Tidy Wiring

So the very last task to finish off the chassis was to tidy up the wiring. Because of the way the motor slides into the body I had to be careful to keep the wires running close to the gearbox and motor side, which was achieved with a bit of masking tape, and then it was just a simple case of shortening the wires and soldering them to the motor to give this...

Of course with the wiring done and the chassis finished the obvious thing to do was to check that it still fitted into the body, and that the body didn't cause a short or rub anywhere that would cause an issue.

And to that the only thing I need to say is "sheer tea cufff, sheer tea cuff" (goodness knows how best to spell that but feel free to leave suggestions in the comments).

(Hopefully) Smoother Motion

As I mentioned in the previous post I think the poor running in one direction was down to the gearbox being able to rock on the axle when travelling one way but not the other. In an attempt to fix that I've bent the retaining clip slightly and added a small bit of masking tape as a shim to try and reduce the rocking as far as I can.

It's still not perfect but I think that's quite a bit better than before. The eagle eyes amongst you may spot that I've also painted the wheel centres and coupling rod retaining nuts red to match the drawings in my book. Just the wiring left to tidy up now.

Coupling Rods: Now with Nuts

In my previous post, having quartered the wheels I tested the chassis with the coupling rods just slipped over the pins. The next step was to add the retaining nuts that will keep the rods from falling off to then cut the pins to length.

Before fixing the rods in place I double checked both rods, removing some slight burrs from the washers that keep them from rubbing the face of the wheels, and opened out the holes in the rods slightly. With the nuts just resting in place this seemed to work nicely so I took the plunge and carefully applied some Loctite 243 to fix the nuts in place. The excess crank pin was then carefully cut away with a jewellers saw.

After a little panic where it wouldn't move at all (one of the wires had come loose from the motor; they aren't soldered on yet) I was more than relieved to see it still working nicely. You may notice it moves smoother left to right than it does right to left. After watching it closely this seems to be becuase the gearbox can rock slightly on the axle when moving right to left as the retaining bracket I fitted doesn't hold it as tight as the chassis does when going the other way. I think that should be easy enough to tweak though.

So next steps are to fix the gearbox retaining bracket, clean up and paint the coupling rod retaining nuts, and then tidy up the wiring. After all that the chassis will be finished!

Joined Up Motion

So having got the pickups working nicely I turned my attention to quartering the wheels and trying the coupling rods. Unfortunately it was at this point that I started to panic.

You may remember from the previous post that I said the live wheels where a little loose on the axles and my plan was to fix these in place using Loctite 243. The reason I started to panic was because I suddenly realised that I had no idea if the Loctite would act as an insulator. If the wheels were insulated from the axle that would be a pain and I'd need to add pickups to the other side, and there isn't much space to do that.

Having used the Loctite to fix the crank pins in place I used my multimeter to check and my worst fears were confirmed; no continuity between the crank pin and the tread of the wheel. After a little bit of head scratching I realised I had a way out.

If you remember, the axles I turned are stepped which makes it easy to set the gauge. It also means that there is contact between the wheel and axle not just within the hole in the wheel but the shoulder on the axle pushes against the back of the wheel. My hope was that if I added the Loctite to the hole from the front of the wheel and then pushed the axle in from the rear it would ensure that there was a nice contact at the back of the wheel. Of course only one way to find out.

Fortunately it all worked nicely. Quartering the wheels was nice and easy (in comparison to every other kit I've built) because I could line up the spokes with the balance weights offset by 90 degrees. In the video the coupling rod is just slotted on, along with some washers to space it from the wheels, so hopefully it works as well once I put on the retaining nuts and trim down the crank pins.

Plunger Pickups

I may have mentioned before that I really really hate fitting pickups to locomotives. It doesn't matter how well built the model is, if it can't reliably pick up poer than it's next to useless. Unfortunately I find making and fitting pickups really difficult. Sometimes it's a problem with the material either causing too much friction (a problem I had with the 24hp Hudson Hunslet prototypes) or that they aren't springy enough and end up loosing touch with the wheels.

When desiging the wheels for Ivor I made the decision to isolate one wheel from the axle, leaving the other live. This means that for one side I can pick up power from the chassis (i.e. it goes through the wheel into the axle, and then through the bearings into the chassis) leaving me with only two wheels that need pickups.

In the past the pickups I've fitted have all been of a similar design, using wire to rub on the rear or flange of a wheel. For Ivor though the kit was designed to use plunger pickups which I'd never even seen before let alone used. I bought a pack of 10 from Alan Gibson, and it's a good job that was more than I needed.

Essentially each pickup consisted of three parts. There is a small plastic insert which fits into a 2.5mm diameter hole in the chassis in line with the back of the wheel. You then fit a tiny spring to a small turned brass plunger and slide that into the plastic housing. With the body of the plunger just inside the housing you bend the thin end over. This means the plunger now can't leave the plastic insert and is springy. A wire can then be soldered to the bent end to provide the electrical connection.

