[N&W] Re: Water Buffalo?

[nw-mailing-list at nwhs.org]

 >Kinks and Bounces:
 >
 >Just speaking as a dumb, old mechanical engineer....
 >
 >Assume that the loco is a 2-8-8-2.  Assume the drivers are all 58 inches in
 >diameter except for one which is 58.5 inches.  Assume this 58.5 inch driver
 >is the third driver on the second motor.  Now, start the locomotive from a
 >dead stop, get it up to speed where the "driver bounce" starts and run a
 >high speed movie of the event with the camera on the ground.
 >
 >Gary Rolih

Gary - if the second engine - or any engine - has a driver that is 1/2"
bigger than the rest, if the rods are on the engine the one bigger driver
will be slipping all the time, because it will have to make the same RPM as
all the rest (the adhesive weight on the one axle with the larger tires will
be roughly 1/4 of the adhesive weight on the other three, so all the wheels
will rotate at the RPM of the ones with the greatest weight).  1/2" was far
greater than the allowed tolerance for tire diameters of one engine.  If
someone put a single pair of wheels that much bigger than the rest under an
engine, he'd probably get fired.  But I get your point.

It's not like one engine has drivers 1/2" bigger than those on the other
engine.

And if the rods are off the engine, the bounce will start far quicker . . .

Diesels, since their axles aren't coupled, can tolerate greater differences
between wheel diameters.  The problem then occurs when you have a wheel slip
detection system such as EMD's IDAC (Instantaneous Detection And Correction)
which measured the current drawn by the different motors.  If a wheel is
rotating faster than the rest, it draws less current; this would activate
the IDAC which would then apply sand and cut the power to all the motors
until the currents were equalized.

But this is beside your point . . .

EdK
_____________________________________________________________
Yer Right again Ed.  Its' the #2(main) driver on the "J".  my typing finger
needs to go on a diet.  (It WOULD BE #3 on a Water Buffalo!!!)

So the photographic process is time consuming and expensive,
and HOW MANY LOCOS DID THEY PHOTOGRAPH??
Were all of them with arrows photographed?
If the question has to do with counterweigh shapes, or size, then the tires
are of little consequence, and the photography would only need to be
conducted on one of each type of rod/ counterweight.
Since it has been implyed from several sources that more than one of the
same engine types were photographed - what were they researching???.
Were they researching Counterweight issues, or finding a specific engine?
If the #2 driver is bouncing, then its pulling #1 and #3 out of alignment
during each bounce!  The rods and bearing must love it!
I understand that the H8 at the B&O train museum has a variation in
wheel/tire diameter of about 1/4 inch from smallest to largest.

did they mark both drivers on the Y class locos (front & Back)??

If no 2 engines have EXACTLY the same driver size, and ONE engine has kinked
the rails, How do you identify the engine from the kinks?  seems like high
speed photography wouldn't be needed...


mark Lindsey


Mark Lindsey
___________________________________________________________
I've got to throw a couple of cents in here.  I contend that any drivers
that are coupled together by rods have to be the same size, or really,
really close.  If they aren't the same size there will have to be
slipping at different rates or the rods will bind.  The same problem
came up with the newer controlled slip GM diesels.  Because they only
have one inverter to control speed per truck the wheel sizes have to be
closely matched.  Practically this means that if one wheel set per truck
needs turning all three wheel sets will be turned to equalize sizes.
The inverter has turned into an electronic connecting rod.  GEs don't
have the same problem, they use a separate inverter for each axle.

Stony