Urbanisation has historically led to issues with property damage and sickness, due to pests such as rats. Traditionally, rats have been exterminated using poison and manually loaded traps. As of late however, more effective and humane means of control have been developed, such as automatic and connected traps. As rats use the sewer system as we use the highway, connecting properties together, it is natural to place traps there. Nomor, a service company that performs pest control among other services, is interested in developing their own automatic mechanical sewer mounted trap for their own specific needs. In this thesis, the fastening mechanism and enclosure for such a trap are developed, with a concept developed in a previous collaboration used as a base. In this concept, a fastening mechanism is used to fasten the trap to the open pipes located in the sewer manholes. Rats passing underneath the trap are executed by the striking of a carbon dioxide driven cylinder. The enclosure surrounds the fastening mechanism and provides an interface between it and the executional unit, which is developed separately. The final prototype, which was made mostly using 3D-printing of PLA parts and some light metalwork, was tested and evaluated using a testing rig made from layered MDF pieces. The rig was constructed with an optimal scenario in mind, with dimensions like those in pipes which Nomor are likely to want to mount the trap in. The main use of the rig was to evaluate the dimensions and fastening abilities of the trap. Tests and analysis of the construction gave that the fastening mechanism and enclosure had potential to meet the requirements from Nomor in a reliable manner, if a more sophisticated method of mounting and a better mechanism for keeping the trap fastened was developed.

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. / Detta examensarbete beskriver utformning och utveckling av en automatiserad råttfälla för avloppssystem. Denna råttfälla har utformats för att ha en arbetstid på 2 månader eller cirka 15 749 träff med mått längd 535 mm, bredd 430 mm och ett höjdintervall på 931 - 1151 mm med avseende på olika avloppsrörsdiametrar. Fällan väger cirka 16,46 kg utan batteri, röranslutningar och stödanslutningar. Fällan har ett svarstidsintervall mellan 0,027 - 0,095 sekunder med ett slående tryckintervall mellan 16,05 - 56,19 MPa vid dödplattan. Fällan har en modulär design för att kunna monteras i olika avloppsrörsdimetrar (100,150,160,200,225,250,300,350 mm). Materialen och komponenterna som används för råttfällan uppfyller alla kravklassificeringar som arbetstemperatur, motståndskraft mot fukt och smuts, korrosionsbeständighet och ATEX-klassificering. Denna råttfälla kommer att användas ytterligare av Nomor AB för att testa den enligt Naturvårdsverket (Naturvårdsverket) riktlinjer och föreskrifter. En bakgrundsstudie om bruna råttarsfysiska egenskaper och livsmiljö, råttbiologi och befintlig teknologi utfördes för att ställa in fällans kravspecifikationer och för att utveckla ett koncept. Vidare avslutas denna avhandlingsrapport med ett föreslaget utvärderat fällesignkoncept och dess detaljerade konstruktion med analytiska beräkningar av dess motorspecifikationer, val av växellåda, fällhastighet, slagkrafter, dragfjäderspecifikationer och fällbatterikapacitet. Dessutom har ett antal lättillgängliga marknadskällkomponenter studerats och valts ut för att underlätta prototyptillverkning. De kritiska komponenterna i råttfällan har identifierats för att validera konstruktionens integritet med ändlig elementanalys. Slutligen innehåller denna rapport framtida arbetsrekommendationer för den automatiska avloppsråttfällan. Denna automatiserade avloppsråttfälla är en unik modulär design och hjälper till att kontrollera den ständigt ökande råttpopulationen i en av sina mest säkra livsmiljöer och är en språngbräda för mer avancerade avloppsråttfällor i framtiden.