Monday, March 26, 2007

The coupling rods

The good news here is that because I've chosen to fit gears to drive all the axles, I don't need to worry too much about getting the coupling rods and crankpin relationship spot-on.

coupling rod etch

That small piece was loose when I first opened the box. I've been worried about losing it ever since so it'll be good to get this done.

Soldered, filed, the holes opened with a broach then finished with wet-and-dry.

The pins are a good tight fit, but I may need to make the holes larger to get things running when I fit the cranks on the wheels.

** May 2007 **

When I examined my prototype more closely I realised there was some more work to be done. The overlays around the crankpins are circular, and very thin. I tried to represent this by filing the overlays thinner and rounding the edges as much as I could.

the lower rod here has been trimmed

Friday, March 23, 2007

Fitting the crankpins

OK, I've changed my mind. Having thought a bit longer, I'm planning to fit the crankpins to the cranks, then fit the wheels then add the cranks.

Three reasons:

I'm finding it difficult to accurately fix the cranks parallel to the wheels.

I don't want to find that the cranks need to be adjusted further down the line.

I can make the crankpin joints stronger if I do them "on the bench".

And also, the instructions suggest doing it this way.

So, how to get the crankpins fixed perpendicular to the cranks? With the crank in a parallel clamp, I can hold the pin in the correct position with a finger while I solder (yes, the pin gets hot very quickly).

Then hold them in a drill chuck to tidy them up. I managed to get some solder around the sides of the cranks making the fold-over joint less obvious.

And now I can use the pins to help align the cranks on the wheels.

Thursday, March 22, 2007

Wheel balance weights

etch with 6 weights (larger weights for the central wheels)

Once removed from the etch these proved to be a test of patience. They're the size of a small fingernail clipping and have to be gripped tightly while the brass sprue is filed away (I use my small parallel clamp for tricky cases).

I fixed them with epoxy, and cleaned the excess off with fine wet-and-dry paper.

They look good, but I know I've got it wrong - the small weights are correct but I'm pretty sure the ends of the larger weights should lie mid-way between spokes not on the spokes as I've positioned them. I can't take them off without risking damage to the spokes so I'm stuck with them :-(

Worse things happen, but I'm disappointed - I think this is my first mistake that I haven't been able to correct.

** 28 March 2007 **

I hadn’t thought of trying to dissolve the glue but after seeing Nigel’s comment I checked on the 2mm Association Yahoo Group for suggestions. There were some posts suggesting using acetone for this.

Didn’t have any acetone handy, but thought I could try Plastic Weld (dichloromethane) which works by dissolving styrene.

This did make the glue soft enough to be scratched away with a pin-head, so I’ve now replaced the large weights in the correct position.

Wednesday, March 21, 2007

Checking out the cranks

I've decided to go with Humbrol matt black for the wheels. I'd rather use paint than any strong chemicals to colour the wheels, as they could get onto the rims and damage the running surface.

Just a first coat - I'm thinking I should fit the wheels before the second coat. But so far it looks quite pleasing.

I need to fit crankpins to the cranks and the cranks to the wheels. Opinion seems to be divided about what should be done before fitting the wheels and what after. The crankpins are so delicate, it seems to make sense to fit the wheels before adding them, but no harm in doing a "dry run" first to see what it all looks like.

crank etch

soldered and trimmed

As can be seen I had trouble getting a smooth edge on the cranks. Perhaps more solder would have helped fill those gaps?

trial fitting of cranks

There's plenty of room on the extended axle for the crank. Should it be close to the wheel or at the outer end of the axle?

With the wheels pushed closely together in the underframe, it looks as though there is still room for the crank well down the axle. Probably best to allow some margin for error though, so I'll put the cranks part-way down.

with a crankpin

These are a very generous length. I'm not sure exactly when I'll have to trim them, but even if I cut them short now, they'll still get in the way when I'm fitting the wheels onto the muffs.

Meanwhile I've realised, having painted the wheels, that I've forgotten to fit the balance weights.

Best plan now seems to be, to fit cranks and balance weights, re-do the paintwork, fit the wheels, get the quartering as good as possible by eye then add the crankpins and finalise the quartering.

Monday, March 19, 2007

Some chassis adjustments

There's a few things I need to tidy up.

When I fitted the rear spacer on the chassis I made it quite short. Now I'm thinking it may be useful to have it a bit longer, to give support to any coupling I may want to fit.

Extra spacer glued on

I haven't decided on a coupling system as such, but I will certainly want a coupling hook which I'll be able to secure on the inside with this extra spacer.

One thing that's been bothering me, is that the muff on one of my stub axles is short and moves from one side to the other when the gears change direction. It doesn't appear to affect anything, it's just annoying. I've been looking for some suitable washers for a while, but eventually find something in my "might be useful someday" box.

