Hey guys, I was hoping someone could set me straight on the two main methods of calculating shaft critical speeds. I have a final coming up but I can't seem to get these two to agree.(adsbygoogle = window.adsbygoogle || []).push({});

What I know:

-Dunkerly underestimates, Rayleigh overestimates

-Deflections used in Dunkerly are those caused by each single mass (eg remove all other masses during calculations)

-Deflections used in Rayleigh are those calculated with all masses "attached"

What I can do:

-Dunkerly's method very well. Wrote a VBA program for it. All calculations agree with all example problems I've run across as well as HW vs solution manual verifications

What I can't do:

-Rayleigh's method. The answers I get from this do overestimate, but are far, far off from that of Dunkerly, when they should be fairly close to one another. I can follow examples very easily and get the correct answers but I'm missing something in practice myself. For example a HW problem I am working pegs Dunkerly speed at 450 rpm, while Rayleigh gets 1050 rpm which is more than x2 Dunkerly

Can anyone point out what I am doing wrong here, at least by my thinking method? I'd be happy to post some of my worked out examples to see if I am just messing math up, but I am positive I am not.

I appreciate any help, thanks all!

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Dunkerly vs Rayleigh Clarification

Loading...

Similar Threads - Dunkerly Rayleigh Clarification | Date |
---|---|

Plate Buckling Deflection Function for Rayleigh Ritz Method | Nov 17, 2015 |

Vibrations - Rayleigh-Ritz Method Admissible Functions | Nov 16, 2014 |

Rayleigh Damping | Apr 9, 2013 |

Rayleigh and Fanno flows: | Jan 20, 2012 |

**Physics Forums - The Fusion of Science and Community**