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Re: What was this DC generator for? [Re: poorboy] #194031 05/05/10 02:44 PM
Joined: Apr 2002
Posts: 7,111
HotLine1 Offline
Member
In addition to a possible projector, old 'arc' spotlights. I don't know the current requirements, but one of the members familiar with old theater equip should jump in.



John
Tools for Electricians:
Re: What was this DC generator for? [Re: HotLine1] #194036 05/05/10 07:18 PM
Joined: Oct 2004
Posts: 803
mxslick Offline
Member
It is most likely for a followspot arc lamp...it could also have been for a pair of film projectors (not too likely in a school, but things were different back then.) I did notice the generator is rated at 72 amps so that favors a followspot instead of projectors. Can you trace where that cut-off feeder goes? You'll find clues as to what it powered at the other end.

As for the oil, because of its age I would say it is most likely mineral oil but it could be pcb contaminated, it would have to be tested to be sure. In any event don't just dump it out!!

As a rough rule, I seem to recall being told that if it's mineral oil it will smell like regular cooking oil or rank if it's gone rancid, and if it has pcb's it has a definite petroleum/chemical smell.

Finally, with a bit of cleaning and some fresh bearing oil, that M/G set will still run like new. I dare any modern motor to last 1/2 as long as this good old stuff.


Stupid should be painful.
Re: What was this DC generator for? [Re: mxslick] #194040 05/05/10 10:02 PM
Joined: Jun 2005
Posts: 124
P
poorboy Offline OP
Member
Was able to get the old blueprints and now see that it fed a unitvent panel. I am not sure why, as the panel also had (according to the print) a set of #8 feeders to it.

Cool set of prints!

[Linked Image]

[Linked Image]

[Linked Image]

The unitvent panel was right under my nose, but has been retrofitted and I had no clue to think it was that close, The pic of the cut out flex in my earlier post aimed right at this wall panel. There was only about a foot of flex to reach the wall, as you can see here.

[Linked Image]

Here is the re-fed and retrofitted unitvent cabinet

[Linked Image]


Re: What was this DC generator for? [Re: poorboy] #194047 05/06/10 10:20 AM
Joined: Mar 2005
Posts: 1,803
Alan Belson Offline
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I do hope this wonderful piece of US history is not going to be cut up just so some jerk can sell the ammeters on ebay for a few bucks!


Wood work but can't!
Re: What was this DC generator for? [Re: Alan Belson] #194048 05/06/10 10:24 AM
Joined: Mar 2005
Posts: 1,803
Alan Belson Offline
Member
@mxslick! Long time no see, welcome back. Hope you recovered well from your illness.
regards,
Alan


Wood work but can't!
Re: What was this DC generator for? [Re: Alan Belson] #194089 05/09/10 11:07 AM
Joined: Jun 2005
Posts: 124
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poorboy Offline OP
Member
The theater in this school has been a widely used venue for many years, so I would not have been surprised to learn that this had something to do with associated equipment.

Now that I know it was not, and was used for the purpose above, what was the reason for feeding the unit vent cabinet with DC? Possibly the fan motors in the units had DC motors at one time, I guess.

Just picking the collective brain of this site out of curiosity.

Anyone??

As far as saving the piece for a museum or such, it would require the dedicated efforts of some people willing to carefully take apart, move and reassemble it in a location that would be a bit hard to find. Sad, but true in many cases of things like this. When you actually do visit a museum, esp. of mechanical things, it is evident from seeing the restored condition of things and the displays that a LOT of volunteer effort went into the whole deal.

At any rate, I did get to see it---now I wonder more about it.

Last edited by poorboy; 05/09/10 11:09 AM.
Re: What was this DC generator for? [Re: poorboy] #194090 05/09/10 11:23 AM
Joined: Jun 2005
Posts: 124
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poorboy Offline OP
Member
I just spent a few minutes looking over a pretty good copy of this print that I brought home. There is no line drawn to indicate the AC feed to the compensator that I see. For that matter, the compensator itself is not drawn but was probably, just as today, not that equipment specific about the disconnects and starters that may or may not come as part of an assembled piece of equipment.

But I wonder why nothing was called out to feed the AC motor of the genset.

BTW, the 3-#8's in 1" pipe that leave the unitvent cabinet go to the other side of the building to a unitvent sup panel.

All the feeds simply go to unitvents, so must have fed DC motors.

Were AC motors less desirable for some things...speed control for instance.

Last edited by poorboy; 05/09/10 11:27 AM.
Re: What was this DC generator for? [Re: Alan Belson] #194109 05/10/10 03:24 PM
Joined: Oct 2004
Posts: 803
mxslick Offline
Member
Alan, Thank you for your kind words. smile I am doing somewhat better, been quite crazy on that front. Will update my other thread.

Poorboy, to answer your question, yes in that era DC motors were much easier to control accurately since there were no AC VFD's invented yet. It is also possible that the damper motors were fed off of that same generator.

As for the compensator, it was most likely an add-on as required by the local power company back then, as the requirement varied by location.

I wish I was close enough to your location to remove that equipment for preservation.


Stupid should be painful.
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