In the previous article, we looked at the relationship between tightening torque and axial force developed, and a formula was given which included the effects of those parameters which, as engine designers, you are most likely to want to change. In this article, we shall look at the effects of cyclic loading – it is necessary to understand this in order to determine the proper pre-load. This process of doing fatigue calculations and checking that the pre-load is sufficient is an...
I have little doubt that, for many of you reading it, much of this short article and those that follow will be a case of ‘teaching Granny to suck eggs’. However, for those who are involved in engine design, possibly as beginners, an understanding of how a fastener develops load via the application of torque is a useful lesson. These articles don’t pretend to be a full guide to fastener and joint design (there are some very authoritative books on the subject), but will help...
A leading race engine manufacturer ran into fastener problems recently when out of the blue they suffered two separate incidents of flywheel bolt failure, each on a different specification of engine, during the same test. One failure had occurred on a standard specification engine and the other on one which had been given an increase in torque of 30%.The manufacturer found themselves with a difficult engineering problem to solve and one which needed fixing very quickly. Receiving no...