Re: 1940-1960 Draftgear & Underframes

John Degnan <Scaler164@...>

Thanks, Dennis. Further replies follow your comments below...

----- Original Message -----
From: soolinehistory
To: STMFC@...
Sent: Tuesday, April 06, 2010 6:15 PM
Subject: [STMFC] Re: 1940-1960 Draftgear & Underframes

> You're doing this without access to any of the Car Builder's Cyclopedias?
> Any of the Cycs will give a multitude of examples. The 1940 as reprinted
> by Kalmbach would be fine; newer originals are only a couple hundred
> bucks, if that, when they show up on e-bay, although I would stay away
> from any newer that the 1957 edition, because the quality and detail of the
> drawings went downhill after that point.

I am familiar with these books and their prices... which unfortunately puts them way out of my universe. But I appreciate the heads-up about the quality of the later issues just incase I am ever able to get a few.

> The first thing to understand is the prototype didn't use a box, per se, they
> mounted forged stops to the inside faces of the center sill webs to hold the
> parts, and a single retainer plate, along with a key through the coupler
> shank hold everything in place. I see you've modeled the key, so you're on
> the right track, but what you really need to ensure is that your "box" looks
> like an extension of the center sills, the same width, and the same depth.

I have managed to figure out most of this so far, and am striving for this very goal... but keeping in mind that some compromise may be necessary for the sake of keeping enough side-to-side swing room for the couplers to operate on less-than-prototypically-tight curves. However, much to my surprise, I have found that not as much compromise as I originally expected will be necessary.

> When I designed the PROTO:HO Accumate box, I made it long enough
> to extend all the way back to the body bolster so the joint would be
> hidden where the bolster bottom cover plate crosses the sills. Since this
> distance varies between different prototypes, making the box long enough
> to be custom cut to length ensures it is useful on many prototypes. I'm
> disappointed that I can't find a good close-up photo on the Accurail web
> site, but this link will take you to a PDF of the instructions, which should
> give some insight to my design intent.

I am well familiar with the Accumate box. I have seen at least three photos/drawings of it recently, and actually have a sample of it installed on one of my HO models (I model in HO as well as S). In fact, the design of the Accumate partially inspired the lengthening of my gearbox to its present length (it was shorter in an earlier drawing). I am considering lengthening it a bit more to achieve the effect you're describing. The three online references I found to the Accumate are listed below :



3. (Exploded Drawing)

I also managed to turn up the following reference today to a cut-away drawing of a 1:1 coupler :


That drawing indicated that the outside to outside distance between the center-sills is 20". This is precisely the kind of info I am looking for. (A bit ironic that this drawing was found on Sergent Engineering's server). But I also need to know the typical height of these sills, as this is not indicated on the drawing.

Would you say that this drawing represents the most common center-sill design and dimensions?

John Degnan

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