mounting a stage light under a platform

[AviatorDrama]

This is probably a ridiculous question, but I have nowhere else to ask and zero expertise.

I need to mount an ellipsoidal on a 2x4 frame underneath a platform that is approx 5 foot high. I need the light to shine up through 5" holes in the platform. I can't use our par cans because they get so so hot.

And I need to control these from our booth. We only have stage pin plugs in odd places on our stage (and have to rent extension cables) I can't control anything that is not on those stage pins.

We have an amazing lighting system in a brand new school, but no one knows how to use it.

Is this safe at all? It's a school, I need to not burn it down....

thanks,
Robyn

 

[JohnManderbach]

Robyn,

I'm not sure I understand the situation but I'll chime in anyway. Do you need to attach the units to the underside of the platform? Can you put them on floor plates? If you have to be right under the platform then I would avoid any incandescent light. Do you have any LED's that would work?

The heat issue with incandescent lights really comes down to distance and time. The closer to the platform and the longer they are on is bad. A few feet of air for only 15 minutes is probably fine.

I'm curious to know more. And I'm glad you're concerned about safety. It often gets overlooked.

 

[JVTD]

Do they need to be on the entire time?

 

[JonCarter]

How big is the platform top with the 5" holes in it? If the top is 5' off the floor, you'll need an instrument with a beam that's VERY wide to cover very much area. (And, a leko is a couple feet tall, so the throw from the instrument to the platform top is only maybe 3'.) What is the light coming through the 5" holes lighting? Any single instrument's beam, spreading over much area at a 3' +/- throw, will be spreading pretty wide. If you're just lighting the pant legs of the actor on the platform a single instrument may work, but you may need several (many?) small instruments, one on each hole in the platform, to do what you want.

 

[FMEng]

I have operated some 1000 Watt lekos in a place with restricted air flow. It resulted in discoloration of the reflector on some of them. In your shoes, I would use the par can with a wide flood lamp, because they are more likely to tolerate the heat. If damage were to occur, I would rather damage a cheap par can.

 

[rphilip]

How bad would it be to operate some 2x4 banks of florescent lights under the platform? Both from the perspective of the quality and beam spread you are looking for and in terms of running it on a dimmer?

 

[porkchop]

PERSONAL EDIT: I'm leaving my super long and reasonably questionable post after this in case it might help, but hopefully this is a better solution and the original post can be skipped over:

How much light do you need? Could you do the effect with something like a VNSP MR16 that is both low power (less radiant heat) and narrow beam angle (can have all of the light go through the hole and still be mounted reasonably far away from the platform). MR16's can be surprisingly bright and come in really narrow beam angles. You need to pay attention to operating voltage as a lot of MR16 lamps don't run on 120VAC, but it could be the ticket for your effect. As always be safe and try things out incrementally up to and in excess of expected use case to ensure safety.


