Maintaining the Continuity of the Segmented Replacement Rail. As the replacement rails are made up of segments, any uneven deformation of the adjacent rail segments due to the varying Gripper loads would hinder the movement of gripper over the segmented replacement rail. The solution was to include a tight fit pin which would transfer the deflection/movement to the adjacent rail. This was modelled in ANSYS and found to be a very acceptable solution. The figure to the right shows the pin being positioned between the two segments of the replacement rail during a test.
Addressing the Cracks at the Gusset Plate/Rail Weld Connections. It was suspected that the cause of these cracks was due to the peeling of the rail, and it further raised the question as to why the gussets were there in the first place. It was suspected that they were originally added as positioners to get the existing rail in place with the horizontal plate for welding. The weld between the horizontal plate and the rail is the most important connectivity. A strategy was required to address the cracking problem which gives rise to uncontrolled corrosion if left unattended. As such two options were suggested and analysed for. Option 1 involved trimming back the gusset plates to the dimensions indicated by Whittaker Engineering and to re-weld at the joints with the old rail. Option 2 was to cut through the existing, vertical weld from the top of the gusset plates to the mouse hole and to redress the weld between the gusset and rail. This would remove all connectivity between the gusset plates and the old rail. Both options were analysed using FEA and from the results it was recommended that the existing vertical welds between the gusset plates and the old rail be cut through and the exposed materials be treated for corrosion protection.
Design Benefit
IDAC were able to carry out many design iterations using FEA in order to establish the repair strategy for the Gryphon Turret Rail. Whittaker Engineering, having worked closely with IDAC, were able to present the recommendations to their client with confidence having gained an insight into the behaviour of the turret rail and adjacent components under various loading situations. Ken Whittaker, the proprietor of Whittaker Engineering, commented on the results of the study. "We rely on IDAC to produce practical and robust engineering solutions when our designs go beyond the realms of hand calculations, they produce an excellent finished engineering package which gives credibility to our designs and products. Whittaker Engineering have been working with IDAC for many years and they are a pleasure to work with."
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small segments and bolted onto the old rail. The number, size and location of the bolts were designed and verified by
the use of FEA. An optimum design of 8 bolts per gusset plate sector was derived. The location of the bolts was also important because of the peel back action due to the large moments on the rail introduced by the weight and jacking force of the Gripper. The graphics above show the final bolting arrangement and von Mises stress distribution on the replacement rail assembly as well as the bolts and nuts subjected to the gripper 