Trick Arrow Trick Shots.
We started the process with crafting the spring mechanisms that would allow us to have arrows lay flat and then quickly spring outward. After some brainstorming, we settled on standard mouse traps as our arrow motivators. At 89 cents each, this was an extremely budget-friendly option. We removed the catches, leaving only the spring and wire loop attached to the wooden base. To make these stand up to repeated use throughout the show run, we replaced the wire loops that held the spring and loop to the wood with 3/8" eye screws. We also needed a system to stop the mouse trap with its wire loop perpendicular to the wooden base. This was done with a simple zip tie attached to the wire loop and wrapped to the back of the mouse trap allowing only the desired travel distance.
To allow the deck arrows to be picked up and broken, we needed a way to hold the arrows to the mouse trap while not permanently attached. We found that 3/8" OD copper tube allowed the arrows to be held but still be loose enough to be pulled out. Being copper also allowed for brazing the pipe on to the wire loop of the mouse trap. For the split arrow rig, we followed the same process but placed two of the spring mechanisms against each other on a board in opposing directions, allowing the arrows to meet in the center. The arrows were then permanently lashed to the wire loop. The arrows were crafted using 1/4" dowel and partial feathers glued on as fletchings. Bright color feathers were chosen to help with visibility. The deck arrows were built with fletchings on only two sides to allow the slit in the deck to be as narrow as possible. To create our split arrow, we used a bandsaw to divide it then soaked it in hot water, bending it to create an obvious split.
Once we had working mechanisms, we set about automating them. Each mouse trap used a small pneumatic cylinder to hold it open. When the cylinder retracted, the trap sprang shut to its preset stop and the attached arrow would snap into position. For our deck arrows, the mouse trap was mounted to a 2x4 cut to 45[degrees]. With the mousetrap open, a cylinder was mounted perpendicular at a height to hold the arrow horizontal (see image above). A 1/2" wide groove was routed into the deck above allowing a 1/8" clearance on either side of the arrow (see image above left). In testing, we found that the arrow would occasionally catch on the underside of the deck. To prevent this, we mounted guides to the sides of the groove, extending below the reset height of the arrow. We also placed a bottom on the guides. This prevented the tube from being lowered too far while being reset and having the arrow slide out of its copper sheath.
For our split arrow, we mounted the traps and cylinders to the front face of an elevated platform. In order to mask the airlines, the cylinders were mounted with their openings upstage. We then drilled through the platform and fed the lines in from behind. A small cloth was mounted in front of the end of each arrow to mask the bright-colored fletchings. It was not necessary to mask the arrow shafts or cylinders as they blended into the set.
To manage the system, we created a pneumatic control board from which all of the effects could be triggered and reset. The board consisted of a ball valve as a safety, a four-outlet manifold, and four 4-way valves to control the cylinders. When the ball valve safety was opened, air fed in from our house supply to the four-way valves. In their neutral position, the air flow stopped there, but engaging the valves to the left or right would extend or retract our pneumatic cylinders to fire or reset the arrows. This allowed us to reset the deck arrows from above rather than crawling beneath to manually reset them. Though our system made use of the more expensive three-position valves we had on hand, it could be replicated for significantly less using a two-position valve. These valves lack the neutral position ours used but would still allow you to fire and reset from one location.
By harnessing the cheap potential energy in a basic mousetrap, we were able to create quick-firing, flashy arrow effects for a very low cost. This method could even be reproduced using a pull string to trigger the traps rather than pneumatics, putting it well within the budget for any theatre large or small. The cost to create the system from scratch is about $1,350 though one could save by using less expensive components. By making use of our pneumatic stock, our true cost was reduced to just under $55 for the run.
By Kyle Spens, Graduate Student: Technical Production, and Andrea Bullock, Properties Master, PlayMakers Repertory Company
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|Title Annotation:||17TH BIENNIAL TECH EXPO DISPLAY AND CATALOG|
|Publication:||TD&T (Theatre Design & Technology)|
|Date:||Jun 22, 2019|
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