Monday, July 9, 2018

Cutting Up A Pony

Next up in the continuing saga that is the process of building Canopus is the rear pony truck -- the original loco had a fixed trailing wheel but it pivots in the kit to help the model negotiate tighter curves. The part is supposed to be built from a simple fold up etch but the instructions go on to state that...

as supplied the bogie frame is for 10mm gauge. For 009 it will be necessary to snap off the fold-up sides of the bogie and refit them 0.5mm inboard of their original positions.
Quite why this part is designed for 10mm gauge when the rest of the kit is designed for a gauge of 9mm is simply beyond me. However, the idea that I could snap off and accurately reattach the parts just 0.5mm inboard was also a bit of a joke so I opted for a different approach.

I found a piece of brass tube with almost the same hole diameter as on the etch (the tube has a slightly wider hole) but with an outer diameter which when rested on the folded up part aligns perfectly with the axle holes. So I folded up the original etch, cut a piece of the tube to the correct size, and then held it in place for soldering using a piece of rod slotted through the original 10mm gauge axle holes and the tubing. The original sides were then simply snapped off and the sides cleaned up and filled back to narrow the truck to the same width as the tube. This was then riveted to the stretcher that will be attached to the chassis frames.

The sharp eyed amongst you may also notice that I've filled away part of the stretched just off centre. Whilst it did just fit, there was practically no daylight between the stretcher and the larger of the gears in the gear box. Even now with that section filed back there isn't exactly a lot of clearance. I'm not sure if this is yet another design issue or if it's related to the change in gears from the original kit, either way it could easily catch out the unwary.

You'll possibly also notice that clearance between the stretcher and the worm gear is also fairly minimal. I've actually reduced the length of the worm quite a bit, having now removed about one and a half turns of the gear from both ends; from one end to clear the fixing screws for the motor/gearbox and from the other end to clear the pony truck stretcher. Fortunately there is still plenty of worm gear to mesh cleanly with the large gear in the gearbox.

Amazingly, baring fitting the pickups, that's the last step of the instructions finished!


  1. It looks good. The soldered joint is a bit spattery. Can you still get Bakers fluid. That is a good flux but don't breath through your nose whilst using it as the fumes make your nose hurt something rotten.

    1. Fortunately it's not actually as bad as that photo makes it look. I took the photo before properly cleaning the part, and so not only is it covered in some left over solder paste, but also filings from reducing the width once I'd snapped the edges off. Having said that I was going for solid rather than neat so yes it could certainly be better.

  2. Powerflow is a better flux than Bakers, it does the job but isn't quite as nasty acidic.

    This is a VERY cruel enlargement of the joint. It's also a joint that needs to be structural rather than pretty. As Mark says, it will look fine in real life - it all depends on whether model railways are built to look at or be photographed.

    1. Yes, sometimes I wished I modelled in a much much larger scale so that photos were less cruel! In this case it really doesn't matter what the joint looks like at all, as once fitted it's on the inside of the chassis and you can't see it at all, and I painted it black just to make it even harder to see -- I find black paint and shadows nicely hides most of my modelling bodges :)