Not sure how good that description was, but hopefully you get the general idea from this photo of them fitted to Ivor's chassis. Note the red wire soldered direct to the chassis to pick up power from the other side; I was originally going toput this underneath the chassis but it was a paint to get the iron in, hence scratching off some paint to solder it on the top.

With the pickups fitted I reassembled the chassis and temporarily wired the pickups to the motor for a test. Initially it was terrible. I think this was partly a lack of weight, but also I'd painted the rear of the balance weights and I think I'd strayed too far towards the edge of the wheels causing the pickups to loose contact with the metal surface. After removing a little of the paint (which you'd never see anyway) and adding blutak for weight we had this.

Clearly not perfect, but not terrible either. Hopefully once the wheels are quartered (the live wheels are slightly loose on the axle) and the coupling rod fitted to drive the second axles things should be a lot better, but given the struggle to get to this point I'm happy with that.

Crank Pins

Before I can start reassembling the chassis I need to complete the wheels by fitting the crank pins. These are simply 14BA bolts slotted through the hole in the wheel.

I'd already prepared the holes (making sure they were wide enough and countersinking the hole so that the face of the screw head was flush with the rear of the wheel) so it was just a case of adding some Loctite 243 into the hole and then pushing the screws through and into place.

The pins are obviously way too long but I'll only cut them down once I've quartered the wheels and added the coupling rods, because if I cut them now it makes adding the retaining nuts more difficult.

A Painted Chassis

Not much progress to report really, but I've moved on from having a single painted wheel to having all the parts for the chassis painted and ready to re-assemble.

The next job will be to fit the crank pins to the wheels, and then I'll need to think about the pickups as I re-assemble the axles and gearbox. Once I have a chassis that picks up it's power from track I can then look at quartering the wheels and fitting the connecting rods. In other words there is still lots to do before I move on to painting the body. No idea how fast I'll get through all that but I'll be sure to post again as soon as there is more progress to report.

A Painted Wheel

In parallel to trying to determine the right colour of green paint to use, I've also been experimenting to try and find the best way of painting the wheels. Obviously I need to keep the paint off the flange and tread to ensure it can pick up power from the track. I initially thought about 3D printing some masks that would allow me to spray (at least the primer) onto the wheels and while they did work, I found they didn't give the best result around the edge of the wheel face. So I resorted to painting them by hand.

My first attempt involved painting on black primer, then the green for the rim, and then painting the spokes red. This worked but I found the very stark transition between the paint and the brass wheel tread was very obvious. What I've ended up doing is cleaning the wheels thoroughly, and then using Birchwood Casey Brass Black to darken the face of the wheel. The tread was then polished to remove any that had run down the side, before again applying paint, primer, and matt vanish; all by hand with a brush.

So far I've fully done one wheel. I'm sure the result could be better, painting between the spokes is a pain, but I'm happy with how it looks. More importantly I think it matches up with the pictures in my book pretty well.

Now I just need to paint the other three wheels.

Colour Matching

With the curved handrail made up, I can think about moving on to painting Ivor. There is still work to do to the body (filling some gaps etc.) before it can be painted but I want to get the chassis painted and fully assembled, including pickups and coupling rods, first. Whilst I can easily paint the chassis black I also need to paint the wheels. These are always depicted as having red spokes and central boss, with a green balance weight (when it's drawn) and rim. The problem is what colour green should I use?

The instructions suggest that the model should be painted using "Plastikote 104S Enamel Paint Garden Green" but to my eye looking at this photo (lifted from the instruction sheet) that is way too bright a green.

Given I'd like to use a paint I can use both with a brush and in the airbrush I had a look at the Vallejo Model Air colour chart I have (possibly a bit out of date now) to try and find a good match. The problem is that the colour of Ivor also seems to change from drawing to drawing in my childhood book and in the end I couldn't find a single colour that matched perfectly, although I did find four colours that seemed close to what I needed. A little bit of shopping later and I had four dropper bottles of paint. Of course paint in a bottle can be very misleading so I made up a quick test piece.

I tried to replicate the final colour as close as possible (I settled on using a brush rather than the airbrush for speed) by giving the brass a black undercoat, then adding a patch of each colour, before sealing with a matt varnish. The numbers are part of the code of each paint so that I know which is which. My inital thought was that the one on the left (Model Air 71.006 Light Green Chromate) might be the best match. I know it's tricky giving varying lighting conditions and problems of the camera trying to correct etc. but does anyone want to have a guess before we go any futher?

Armed with the test piece the next step was to try it against some of the plates in my book. First stop, the front cover

Now I've always thought that the front cover image is a bit dark, but my first thought of the paint on the left does look like a reasonable match, at least amongst the four paints on the test piece; the two on the right have way too much blue in them.

Next I had a look at the classic drawing of Ivor singing with the choir for the first time.

As you can see the colours are much brighter than on the front cover, and now I think the second colour (Model Air 71.095 Pale Green) is a much better match, although not perfect.

I had a further flick through my book though and settled on this plate from the story where we first meet Idris

Now to my eye that second colour is an almost perfect match to that plate, or at least as good as I'm likely to get without trying to mix my own custom colour. What does everyone else think?