Machine Design

Bearing equations online

Bearing maker SKF has established a central library on its network to store engineering calculations for reference and general use.

SKF's Kellstrom devised the Carb toroidal roller bearing and put the equations that define its details into the MathCAD library. The bearing combines the self aligning capability of a spherical roller bearing, the axial displacement of a cylindrical roller bearing, and the low section height and carrying capacity of needle roller bearings.

Using MathCAD as a calculation library lets SKF potentially create hundreds of designs for toroidal roller bearings in sizes from 50 mm to 2 m.

The library is built on MathCAD calculation software from Mathsoft Engineering & Education Inc., Cambridge, Mass.

( The equations compute a range of bearing qualities, from basic dimensions to finished products with tolerances. The equations also guide material choices. Calculation sheets spell out methods, assumptions, data, and context behind the equations.

"The software makes it easy to follow the design process," said Magnus Kellstrom, inventor and manager of design and development for SKF's Toroidal Roller Bearings team. "The program lets us quickly try design variations. When we find an acceptable design, the library saves it as an Adobe Acrobat PDF file. Every bearing designed with the software is completely documents as to how and why each dimension and tolerance was chosen." The design process generally take just minutes. SKF manufacturing units located elsewhere can access the data through a Web interface. Paul Dvorak



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