Re: broken plastic parts (was charter revision)


Ed Hawkins
 

On Thursday, July 8, 2004, at 10:06 AM, Andy Harman wrote:

I saw some early samples which would have been see-through, but too many
problems filling the mold. Kadee's method must be a trade secret. BL
compromised by tooling a see-thru overhang on the ends and making the rest
solid. But I still prefer to use the Kadee walks when I take the time to
change them.
Andy and Brian,
Regarding the HO scale running boards, both Kadee's and Branchline Trains' running boards best represent the Apex Tri-Lok, which was the most common type used during the 1940s and '50s. Having done some research for an upcoming article on the subject of running boards for RP CYC, I have learned some interesting stuff about them. The Apex running boards had 13 longitudinal members that were 1" high with a 1/8" serrated top edge for footing. The 1/8" serrations are lost when reduced to HO scale.

While I agree wholeheartedly that the Kadee R/B looks terrific (I also use them extensively), it is actually not prototypically correct as it has only 11 longitudinal members. The BT R/B has the correct amount of 13. Kadee must have chosen to compromise the prototype design in order that the mold would fill. Kadee's crosswise members measure just over 4" apart and the BT crosswise members measure 6" apart.

Apex R/B built from 1938 to approximately 1953 had crosswise members spaced 3-1/2" apart. Apex changed by 1953 and increased the spacing to 5-7/8". Blaw-Knox, who had running boards that were similar in appearance (from a distance) to the Apex also increased their crosswise member spacing by circa 1949/51 (per the CBC) from 4" to 6". There were more changes but these were the most significant from an appearance standpoint.

Kadee uses acetal plastic that flows better and fills easier than styrene. I understand that BT uses a form of styrene. Kadee's detail parts made of acetal plastic are virtually indestructible. The downside to acetal plastic is that it doesn't hold paint and that is why Kadee molds the parts with color rather than painting them. The BT running boards and other detail parts are paintable. The BT running board mold must be getting worn because I've noticed more flash on the running board detail compared to a few years ago when the 40'-6" box cars were first introduced.

Jack Spencer showed me a method that he uses to remove material from the bottom of the BT running board such that the remaining portion is scale thickness and open-grid. The process is labor intensive, but it yields an excellent running board when the job is completed. Even after all this work, the BT running board is accurate for cars built 1953 and later with the 6" crosswise spacing. While in HO scale I don't get overly concerned about all this, I believe the visual differences in O scale (and even S scale) would be quite noticeable.
Regards,
Ed Hawkins

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