Design and development of an automated rat trap for sewage system

Abstract: This thesis report describes the design and development of an automated rat trap for sewage system. This rat trap has been designed to have a working duration of 2 months or approximately 15749 hits with trap dimensions length 535 mm, width 430 mm and a height range of 931 – 1151 mm with respect to different sewer pipe diameters. The trap weighs about 16.46 kg without the battery, pipe connectors and support connections. The trap has a response time range between 0.027 – 0.095 seconds with a striking pressure range between 16.05 – 56.19 MPa at the kill pad. The trap has a modular design to be able, to fit into different sewer pipe dimeters (100, 150, 160, 200, 225, 250, 300, 350 mm). The materials and components used for the rat trap satisfy all the requirement classifications such as working temperature, resistance to moisture and dirt, resistance to corrosion and ATEX classification. This rat trap design will be further used by Nomor AB to prototype and test it according to the Naturvårdsverket (Swedish Environmental Protection Agency) guidelines and regulations. A background study on brown rat physical characteristics and habitat, rat biology and existing trap technology were performed to set the trap’s requirement specifications in order to develop concepts. Furthermore, this thesis report concludes to a proposed evaluated trap design concept and its detailed design with analytical calculations of its motor specifications, gear box selection, trap speed, impact forces, trigger spring specifications and trap battery capacity. In addition to, a number of easily available market trap components have been studied and selected to aid with the prototyping. The critical components of the rat trap have been identified in order to validate the structural integrity of the design by finite element analysis. Finally, this report includes future work recommendations for the automated sewage rat trap. This automated sewage rat trap is a unique modular design and will help to control the ever-increasing rat population in one of its most safe habitats and is a stepping stone for more advanced sewage rat traps in the future.