing I did not see in this thread is the reason the fitting inside the plug get loose. I believe it is the 60 cycle hum from the AC electricity. Aside from looseing the clamps in a twist lock they also will cause lights that are on a long running show to lose focus.

In my case loosen the nuts and bolts that hold my electrics grid together (60'X40' TV studio grid). In some lamp sockets it can cause enough of a problem to cause the pins of a lamp to arc and weld to the scocket.

Loose plugs can cause the plug to overheat when the contacts arc rather then transfer electricity evenly across the contacts.

 

[icewolf08]

One thing I did not see in this thread is the reason the fitting inside the plug get loose. I believe it is the 60 cycle hum from the AC electricity. Aside from looseing the clamps in a twist lock they also will cause lights that are on a long running show to lose focus.

In my case loosen the nuts and bolts that hold my electrics grid together (60'X40' TV studio grid). In some lamp sockets it can cause enough of a problem to cause the pins of a lamp to arc and weld to the scocket.

If your AC hum is that bad that it is loosening bolts in your grid I think you have a serious problem. There really shouldn't be enough vibrational energy coming from your electrics to do that. I think you might want to look into seeing how your HVAC system is laid out around your grid and see if that is causing the vibrations.

Now, on SCR dimmers you often run into issues with "singing filaments" but this is due to the way the SCR chops the AC cycle That square edge on the wave can cause the filaments to vibrate and "sing", but I have never heard of this affecting anything really. I can see where it would affect the bench focus over extreme periods of time, but chances are in a 2-3 week run of show, the hang and strike of the fixtures is more detrimental to the bench focus.

AC "hum" also should not cause arcing in your lamp bases. If there is some serious vibration going on, you can get a bad connection, but if it were the AC power that was causing the problem I think more people would have exponentially more problems like you describe. I would have your space checked out.

 

[Chris 757]

I have worked for the Virginia Beach City Schools for about 10 years. I have seen this problem a lot. The repair work that you are describing needs to be done by an electrician - your profile says you are 16, so I am assuming you are a student. Your school should have a electrician available to them for such repairs. You should let your teacher or principal know about this problem. If it is not done correctly you can have a fire or hurt yourself. Please do not try and fix this yourself.

 

[len]

A good shop will take apart the connector on every fixture and cord, and tighten them. I see it getting done every January, when things are slow. It's better to do it at the shop than at the show. And if there's that much dust on the fixtures then it probably hasn't been done in years, so a thorough troubleshooting and cleaning is in order.

As for 2P&G or twist or edison or whatever, most places I've worked at tape the connections, except for twist. They feel that a twist lock is the only one not needing a taping, so logic would say they believe twist to be the best connector. Not saying that's definitive proof, but that's what they think.

 

[gaffer240]

If your AC hum is that bad that it is loosening bolts in your grid I think you have a serious problem. There really shouldn't be enough vibrational energy coming from your electrics to do that. I think you might want to look into seeing how your HVAC system is laid out around your grid and see if that is causing the vibrations.

Talking small scale problems. When you have say 30,000 watts on day after day, year after year, there get to be small problems here and there. In our facillity the HVAC is shock mounted and isolated from the studio (or so they tell me).

In addition all our circuits are on pigtails creating even more isolation.

I do not believe that you can completely discount AC hum. I was always taught that it created vibration, though small, that over time will loosen things. My experience seems to support this.

(side note: the grid is ares pipes laid out in a 4'X4' square patern with bolts at all intersectionsin.)

 

[ship]

I do not believe that you can completely discount AC hum.

Sounds just logical enough that I'm going to have to use it as the next attempt to do something to the new guy...

Already had an Assistant Shop Manager going to Menards to get some checkerboard paint, and the head of Leko Dpt. going to moving lights repair for a arc lamp pressure test kit, and others searching the building for an ID10T form, I now have a new concept in gaming with people. Back in the military there was the cans of elbow grease and muzzle flash, and as a carpenter there was the sky hooks and board stretchers.

AC 60Hz doesn't have anything to do with bolts loosing tension or fixtures falling out of focus. Air Conditioning, sound systems, expansion and contraction, wiggling about on the grid etc. all can play a factor, AC power is not a factor. Also most modern lamps are designed to prevent the filament humm.

 

[ship]

Just for point of reference and I have a ton of "modern" stage pin plugs as with other plugs on my wall of shame in a similar melted condition no matter the type and especially 60A stage pin. Here is a top of the line "Bates" plug that had a wee melting problem due to a screw that was a wee bit loose. Get the idea that twist lock plugs are just plugs, what goes wrong on them is not due to their nature, just due to their maintaining.

