The Caffeinated Engine Driver

If you cast your mind back about a month (before I finished the Clayton and started back on Canopus) I was looking at tiny chassis for a project, specifically the power bogies from a KATO Centram. Having settled on a chassis I've been slowly designing the rest of the model.


So far I've finished the footplate downwards; the body will be an all etched affair that slots onto this base. The test print fitted fairly well (a couple of support pins need resizing slightly for a better fit) so I better get on with designing the rest of it.

As to what it's a model of...... I'll let you guess a while longer yet.

A couple of posts back I talked about converting the KATO 11-107 to a tiny 4 wheel chassis in the hope it would be small enough to fit a model I'm working on. Turns out that although it's small it's not small enough, not by quite a long way, so I've had to have another look at power options. The result is that I'm trying another well made KATO power unit but this time taken from one of their Centram models.



Not only is the tram model tiny (it's N gauge after all so a scale of 2mm to the foot) but it's been modelled so as to leave the inside empty so you can add your own passengers. This means that all the drive components are hidden under the floor. In fact the model contains two completely independent power bogies which when removed look like this.


Each wheel is just 4mm in diameter which gives you some idea of just how small and compact these are. The circuit boards drive the lights as well as reducing the track voltage to protect the tiny motor, and can be replaced by a simple resistor if you want to make things even more compact.

The problem though, is that when removed from the model there is no connection between the pickups and the circuit board and motor meaning they don't work. The tops of the pickups are the rounded brass pieces sticking up on either side between the wheels. When assembled into the Centram these rub on phosphor bronze strips which connect the pickups to the circuit board which in turn powers the motor.

Now most people solve this problem by soldering wires to the pickups, but you have to be fast. Not only are the pickups touching the plastic casing, but inside the chassis a set of plastic gears run alongside each pickup and they are easily melted if you get the pickups too hot. While you might get two chassis from one model, the model still costs between £80 and £90 (you have to shop around but this is a common price; I got mine cheaper by buying a second hand "as new" model) and so you don't want to destroy a £45 chassis by lingering too long with the soldering iron.

My solution was to design a small clip (which you saw in the earlier post balanced on a 5p coin) which could retain two pieces of phosphor bronze rod which would in turn rest upon the pickups.


It's not the most innovative piece of design work ever but it does the job. The slots for the rod to fit in are slightly undersized, to ensure a tight hold, and directly inline with the pickups so that the rod has to flex slightly ensuring a good push against the pickups. It means that all the soldering can be done away from the chassis and then the rods just clipped in place, and can be easily dismantled again if need be.


You could cut the wires on the chassis and solder them directly to the rods (via a resistor) but I'm going to retain the circuit board for now to use the lighting circuit so I've just soldered on loose wires to prove the system works, which were then wrapped around the terminals on the circuit board. The nice thing is that it opens up using the chassis for anyone who owns a soldering iron no matter how bad their soldering is, without any chance of damaging the chassis, so I'd call that a success even if, as I said before, the design isn't going to win any awards.

While I've not had lots of time for modelling recently I've been pondering a number of locos that, given the time, I would like to model. As with a lot of the other locos I've modelled in the past these tend to be quite small engines leaving me with few, if any, options for powering them. When I hit this problem with the Hudson Hunslet 24hp diesel I ended up designing a custom chassis for it, and I might still take this route, but in the interim I've been looking to see what existing chassis I might be able to adapt.

The KATO chassis from Japan have a good reputation for reliability even if they can run a bit fast; I've used one in the past when I built my first OO9 loco. Most of their chassis are, however, quite a bit bigger than I'm currently looking for. Or at least that was what I thought until I read a short article by Roger Lycett-Smith in issue 263 of Model Railway Journal (MRJ).

Roger had built a model of a tiny open-cab 4 wheeled Ruston using a KATO 11-107 chassis which starts out looking like this.


Clearly as it arrives, it's not going to be much use for building a 4 wheeled loco. It turns out though, that inside the white casing the motor sits above one of the bogies (which isn't driven) and is connected via shaft and universal joints to the gear train on the other bogie. What Roger had done was to rearrange this setup so that the motor was directly connected to the gear train. My attempt at replicating this resulted in...


