Development of a New Roof Hatch Solution for Military Trucks

Abstract: This report is a result of a Master Thesis project in mechanical engineering by Andreas Byström and Josefin Salomonsson. The thesis was carried out at Scania CV AB at the department for Special Vehicles and the Division of Machine Design at the Department of Design Science at LTH from November 2009 to April 2010. Scania has a long tradition of designing and deliver vehicles to national defence forces. Scania’s military trucks are built with small modifications from the civilian truck platforms. This gives Scania the ability to offer reliable and cost effective vehicles for military applications. The majority of the military trucks are equipped with a roof hatch. New requirements, due to larger personal body armour and more equipment among the military, demands a larger roof hatch. These demands are expected to increase in the future and to be competitive in this market Scania wants to offer a new roof hatch solution. The aim of this work has been to design a variant of the current cab roof adapted to support a larger roof hatch. The annual volumes of these trucks are relatively low why the vision to manufacture the solution in the existing cab factory, with limited investments, has have a major impact on this project. By investigating the conditions and starting a dialog with personnel from market, production and development a good view of the specifications required was obtained. This dialog continued throughout the process to ensure that no requirements were neglected. The project has in some degree followed the product development process presented by Ulrich and Eppinger and involves development of design concepts, a concept selection and prototype sessions to verify and test the results. The proposed design shows that it is possible to come up with a solution that fulfil all the demands and is adapted to be produced in the existing cab factory in a cost efficient way. It was also found that a flexible design, which is more or less independent of the roof hatch design, is preferable. Not only due to the lack of decisions whether or not the roof hatch should be designed by Scania but also to be able to meet specific customer requirements more convenient. The final solution presented in this report consists of a border that is spot-welded onto the cab roof. On top of this border an external platform is mounted where the roof hatch can be installed. The hole in the cab roof is significantly larger than desired to accommodate various roof hatch designs and potentially be applicable for other applications. In parallel with our project; implementation of a larger roof hatch was carried out on a military truck delivered to Scania Deutschland. It was a great recognition and shows that we are heading in the right direction when they chose to use our border solution for their roof hatch installation.