May 2011

Engineering Case Histories

Case 62: Useful shaft stress equations to remember

Committing several equations to memory can be useful

Sofronas, T., Consulting Engineer

Remembering complex equations is not required for reasonable on-the-spot answers. Neither are sophisticated computer studies when a quick screening study will be satisfactory. This case history shows simple equations1 that have been useful for making quick decisions. Failed solid circular shafts. Too much shaft torque can cause failures; so it’s good to remember this torque equation: Torque due to horsepower (HP): T = 63,000 3 HP / rpm in-lb Torsional shear stress failure solid circular shaft is: Ss = 16 3 K 3 Tin-lb/ (π 3 Din3) lb/in2 K is the stress magnifier caused by sharp corners such as keyways and steps (shoulders). K = 2 can be used for both torsion and bending. Assum

Log in to view this article.

Not Yet A Subscriber? Here are Your Options.

1) Start a FREE TRIAL SUBSCRIPTION and gain access to all articles in the current issue of Hydrocarbon Processing magazine.

2) SUBSCRIBE to Hydrocarbon Processing magazine in print or digital format and gain IMMEDIATE ACCESS to the current issue as well as to 3 articles from the HP archives per month. $239 for an annual subscription.

3) Start a FULL ACCESS PLAN SUBSCRIPTION and regain IMMEDIATE ACCESS to this article, the current issue, all past issues in the HP Archive, the HP Process Handbooks, HP Market Data, and more. $1,695 for an annual subscription.  For information about group rates or multi-year terms, contact J'Nette Nichols-Davis at or +1 713.520.4426.

Related Articles

From the Archive