Having now done this myself, I've discovered that the instructions in MRJ don't quite make sense. Roger states that...

The power bogie, worm removed from it's carrier and fitted direct to motor shaft, which has been slightly shortened and a brass strip made to secure the motor to the bogie

Unfortunately the shaft on the motor is no where near long enough to pass through the worm, and certainly not long enough to need shortening. In fact if you only attach the worm to the motor shaft it wobbles around quite loose in the housing; this might be partly due to me not having permanently fixed the motor in place but even so I would imagine it might lead to unnecessary wear of the gears if they are moving around too much. My solution, has been to fix the worm to the motor shaft and then insert the original pin the worm was on from the other end. This means the worm is now supported at both ends as before. It also means I have a rotating shaft onto which I'm wondering if I could fit a small flywheel; a job for the lathe next time I have enough desk space to turn it on.

I've not soldered wires onto the pickups yet as I'm considering some more radical butchering to fit the loco I want to model, but I have tested that it runs nicely like this by attaching power direct to the motor terminals.

While it's certainly not the smallest chassis, it has the advantage of being made from reasonably high quality parts which are known to be reliable, and it uses a proper 12v motor. Plus the chassis are cheap; you can buy them in the UK for about £24, although if you are happy to wait you can get them direct from Japan for around £14.

While in the UK many of the ready to run locomotives are produced by Hornby, Bachmann, or Dapol there are many other companies which produce locomotives and roling stock. In Japan, for instance, KATO are one of the main manufactures of HO and N gauge models. One of the ranges they produce in N gauge is the Pocket Line Passengers. I'm guessing the name comes from the fact that the range is quite cheap, and so could be bought with pocket money, and in fact a full set consisting of track, controller, a steam locomotive and two carriages costs just £45. Mind you its cost is reflected in the quality of the models, as you can see from this publicity shot.


Now you may be wondering why am I telling you about a cheap Japanese N gauge train set? The answer lies in the carriages.

To anyone who has ever handled an N gauge steam locomotive it will probably be obvious that the locomotive in the photo doesn't actually contain a motor, there is simply no where to put one; even a micro-motor with a belt drive through the smoke box would struggle to power that model. The solution KATO have gone for is to fit the motor into one of the carriages. Basically the entire bottom section of the carriage, everything that is black, including the hand-rails on each end, is part of a small powered chassis. Now not only do KATO sell the full train sets but they will happily sell the chassis as spare parts, and it turns out that they are perfect for providing power for OO9 gauge locomotives, such as the Baguley-Drewry diesel locomotive from Narrow Planet that I'm intending to build. So a few weeks ago I ordered the chassis (it's KATO part number 11-104) from a supplier in Japan, via Amazon, for a total price, including P&P of just £13.01. It arrived last weekend, but I've only just got around to doing anything with it, and the first thing I did definitely voids any warranty it might come with!

Although the chassis is very small it is too long and slightly too wide to fit in the body shell of the Narrow Planet kit. Fortunately making it fit is fairly easy. Narrowing the chassis is simply a case of filing off the axle boxes and leaf springs, making it shorter, however, requires more drastic action.

On the way to work yesterday (after being slightly delayed after a truck hit the railway bridge in Penistone), I briefly called in at antics model shop and picked up a razor saw (specifically this one from Expo Tools). With the razor saw hacking the ends off took just a couple of seconds, leaving me with a 46mm long chassis (or around 11 foot 6 inches at 4mm to the foot scale), perfect for powering the Baguley-Drewry. One precaution I took, and which I'd recommend, was to use masking tape to cover the top of the central section while making the alterations to stop small bits of plastic getting into the motor and drive assembly.


As I haven't done anything about a track plan yet, I tested the chassis by running it around Jerusalem for an hour or so in each direction to make sure it was well run in, and it runs perfectly at both high and low speed, even over the points. So now I have the chassis sorted I can start thinking about assembling and painting the body.