The NAC Solution
The following shows how the National Arts Centre’s prop makers solved the challenge. Their solution emerged from the combination of materials, resources, brainpower, time constraints and budget. Your students will have different resources and ideas, and may have come up with something as (or more) efficient, esthetically satisfying and cost effective. The NAC props makers wish them well!
Remember not to direct students to these pages until the class has completed the first half of the activity, as the NAC solution will be revealed and your students will miss the creative process.
These are before and after chalkboard diagrams illustrating the key component of how this props challenge worked out from the NAC perspective. The diagrams outline the physics of how the most important elements work.
The table: The latch mechanism is composed of three components: the knife carrier, the latch cog and the upright lever. There is a strong spring at the pivot point of the knife carrier. This applies a strong force against the latch cog which is held in place by the upright lever. When the rod pushes the lever the latch is allowed to pivot releasing the knife carrier.
How it Works
The following photos and step-by-step video demonstrating the NAC prop shop solution to the challenge.
We decided for safety reasons to not actually throw the knives. The knife thrower would have only one knife that he would appear to throw several times. The assistant would control a different set of knives hidden inside the table that would appear to land around her.
The designer of the show requested that an old table top be used as the surface. Because the audience was seated on both sides of the set, they were able to see all sides of the table, so it was decided to use a completely self contained, hidden system, using compressed air and pistons to make the knife mechanisms work from within the table.
To keep the thickness of the table to a minimum, the knives needed to be oriented vertically and pivot through small trap doors in the table surface. A special sprung carrier, lined with Teflon allowed the knife to pivot into place and then be removed through a very thin slot in the table surface.
The knife thrower wore a special suit jacket that allowed him to conceal an elastic cord attached to both the tip of his throwing knife and a ring on his opposite hand. This allowed him to release his knife from a pouch in his sleeve and appear to pick up a new knife before setting himself up for the throw. As he threw his knife, the elastic retracted, and the knife would quickly slot into the pouch hidden in his sleeve.
At the other end, the assistant depressed a switch hidden at her fingertips just as the knife thrower appeared to release his knife. The switch triggered the mechanism in the table and a knife would appear instantly beside her body. Five independent mechanisms inside the table allowed the trick to be repeated five separate times.
At the end of the scene, the knife thrower thanks the lovely assistant and removes the knives from the table, reinforcing the illusion that they had actually been thrown.
The Final Effect
Watch the video showing the NAC’s solution; this is a recreation of the final effect from the audience’s perspective.