Issues in public assembly facility design, operation and maintenance.

I was recently working through some preliminary information on the lighting system for one of our current consulting projects.  One of our responsibilities when designing a dimming system is to provide a tremendous amount of information on anticipated power needs (to the electrical engineer) and heat generated by the system and the lights themselves (to the mechanical engineer).  In the process, I realized that we may need to reevaluate some of the assumptions we make.  Here are some examples:

• Number of dimmed circuits required.  We always attempt to maximize flexibility.  This has usually meant more circuits in more locations.  This is based on an assumption that all or most of the lighting being used is halogen incandescent and requires a dimmer to be controlled.  LED fixtures are rapidly improving, catching up or surpassing their “conventional” counterparts.  This is especially true for cyclorama and back drop lighting, an area that has typically required a fair quantity of 1,000 watt fixtures ganged together.  Now we see LED color changing fixtures that actually out perform the conventional fixtures.  Although on the surface they are more costly, it’s worth noting that the LED fixtures don’t require on-going lamp changes and use much less power–and don’t need 3-4 dimmers each.  We saw at LDI (Lighting Dimensions International) last year LED-based ellipsoidal spotlights.  They weren’t ready for “prime time” yet, but they do have the major features required in a fixture of this type–hard edges, ability to be shuttered and the ability to project patterns.  Moving fixtures are showing up more and more frequently in all types of venues.  If planned for carefully, these are able to replace 2-3 conventional fixtures each.  Finally, tried and true color scrollers, changers and faders are allowing one fixture to do the job of several.  All of these lead in a direction of allowing fewer dimmed circuits to do the same, or more.  There is a need for more non-dimmed power, on the other hand, but this is typically far less expensive.  This also means that the data network and controller has to be more ubiquitous, flexible and powerful than ever before.
• Amount of “diversity” assumed.  We’ve typically allowed that the 2.4kW dimmed circuits in a theatrical system will not ever be loaded to more that 50% of their OVERALL capacity–meaning some may carry a full 20 amp load while others carry none.  This assumes, however, an average lamp size of approximately 1,000 Watts.  Looking at the fixtures commonly available at present, many conventional fixtures are actually capable of a maximum 575 Watts or 750 Watts.  This has been made possible by advances in optical technology and design.  It may be that we’ll be able to assume a much lower overall load on the dimming system–750 Watts on average instead of 1,000 Watts per circuit.  This translates to smaller power feeds into the dimming system.

The day when we have a fully functional theater facility with only a few, or even no, actual dimmers is not inconceivable.  Already there are several commercial lighting manufacturers that have LED equivalents to the 250 Watt downlight.  And these are fully dimmable without the use of a traditional line-voltage dimmer.  LED ellipsoidal spotlights are already out and being improved.  LED PARs exist and are rapidly improving.  LED cyclorama fixtures have already surpassed their traditional predecessors.

This was a good show for us!

Here are the answers to the questions we submitted (the organizers of the show chose to use the light source technologies question).

Four options to support and access performance lighting in front of the proscenium include catwalks, tension grids, dead-hung battens and battens (pipes) on some type of hoist or lowering system.

• A catwalk (or lighting platform–this is NOT your classic catwalk as the railings are intended and spaced to support lighting functions) allows easy access to fixtures but must be carefully placed to be effective.  Too close and the light will be aiming almost straight down, causing heavy shadows particularly in the eyes.  Too far, and the lighting becomes very flat and uninteresting.
• Tension grid, which is a woven steel cable mesh, provides the greatest flexibility.  Lights are above the mesh and shine through onto the stage below.  The mesh does not affect lighting (or sound) going through it with one exception: PAR fixtures.  The beam of light is parallel enough to project the image of the mesh to the surface below.  Lights can be used anywhere above the surface as needed.  The cost is about the same, per square foot, as catwalk while weighing less.  It is also possible to rig through tension grid.
• Dead-hung battens are surprisingly common and about as inconvenient as possible.  This is also the least expensive, initially, of the available options, as it is nothing but a pipe suspended from chain, cable or threaded rod directly from the structure above.  Like catwalks, these must be carefully placed to be effective.  Access for maintenance and focusing is ideally from a lift (although seats frequently interfere) or from a ladder, if low enough.
• Hoists for this application come in many flavors, each of which has its strengths and weaknesses.  Lineshaft winches, dead-haul drum winches, package hoists, self-climbing trusses, trusses with chain motors, counterweight assisted winches are just some of the options.  There are also manually-cranked winches and other variations.  The major weakness, other than placement, is that focus (aiming) of the lights will take extra time as the hoist has to be raised and lowered repeatedly to focus the lights by trial and error.

