Re: Scale Coupler Application

Denny Anspach <danspach@...>

The recent interesting thread on scale couplers and boxes and their applications motivated me to do some measurements and experimentation today on two new-in-box Fifth Avenue Car Shops Milwaukee ribside double door boxcar kits, MILW 6600, and MILW 7037. Both cars had the standard moulded industry-standard draft gear boxes designed for drop in Kadee-type couplers, essentially identical to that found with almost all other contemporary styrene and urethane kits currently, and historically on the market.

My purpose was to first measure, and then install Kadee #78 scale couplers and boxes on one car, and install Accurail Accumate Proto scale couplers and boxes on the other, and compare experiences. Note that I have been installing the Accumate Proto couplers for some time (about 100 cars), and this was my first experience with a #78.

Because the coupler measurements have been gone over a number of times in the past on this list and elsewhere, I will simply stipulate that although both couplers have pluses and minuses in their details, both seem to look acceptably prototypical to me. The #78s, although fresh from the LHS, had the notorious "Gap", which I understand has since been corrected.

The measurement of the boxes against prototypes is listed below. Understand that draft gear "boxes" or housings are simply seemless extensions of the car's normal center beam or center sill, so are really not truly ever prototypically "independent". Their dimensions should reflect this by only sharing the same cross sectional measurements as the center sill.

In the figures below then, the "length" of the average prototypical draft gear "box/sill" (such as might be common on any 40' car) is as measured from the outside face back to then nearest margin of the body bolster.

Box Dimensions Kadee #78 AccProto Prototype

Length OA 0.475" (3'5-1/4") 0.640" (4'7-3/4") c. 4'4-10"
Width OA 0.258" (2'9-1/2") 0,236" (2'8-3/4") c. 1'6" (over flanges)
Depth OA 0.125" (1'1") 0.139" (12") c. 12-13"
Depth without bottom N/A 0.106" (9-1/4") N/A
Minimum length (cut) N/A 0.380" (2'9-1/4") N/A
Detailing None (box is trapezoidal) Some N/A

Preliminary Summary:

Both boxes are still much wider than the prototype (presumably a functional necessity). The overall depths are pretty accurate. The Accumate Proto box is long enough that it can stand in for the entire sill from the bolster to the draft gear face. The Kadee is too short in this regard. Shape and detailing (such as it is) is superior on the AP. The unusual trapezoidal shaped of the Kadee box is pronounced (presumably representing draft angles). This said, however, once installed these box differences will rarely in real time rarely be noticed.


I posted several days ago on the list my particular method of installing the AP boxes and couplers on my cars, and that is what I did today on car #1. Because the bottom or floor of the moulded box on the car under frame already represented the defined plane for the coupler shank, I nested the AP box into the larger box only after removing the smaller box's bottom lid. The AP box was also far too long to fit into the larger box without alteration. I could either cut the AP box short (which it is designed to allow to a defined location [see above], or I could remove the back wall of the larger box, along with the short center sill section just behind so that the AP box in toto could be set it place with its end abutting the body bolster- very prototypical. The latter is what I did.

After all tools were in place, the entire installation of the new AP couplers and boxes, and removal of all but the floors of the original moulded boxes took about 10-12" at most.

The second car was slated for the #78s. There was a cautionary hint of coming trouble when I read the very first sentence of the instructions on the packet:

"The #78 coupler is not designed to be used in the 'molded-on' round post coupler draft gear boxes [sic.]. We recommend using our scale #58 instead".

Well, you learn why very quickly: The principal 0-48 (or 0-80) fastening screw has the identical centering of the round post of the larger box (the hole in which is usually designed to house a much larger 2-56). Well, this was solved by filling the old post holes with some styrene rodding. Because of the relative shortness of the box, I also trimmed the back wall of the moulded box and the adjacent centersill so that the #78 box could set right in. The trapezoidal shape of the back of the box created only a minor fitting problem.

The second (and much bigger) problem is that unlike the AccProto box, the depth of the #78 box *cannot* be reduced to accommodate the thickness of the moulded box floor already in place. Bummer. The only solutions would be to 1) machine down the moulded box floor- not an easy job, or a job without hazard for those not prepared for it; or 2) Mount the intact box on top of the old floor and then just jack up the trucks. Since I was not inclined to do the former (I have tried it in the past and- what a lot of work!), and because the latter could be undone, I mounted the boxes intact. To get the couplers to a standard height (Kadee height gauge), however, I had to jack up the trucks a full .060" (the car looks like it is in flood pants).

Well, after small squirts of Kadee "Grease-Em" in all the new boxes, both cars went onto the layout. All coupled well repeatedly with each other, and with other cars on a 42" curve. Sometimes I thought that the #78 tended to couple easier, but if so, it wasn't consistent, or in the end- persuasive.

So, what are my preliminary conclusions, assuming my "given" that scale couplers have to be housed in scale draft gear boxes: For the majority of kits out there with already moulded-on draft gear boxes, the Accumate Proto couplers would still seem to be near the only game in town.

Although I will be removing the #78s and replacing them with the Accumate Protos, I will be saving the former to use on some brass cars that do not share the same inherent problems of the moulded boxes.

Two other packages of #78s will be returned to the LHS, to a great extent because of the "Gaps"--, which *are* truly disconcerting.

BTW, these new Fifth Avenue DD ribside cars are beautiful, and beautifully finished. I am doing some (but not a lot of) redetailing, folllowing some of Mont Switzer's good suggestions recently in MM. (I cannot work half as fast as he does- routinely).


Denny S. Anspach, MD
Sacramento, California

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