Journal Bearing Design - Does anyone use Raimondi & Boyd?

[wdornfeld]

I've been teaching ME students the use of Raimondi & Boyd's Sommerfeld number ->
dimensionless variable charts for years. The method is in every machine design text,
but I am curious as to if anyone actually uses it in practice. It doesn't appear to have
changed much since 1958 (not that that's a bad thing). I would appreciate hearing from folks who use it, and also from current alternative methods of journal design - even if it is commercial or proprietary software.

 

[therealkilkenny]

Do you have the equations that govern the Raimondi and Boyd , charts? I have found the charts in many books, but i need to write an excel spreadsheet that is able to tell me the Sommerfeld number for a given eccentricity and L/D.

http://www.tribology-abc.com/software/default.htm

has one but the answers are wrong.

Any suggestions?

 

[wdornfeld]

I suggest that you get a good clean copy of the Min Film Thickness chart and build a table in Excel. Maybe see

http://www.utm.edu/departments/engin/lemaster/machine_design.htm

and click the 26th class notes, slide 13, which is Shigley 6Ed Figure 12-14.
The Min Film Thickness variable h0/c = 1 - eccentricity.
Carefully read off a four sets of h0/c numbers for a given Sommerfeld number at each of the four curves for l/d. Plot the four curves in a semi-log chart. Then add a trendline to each curve (right click with curve selected) - experiment with the type to get a good fit, and go to the Options tab and click the "Display equation on chart" box to see the best fit equation. You may have to limit the fit range to get very good fits. Shigley's equation 12-15 is Raimondi & Boyd's interpolation equation for ratios of other than the four given l/d ratios.

Regarding tribology-abc, I don't understand several things. First, they define S^G as the Sommerfeld number, but it is 2 times the INVERSE of Raimondi & Boyd's S. The factor of two comes from trib-abc using a radius R in the denominator. Next, the PHI that is shown as the X axis of their design chart of Sassenfeld and Walther used a diameter D in the denominator. The chart is clearly for an inverse Sommerfeld number (at least compared to R&B's), since the lines slope up to the left instead of up to the right as in R&B's. I have Raimondi & Boyd's paper, but not Sassenfeld and Walther's or Sommerfeld's papers, so I can't really say which is correct.
Next, the S^G number generated by their program doesn't agree with the PHI value from the Sassenfeld and Walther chart, but is sort of close to twice PHI, accounting for the radius vs diameter factor. For example, a B/D of 1 and eps of 0.85 (same as hmin/deltaR = 1 - 0.85 = 0.15) solves to an S^G of 9.12, whereas PHI from their chart is 5.3. Shigley/Raimondi&Boyd gives S = 0.03 = 1/33, which doesn't seem to relate at all.
To be picky, trib-abc also misspells Ocvirk as Orcvinck.

Maybe I'll write tribology-abc and find out. Good luck!