Next up are the three most common stage rigging technologies being installed in current theaters, churches and auditoriums.  Those are manual counterweight, powered hoists and dead-hung.  What is appropriate for a given stage and application varies with the space, the users and the intended uses of the system.

• Manual counterweight systems operate by balancing the load (lighting or scenery, typically) with steel counterweights.  There are variations even within this type of system (single purchase, double purchase, motor assisted, etc.)
• Powered rigging systems are most commonly seen in the form of package hoist systems.  These are standardized zero fleet-angle winches that operate on a common backbone (power and control) and usually have a common control point that often allows grouping and presets.  Other types include lineshaft winches and dead-haul winches.
• Dead hung rigging includes any rigging suspended in a static manner from the structure above.  Some examples are studio pipe grids and curtain tracks that do not fly.

The two dominant lighting source technologies at the present in the theater world are tungsten-halogen and LED.  Fluorescent is used heavily in TV studio applications.  LED technology is rapidly evolving and quickly gaining ground on traditional halogen sources.  Already, LED cyclorama lighting fixtures outperform their conventional counterparts–at least when the rich colors typically used on a cyc are involved.

Finally, the role of a theater design consultant.  Primarily, the design consultant’s role is to provide options to the design team.  Once the function of the facility and its primary program functions have been determined, HOW to accomplish those goals becomes the next puzzle.  In presentation environments, there are many ways to accomplish the same end–and each has its own strengths and weaknesses.  What is right for one user may not be appropriate at all for another.

We’ll be exhibiting at the Trade Show sponsored by the East Kentucky chapter of the American Institute of Architects and the Bluegrass Chapter of the Construction Specifications Institute.  Look for us in Booth 31 at The Crowne Plaza Campbell House in Lexington, Kentucky.  We’ll be happy to help answer the questions to Construction Jeopardy.  Our questions:

• What are four options to support and access performance lighting equipment location in front of the stage (over the audience)?
• What are the three most typical stage rigging systems currently being supplied and installed on stages, in auditoriums and churches?
• What are the two dominant lighting source technologies at present for theatrical presentation facilities (including churches)?
• What is the role of a theatre design consultant in a typical project?

(Answers later or come see us in Lexington!)

Today’s topic: the little seen, usually ignored smoke vents over the stage.  They typically are completely forgotten until they either leak or blow open…but these are a critical component of the fire safety system in the stage.  Perhaps even the most critical component.

What are they?  Smoke vents are doors or hatches above the stage that, in the event of a fire, are designed to open automatically.  They’re typically either spring actuated (if they open upward) or gravity actuated (a typically older style that falls outward).  Visualize a typical stage cut through the centerline–it bears a striking resemblance to  a fire place with the audience chamber as the hearth and the fly tower as the chimney.  Open the vents and it behaves very much like one, also.

An interesting book that touches on this subject is John Ripley Freeman’s book “On the Safeguarding of Life in Theatres.”  This book is available for reading online through Google Books.  Freeman was a mechanical engineer who did a thorough review of the Iroquois Theatre fire in 1904.  Among the many things that went wrong at the Iroquois, the smoke vents failed to operate.  It was later determined that the contractor had failed to remove nails holding them shut.  Keep in mind that cooling in theaters of this era was generally natural air movement–windows or vents low down allowed fresh air in and fans or vents at the ceiling pulled it out.  The Iroquois had vents at the very back of the uppermost balcony.  This combination of factors allowed a deadly sequence of events to unfold as the fire spread throughout the fly space into all of the hanging scenery:

• Stagehands attempted to deploy the fire curtain (“asbestos”).  It caught or jammed partway down and did not fully cover the proscenium opening.
• Theatere staff, attempting to save the lives of the performers and workers on stage, opened the large loading door to the stage.
• The sudden rush of oxygen immediately caused a massive increase in the size, heat and power of the fire.
• The open vents at the rear of the balcony provided a “chimney” for the smoke and gasses–helping to pull them into the auditorium and out of the stage rather than up and away from the audience.

In the end, the vast majority of the deaths in the auditorium itself were in the uppermost balcony.  As in most fires, the majority of these people did not burn: they were suffocated.

Freeman’s conclusion was that if the smoke vents had operated properly, almost all of the audience would have walked out of the Iroquois Theatre.