 

[photoatdv]

We have stagepin and we probably replace 1-2/ major show on average (So like 5-10 a year) because they start melting. It is generally high resistance creating heat on one of the connections within the plug. We had one that melted the two plugs into a giant blob (still worked believe it or not-- we found it right before a show and didn't have a spare on site). Biggest issue we have with replacing them is that it's a huge pain to get to our dimmers to turn them off. By the way are you sure that the Strand CD80's have a current at zero? Pretty sure ours don't (Our TD thinks he's indestructable-- and I have to admit he does the craziest stuff and has never gotten hurt other than some minor scratches and a couple (okay well a few more that a couple) of shocks, but how many techs haven't been shocked on occasion).

 

[jonliles]

I don't care who you are. Getting shocked is no fun. If it is a portable pack, I unplug it. If it is a pigtail, I trip the break, then I put a zip tie through the breaker so no one else can energize it. I may be a bit over sensitive, but I've seen a couple of electricians die (non entertainment related) from forgetting to do the simplest of things - ISOLATE THE ENRGY SOURCE. I work with industrial power plants - those OSHA reports are not fun.

My daughter's school has the same issue with 20 yo stage pins. The county electrician said "they're fine." Regardless of what the coutny electrician says, I isolated the circuit (tripped and locked out circuit) & removed the plug to prevent future use. Supposedly, this summer the theatre is being renovated under "SPLOST."

Footer can chime in about our county's maintenance practices.

 

[chieftfac]

Just Finished 6 days of "Benching Fixtures" (after two years) All cleaned, shined, plugs checked (twist loc), Strain reliefs checked, ... surprising number of loose wires into those plugs. Those screws really do work themselves lose over time...(only about 18 in 178 fixtures, but still!!) All I can say is MAKE the time to go over your equipment... It is so nice to hear a touring group compliment you on the professional state your space is maintained...

 

[epimetheus]

I can comment on the 60Hz AC hum. I design high voltage substations with power transformers rated for over 3000A. Those babies hum. With the range of current you see in most theater branch circuits, you're not going to have physical vibrations. 60Hz vibrations are mostly limited to transformers anyway.

 

[venuetech]

the previous posts have plenty of solid information that i shall not repeat

Learning how to take care of your cables/connectors is what you need to do. so it will serve you well to read all the instructions that come with the new connector. If you have any questions be sure to ask the school maintenance guys. be sure to get the strain relief done right

State/local codes may be the determining factor on whether you can convert to stage pin. So you may wish to look into that before you leap.

Once you get the past twenty years of failures replaced, then you can start lighting the show.

you may want to keep some spare connectors/plugs around as you never know when you might need one.

 

[MircleWorker]

I second Ship

 

[teqniqal]

If you have fasteners coming loose in your pipe grid, look to see several things:
Are the bolts and nuts and washers grade 5 or stronger (three radial lines on the bolt heads -- nuts and washers are harder to figure-out)?
Are there lock washers under the nuts?
Are the bolts / nuts torqued to spec with a torque wrench?
If 'no' is in any of the answers, therein may lie your problem.

 

[Chris15]

If you have fasteners coming loose in your pipe grid, look to see several things:
Are the bolts and nuts and washers grade 5 or stronger (three radial lines on the bolt heads -- nuts and washers are harder to figure-out)?
Are there lock washers under the nuts?
Are the bolts / nuts torqued to spec with a torque wrench?
If 'no' is in any of the answers, therein may lie your problem.

Does not the grading refer to tensile strength?
Can someone enlighten me for the need of a tensile strength in a washer? I can understand the bolt for obvious reasons and needing a high grade nut to mate also makes sense. The washer has me stumped.

Lock washers are not normally needed if Nylocs are used.

 

[epimetheus]

Does not the grading refer to tensile strength?
Can someone enlighten me for the need of a tensile strength in a washer? I can understand the bolt for obvious reasons and needing a high grade nut to mate also makes sense. The washer has me stumped.

Lock washers are not normally needed if Nylocs are used.

I think the grade of the washer has to with it's resistence to deflection. The whole purpose of the washer is to distribute the force. If it bends too easily then the force will be localized to the center of the washer, which is the same as not having it there at all. At least that's my theory until somebody corrects me. Also, I prefer a spilt lock washer, or even better a Belleville, over a nylock. I've have too many bad experiences with nylocks galling up on me.