| A Prototype |
 David Elben sent me a couple photographs his brother had taken of a small Plymouth locomotive. I got an approximation of the dimensions from scaling off of the photo.
Interestingly, the wheelbase was only bout 4-in shorter then the Stanton drive I purchased so this is a good locomotive to use as a basis for mine – if for no other reason that it gives me a general idea of the size in width, height and length. |
| A Side-Frame |
 Following the pattern of the side-frame above, I extended it enough to match the wheelbase of the Stanton drive. It was around .1 in .. pretty close. In this pic I just aligned the side-frame wheel centers to the wheel centers of the Stanton drive and then moved the side-frame in to just outside the wheels. The large square thing on top is the ‘guess-ta-mated” top of the frame. Notice that in this pic it is the width of the cab.
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| Ver 1 |
 Some progress on the design. I’m trying to come up with a design for the thing so I can have the various parts 3D printed. At this point .. the sideframes, coupler pocket and bearing assemblies require only three molds. I’m trying to design it so everything locks together with tabs of some kind to keep it all fitting correctly.
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| Kadee No.5 |
| While the design of the loop and pin coupler pocket is taken from the photo of the Plymouth – this is to be an On30 critter. Since Bachmann fixed the coupler height for On30 the same as HO the next step was to see how this affected the design. |
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Not sure if this is the best – but at the moment I found this:
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 Here’s where I am at. I colored the lower half of the coupler pocket/end sill in yellow so it would stand out from the transparent blue top. The No.5 coupler/draft box is left in white. Normally the draft box is secured to the vehicle by screws from the bottom. It looks to me like I can attach the draft box through the holes from the top and into the lower coupler pocket (yellow). The blue upper bit would then also be attached to the lower bit via screws.
I had originally planned to glue everything together but the coupler pocket needs to dissassemble when needed to get to the No.5 assembly. I’m thinking the lower coupler pocket can be glued to the side-frames but I need to figure out how to attach the blue bit to the yellow bit without any screws showing. |
I went by my LHS and ended up with a Kadee No.5 coupler/draft box. The photo to the left shows a side-view of the No.5 as provided by Kadee. With this showing me the 29/64″ needed to mount the draft box I could then model the coupler in Sketchup. That allows me to play around with some designs.
| Part I | Part III |