Class J's - trackworthiness?

[nw-modeling-list at nwhs.org]

I believe this refers to Mike Ritchdorf (I think I misspelled his name) and
he lives near O'Hare airport.  His layout is HO scale with color position
light signals and scenery. I have been there and watched him move a
trainload of loaded (with a real load, not a fake) hopper cars from a mine
that actually dumped the coal into the cars to a rotary car dumper.  I think
he would be glad to have anyone visit him if you gave him enough notice that
you were coming from this distance.  I can find out his e-mail if anyone is
interested.

Bob Folsom
Clemson, SC


On 10/5/06 4:59 PM, "nw-modeling-list at nwhs.org" <nw-modeling-list at nwhs.org>
wrote:


> Hi Gary,

> 

> I love seeing a long post about an engineering topic--figure it must be one of

> yours and I'm sure to learn a lot.  Would you mind if I quibble just a bit

> about one statement?  You wrote:  "Even with computers, only an iterative

> solution is possible (iterative = run the numbers and see what comes out)."

> Iterative in this sense refers to a mathematical method based on the calculus,

> such as Newton-Raphson, that starts with empirical data involving measurements

> on several variables and a model equation based on physical theory that

> interrelates those variables through a set of parameters whose ideal values

> are unknown; "ideal" being defined as those values that minimize some other

> "loss" or "objective" function.  If the model equation is linear in the

> parameters, then generally an iterative solution is not required, as in

> multivariate linear regression.  Here calculus isn't involved, only algebra.

> Iteration involves finding an approximate solution, then using that solution

> as a starting

> point to find a better solution, and continuing this process until the gain as

> measured by the decrease in the loss function is negligible.

> 

> I must be getting old.  My pedantry on the point reminds me of a manager at

> Illinois Bell from thirty years ago, long before email. About 10-15 paper

> memos a day would circulate through the department, with a little sheet

> stapled to each where you'd check off your initials after reading it.  Frank

> C. would go through every one and mark it up with spelling, punctuation and

> grammar corrections before passing it along.

> 

> Sorry guys.

> 

> Tom Leuthner

> 

> P.S.  I believe someone on the list modeling the N&W lives in the greater

> Chicago area.  Ever have an open house?  What scale?

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