ORIGINAL SUPER LONG POST:
The first question is how long is the effect on for and at what intensity? If it's at full for 60 minutes that might be a problem. 15% for 30 seconds, maybe not. Given your concern about heat I'm going to continue based on the assumption that the fixture is on for a while at a decent intensity.
Do you have access to any ellipsoidal fixtures with narrow beam angles (Source 4, Shakespeare, SPX, 360Q, etc...)? They should work fine with your current dimming system and would allow you to narrow the light's beam. This would reduce the amount of light (and therefore heat) directed at the platform while increasing the amount of light the goes through the hole. The increase of light going through the hole may allow you to run the fixture at a lower intensity further reducing the amount of heat the platform has to absorb. Doing rather shady math, mostly in my head, a 14 degree source 4 should work for the application you've described provided that a light source ~2.5 feet from the hole in the platform would give you a wide enough effective beam angle after the hole in the platform worked basically as a 5" round gobo (9.5 degrees? it's been a while since I've calculated this kind of stuff).
Regardless of the fixture you select, while testing this effect I would closely monitor the platform. Before you completely OK this effect, step up slowly until you're running the fixture at a bit more intensity than you think you'll possibly need for a bit longer than you think you'll possibly need to run it (keep in mind run times in rehearsals as you may be asked to have a look up for much longer than it's used in the show). Then see how much heat is transferred to the platform. If you can touch it with your bare hand immediately afterwards then it's probably safe provided you can ensure that the platform is never subjected to more heat than you tested for, which is admittedly hard. Patching the channel controlling the effect so it's limited to a maximum intensity of whatever you deem safe and necessary to do the effect is a really good idea (why give a board op the ability to run the fixture at 100% when 50% will do?). If, during your testing, the platform starts smoking or you can feel the resonant heat in the platform through thick welding gloves, then you need to figure out a different way to do this. If it's somewhere in between those options (the most likely situation) then it's a decision you, and any other technical staff, have to make based on what you think the risks are, how qualified you are to make that decision, how much risk of something going wrong you're permitted and willing to take on (insurance may have a say in that), how much this effect really needs to happen, and what other qualified people agree with your assessment of the risks involved. That may sound scary, actually it probably should, but that's the kind of information you'd be asked for if something did go awry.
Obviously take precautions during the testing process. If you have any suspicion that the light will be too hot for the platform you should have a person right next to it with a fire extinguisher and another person that can turn the light off at the first sign of danger.
This is a less scientific process than I'd like, but if you err on the cautious side of both the physical safety of the effect and the inherent safety of the people operating the it then this is certainly something that can be done in a safe and controlled way.

 

[gafftaper]

This really sounds like a bad idea. If I were you I would play around with the idea of using LED flood lights available at your local hardware store. They are bright and cool.

 

[DELO72]

I did this decades ago. I mounted Intermediate (E17) Screw-base sockets onto some boards, and used MR-16s (Narrow Spots, JDRs, 75W, same as used in Birdies) to shine up through the holes. Hmm... come to think of it. I guess I could have just mounted the Birdies...*laugh* this is very funny in retrospect to consider it now....I think I only had 3-4 birdies in inventory and needed 8 for the show. Anyway...I'm rambling off topic...sorry.
A fixture is likely going to get WAY too hot, or put out way too much spill light. I would suggest looking as smaller, point source solutions-- (lamp & socket) vs. full fixtures. It depends on how much light you need to pump through that hole in the floor as well.

 

[AviatorDrama]

Wow, some great answers here! And several aspects I didn't even consider when hatching this plan.
To clarify: This project would be easy as pie if I just put some lamps or fluorescent lights under my platform as suggested above...but I need to control these from the booth.
The plan: I need a 4x8 platform about 5' high to hold two small girls. On the platform will be a workbench or shelves of sorts that contain 8+ glass bottles with colored liquid...they need to be lit through a hole underneath in an "evil lab" kind of way...again controlled from the booth, meaning I can't just plug some lamps into an extension cord and flip them on and off.

Our school was built a few years ago, amazing auditorium but they only hung three of the four rows of lights and left all 33 lights just sitting in a closet. I've been using these in different projects on the floor, but never with anything over them.

JonCarter: I didn't think of that...I guess only one light wouldn't light the whole underside.
JVTD: No, they don't need to be on the entire show, only 15 minutes at a time, three times per show, four shows....and I don't need to put them at 100%.
FMEng: I'm only learning as I go and one thing I know for sure is that our strip lights and par cans get *&%$ hot. I used our strip lighting (3 per) on our last show, on the floor shining up into trees. Even at 30% they were smoking and melting...right next to the children and I didn't know til the day before the show because we have to RENT 12' cables, we have none and our stage pin holes are in weird places.

If I were to build a rig to hold two or three of these ellipsoidal lights straight up, could I use a common house fan underneath the platform to cool them down? is that silly?

Thanks for all the expert advice...
Robyn

 

[Joshualangman]

I've done essentially this using 150 watt R40 flood lamps in clip lights. It worked pretty well, as you can see: http://jltheatricaldesign.com/vilnas-got-a-golem/0chgugnnwg2detl9sxrif54xyhx55d

This was about a 2 ft platform with the clip lights essentially sitting on the floor under the deck.

