having got the chassis for the Hudson-Hunslet diesel to work the next stage was to fit the pickups so that it could collect power from the track. As the chassis is brass and will conduct electricity this process is simplified slightly as I only need to add pickups to the insulated wheels the other wire from the motor is then soldered directly to the chassis. The process is complicated though by the need to include a resistor to protect the 6V motor from the full 12V that can be supplied through the track.
As you can see there isn't exactly lots of space to add the pickups and resistor. The pickups are obvious, and they are soldered to one end of a little black rectangle which is the surface mount resistor. This is soldered to a tiny bit of copper clad board which is stuck to the chassis. The board is pretty much the same size as the resistor so you can't really see it. The black wire from the motor then feeds down through the inside of the chassis and is soldered to the other end of the resistor (the blob of solder at the bottom of the resistor in this picture). As you can probably imagine this is kind of fiddly to fit, although I amazed myself by getting it on the first attempt. I think the trick was to not use electrical solder from a roll, but to use the solder paste I've been using for kit building. As well as being easy to accurately position using the syringe it helps to hold things in place and then just a quick touch of the soldering iron creates a nice small joint. Of course the real test would be if it actually worked when placed on some powered track.
As you can see the answer is partially. The problem is that the worm nearest the pulley is now completely loose (I mentioned in the previous post that it seemed loose) and so the front wheels aren't turning. I've been given a suggestion of how to fix this without completely stripping the chassis down but I haven't had the chance to try it out yet. Either way I'm really happy now that it's picking up power from the track and moving, albeit slowly. Yes there are things to adjust to make assembly easier and I need to find places to add extra weight but I think that I've more than proved that the idea works.
To give you an idea of just how small this locomotive is here are a couple of photos of it with my other two completed OO9 locomotives, neither of which is very big.
Yes it really is tiny. In fact the body measures just 15mm by 30mm and is just 20mm tall. Not quite watch-making level of tiny but not far off!