CJW
LAUNCHER - MECHANICS FOR DESIGN PROJECT
Aim
The mechanics group project aimed to launch a squash ball more than 50 metres. Using a purely mechanical method.
Calculaions
In the initial stages of the project our group drafted ideas for launching the ball. This was restricted by the module to exclude any pneumatics / hydraulics / explosives. We looked at slingshots using elastic and a rail system using springs, but concluded that two crossbow limbs acting as a single slingshot was the best way to achieve the highest force. Providing both crossbow limbs were of equal specification, this also naturally centred the ball.
Functionality
We selected two 80lb crossbow limbs, a 5 tonne ratchet strap as tensioning method, and seatbelt buckle as the release method. Using high strength fabrics provided reduced weight and provided more acceleration on the ball. It also reduced the risk of projectiles in the event of a breakage. This was all fitted to a steel frame we designed in CAD and welded/bolted together. We used our calculations to ensure there was a large factor of safety from all of the equipment used.
Results
Our launcher came in 1st place on the module, with an average launch of 62.9m and max of 64.2m.
This distance is less than our calculations predicted, which is highly likely due to other external factors unaccounted for. Such as the equipment being wet, the rain, wind and energy losses such as noise and heat.
