Concept Generation of Draft Gear Vertical Support

Sammanfattning

Dellner Couplers is a company in Dalarna, Sweden, that manufactures train couplers. The couplersare used on many different types of trains, including commuter trains, high-speed trains, andfreight trains. The main purpose of a train coupler is to link carriages together to form a largertrain. Though, to allow the train to follow the tracks, the coupler must permit movements, couplermovement also helps make the ride smoother. Modern trains also have numerous electrical systemsand pneumatics that are transferred between carriages. These systems make the coupler heavy,which in turn means it cannot remain horizontal without vertical support. This support is whatthe thesis project aims to develop new concepts for.The well-known method according to Ulrich and Eppinger was used to develop the concepts. Needs,requirements, and concept selection were done according to this method. The actual generationof concepts was done using Liedholm’s FM tree. The main needs were to allow movements of thecoupler, permit a crash sequence, and most importantly, to support the coupler. The needs weretranslated into requirements that were combined with Dellner’s requirements. Ten concepts werecreated, of which three were selected using the “Datum Method”.The thesis work resulted in 3 unique concepts for a new vertical support to the draft gear:The first concept being the airbag (also known as the air bellow) is made of nitrile rubber and can,with a diameter of 138,2 mm and inside pressure of 8 bar, support loads of up to 12KN (3620Nm).It can be deflated in coupled mode and therefore does not hinder any movements. When the trainis uncoupled the air bellow collides with a sharp edge on the draft gear and ruptures resulting insuccessful crash management (IRS). The exact lifetime of the concept is not certain but can beexpected to be somewhere between 5-10 years.The second concept features a vertical support that withstands the torque of 3620 Nm thanks tofour large steel springs. The springs are dimensioned such that they have a pretension of 1750 N anda spring constant of 200N/mm each. The springs will together support the force of 12KN generatedfrom the torque by extending 6,25mm. The springs have an infinite life for a vertical deflection onthe draft gear of 2 degrees and allows IRS when the hollow tube crumples and ultimately is cut intwo.The third, and last, concept is the bending beam. The beam can provide necessary horizontalmovements around it’s rotational axis and has an infinite fatigue life when the torque is only3600Nm. The beam itself has a maximum vertical displacement of 1,76mm and the rubber verticalsupport ensures the concept meets the required vertical angle of the draft gear from the technicalneeds.