BulbCollector Forums
BULB DISCUSSION BOARDS => Antique Bulb Discussion => Topic started by: Yoshi on August 05, 2004, 10:42:00 pm
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Hi all, I found something just plain weird in one of my cage filament bulbs. See for yourself (look at the black arrow):
http://bulbs.2yr.net/images/forum/defect.jpg (http://bulbs.2yr.net/images/forum/defect.jpg)
This is the first time I've ever seen such a thing. Have any of you come across similar defects?
-Yoshi
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Hello!
I have a bulb with a similar defect. At first I wondered if they may have been from the same "batch". However, mine is a later tipless G.E. Mazda 40 watt 120 volt which is also stamped "Detroit Edison Rating" (the Detroit Edison company used to exchange burned out lamps for new ones for customers).
In my lamp, one loop of the filament appears to be twisted one full turn as it goes up to the support. Is yours twisted only once, or more than once? Curiously enough, the defect is in the same position in both bulbs- going up from the left lead-in wire (as you face the side the leads are angled toward) to the first support.
It kind of makes you wonder if this was a common defect or not. Either way, I'm guessing that not many would have survived as short-circuiting the filament in this way would surely have shortened the bulbs life in use.
I hope someone can provide some information regarding this.
Regards,Bill.
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Hi Bill,
Mine is a tipped Bryan-Marsh Mazda. I think it is a 25 watt. The filament is twisted twice. Certainly, the twists make the active portion of the filament shorter and thus increase its light output, while also reducing its life. Mine has a break in the filament, and it appears to have been used many hours despite the twisted filament. (btw, this bulb still works because the break overlaps).
I thought this bulb was completely worthless, till I saw the twist! (http://www.bulbcollector.com/ubb/smile.gif) Now it's a keeper.
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I have never seen the mistake before in a finished lamp, but having mounted hundreds of these filaments myself over the years, I can confirm its something that occurs very easily.
You begin with tungsten wire which passes through a device called the Jazz Machine, which kinks the wire at regular intervals, where the supports will be. It's kinked in one continuous length of a few miles, and so strong is the 'set' applied to the wire, that you can coil it back up on another spool for subsequent use.
The kinked filaments don't coil up on the spool smoothly though and sometimes twist. Then when you unwind them and begin looping the filament over its supports, you always find that the filament has the incredibly annoying habit of suddenly springing around and twisting itself up like this. When it happens you have to take the filament off its supports and begin again. No doubt some production operators got so fed up with this, I can understand that maybe on a Friday afternoon when you've had enough, a few defects will slip through!
James
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Thank you James for the insight into the manufacturing process and how this defect could have occurred. I would have never suspected that the wire was "pre-kinked". From your description, I can understand how this type of defect could easily happen.
Regards, Bill.