Tuesday, March 12, 2019

Alan Keef K12 Diesel: Origami

The K12 diesel loco features the most complex etch parts I've ever drawn up. The first version was complex enough, but once I'd realised that I'd got the bonnet side panels wrong they become even more complex. The problem is that there are two many layers involved to be able to etch the bonnet as once simple piece. What I eventually came up with is this odd shaped piece.

What you are looking at on that side of the part is the inside of the bonnet front, but the outside of the side panels. You can see two etched rebates down the sides of the bonnet front into which the detailed etched side panels will fit so that they correctly fit behind the front wrap-around.

To bend this part to shape we start by doing something odd; folding the part the wrong way. Usually you fold a part so that the half-etched line is on the inside of the fold. In this case though, to make sure the parts will lay flat against each other, we bend it so that the etched line is on the outside of the fold. Here you can see this half way through being folded flat fro both sides; note I've coloured in the rebates using a permanent marker to both highlight them and to stop glue filling them in.

Adding a small amount of glue next to the rebates and into the fold line, and completing the fold to squash the parts flat results in this slightly more normal looking piece, where the outside of both the front and sides are now on the same side of the part.

What you'll notice though is that there is metal behind the peak of the bonnet front which is clearly wrong. If we flip the part over it's easy to fold this part and snap it off; it was a sacrificial piece designed to strengthen the part during the initial folds and to ensure both sides were folded equally.

We now have an almost normal looking part which simply folds along the sides of the bonnet front.

After assembling the cab and attaching the bonnet to it, the detailed side panels then simply slot into the half etched rebates behind the front wrap-around and glued into place.

As I said, it's by far the single most complex etched part I've ever drawn, but it's both easy to assemble and allows me to accurately represent the prototype so I think that was a success, even if it did take me three attempts to get it right!

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