Inverted Powered Kabuki?

[pjay]

I work for a 23k seat basketball arena that made there own kabuki system, very similar to Rose Brand's system. Every home game for the last three years, we have dropped four 40' x 60' sheets around our scoreboard (portrait style) and projected video on them with the lights out to introduce the players.

One of the flaws in our system is the potential that the sheets will unveil correctly but an electrical failure would prevent them from dropping to the ground. If that happened before a game, the team would get penalized for a delay of game as I would rush to either rappel out and hit a manual release or spend the time to lower the entire truss to get them all off. We've had failures like that during rehearsals but (thankfully) never before a game.

I think it's time to get a professional kabuki system. However, I've noticed that as a matter of safety, all the systems I researched refuse to drop if they suffered a power failure. I'd like the exact opposite. I would like a system that requires power to hold the sheets and would drop them if it lost.

My thoughts are that I would put the system on relay modules of our dimmer racks and tell the configuration of the rack to treat those channels inversely (0 means power, full means off.) Then, if we had a failure, it would just be a matter of unplugging it from the rafters or pulling out the rack.

Does such a system exist?

 

[SanTai]

I have never heard of any one selling such a system, but there might be.

I sounds very easy to construct something that does that yourself.

I have never created an inversly controlled kabuki, but these were my first thoughts on the subject.

You could probably use the kind of electromagnets used to hold doors open. They are strong, made to hold a load for a long time and when you de-energize them they will drop the load. If you want them to drop it faster you could just invert the polarity for a short time.
I have one here that runs on 12V and holds 750N.

 

[pjay]

That's a solid idea. Without having to engineer my own digital device, is there something that would let me switch the leads via DMX (to reverse the polarity)?

 

[SanTai]

That's a solid idea. Without having to engineer my own digital device, is there something that would let me switch the leads via DMX (to reverse the polarity)?

Use some kind of DMX decoder to control relays that control the power from the DC supply and use two channels. One channel to control power and one for polarity.

 

[Footer]

If you are going to go this route and want to stay with DMX you are asking for trouble. DMX is not meant for this type of thing, too many issues with it in order to run any type of automation directly.

That being said... the traditional kabuki is done with "pull" solenoids, meaning power application pulls the plunger into the device. What you are looking for is a "push" device, so when power is applied the plunger comes out of the device. I'm sure rose brand would build them this way if you want. I would advice that the first drop mechanizm be a pull style just for extra safety.

I think though that if you are having power issues you have a much bigger issue. Installing pull solenoids is just a band-aid. Your better bet is to replace all of the devices and wiring with quality stuff.

When you had issues in rehearsal, was something jammed up or did you suffer a power failure? My thought is if you have a power failure you should not be able to do the game anyway to the point is moot.

 

[SanTai]

If you are going to go this route and want to stay with DMX you are asking for trouble. DMX is not meant for this type of thing, too many issues with it in order to run any type of automation directly.

That being said... the traditional kabuki is done with "pull" solenoids, meaning power application pulls the plunger into the device. What you are looking for is a "push" device, so when power is applied the plunger comes out of the device. I'm sure rose brand would build them this way if you want. I would advice that the first drop mechanizm be a pull style just for extra safety.

I think though that if you are having power issues you have a much bigger issue. Installing pull solenoids is just a band-aid. Your better bet is to replace all of the devices and wiring with quality stuff.

When you had issues in rehearsal, was something jammed up or did you suffer a power failure? My thought is if you have a power failure you should not be able to do the game anyway to the point is moot.

If you use a push-soleniod be certain to study the datasheet before you design the system. Many of them will burn out if run on full power for to long and make sure reversing the polarity wont have any ill effects, you might need too if the spring is too weak.

Having a simple switch is of course better if it is possible. It gives you a higher chance of successful and repeatable operation. It is sometimes not possible for different reasons. Always go for the simplest control solution, if you are good with the soldering iron it will work every time.

To be clear, if early release of the sheets could ever be dangerous a system that release them if they lose signal is not acceptable.

 

[MPowers]

For a fail safe drop, use friction rather than grommets and pegs to hold the fabric in the up position. A few years back I did an Othello that the director and designer envisioned the show starting with a mime prologue on the apron, in front of a full stage gauze drop at the proscenium. At the end of the prologue, the gauze fell, revealing the opening scene. Gauze doesn't fall, show doesn't start.

The mechnism was basicly two1x4 hogs trough 45' long. They were hinged at the apex with spring loaded screen door hinges, forming a "T" with the hinge joint at the center of the top and the stem had two boards face to face. The springs forced the two pieces of the "T" stem together. The bottom edge of each stem was lined with a 1/2 piece of 1" e-foam rod, sanded to kill the "slick" surface. The e-foam pinching together was what held the gauze in place. Because the gauze was held at every point along the top it didn't take very much force to hold it in place. If there had ever been a "fail" situation, one of the actors was instructed to simply grab the gauze at either end and pull while walking across the stage. As long as it was pulled it would continue to come loose. If the actor stopped, the gauze would stop coming loose. We rehearsed the fail mode but never had to use it. The planned release was pneumatic rather than solenoid, a set of 6 or 7 (been a while, I forget) 1" throw cylinders pushed the faces apart to release the gauze.

In your case a 1/4" line down the edge of one of the banners to operate the release or, if the banner can be reached from the floor, the banner becomes the release cord for either method. either way the gimmick can be released from the floor without a ladder or gear.