Smoke vents are only one of several fire safety devices commonly found on stages.  Coming soon: information on interesting new research into what works–and what doesn’t.

I was speaking with an architect a few weeks ago and mentioned that, as a consultant, we carry professional liability (“errors and omissions” or E&O) coverage for our design services.  We see this as a tangible benefit to our clients and potential clients.  Why?  And what does it mean to you?

In very general terms, a professional liability policy covers us–and our clients–for damages (economic or bodily injury) that are incurred as a direct result of the performance of our specific design consultation services.  Our policy is much the same as that issued to a licensed design professional–an architect or engineer.  It’s important that all of the design professionals involved in a building carry this coverage.  The major reason why is buried in our commercial insurance policy, which is likely very typical in that it excludes liability from professional design services.

One requirement of our professional liability policy that is, again, likely very typical: we are required to ensure that our design subcontractors carry their own E&O coverage.  The implication of this is that an architect or engineer that hires us as a designer should be requiring this coverage from us, as well–it’s likely to be a requirement on their policy as well as, we think, a generally good idea to protect both themselves and the end client.

We were recently asked for our advice regarding stage drapery and humidity control.  Below is essentially the text I shared.  This system is fairly typical of many auditoriums: all of the drapery is manufactured from cotton fibers and is hanging from a counterweight rigging system.

Cotton fiber, without any treatment, is flammable.  To meet building code requirements, the cotton fabric used in your drapes was run through a flame retardant solution.  This solution is a blend of metallic salts that help to prevent the fabric from sustaining flame.

We strongly recommend maintaining a humidity-controlled environment for natural-fiber fabrics for several reasons.

1. Untreated natural fibers in a humid environment will deteriorate at a faster rate—moisture accelerates decay.
2. The salts used to flameproof this fabric are hydroscopic and will “pull” moisture from the air.
3. Salt, combined with moisture, is corrosive and will further accelerate decay of the fibers.
4. Large drapes can soak up a significant amount of water from the air.  Even if the rigging system was left balanced, the water in the drapery can dramatically change the balance of the lineset.  This is, at best, an unpleasant surprise for the next operator of that lineset.  At worst, this is a recipe for a runaway lineset that can result in serious injury.
5. When the fabric is weakened, the additional moisture (weight) has the potential to tear the drape away from its reinforcing webbing at the top.  This has a similar result to the scenario described in #4, above, except that the out of balance condition is in the other direction.  The results have the potential to be just as unpleasant.

There are other drapery fabrics that were either not available or not of an acceptable quality at the time the system was purchased.  These velour fabrics are made from polyester and are inherently flame retardant—meaning that they do not require treatment and the side effects that come with it.  These fibers will not deteriorate because of moisture.

As long as the drapery in use is fabricated from cotton, we believe that their environment must be humidity controlled.  One of the fabricators that we work with regularly states that they will not warranty cotton drapery that has been subjected to more than 65% relative humidity.  Failing to control the environment both creates a significant safety hazard (that increases that the drapery ages) and shortens the life of the fabric.

This is probably the oldest, and simplest, style of stage rigging technology.  This label for overhead rigging generally includes:

• spotline rigging (one or two lines placed temporarily to raise and lower or otherwise manipulate a single scenic piece)
• 3 or 5 line linesets
• head blocks (with multiple sheaves) and loft blocks
• rope used as the lifting material
• one or more pinrails

Flipping this list around, an essential piece of this technology is the pinrail.  On a sailing ship, which is the source of much of this technology, this would be either the fife rail (around the base of the mast) or the pin rails at the bulwarks.  In the theatre, this is either a timber or pipe, typically with holes punched every 12-18 inches for the belaying pins.  Traditionally, the belaying pins are removable for the simple reason that you can release a line very quickly by simply pulling the pin out (preferably while holding the rope!).  Modern pin rails are sometimes fabricated with pins welded into place.  Like so much theatre technology, pin rails have not disappeared with the advent of newer systems; many new theatres are still built with this device.

The rope, on the other hand, has changed.  Natural fiber (hemp or manila) has been nearly universally replaced with synthetics.  The simple reasons are strength and longevity.  Natural fibers are sensitive to moisture and will deteriorate over time.  This is not an issue with synthetic fibers.  There are trade-offs, however.  The synthetic fibers can be more slippery and can me more costly.

