Sunday, November 8, 2015

Canopus: Altering the Kit Parts

It's been almost a year since I discovered that a number of the parts in the Backwoods Miniatures kit of Canopus that I was building were the wrong size. Annoyingly this seems to be a fairly well known problem so anyone who builds the kit finds themselves having to alter or replace a few parts. Specifically the slide bars sit too close to the frames and the connecting rods aren't long enough. I solved the problem of the connecting rods by having a new set etched back in February, but the slide bars needed surgery.

Having now released the kit for the Hudson-Hunslet and finished my entry to the Dave Brewer challenge I really had no excuse to use to put off having another go at finishing Canopus so today I set about altering the slide bars and building up the crossheads and piston rods.

It turned out that altering the slide bars wasn't as bad as I expected. Basically I cut them in half soldered in a piece of scrap etch and then filed back some of the central mount to allow the wider version to sit in the frames properly. From a trial fitting this looks to have worked nicely.

Strangely the crossheads and piston rods were much more trouble to assemble than altering the slide bars. Each crosshead is made from two layers soldered together with the piston rod wire trapped between them. While folding the etch in two and soldering things together works well cleaning up the grooves to allow them to run smoothly on the slide bars is a bit more of a pain. After a bit of swearing and filing they do now seem to fit and slide nicely. A quick test fit of one of my replacement connecting rods also shows that these fit within the crosshead nicely. This means the next step is to use a rivet to join the crosshead and connecting rod. Hopefully you won't have to wait almost a year to see how that turns out.


  1. I note that you haven't laminated the connecting rods, are you just using them as is? That crosshead design appears really crude! But it looks to be simple and robust.

    Do Backwoods know about the mods. required to the con. rod and slidebars I wonder?

    1. In the end I decided with the small clearances etc. I'd just use a single connecting rod rather than laminating as that means they fit nicely inside the crossheads. The crossheads themselves are very plain but seem robust to handling, especially given the amount of filing I needed to do after soldering to make them slide smoothly.

      I'm assuming Backwoods now about the problems as the first comment you get when building a Canopus is that the kit is wrong. There was even a three page article in 009 News back in 2006 describing all the problems and offering solutions. I'm guessing that given the number they sell it's not worth changing the (probably hand drawn) artwork for the etched parts.

      I've now hit another snag though as having test fitted everything it was binding like mad. Stripping the connecting rods off I've found that they aren't to blame and the chassis that was running smoothly a year ago, now isn't. I'm hoping a little bit of oil should loosen it up.

    2. There's no need to redraw the entire artwork, an additional etch could be provided with the kit to sort out that problem. Its a solution used by a least one other etched kit manufactorer.