I found this out when creating the spreadsheet for Lateral Design. My
opinion has changed, as a fudge factor does not help the engineer understand
how the formula was derived. We had a number of threads regarding the
Diaphragm deflection calculations and many responded that the formula was
derived empirically and therefore many of the values contained constants.
However, one engineer (or two) wrote in with a more complete explanation
that showed us how to derive the formulas and proving that there were no
constants or empirical formulas based on "fudge factors" but rather a
rational derivation from the common deflection formula for a uniform load
applied on a simple beam.
My point is that before assuming that you need to apply a fudge factor
because the formula was written in part to be unitless, there may be another
reason based on actual derivation where the units are accounted for.
Just my opinion that we can't simply assume unitless formulas when we might
learn more if we dig into the history of the formula.
From: Mark Gilligan [mailto:MarkKGilligan(--nospam--at)compuserve.com]
Sent: Monday, January 29, 2001 8:56 PM
Subject: Re: Mathcad question
While you are lobbying Mathsoft you might ask them to include a standard
system of units where a pound "lb" has force units.
Another difficulty that I have is if you implement many of the many of
the formulas in the codes in Mathcad, you will find that you do not get
the right units and the correct numerical value until you add a fudge
factor. There should be a special function that takes the result of the
numerical operations and assigns the desired units to the result.
I just got an e-mail last week from the Mathsoft people (it took a long
while for them to respond) on this very topic. There isn't any way to
display intermediate results, which is too bad because this would make the
calculations very readable and easy to spot errors. The reason given to me
was that there probably wasn't enough interest in this feature to warrant
Mathsoft incorporating it. Maybe we could form a lobby to get them to