Like many things, there are advantages and disadvantages to this style of rigging.  Some advantages:

• Flexible–especially in a stage with a gridiron, setting a spot block and running a spot line is a very quick, simple process.
• Nearly silent–if the equipment is in good repair, the only noise from a rope system is the rope whispering over the blocks.
• Trimmable–it is very simple to adjust for trim (level) across any given lineset.
• It is possible to add counterweight, with either a Sunday or trim clamp.

There are also some drawbacks:

• It takes a very high level of skill to set up and use a rope system.
• Much of the time, the linesets are unbalanced.  This is an inherently unsafe scenario and has to be handled thoughtfully and with caution.
• It is very easy for a lineset to get out of trim (level).

The type of facility you would typically see a full-blown rope system would be in a smaller facility that most frequently utilizes painted fabric scenery–essentially, the average theatre from the 1930’s and earlier.

Spot line rigging, on the other hand, is common in many theatres and most especially in those with a gridiron, as the gridiron makes it very easy to rig.  This includes theatres currently in various stages of design or construction.

A technician working with a rope rigging system needs:

• to be able to estimate weights
• to be able to handle the amount of weight hanging on the other end of the rope
• a basic knowledge of knots

Like any rigging system, a rope rigging system should be regularly inspected, including having a periodic professional review (we recommend annually with all rigging systems).  The other major maintenance items are keeping the lines coiled and neat–off the floor, away from dirt–checking the condition of the rope and ensuring all knots are securely tied.

This is the kind of rigging system usually visible in movies showing a theatre.  It is far more “theatrical” and interesting visually than counterweight sets or winched sets–in the case of the last, there might not be anything to look at except the controller!  Watch for sandbags and coils of rope on the screen.

All stage rigging systems have essentially one goal: to hold material (scenery, lighting, masking drapery) in the air–safely.  There are many similarities between the various systems that have been devised to do that job.  There are also significant differences, mostly dependent on exactly what you want to do with the scenery and how you want to do it.  Here’s an overview of each type of system.  Later articles will look at each type in detail and discuss the strengths and weaknesses.

Dead-hung.  This refers to rigging systems that cannot be moved vertically.  Typically, this consists of pipes or tracks suspended directly from the building structure with chain or cable.

Hemp.  These are the systems we see frequently in old movies with 3-5 ropes and sandbags.  The name comes from a frequently-used rope fiber–although it is interesting that the majority of natural-fiber ropes used in the modern theatre building are spun from manila rather than hemp.  But that’s a different discussion!  The equipment is able to be moved vertically.  The sandbags are used to balance the load applied.

Counterweight.  It is probably a safe guess that this is the most common type of rigging system installed in theatres in the United States.  There are many variations within this category.  two big ones include how the arbors are guided and if the system operates in single or double purchase.

Manually winched.  The most common example of this type of system has one or two hauling lines from the winch to a clew, then multiple lift lines out from the clew to the batten.  These are typically used on equipment that needs to be accessed relatively easily but not rapidly or frequently.

Powered winches.  This is easily the most diverse category.  Hydraulics, packaged hoists, counterweight assist, dead-haul…the list goes on!

As I noted above, later articles will discuss each category in more depth and touch on the options, strengths and weaknesses.  In the meantime, regardless of the type of system, remember that it is suspending thousands of pounds of weight over people’s heads.  These systems should be inspected on a regular basis.  We recommend annually!

Last year, one of our projects featured examples of four of these–on the same stage, at the same time.  There were dead-hung line sets, some hemp sets (with one really old sandbag that basically disintegrated when it was touched), two different versions of counterweight and even a manually-winched set.  There were a lot of interesting “features” to that system.  One of these was the access system devised to allow relatively easy re-rigging of the hemp sets.  One of the down sides to a rope system is that if you accidentally let go of the rope, there is a distinct possibility that the rope will snake its way right out, over the block and into a nice pile–at the floor.  Since this particular auditorium did not have a gridiron, the designed solution from the 20s or 30s was this.  A center catwalk was installed running from stage left to stage right.  It was long enough to reach all three of the primary rigging beams.  At the far downstage and upstage ends of the rigging beams, there were squared steel “loops,” about 12 inches wide, hanging down to approximately the elevation of the catwalk.  We could not figure out what they were until we noted the 2×12 plank laying on the floor.  We finally made the connection.  The intent was that you’d carefully extend the plank out from the catwalk into the loop.  One end of the plank rested in the loop, the other on the edge of the catwalk.  That allowed a worker to walk out, balancing on the plank,to re-reeve the offending line into the block.