 

[robartsd]

This project would be easy as pie if I just put some lamps or fluorescent lights under my platform as suggested above

Any fixture (what most peole might call a "lamp") using an incandescent (including halogen) lamp (what most people might call a "bulb") can be attached to a dimmer (to be compliant with codes, the fixture must be used in accordance with its UL listing).

our stage pin holes are in weird places

FYI: if you're referring to holes in the stage floor containing stage pin outlets, they are generally referred to has "floor pockets" or just "pockets". Pockets may also contain DMX, network, audio, or other data connections in addition to (sometines instead of, especially for audio) power. Most often pockets for lighting circuits are located allong the sides of the stage to connect lights on boom bases for sidelighting. Some question the usefulness of pockets because they are often: 1) not in the place you need them, so you still have cables crossing the deck and 2) hard to keep clean and functional.

I think something with an MR-16 type lamp would be ideal for your design, but it sounds like your budget means you work with what fixtures you have on hand. Perhaps listing the types of fixtures availible (as much detail as you can) will help someone here make a practical suggestion of what to do.

I've been using these in different projects on the floor, but never with anything over them.

How do you set these up on the floor, do you have floor bases for them? You should have no problem with something over them as long as it has clearance (I'd want at least a foot, preferably 2) and the hot air has a place to go so it does not build up. The tricky part is providing the ventilation desired without unwanted spill. The best plan is probably open back allowing air to freely move with something black to absorb the light that excapes.

Any incandescent light source gets hot - that's simply how they work. The higher the wattage, the more heat produced. Many incandescent theatrical fixtures have a "burn in" period when new where they produce a bit (sometimes quite a bit) of smoke, but they should not melt - all are designed with the assumption that air will freely move about them to allow heat to dissapate.

 

[gafftaper]

First off never let your desire to get "THE perfect look" lead you to make unsafe choices, when a good alternative is much safer. I did the same sort of look for the aliens at the end of Rocky Horror a few years ago. I used two "Birdies" which are little mini-pars 16 fixtures for about $30-$35 from any theater dealer. Birdies are only about 5" long. I mounted them upright on top of the platform in the two front corners. Yeah I would have rather mounted something out of sight underneath, but Birdies were a safe and easy alternative. Throw some green gel in and they were CREEPY. Not as bright as your idea, but way less hassle and perfectly safe.

I can't just plug some lamps into an extension cord and flip them on and off.

Ah but you can...
All you need is one of these:

or one of these

If you have the flat kind of plugs like the first picture you need a "Male Stage Pin to 2P&G (Edison) Female" Adapter if you need the second picture it's a "Male L520 "twist lock" to 2P&G (Edison) female" adapter. Any theater supply store will carry them for about $20.

If I were to build a rig to hold two or three of these ellipsoidal lights straight up, could I use a common house fan underneath the platform to cool them down? is that silly?

It all depends on how far away the ellipsoidals are from the bottom of the platform and how long they need to be on. I think I would be comfortable with the fixtures being about 1' from the hole and 1' from touching anything on any side. I would use a fan and I wouldn't leave it on for more than a few minutes. And test it very carefully paying close attention to the temperature of the wood. I put an ellipsoidal inside the pedestal for the magic rose in Beauty and the Beast. It was a pretty tight enclosed space, but open on the back side and 18" between the lens and the plastic in the pedestal (carefully unfocused so that there wasn't a focal point on the plastic). It worked fine, but it was also never on for more than 30 seconds at a time.

If you don't have a local dealer call Controlbooth member @BillESC or long time friend of Controlbooth Production Advantage they can help you purchase these items.

It sounds like you are trying really hard but could really use a little expert help. There's no reason for those extra lights to just be on the floor, they should be hung and useful. Do you have a University in the area with a theater program. Give them a call and ask if there's a lighting student who might be willing to come help you with your system. You can probably work out something where the student earns credit and you get some free help.

 

[JohnManderbach]

Robyn, does this help?

Here is a 50° Source 4 (575w) on a base under a 3' tall platform. I burned the unit at full for 15 minutes and found that it warmed the plywood surface somewhat but not nearly to a dangerous level. Note that this only has 1' of air between the lens and the plywood surface.

