Nieuw uitschuifconcept voor de mast van een mobiele vouwkraan 2008.TEL.7264
iv
Summary
A mobile folding crane is a tower crane which fits on one truckframe when completely folded. The largest crane, currently produced by Spierings Cranes, can lift a load till a height of 35 metres. There is a demand to produce cranes which can lift a load even higher, up to a height of 45 metres. Therefore the mast needs to extend from four parts instead of three, which is now the case. To make this possible a new principle is needed for the extension process. The conceptual design of this extension mechanism is the subject of this research project.
The first step was to perform a literature study on the principles used in other types of cranes, like telescopic cranes. The results of this study and the design of the mobile folding crane currently produced where the basis for the formation of five concepts, which are shown in the figure on the next page. The first two concepts are a further development of the current crane with the use of a cable system. The other concepts will use a single hydraulic cylinder which can be coupled to the part of the mast that needs to be extended. In this manner all parts can slide out with the means of one cylinder.
For all the concepts formed the forces are analysed. These forces are used to determine the minimal size of the cylinders and cables to make the concept work. The concepts one and two would need such big cylinders that they wouldn’t fit into the mast. Therefore these concepts are withdrawn. The remaining concepts are analysed in more detail by taking a closer look at the extension process of the mast and particularly the principle of locking the cylinder to the different parts of the mast. Another point of investigation was the locking mechanism between the parts of the mast. This will be done by a locking pin connected to one mast and pushed by a spring into a hole in the next mast. To unlock the pin some mechanism connected onto the hydraulic cylinder will pull the pin inwards against the spring and out of the hole of the outer mast. The locking mechanism of the cylinder to the mast will be by means of a pin or block which can move in and outwards to support the mast.
All three concepts are compared with the use of a number of criteria to indicate the best alternative. De most important criteria are the time needed to extend the whole mast and the total costs. These are determined to be:
• Concept 3: time to extend the mast 5,5 minutes costs €29.000 • Concept 4: time to extend the mast 9 minutes costs €29.000 • Concept 5: time to extend the mast 7,5 minutes costs €22.000
Nieuw uitschuifconcept voor de mast van een mobiele vouwkraan 2008.TEL.7264
v In the figure below the final value given for each concept is shown. This indicates that the fifth concept is the most favourable option, which is mainly caused by the low costs. Therefore it is recommended to take this concept as a starting point for the development of a new crane with a mast consisting of four separate parts.
Hydraulic cylinder Cable
Cablewheel
Hydraulic cylinder with locking mechanism
