“The Trojan Horse”

Background Information:

The goal of the Trojan Horse was to  launch a metal sphere to strike a target (a metal shield). The Trojan Horse l was to launch the projectile such that  it covered a range of 6 meters and reached a maximum height of 1.4 meters. The Trojan Horse also required a trigger system that could be activated remotely, from a distance of at least one meter. The trigger system of the Trojan Horse also had to be suitable for all terrains and must have utilized a latching or locking mechanism. The Trojan Horse and the trigger both had to allow for multiple, consistent launches.

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The Trojan Horse was intended to be a ballista as ballistae propel loads with great accuracy. Ballistae are also easy to assemble, carry, and launch, allowing easy aim at a target. When deciding the build the Trojan Horse as a ballista, the necessity for a payload and multiple complex and rotating  parts (such as those used in trebuchets, mangonels, and onagers) was avoided. This would make the Trojan Horse energy efficient as the energy supplied to propel the projectile would not be wasted in, for example, rotating a launcher arm. This would cause the load to be shot out with considerable force.

Individual Design:

The Trojan Horse’s trigger was a simple pin trigger. The pin trigger consisted of a pin that would be pulled out from a “housing” to release the launch arm. This trigger did not require complex structures (such as the gears used in an “opposing gear” trigger). The pin trigger was also easy to build and pull out as it required minimal parts ( i.e. a pin, a string, and a housing) as opposed to, for example, a shimmied hook trigger which requires a shim, a trigger hook, a pivot, a base, a bow string, and a pivot hole. The pin trigger mechanism also creates minimal friction as it releases the piston, which allows the piston to move with greater energy and have maximum efficiency.

Trigger Design:

Preliminary Design:

The Trojan horse is built following the design of a mangonel. Compared to the other launchers, the mangonel was the simplest to understand, as the physics behind its working is fairly direct. Taking consideration on the short amount of time allotted to build the launcher, the mangonel was  the easiest to assemble and move around, easier than the ballista, as it required only minimal parts and lightweight materials. The mangonel was the best launcher to propel objects from low angles due to its low height. The mangonel was also the best launcher to throw balls due to its cup-shaped loading bucket which is ideal for holding spherical objects.

Preliminary Design:

The trigger system designed consisted of a rod passed through two brackets. An allen key was hooked, with its shorter end facing upwards, on the rod. A string of 1m was attached to the shorter end of the allen key and another string was attached to its longer end, which was connected to the arm of the launcher by a hook. When the 1m long string was pulled, the allen key would be unhooked from the arm and released from rod, allowing the arm to rotate and fire the load. This idea was chosen because it seemed like a hassle-free and fairly straightforward method of triggering the launch.

Trigger Design:

Material Specifications:

●       PVC pipe (frame width front) – Length : 0.45m – Thickness : 0.05m – Inner Diameter : 0.025m

●       PVC pipe (frame width back) – Length : 0.45m – Thickness : 0.05m – Inner Diameter : 0.025m

●       2 PVC pipes (frame length) – Length : 0.43m – Thickness : 0.05m – Inner Diameter : 0.025m

●       2 PVC pipes (frame length) – Length : 0.14m – Thickness : 0.05m – Inner Diameter : 0.025m

●       PVC pipe (frame length) – Length : 0.16m – Thickness : 0.05m – Inner Diameter : 0.025m

●       PVC pipe (frame height) – Length : 0.42m – Thickness : 0.05m – Inner Diameter : 0.025m

●       PVC pipe (launcher pivot) – Length : 0.45m – Thickness : 0.05m – Inner Diameter : 0.0127m

●       PVC pipe (frame width back) – Length : 0.45m – Thickness : 0.05m – Inner Diameter : 0.025m

●       3 #9 Rubber Band – Spring constant : 476 N/m – Unstretched Length : 0.23m

