--- In STMFC@yahoogroups.com, Richard Hendrickson <rhendrickson@...>
Mr. James Dick of the Northern Pacific Railway Historical Association
sent me copies of a bunch of NP company correspondence about these
roofs, which unfortunately raises more questions that it answers. Many
of these letters appear to be testimonials in response to a request
for same having been sent out by Mr. H. M. Robertson MCB of the
Northern Pacific Ry.
Here are some highlights:
A letter from the Twin City Joint Car Inspection Association dated
9/11/23 refers to the roof as the "Gilman-Robertson Circular Roof."
and states that it dates to 1909. It also states that the
Chicago-Cleveland Car Roofing Co. are to sell this style roof.
There is a memo from the NPRy. Mechanical Dept. dated 12/26/24
comparing the weight and cost of the "N.P. Composite Circular" roof to
the Hutchins All Steel roof and the Murphy X.L.A.
There is a request of information from the Norfolk Southern Railroad
dated 2/2/26, and the response on 3/8/26 which claims that, "This
construction is covered by a patent issued to our master car builder,
Mr. H. M. Robertson, and I understand the royalty for use of same is
$1.00 a car." However, I have not been able to confirm the existence
of this patent.
There is a letter addressed to Mr, Ralph Simpson, Mech'l Eng'r, Mps.
St.P. & S. Ste. M. Ry. (Soo Line) dated 6/21/27 asking if he would
please send, "a duplicate set of prints showing Mr. Robertson's design
of circular roof applied to the 500 boxcars which you recently had
built." Mr. Simpson responded in the affirmative 6/25/27. I feel that
this confirms that the arch roof cars the Soo had built in the late
twenties did indeed use the same roof the NP was using.
A letter dated 8/8/27 that appears to be signed by H. M. Robertson
concerning a inquiry by the Milwaukee Road states, "I informed him
that the patent covering the roof construction had been sold to the
Hutchins Car Roofing people." This surprises me, as the Soo purchased
additional cars with this roof in 1928, 29, and 30, and the Soo
equipment diagram claims the roof is Chicago-Cleveland.
There is a letter dated 8/11/27 to the Mech. Supt. of Fruit Growers
Express that states that the roofs on the NP 93000 series of
refrigerator cars, "were purchased from the Hutchins Car Roofing Co.
and that company also controls the diagonal roof board construction."
Speaking of the construction. These were simple outside metal roofs,
the light guage sheet metal being supported by wood sheathing. Reading
this correspondence, I realize the design intent was to allow the
entire roof to be one unbroken plane, so that the sheathing could be
laid at a 45* angle to the car, which improved the stiffness of the
roof structure and lessened "weaving", the tendency for the roof to
rack back and forth. This plane was bent into a gentle arch and
covered with sheet metal to shed water, but the important part of the
design was the diagonal sheathing.
As far as I can tell from this correspondence, while several other
roads inquired about the design, only the NP and Soo actually used it.