What is it #1978v2

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Snapped a shot of this today:


So, what is it? What is it used for? Would they still be installed today?

Usual 1 week delay for anyone who considers themselves a pro or was born before 1990.
 

MPowers

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Hint, It is not a single purpose device. It basicly does one thing electricly, but can be used in many different ways.
 

BillConnerFASTC

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Looks like from cinema for some reason. Maybe a star twinkle kind of machine? Could have played some sort of musical thing as well. Clearly an early programmable switch device.
 

derekleffew

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Related (I think*) questions:
What are "motor shades", and how do they work (in reference to the apparatus in question)?

*EDIT: Footer tells me this isn't what I (and others) thought it was. So let's come back to the motor shades thing after the original question has been answered.
.
 
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STEVETERRY

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Snapped a shot of this today:


So, what is it? What is it used for? Would they still be installed today?

Usual 1 week delay for anyone who considers themselves a pro or was born before 1990.

Anything to do with a curtain?

ST
 

DavidNorth

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Anything to do with a curtain?

ST

I don't know what it is, but I could easily see that. I have an application in mind. It's interesting that the lobes of the cam are essentially mirrored from the center out.

David
 

Aman121

Active Member
I think I've seen something like that in the machine room of the duquesne incline we have here in Pittsburgh. I belive it had something to do with the automation/sequencing of the motor and brakes and associated machinery. So my guess is something to do with an elevator or lift machinery. And if that is what it's for I would also guess that they are still installed; as they are likely reliable and ideal for critical applications where a computer failure could be very bad.
 

MPowers

Well-Known Member
In simple essence, it is a mechanical version of a PLC. It, as others have noted, controls, via shaped cam lobes (note they are not all simple teardrop shaped) , a series of momentary contact switches which might be either NO or NC. Because there are a number of possible applications for this particular device, including stage machinery, we might not guess the actual use. However, its presence on this forum would seem to presuppose a theatrical purpose, so I'll vote for the contour curtain as one reasonable possibility.
 

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So, I believe Steve has been in my space, while it was a long time ago. I'll throw this out there, I have two of these in my larger room.
 

n1ist

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I remember seeing similar units in traffic light controller boxes and in animated neon signs long ago...
/mike
 

Les

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I remember seeing similar units in traffic light controller boxes and in animated neon signs long ago...
/mike

I was going to mention similar relays being used in chasing neon signs. I used to work at the theatre pictured below, where the three-story neon sign needed periodic maintenance (usually tube or transformer replacements). While we had a sign company take care of this, I did get to look up inside it while it was operating once. It was like a mad scientist's laboratory in there!

The chasing elements of this sign were the "chevrons" which run vertically up the CAMPUS portion of the sign as well as the upper and lower perimeter of the marquee. Made a nice zap zap zap sound as it ran :). The sign dates back to when the theatre was a single-screen movie house (1949).





I was going to say that or the crankcase of an early Ford Model A ;).
 
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BGW

Active Member
Reminds me of the old school motor starting switches. This video is of a 3 speed + reverse (5 total positions) switch. It's for a very old (and very large) exhaust fan in an old theater. The video is sideways, but the switch is mounted vertically on the wall with an egg-shaped handle on top. http://sdrv.ms/11KZSTk

I once had the chance to snag this massive variant. It's in the lower left of this photo, in the full speed position. http://www.coloradoskihistory.com/images/idlewild_large_0003.jpg I wish I had a picture of the innards to share with you. It was very impressive. Quarter sized contacts. I'm not sure how many positions it had, but it worked as smoothly as velvet. I kick myself for passing it by every time I think about it. For people who might not already know, such a switch was necessary before semiconductor powered motor drives were developed. Instantly applying full power to a motor of that size (even unloaded) can actually cause the rotor to peel apart and/or the stator and windings to collapse. This switch was wired to a gigantic bank of resistors; as the switch was operated, it would connect various combinations of resistors inline with the motor windings until finally shorting out the resistors on the "full speed" stop.
 

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So, this thing is a "Rotating Cam Switch". We have two, one tied to each of our pit elevators. It is a very crude but ingenious was of motion control before the days of PLC's and digital encoders. Square D made this one. Each cam on the shaft is a different shape. This thing is connected to the drive on one of our screw jack motors. Depending on what combination of switches are hit you can figure out where the lift is. It is accurate to an inch or two. Our lifts use this switch to determine when they are at the orchestra and seating levels. There are hard limit switches that make the lifts stop at the stage level and storage level.



The switch is the gray box in center of the picture.



Each lift can run independent of each other.



In this shot you can see the tracks the seating carriage rid in (yes, everything is curved in the building).



Finally, this is what happens when a 14 ton seating carriage breaks.

 

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