| Abstract | Shear pins are used to attach C-SCOUT's fins to their actuating motors, so if something impacts the fins, the shear pins will break and the fins will fall off, thereby protecting the motors from damage. An analysis of the strength of the existing Garolite shear pins showed that they will fail during normal operation. It is possible for the fins to break off when the vehicle speed exceeds 2 m/s. Exact failure speeds depend on the angle of attack of the fins. To fix the problem, re-design of the shear pins was attempted, basing the new shear pin strength on the load required to damage an actuator. It was found that the bearings in the actuator's gearbox will be damaged during normal operation, at speeds exceeding 1.3 m/s. Therefore, the motor will be damaged before the shear pins break, so creating stronger shear pins is not a solution that will protect the motors. Stronger fin actuators should be purchased. The potential for damage to the motors due to operational and impact loads should be considered when selecting a motor. Once new motors are selected, the method described in this report can be used to design appropriate shear pins. Until new actuators and shear pins are installed, C-SCOUT testing can proceed under a 2 m/s speed limit. |
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