Dagens garagedomkrafter är svåra att förflytta, där positionering ofta kräver många manuella rörelser och relativt höga manuella krafter. I samarbete med REHOBOT Hydraulics AB utfördes ett projekt fokuserat på att underlätta förflyttningen av garagedomkrafter. Enligt uppdraget ska detta lösas med hjälp av pneumatik som skapar en lufthinna mellan domkraftens undersida och golvet. Detta innebär en konstruktionslösning med mycket låg friktion, vilket i sin tur möjliggör enkel manuell förflyttning av domkraften utan riktningskrav. En förstudie utfördes som undersökte konkurrerande garagedomkrafter, ljudergonomi, kvaliteten på verkstadsgolv samt metoder för att bära en massa med hjälp av aerostatik. Funktionsmodeller skapades utifrån de aerostatiska metoderna. Informationen insamlad i förstudien sammanfattades i en kravspecifikation. Kravspecifikationen användes som stöd vid konceptutvecklingen. Resultatet bygger på användandet av två lyftenheter där den principiella konstruktionslösningen innebär att lyftenheterna kan integreras i företagets nuvarande domkraftskonstruktioner med endast ett fåtal modifikationer. Lyftenheternas placering och utformning innebär möjlighet till förflyttning, både med hjul samt med aerostatik. Slutkonceptet utvecklades vidare i en detaljkonstruktionsfas. I denna fas beaktades tillverkningssätt, utvärdering av miljöpåverkan samt montering och demontering. Examensarbetet avslutas med majoriteten av detaljkonstruktionsfasen återstående, med en diskussion kring projektet i stort och rekommendationer för fortsatt utvecklingsarbete. / Today's trolley jacks are difficult to move, where positioning often requires many manual movements and relatively high manual forces. In collaboration with REHOBOT Hydraulics AB, a project focused on easing the movement of trolley jacks was carried out. According to the assignment this is to be solved with the help of pneumatics that creates an air film between the jack and the floor. This means a technical solution with very low friction, which in turn enables easy manual movement of the jack without directional requirements. A study was conducted that examined the competing trolley jacks, noise ergonomics, quality of shop floors and aerostatic principles. Models were created to test different aerostatic principles. The information collected in the pilot study was summarized in a requirements specification. These specifications were used to support the concept development. The project’s result is based on utilizing two lift-units which can be integrated into the company's current jack designs with only a few modifications required. The lifting units' location and design gives the possibility of movement using both wheels or with aerostatic bearing. The result was further developed into a detail design phase. This phase considered manufacturing processes, environmental impact assessment, as well as design for assembly and disassembly. The thesis concludes with the majority of the detail design phase remaining, with a discussion of the project in general and recommendations for further development.

The compressor for air supply to the fuel cell stack is a critical component of the balance of plant, especially for mobile applications. The main requirements of the compressor are the performance regarding pressure ratio, mass flow and efficiency at minimal size and weight. The turbo compressor technology is ideally suited to cope with these requirements. The lifetime requirement and the necessity of oil and particle free air supply advised to employ air bearings. The fuel cell air supply requirements are in conflict with the turbo compressor pressure ratio and mass flow characteristics. Possible solutions and their impact onto compressor design and fuel cell operation are described in this paper. The chosen system design approach considering all design aspects and its interactions during the design phase is beneficial in order to achieve the most lightweight and efficient air supply system for fuel cells. Experimental validation of an air bearing turbo compressor for a 100 kW fuel cell stack on an aerodynamic test rig verifies the predicted performance.

Air bearing radial turbo (also called centrifugal) compressors prevail in most mobile fuel cell air supply applications due to the small size and weight, the high efficiency and the oil- and maintenance free operation. An important aspect in mobile fuel cell applications is the vibration resistance of all system components, including the compressor, with vibration requirements up to 20 g in automotive applications. This paper gives the background of the air bearing vibration characteristics, depicting the dependencies of vibration resistance on inlet conditions and operating points. The critical operating conditions concerning vibration resistance are identified, and it is outlined how vibration requirements can be included in the design process of an air bearing turbo compressor. A visualization of vibration resistance in the commonly used compressor map is presented, allowing the fuel cell system integrator to take qualified decisions for the mechanical integration of the compressor concerning vibrations.