PD on the truss?

[ProgrammerInTraining]

ok, idk if this is done often but it's the first time I've seen it.. I was doing a freelance strike yesterday and as they were lowering the motors bringing down the truss I noticed a box on top of the truss, I knew it was too big to be a repeater, breakout box or ballast. once down I saw that it was a PD ratchet strapped onto the truss with the 4/0 coming straight from the genie. is this type of thing common? I've never seen this done.

[shiben]

ok, idk if this is done often but it's the first time I've seen it.. I was doing a freelance strike yesterday and as they were lowering the motors bringing down the truss I noticed a box on top of the truss, I knew it was too big to be a repeater, breakout box or ballast. once down I saw that it was a PD ratchet strapped onto the truss with the 4/0 coming straight from the genie. is this type of thing common? I've never seen this done.

Depends how much stuff was on the truss... It might be cheaper to run extra feeder then to rent a loom of a few dozen mults... Or the PE figured that it would be safer to keep the distro with the truss at all times, so it never got plugged in to the wrong place... Lots of possible reasons.

[derekleffew]

Hoist distro, yes, quite frequently. Moving light distro, almost never. (I've done it twice, I think, in 20 years.) How are you supposed to give a fixture a hard reset?

[MNicolai]

How are you supposed to give a fixture a hard reset?

Cycle the company switch -- duh!

[JD]

Don't know how comfortable I would be with the concept of flying feeders and the ramifications on rigging cables burning off like nichrome wires should a short occur. Can't recall anything that specifically forbids it. Maybe ST can?

[mstaylor]

There was a truss system years ago that the dimmers lived in the truss. You ran feeder to the truss and jumped it out from there. I believe Feld's ice shows also fly distros on their trusses.

[Footer]

There was a truss system years ago that the dimmers lived in the truss. You ran feeder to the truss and jumped it out from there. I believe Feld's ice shows also fly distros on their trusses.

I believe this was a pretty common thing back in the 80s with par rigs. I have also seen broadway style shows put a sensor 24pack riding on top of the FOH truss.

[mstaylor]

The PAR trusses were definitely '80s. The jumpers from section to section were twecos.

[techieman33]

I've seen the distro on truss used for feld ice shows, and I'm pretty sure I've seen it in use on a WWE show a few years back.

[jstandfast]

Yes, one of the west coast shops back in the 80s had trussing with integral dimming( made by LMI, if memory serves); each section got fed from a 30 amp 3 phase twist lock in turn fed by a huge truss mounted distro.

[derekleffew]

In the 1980s, Morpheus Lights of San Jose, CA was perhaps the largest proponents of power distribution in the truss. (They also pioneered traveling moving lights inside the truss: FlipBox, the antecedent of today's SwingWing.) Several attempts have been made to put dimmers in the truss (McManus, See Factor, HiLights, etc.) but all have failed.

Note that dimmers/distros in the air is not a new concept:

...Many of us have seen the Rack vs. "dimmer at the fixture" debate before. In the 1980s some Rock&Roll lighting companies tried to convince us "dimmers in the truss" was the future. I don't know of a single touring company doing that today. Of course, I had the same thoughts about powered speakers.
edit: Research shows that the concept of "dimmer at the fixture" was proposed in A Digital Lighting System for the Theatre, Master Thesis of Fine Arts Yale School of Drama pp. 1-48, May 1974 by Dirk Epperson. Once an assistant to LD F. Mitchell Dana, Mr. Epperson today is VP and Co-Founder of TIBCO | Telecommunications, a software solutions company.

From High rollers: The roster of Las Vegas players :

The control system in Callahan's crystal ball had the dimmer at the fixture by 1988. While a few touring companies kludged together SCR dimmers in truss-mounted applications, the real possibilities and pitfalls for dimmer at the lamp did not become clear until the commercial application of chokeless transistorized dimmers to distributed dimming systems in about 1991. And despite the fact that distributed dimmers have become reliable, the market has been slow to adopt them en masse. Perhaps we will have to wait for the arrival of two new advances to finally and fairly evaluate distributed dimming: dimmer in the fixture, to completely avoid a separate dimming device, and the advent of cheap, reliable wireless data transmission technology, to get rid of all those pesky data cables! Both these advances should be just around the corner.

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...I have also seen broadway style shows put a sensor 24pack riding on top of the FOH truss.

If one happens to put a half-coupler through each of the bottom holes of an SP6 or SP12 pack, one may find that the couplers are perfectly aligned to fit 20.5" truss. I wonder if they planned it that way?

[bishopthomas]

There'd better be a really good reason for it being in the truss. I can think of many good reasons not to fly the PD but not a single reason why it should go in the air.

[mstaylor]

I believe Feld does it to cut down on cable falling off the truss. Their cable pick on an ice is already huge. They run everything for three to five trusses through one cable pick.

[FatherMurphy]

The local arena here used to do a lot of pro wrestling pay-per-views, the dimmers were almost always flown on a separate platform, complete with a tech sitting up there during the show in case of trouble. They were trying to free up floor space as well as concentrate cable runs, as best I could tell.

The main problem with flying dimmers and distros is access, if something needs doing, it's harder to get out on a truss mid-show than to a floor level spot.

[mstaylor]

I did the dimmers on the platform trick during the gala before Clinton's first inaugeral. They were saving floor space also.

[jstandfast]

Yeah, flying the dimmers was just about SOP on big rigs @ the old DC convention center........

[chausman]

Can someone please explain to me what PD stands for?

I can think of a few but I don't know what you mean by it.

Power Distro
Power Dimmer
Portable Dimmer
Particle Disintigrator - while highly unlikely, anythings possible on this forum...


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[mstaylor]

I think I was only in there once. The Clinton gala was at the old Cap Center.

[rochem]

Can someone please explain to me what PD stands for?

I can think of a few but I don't know what you mean by it.

Power Distro
Power Dimmer
Portable Dimmer
Particle Disintigrator - while highly unlikely, anythings possible on this forum...


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- Sent from my iPad using Tapatalk

Power Distro. I'm not sure if the distro in the OP's situation was a hoist PD or a ML PD or something else, but my guess would be a hoist PD.

[metti]

It is also possible, though unlikely that it was a sound distro. Amp racks are flown on a semi-regular basis and, some companies actually design amp racks that are designed to be flown. I have seen a show in which the flown amp racks were fed via a flown distro.

[meatpopsicle]

You might be interested to know that in the film business distributed dimming solutions are more frequently used than in the "live" side of the business. As to putting power distro in the truss - thats de riguer for us. We'll put 4/0 anywhere. Without the access issues of a live venue, distributed dimming offers a great cable saving advantage. Frequently the amount of multicable on a show over a long period of time can really add up.

On my last movie i designed a system that we put in place for a hospital ward set with 80 2circuit flourescent fixtures. The flourescents had three lamps and 2 circuits. This allowed for 1 bulb on, 2 bulbs on or three bulbs on. In this instance the distributed dimming came along with the original requirement - a low wattage dimmer with a switch only mode. Both Elation and Chauevet make a "shoe box dimmer" that handles 4 circuits and allows switching between dimming and switch only mode. By using the switch only mode I was able to control all 160 circuits with out any of the problems associated with putting flourescents on dimmers that are profiled to full at 1%. We eliminated flickering fixtures and blown ballasts on a set that was standing for 7 weeks. We did have to attach a snubber load to increase the load on the dimmers.

On a standing set with catwalk access the distributed nature of the system really lent itself to reducing the amount of equipment and rigging involved with long multicore bundles running out from the dimmer room.