●       8 T connector – Outer Diameter : 0.04m – Mass: 0.071kg

●       4 L connectors – Outer Diameter 0.04 m

●       “Bucket” connector – Mass : 0.113 kg

●       2 Screws – Length :0.0508m – Mass: 0.014 kg

●       Washer – Diameter : 0.01m

●       Paracord (colored)- Length : 2.6 m

●       Paracord (black)- Length : 1.3 m

●       allen key – Length : 0.09 m

●       String – 0.2m

●       String – 0.1m

●       Duct tape

●       2 pieces of Cardboard (for pivot) Length: 0.225m Width: 0.03m

●       16 pieces of Cardboard (for base) Length: 0.04m Width: 0.02m

●       2 weights – mass : 5kg

●       2 weights – mass : 2kg

Calculations:

Assembly:

(To make the frame)

Connect two l-connectors to the 0.45 m pipe to create the front end of the frame.

Connect and mallet-in two 0.43 m pipes to either l-connector of the front end of the frame.

Connect and mallet-in two t-connectors to the other end of the 0.43 m pipes.

Connect and mallet-in two 0.14 m pipes to either horizontal open-end of the t-connectors on the 0.43 m pipes.

Connect and mallet-in two 0.42 m pipes to either vertical open-end of the t-connectors on the 0.43 m pipes.

Connect and mallet-in two l-connectors to either of the two vertical 0.42m pipes such that the open ends of both connectors face each other.

Mallet-in a 0.45m pipe that connects the two l-connectors on the 0.42m pipes.

Tie three #9 rubber bands side by side towards the center of the 0.45m pipe that is perched on the 0.42m pipes.

Connect and mallet-in two t-connectors to either of the 0.14m pipes such that the open ends of both connectors face each other.

 Put a t-connector through a 0.45m long, 0.0127m diameter pipe and connect this to the t-connectors on the 0.14m pipe.

Fold and duct-tape cardboard rectangles that are 0.225m long and 0.03m wide to prevent the t-connector on the 0.45m long and 0.0127m diameter pipe from sliding.

Connect and mallet-in two 0.16 m pipes to either horizontal open-end of the t-connectors on the 0.14 m pipes.

Connect and mallet-in two t-connectors to either open-end of the 0.16 m pipes  such that the vertical ends of both connectors face each other.

Connect the two vertical ends using a 0.45m pipe.

Connect a t-connector to the end of the 0.53 m pipe.

Stack 4 pieces of cardboard that is 0.05m long and 0.02 m wide and duct tape it to one of the corners of the frame.

Repeat step 16 for the other 3 corners of the frame.

Weigh down the frame by placing the 5 kg weights on the back corners of the frame and the 2kg weights on the front corners of the frame.

(To make the launcher arm)

Connect a “bucket” connector to the end of the t-connector.

Drill two holes at the center  of either side of the bucket connector, and drill a hole at the bottom of the “bucket” part of the bucket connector.

(To make angle control mechanism as seen in detail 2)

Pass a washer tied to 2.6m paracord through the hole at the bottom of the bucket connector

Drill two holes through the center of the 0.45 m pipe at the front end of the launcher and pass a screw through the two holes.

 Pull the paracord on the 0.53 m to a 45 degree angle and wrap the excess paracord around the screw on the 0.45m pipe.

(To make the trigger as seen in detail 1)

Pass a screw through the two holes at the center of the bucket connector and tie the 0.1 m string ends on either end of the screw

Tie the 0.2 m string to the 0.45 m pipe at the front end of the launcher.

(To make the trigger pin as seen in detail 1)

Connect two allen keys using duct tape so that they are back-to-back.

Tie the 1.6m paracord on the allen keys

Schematic:

Bibliography:

Ludlam, Eric M. “How to Trigger a Siege Engine.” Siege Engine.com: How to Trigger a Siege Engine, Team Tormentum, October 5th, 2009. May 10th, 2019.www.siege-engine.com/TriggersAndCatches.shtml.

N.A.“History of Catapults – Physics of Catapults.” Google Sites, , n.d. May 10th, 2019. sites.google.com/site/physicsofcatapults/home/history-of-catapults.

Normani, Franco. “Catapult Physics.” Real World Physics Problems, Real-World-Physics-Problems.com, n.d. May 10th, 2019.www.real-world-physics-problems.com/catapult-physics.html.