SHAFTKIT FAQ

 

Has SHAFTKIT been verified ?
Yes. Results from SHAFTKIT have been verified both at full-scale, and against other finite element programs.

Can I use the results from SHAFTKIT for submission to classification organizations for approval of vibration and alignment ?
Yes. A number of vessels have had SHAFTKIT calculations approved by classification organizations.

Does SML provide shaftline analysis and measurement services ?
Yes. SML has conducted a number of theoretical analysis and full-scale measurements of marine shaftline vibration and alignment conditions, including shaft alignment measurements using strain gauges. Please contact SML for further information.

Does SML offer support services ?
Yes. SML offers a range of support services, in addition to our extended support with SHAFTKIT. Please contact SML for further information.

Can I apply offsets to account for thermal expansion of gear bearings ?
Yes. There is an option to input an offset from datum for each bearing.

What options are there for applying viscous damping ?
Viscous damping can be applied at the propeller, or at any location along the shaft. Viscous damping is an input parameter for each bearing. The bearing stiffness can be set to zero if the user wants to apply concentrated viscous damping without a bearing support.

What options do I have for applying alternating torsional sstresses on shafts ?
Sinusoidal torsional loads can be applied at any location on the shaft, and at any frequecy. Multiple sinusoidal loads with varying frequencies and magnitudes can be applied at any location on the shaftline.

Can I apply my own custom input force time history ?
A simple quick basic utility program is available that will enable the storage of a custom force time hstory that the SHAFTKIT program can read and utilize. We are planning to include an option to allow for the direct input of additional load time histories, such as prime mover transient loads, in the next version of SHAFTKIT. Please contact SML for further details.

How do I account for propeller overhang when constructing a static alignment or lateral vibration model ?
The overhang of the propeller is produced by inserting a shaft element between the propeller and the aft end of the tail shaft. This element should have a length that is equal to the distance from the aft end of the propeller shaft to the centroid of the propeller, a density of zero (0), an outside diameter approximately equal to the propeller hub diameter, and an inside diameter of zero (0). The default elastic modulus for steel is sufficient (2.07 Gpa). Other alternative methods can also be used. Please contact SML if you require further information.

How do I calculate the forward and counter whirl frequencies from the lateral vibration natural frequencies ?

The gyroscopic effect of the propeller results in a forward and counter whirl frequencies which generally differ from the lateral vibration natural frequency by only a few percent, and it is commonly neglected in whirling (lateral) vibration calculations. However, an estimation of the ratio of the forward and counter whirl frequencies to the lateral natural frequency can be made by using various algorithms. Please contact SML if you require further information.

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