Hello again Steve,
Yes it is hard to get these points across i agree. But all the variables i have used appear in the book, no more come from outside except the fact that i have seen this before and know what good books say.
The book refers to a certain number of variables, and that is all that we need to understand the point of the book. Bringing in new variables such as disturbance torque is OUTSIDE the realm of the book, but conversing over the variables that were mentioned in the book is valid in determining what the book would have said if they took more time. And if you were to create a list of preferred methods even with more outside variables, the time constant comparison technique would still be above that of purely R and L alone in any way. It would be such that the new variables taken into account would merely be above just R,L and J,f at that point, because obviously a new variable of significance needs to be looked at and that trumps anything that does not that take into account, again this is obvious. And when we seek to understand something we do not attempt to make the problem more difficult we try to make it more simple. In other words, we dont add more variables and then exclaim, "See, nothing works!". For example, did we take into account relativistic effects yet
We dont take into account sticking friction because the book does not talk about that at all, and this is more typical too of other books which have a goal to convey other more basic information.
A more light view of this would be to examine the song i think from the late 1960's, the Ode to Billy Joe. Billy Joe was a fictional character invented by the song author. But after the song became a huge huge success, many people began to question why Billy Joe jumped off the 'famous' bridge and killed himself. I think they questioned this because all of the places mention in the song were real life objects located in Mississippi, but Billie Joe was fictional or may have been an old wives tale. But anyway there were various theories that came up about why he killed himself, yet there was no clear cut reason for this. But still people went on and on taking the smallest clues from the song to build a case upon.
Now the point is if we create a theory, it may or may not be right, and we have no way to prove it. But if it was a historical fact, then we could perhaps look in other references to find out the real truth. The truth is not given in the song, but if a record was noted by the local sheriff for example then we would know for sure. But the details are not to be found within the song, so we have to look elsewhere. If we take artistic liberty then there is a chance we will be wrong, but if we look at other references there is almost no change we would be wrong.
But anyway, rather than go on and on about this, i propose that we present a list to PG. A list of preferred methods of determining whether or not the inductance is significant or not. The list could be presented in order of what it takes into account and why it is better than the lower grade method.
We can still talk about this, but it will be much easier to discuss then and the result will help PG rather than make him wade though a mountain of text
Here is the list i propose we start with. Your job then is to reorder the list if you would like to.
Note that f is quoted as b0 in the book itself. Consider this task fuzzy logic.
1. Compare the time constant of R and L with the time constant of J and f.
2. Compare just L with J.
3. Compare wL with R (am still not clear how you would determine a value for w)
4. Compare L with R.
5. Think about L alone.
Note i am still not clear how you would determine a value for w because it's hard to say what frequency is good for a system when it may operate in several basic modes.
The reason i rank #1 as such is because it works in EVERY case that the book works for, and the book was the original subject of the question. I did not include the 'poles' explanation because that is the same as the time constant explanation.
So anyway, you can reorganize that list if you dont agree with it, or add to it, or make some elements have the same rank (such as R and L vs wL and R might both be ranked #2 or #3 or whatever. I think this will show me more about how you are thinking about this.
BTW i do value your views and opinions on these topics as usual.
Perhaps you would like to see an analysis of the system.
Also, maybe you would prefer to read a reference from a better book?