If you use a longer throw lens (19° for example), try to focus as much light through the holes and shutter the spill.

If you put color in the unit it will trap heat and perhaps burn having nothing to do with the platform and everything to do with the density of the color.

I would set it up and run the cue for 30 minutes and stick your hand in there. If it's hot, get a fan. The holes that pass the light will help with ventilation enormously.

I would be comfortable doing this for 15 minutes with actors (including children) above.

Dislclaimer: Older or higher wattage units such as Altman Q360 will be much hotter and I would not do this without additional precautions.

 

[AviatorDrama]

Gafftaper...you gave me exactly what I needed to solve my problem...no really. This is why I should not be doing this job because I had no idea such an adapter existed.
Problem solved! I will call 4Wall today and get a used one to test out with different lighting that we have on hand...then build the rig to suit.

Also, I love your last paragraph. I've made so many phone calls and begged so many people to come look at our system...no one wants to do it for free, not even college students, even though it's brand new and awesome. We are east of Nashville for anyone reading this willing take a bite!! Unfortunately, I quit my theater major before I learned much about lighting and next to zero about equipment and that has been...ahem...a few years ago. I've gotten more answers here than every book I own, including the system manual.

John Manderbach...that is exactly what I had in mind! I was going to pushpin the gels underneath the platform but essentially that is what I was trying to convey.

Thanks yet again for all the great advice, I'm sure I'll have some other ridiculous question soon.
R

 

[derekleffew]

Gafftaper...you gave me exactly what I needed to solve my problem...no really. This is why I should not be doing this job because I had no idea such an adapter existed.

Before @gafftaper gets a big(ger) head, the pedantist in me can't let this one pass...

need a "Male Stage Pin to 2P&G (Edison) Female" Adapter if you need the second picture it's a "Male L520 "twist lock" to 2P&G (Edison) female" adapter.

A 2P&G is a stage pin connector, not Edison. The above should read

need a "Male Stage Pin (2P&G) to Edison (NEMA 5-15, PBU: parallel blade U-ground) Female" Adapter. If you need the second picture it's a "Male NEMA L5-20 (twist lock) to Edison (NEMA 5-15, PBU: parallel blade U-ground) Female" adapter.

I've avoided replying to this thread because I didn't/don't see what all the fuss was/is about. I'd have no problem putting a Source Four 19°-50° pointing straight up under a 5' high platform. Sure I'd check on it, but don't really feel that it would be problematic. That being said, I once almost burned down a theatre while using a 1K scoop as a ghost load. The scoop was sitting on the floor, aperture down, and someone moved it from the concrete to the carpet without me noticing. (Melting carpet smells awful, BTW.)

 

[Kelite]

<The scoop was sitting on the floor, aperture down, and someone moved it from the concrete to the carpet without me noticing. (Melting carpet smells awful, BTW.) >

I did a demo at Kmart's corporate office with a 575W S4. Plugged the 'nose down' unit into the wall outlet as I picked it up off the carpet. Whoops!
(*Great way to start a meeting, I'm telling you!)

 

[gafftaper]

Before @gafftaper gets a big(ger) head, the pedantist in me can't let this one pass...
A 2P&G is a stage pin connector, not Edison. The above should read

I like to rewrite my posts WAY TOO much. Sometimes I rewrite so much I remove the correct content. Couldn't decide if I should call it a stage pin or a 2P&G and I went back and forth so long rewriting the same sentence I ended up deleting the 5-15 instead.

 

[BillESC]

Seems to me, you don't need a bunch of power but a concentrated light source for each fixture.

A simple Par38 fixture or even Edison sockets mounted to a board with a 75PAR30/HAL/NSP lamp in each will do the trick. Mount the fixtures so they are six to eight inches below the holes and have fun.

 

[lwinters630]

The scoop was sitting on the floor, aperture down, and someone moved it from the concrete to the carpet without me noticing

I thought I was the only one to leave a nice black burn on a new oak stage. Some how it was plugged in and set down. After the board was turned we all wandered why there was a burning smell. They though it was just new fixtures burning in. Not.
Since then I've never put a fixture open down plugged in.