Monday, July 16, 2018

Track Power

When it comes to making working models getting the pickups right is really important; no pickups means no power which means the loco doesn't move. Unfortunately I always seem to struggle with pickups be that on a kit I've bought or one I've designed. As I mentioned previously, with Canopus I only have to fit pickups to one side as the chassis is live to the other wheels (a change from the original kit design) but that still means I need to fit three pickups. There is a suggestion in the instructions but no mounting point, you are just given a bit of copper clad board and some wire. After a bit of head scratching this is what I came up with.


What you can't see is that I've filed a gap in the underside of the board so it sits down nice and secure on the stretcher between the slide bars. This made it easy to position and glue in place. Phosphor bronze wires then run from the board to rub on each wheel. Amazingly it all seems to actually work. I did have to clean the wheels well, but given the amount of handling the chassis has had since I started the build that's not entirely surprising. Anyway here she is running for the first time under track power.


Not bad if I do say so myself. As far as I can tell the loco is now complete so next step will be to start thinking about a paint scheme.

Friday, July 13, 2018

Short Circuit

Short Circuit was a great 1980s film that I quite enjoyed as a kid (not my favourite 1980s film but not bad all the same), but when it comes to railway modelling the last thing you want is a short circuit; it's more likely to end in tears and you pulling your hair out rather than laughing hilariously. Now imagine my surprise that I've had to solve a short circuit issue on Canopus.

In fairness I think this issue is down to the original wheels the kit was designed for not being available when I bought mine and so a different set were provided. Originally both wheels were isolated from the axle. This means that you had to fit pickups to the wheels on both sides of the model, but that the model itself was insulated from the track. The replacement axles have only one wheel isolated and the other is live to the axle. This means that I only have to fit pickups to the isolated wheels as I can just connect the motor direct to the chassis as the power will flow from the wheels to the axle, through the bearings and into the chassis. So far so good; I hate fixing and adjusting pickups so I'm more than happy to halve the work involved.

The problem though is the trailing wheel. If you remember from a couple of posts back the wheel is mounted on a metal truck that pivots from the chassis. Now while both wheels are isolated from the axle, there is enough movement to allow the wheels to both touch the chassis and for the back of each wheel to touch the pony truck. If this were to happen to the wheel on the same side as the insulated driving wheels we'd have a short as both rails would now be connected to the chassis.


My solution to this involves two modifications. The easiest bit was to ensure that the wheel couldn't short against the chassis frames. I've fixed this by putting a piece of masking tape on the inside of the frame. To try and make sure it doesn't come off I've run a small bead of superglue around the edges and then painted it black to hide it against the frame (it's unpainted in the photo). Making sure the wheel can't short against the pony truck was harder. I went through a number of ideas for this but in the end I thinned the truck slightly and then glued a thin piece of plastic to the side (so that with the plastic the truck is still the right width).

As far as I can tell these two modifications should ensure that the wheel now can't cause a short circuit, but the real test will of course come when I finally wire up the pickups and test the loco on the track. Fingers crossed.....

Tuesday, July 10, 2018

Cylinder Drain Cocks

Whilst I may have finished most of the build of Canopus there are still a few detailed bits and pieces to work on. One issue with replacing the cylinders was that the front face didn't have any of the detail of the cast parts. I did contempate etching some covers with rivet detail, but in the end decided it would be easier to use up some scrap wire and tiny brass washers and model the cylinder drain cocks which were quite a prominent feature on the prototype.


As you can see these things are tiny and took four or five different attempts until I managed to produce something I was reasonably happy with. Each is made from two pieces of 0.45mm wire slid through a tiny brass washer (I bought the washers to fit on the crank pins). One of the wires had two 90 degree bends put in it to form the tap handle. Everything was then soldered solid nicely forming the body of the tap. The wires were all then trimmed back and the spout gently formed before being glued to the front of the cylinders.


Compared to photos of the original loco they are a little over scale, but given how tiny the parts are I'm not sure I could sensibly make them any smaller. Once everything is painted they should also be a little less obvious, and if necessary I can file the spout and handle back a little more.

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!

Friday, July 6, 2018

Powered Waggly Bits

So having fixed the cylinders to Canopus it was clear that the clearances were minimal behind the crossheads. Slowly turning the motor over by hand and everything seemed okay, although on one side it did look as if the crosshead was pushing on the retaining nut on the front flycrank. Under power everything did move but it was very jerky as the two parts rubbed against each other.

On closer inspection it turns out that when I widened the slidebars I didn't refit them completely central, so while one side was very tight for clearances there was quite a lot of space on the other side. So I've now removed the cylinders and slidebars, refitted the slidebars more centrally and then refitted the cylinders. Although the clearances are still tight I can now see daylight between the parts all through a full rotation of the wheels. More importantly under power it seems to run quite nicely.


Next up is the pony truck, which unsurprisingly will need modifying before it can be fitted, but more on that next time.