Thursday, June 28, 2018

A Blast From The Past

Having finished the Clayton commission I decided I'd try and finish some of my stalled projects before starting anything new. First up on the workbench is my build of Backwoods Miniatures Canopus. Last time this appeared on the blog was November of 2015, when I was in the middle of trying to fix all the issues with the parts supplied with the kit; on that occasion the slidebars being two narrow. While problems still remain the model is really quite close to being finished, and so I'm going to make a determined effort to see it through to completion.

After altering the slidebars and riveting the connecting rods to the crossheads, the next step in the instructions is to fit the cylinders. Not entirely surprising but it turned out not to be as simple a task as it sounds. In theory all I needed to do was drill a 0.8mm hole through each of the two whitemetal castings for the piston rods to slide through. I drilled the first cylinder with no problems at all, but drilling the second one seemed impossible. Not only did I break a drill bit but even when I'd found a second drill I just couldn't get it to drill through. I'm guessing an impurity of some form in the casting. Either way this left me with only one usable cylinder, so I decided to turn up a replacement. Fortunately I checked the one good casting against the loco before starting as in the end I had to turn up a pair of cylinders.

The instructions suggest that the cylinder should have two notches on one end into which the slidebars fit into. My castings didn't and worse still when the cylinder is held in place against it's bracket the slidebars are almost a millimetre too short to meet the face of the cylinder. So my turned replacements are the same diameter as the cast parts but about 1mm longer so that they fit in the bracket and against the slidebars.

While the cylinders are now a bit longer than they should be I don't think they look too out of place on the loco. Even having moved the slidebars outwards (back in 2015) the clearances are still really tight but turning the motor by hand seems to suggest there is enough space for everything to move past each other.... just. The test will be when I find where I've put the rolling road so I can give it a powered test where I can watch everything closely.

Thursday, June 21, 2018

Clayton #5843 in Ex-Works Conditon

It's been three years since I first started work on a model of Clayton #5843, and in that time I've worked on three different models. The first had issues around the print bending and was never finished. The second was built for running on Rhyd but balance issues meant the heavy pewter driver figure caused the loco to kangaroo along the track, so he had to be replaced by a plastic figure. I've now finally finished the third iteration of the model (another commission so I've still not built one for myself) that includes more weight and finally allows the nice pewter figure from Andrew C Stadden to take it's place in the "cab".

It's new owner has requested it in ex-works condition (so they can have it weathered to match existing stock) and so here it is fresh from the paint shop.

While it would benefit from a little more running in (difficult on my short O14 test track) it's running a lot smoother than previous versions with the driver figure on board and is showing no sign of bouncing along the track.

Now I really should get another set of parts together and build one for myself, but first I'll need to take a trip to the post office to get this one on the way to its new home.

And Smaller We Go...

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.

Tuesday, June 19, 2018

Test Print

A Shapeways order arrived today so I can restock a number of Narrow Planet kits, but it also included a test print....

I'll explain in a later post, but anyone want to take a guess?

Saturday, June 9, 2018

Power Options

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.