I've just had an exchange off-list about the true nature of these things
and I though I'd post my theories/suppositions to the List to see what your
theories/opinions/suppostitions are.
The momentum car falls into that category of things whose physics I don't
fully understand, but which work, and I accept them as they are because I
like what one does for the running characteristics of my locomotive. There
are no doubt many locos that won't benefit from one all that much but the
Pannier is one.
What little thought I've given this has left me with the opinion (as
opposed to knowledge) that a mo-car as simply an "energy sink" (as in
heat-sink in electronics) which absorbs and dissipates the excess energy of
the locomotive which would otherwise appear as unwanted behavior (like
excess speed, accelleration, or poor control from sensitive throttle, etc).
However the end result is achieved the result is a calming effect on
overly-enthusiastic locomotives and/or a work load for powerful lcoos,
whichever is needed.
In thinking about them, and for lack of a better explanation, I liken the
mo-car to two things. The first is the R/C "de-glitcher", which is a
circuit which retards or buffers the servo signal so that very small
interruptions or changes in radio signal at the receiver do not appear as
jerking at the servo, yet the servo may still do its job. I seems to me
mo-car has the same effect on a locomotive, smoothing the behavior by
reducing its ability to respond to erratic or excess signals (steam supply)
and yet not prevent it from doing a job.
The second thing is I liken it to is a boat hull. As I understand it any
given boat design has a maximum "hull speed" and after reaching design
speed no matter how much horsepower one throws at it the hull will not go
appreciably faster through the water. I see the same behavior with a drag
car, after a certain point a given locomotive & drag car hookup will reach
a speed after which it will not continue accelerate, although truthfully
I've never attached a drag car to my engine and opened it up to see what it
would do. But it appears that for any given intermediate throttle setting
it will reach a speed and not accelerate appreciably.
Your responsible, intelligent, non-expletive laden, comments will be
appreciated and considered.
Regards,
Harry
