[N&W] Re: Y3/Y3a tender wheels in the early '50's

[nw-mailing-list at nwhs.org]

Harry,

Sorry to be so tardy replying about U-1 wheels.

Now, to the U-1 wheels that were prohibited in interchange service by the
AAR in late 1970's or early 1980's according to Interchange Rules books in
our archives.  The U-1 wheels were "Southern" brand wheels (no relation to
the railroad of that name) manufactured by Abex (earlier, American Brake
Shoe Co.; later ABC Rail) in that company's plant in Calera, AL.  They were
one-wear, 33" diameter, 70-ton, straight-plate,
un-heat-treated, cast steel wheels with a carbon content somewhat over 1%,
which may have made them wear somewhat better, and which also made them
cheaper to manufacture because the steel did not have to be refined as much
to get the carbon content down (0.77% carbon is the maximum now specified by
the AAR for freight car wheels).  Apparently, the combination of high carbon
(brittle steel?) and the straight plate design (resultant high tensile
stresses in the rim after overheating from heavy tread braking whereas
compressive stresses are desirable) caused an unacceptable number of wheel
failures in service (read: derailments).  The act of burning a hole in the
plate of a U-1 wheel was not mandated by the AAR, but apparently it was done
by the N&W to insure that the wheel could not be inadvertently returned to
service.

Here is some info on freight car wheel details mentioned above for those who
might be interested.  Freight car wheels have been manufactured as one-wear
(1-1/4" to 1-1/2" rim thickness depending on diameter), two-wear (2" rim
thickness), and multiple wear (2-1/2" rim thickness).  The N&W used a lot of
multiple wear wheels on its freight cars until the 100-ton car era when
two-wear wheels prevailed.  To save on light weight of the car as well as
the cost of carrying the extra weight of wheels with thick rims, some other
roads chose the cheaper one-wear wheels.  Freight car wheels have been
manufacured in diameters of 28" (low-floor flats such as tri-level auto
flats), 30" (low-deck, heavy duty flats), 33' (70-ton cars), 36" (100-ton
cars), and 38" (125 ton cars). The plate of a wheel is the portion of the
wheel between the rim and hub.  The AAR now requires all new wheels to have
curved plates to provide more elesticity as the wheel rim expands because of
heat from heavy tread braking.  The cast steel wheel manufacturers prefer a
papabolic plate shape, whereas the wrought steel manufacturers favor an "S"
plate shape.  A heat-treated wheel actually has just the rim heat treated to
place the rim into a compressive state, which helps to protect against crack
propigation that would otherwise occur if the rim were in a tensile state.

Gordon Hamilton


----- Original Message -----
From: "N&W Mailing List" <mailing-list at nwhs.org>
To: "N&W Mailing List" <mailing-list at nwhs.org>
Sent: Monday, February 24, 2003 10:46 PM
Subject: Re: Y3/Y3a tender wheels in the early '50's


 > All right, Gordon, any comments on the U-1 wheel ? Manu-
 > facturer ?  Why they failed ?  N&W (and I suppose others) were
 > burning holes in them.
 >                                                  Harry Bundy
 >