The development of a grass collection system for the Skil Urban Trimmer

This master thesis covers the development of a grass collection system and grass catcher for Skil Urban Trimmer. The number of people that live in an urban environment is rapidly increasing. A result of this urbanization is the growing demand for products that are specialized for urban needs. This demand has driven Skil to launch the urban series: gardening tools specialized for owners of small urban gardens and little space for storage. The Urban Trimmer will be a new addition to the urban series. On average, owners of urban domestic gardens have, as one might expect, a smaller lawn area and less storage space compared to residents outside of the city. As a consequence, their needs differ and currently offered electric mowers are too bulky and their features are superfluous for these small gardens. Prices are too high and they take up too much storage space relative to the area of lawn that they are needed for. The Urban Trimmer should appeal to its target group by offering the basic features of a lawn mower in a more affordable and compact product. One of these basic features is the collection of grass clippings, the goal of this graduation project was to develop the grass collection system for the Urban Trimmer. Skil aims to achieve the compact size and low cost price, by utilizing a small electric motor and fitting it with a light-weight cutting head. This cutting head will be mounted with replaceable plastic swivel blades. Ordinary grass collection principles rely on the suction that is generated by the propeller like shape of the cutting blade. The flat swivel blades of the Urban Mower do not create the lifting airflow required for this type of collection system. A new type of collection system had to be developed within the size and cost restrictions that were set for this product. The collection system that was developed during this project utilizes the cooling-airflow from the electic motor, in combination with the circulation of air inside the deck for the collection of clippings. By utilizing these sources of energy that would otherwise be lost, power consumption is kept low. The cooling air is directed into the collection discharge at the rear of the deck. The tapered shape of the deck and the lift inducing cutting disc transport the clippings out of the trajectory of the cutting blades. From tests performed during this project it can be concluded that it is not possible to realize a reliable grass collection system within the power and price restrictions set for this product. More motor power is necessary to drive the cutting head and collection system without clogging, and the cost price of the mower exceeds the 20 dollar limit predetermined by Skil. The collection system that resulted from this project was proven to work with a small increase in motor power. In addition to the collection system, a grass catcher was designed specifically for the Urban Trimmer. This new grass catcher solves the problems that were encountered with existing collection reservoirs. The safety guard automatically opens when the grass catcher is attached, eliminating the need for a second hand during this process. The position of the connection of the bag on the top of the mower offers better visibility of the connection of the bag. The frame of the bag can be folded flat for compact storage.

Subject

Skil
lawn mower
grass collection

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master thesis

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