As the flame activated powder cartridges need to cover a range of 8m2, they will need an initial velocity.
Throughout this section of the report, I will be demonstrating how I achieved this.
Test 1
- Hypothesis: Using motors, the cartridges will pick up momentum before exiting the unit.
- Application: A 3D printed assembly was produced. Ping pong balls were used to represent the cartridges and passed through four shafts, each attached to a high speed motor.
- Outcome: A slight variant in ping pong ball size meant the shafts were not always in contact. An inwards force is required to ensure contact.
Test 2
- Hypothesis: Using springs, the motor shafts will provide an inward force. The cartridges will pick up speed when they overcome the force.
- Application: A 3D printed assembly was produced. Three shafts were used instead of four to ensure contact.
- Outcome: The cartridges travelled a disappointing distance after exiting the mechanism. This may be due to the lack of time the cartridge has in contact with the shafts, reducing the energy transferred.
Test 3
- Hypothesis: Energy needs to be stored and passed onto the cartridge. This will increase the distance travelled.
- Application: Using scrap wood and a spring, a ‘flicking’ mechanism was created. Energy will be stored in the spring and transferred upon impact.
- Outcome: This method provided the furthest distance travelled so far, however I was concerned about the initial impact. It works for the ping pong ball, but the cartridge will be made from polystyrene that could potentially brake on impact.
Test 4
- Hypothesis: By keeping the cartridge in contact with the ‘flicking’ mechanism, it will travel the same distance without the risk of breaking on impact.
- Application: A catapult like mechanism was produced using scrap wood and two springs.
- Outcome: The distance travelled by the cartridge substantially reduced proving that it was the impact force from test 3 that caused the cartridge to accelerate. Friction also reduced the force.
Test 5
- Hypothesis: Test 3 proved that increasing contact time increases the distance travelled. If test one used larger shafts, the contact time between the cartridge and the shaft would increase, thus projecting the cartridge further.
- Application: A high speed motor was attached to a large cog and placed into a 50mm pipe.
- Outcome: The distance travelled by the cartridge exceeded the distance required proving test 5 a success. Cartridges travel noticeably further when there is no force provided behind them from other cartridges (notice in the video how the last ball travels much further). When feeding the cartridges to the launcher, a mechanism that equally spaces them will be required.
Application Of Prototyping In Final Product
Two large spinning disks highlighted in blue are placed inside the exit point of the device. The disks are powered by a motor on the side of the exit point which connects to each disk via a series of gears.