I think these nuts came with the Peco N-gauge wagon kits. Inside diameter is pretty near perfect for my axle steel, I just need to file one to rather less that half its width.

Works well. I could do some even thinner ones for the other muffs, but with a big model railway exhibition coming up I'll see if I can get anything there first.

Now to blacken the chassis sides (again).

I think only the lower part will be visible to any extent. I just slapped some more blackening liquid on the existing surface, taking care to avoid the spur axles. I think it's produced an interesting effect - messy black in a slightly uneven way.

Sunday, March 11, 2007

Thinking about painting

I’m now reaching the point when I need to start putting the various parts together. But some parts would be better painted first, which is giving me a headache at the moment.

Of all my modelling skills, such as they are, painting is probably the weakest. I don’t want to spoil my lovely model with poor paintwork, but looking at the “wasp stripes” on the loco ends is quite dispiriting - I know I couldn’t do that justice with my current level of skill.

Photo: Paul Appleby in Rail Photo Archive

There are also large flat areas on the sides and having just practiced with my best paintbrush, some enamel paint and an old piece of brass, I’m not sure I can even do a flat surface free of brush marks.

I’m considering three options:

1) Finish as much of the work as possible while I wait for inspiration (current plan)

2) Pay someone to do a proper job (sounds good, but might be complicated)

3) Complete it unpainted, with key parts removable for painting at a later date

I’m completely undecided over this at present, but there is some good news. Almost everything below the footplate is shades of dirty black, and my chassis, even after ten weeks of manhandling still has some of the original blackened areas. Once the wheels are on I wouldn’t expect this area to get that sort of treatment so I’m going to blacken the chassis again then put the wheels and coupling rods on. This way I can put off any decision for another few weeks.

Meanwhile I need to practice my brushwork, experiment with masking tape, and develop an idea for a stripe-painting jig.

Tuesday, March 06, 2007

The footplate overlay

The footplate overlay etch has to be secured onto the underframe. It must remain flat for a quality result, I’m told. A bad start when I cut it from the etch and it springs into a banana-shape.

There are holes for screws at each end to secure it to the chassis. My kit included 10BA screws but I’d ordered some 12BA as these were recommended by others building this kit.

Think my best chance of a secure join is a generous portion of Araldite with the screws locating it in place. Once set I check that the sections are still electrically isolated, then have to file away the excess glue squirting out the sides.

I’d filed the PCB footplate side smooth earlier, but now I look again there are a couple of places still looking a bit uneven. I fill these with a smear of superglue and file away when set.

The photo shows that the edge is still not as smooth as I’d like. This will be very obvious on the finished model, so I give it a few strokes of fine wet and dry paper. This photo also shows a gap where the PCB footplate is shorter than the etch. I need to make up the front steps to check the correct length.

Laying the steps in place, turns out the clearances are very tight here. I have to file the footplate back to make room for the steps.

The steps shouldn't protrude forwards beyond the front bufferbeam. I've filed the footplate right back so the steps will be in contact with the front sandboxes (to fit in those recesses on the side frames).

Finally the nuts have to be soldered over the holes in the overlay. Wanted to be sure I got this exactly right so I tried to solder around the outside of the nut with the screw already through it. Hopeless - as I half-expected, I soldered the screw onto the nut. Found it much easier with quick-setting glue. I hadn't really used this stuff in the past, but I'm definitely getting to like it.

Thursday, March 01, 2007

Getting the motor working 2

Some good progress in this area since last month's post.

I took off the wormwheel and cleaned thoroughly between the teeth with a glass-fibre brush, particularly what appeared to be the problem area. Still not smooth running, but an improvement.

More running-in and more lubrication continued to help.

Then I did what I should have done earlier - soldered the electrical leads to the motor terminals. With the wires supported to relieve pressure on the motor this is a very noticeable improvement. Perhaps the slight movements of the motor were causing momentary power loss from my loops of wire around the terminals.

Following up a comment on the previous post, I wired up my cheap multimeter to test the current. After some teething trouble (I'd never used it as an ammeter before), I found that the needle flickers at the "stiff" points. But this depends on the position of the motor - when it's unscrewed a quarter-turn, the flicker is more like a gentle sway. I'll have to devise a way of ensuring that the motor stays in this position once the body is fitted.

At the slowest speed without stalling, the driving wheel axles now make one revolution in over a minute in either direction.

Meanwhile I've bought a new controller - a Kent Panel Controls KFS/FC. It's fitted with a switch to turn feedback on or to a minimum. With feedback on minimum, at the lowest voltage the driving axles make one revolution in about 90 seconds, at a fairly constant 1.5mA. And at increasing speeds, the current rises to around 3-4mA.

Of course I still have to add wheels and coupling rods, but for now this seems as good as I can hope for.