I'm surprised to see how long it's been since I've posted a blog update - doesn't time fly? Thinking back, a lot of the modelling I've done

in the last few months either hasn't been very exciting (wiring, ballasting, tidying up fascias, that kind of thing) or hasn't been relevant

to the blog (Mustangs, radio control etc). Not that that's stopped me before!

 

As an attempt at something vaguely relevant, I thought I'd post a few shots of the current project, which is the provision of a new Comet chassis

for an elderly Hornby Fowler 2-6-4T 4P locomotive, to be followed by some remedial work on the loco body.

 

 

The story behind this model is that I've had it for about 40 years, since its original release in around 1980. Mine never ran terribly well,

alas, being grindy and prone to stalling, and with a pronounced waddle. It was in LMS red livery which was very well applied, but when

I returned to the hobby in the 90s, I set about updating all my older models to BR condition, and so the 4P was modified and repainted

and relined in black. The mods consisted of filling in the rear cab cutout,, which was altered on the real locos under Stanier's tenure,

adding outside steam pipes, and a few other details. I also added extra pickups to the chassis, but it was still not a great runner.

 

With the old-style open frame motor, I considered it not a good candidate for DCC (aside from the running qualities) so a few years

ago I acquired a Comet chassis kit for this class of engine. Getting the wheels then took another year or two as there has been a problem

with Markit's supply.

 

Last week I made a start on the basic chassis:

 

 

It looks very weird without the other wheels and gubbins but importantly it works and was already a better, quieter runner than the original! The motorgearbox, by the way, is a DJH AM10 with 50:1 gearing. It's more than enough for my layout but as these things could get up to 80 MPH, a 40::1 gearset might also be appropriate.

 

The next step was to add pony and bogie wheels - already looking a bit more presentable:

 

 

In this condition I did some extensive testing and found that the model ran quite reliably once I had a bit of weight in the body. A slight tendency to derail was cured by adding more weight in the smokebox.

 

It was then time to start adding cylinders and motion:

 

 

In this picture, the cylinder etches are in place, with slidebars added, but nothing else. However, it's enough to establish that there aren't going to be any clearance issues with the moving parts. There's ample room for the crossheads not to foul the coupling rods, and the bogie swing is unaffected by the cylinders.

 

One thing I did do, to help with clearance, is to file a rebate into the front of the double-later coupling rod, so that the first crankpin washer is able to sit a bit nearer to the wheels than the second and third  one. Once soldered on, the crankpin washer was also filed down as far as II dared, while still enabling it do its job. However, as mentioned, the clearance turned out to be generous. As a note, I also added one fibre washer to the front axle to restrict the side-play to the minimum.

 

Then into the fun zone!

 

 

Connecting rod and cross-head (with drop link) fitted. I do this one side at a time and test thoroughly before carrying on. With these Comet slide bars, I make up the slide bars as per the instructions, then do a minimum of fettling on the slidebars themselves. The crosshead, instead, gets all the major attention with files, until it's free to move the entire length of the necessary travel with no resistance. Any slight stickiness at this point tends to vanish with a drop of lubrication. Note that the connecting rod is unconstrained on the center axle, but the model runs quite happily in this condition.

 

The lost wax crossheads are supplied over-long so need to be trimmed to length. I've learned the hard way to take this slowly, nibbling away a bit at a time, rather than ending up with a crosshead that's too short!

 

Onward:

 

 

In this image, the front bit of the valve gear has been fitted and tested, but the return crank is still be assembled. Again, it's a question of testing one bit at a time. Valve gear isn't that hard to assemble, compared to its reputation. The trickiest bit is settling on a preferred method to articulate the moving bits, be it rivets or soldered pins. My first two sets of valve gear were rivetted, because I couldn't get to grips with the pin method (mostly because I was being thick - see footnote below!, but the pin method turns out to be much quicker, easier and is more easily reversed if a problem occurs. With Comet gear. as here. there shouldn't be any snags because it's all well designed and works as intended. I didn't have to adjust, shorten, lengthen or do much more than adding a few subtle bends to aid clearances.

 

The only thing where valve gear can cause a little trouble, I've found (and bear in mind I've only done five sets) is that the connecting rod can snag on the ends of the slidebars when the wheels are at 6 or 12 o'clock, or indeed both. This can be solved by a combination of adding a slight but barely detectable bend to the connecting rod, near the crosshead joint and/or filing or very slightly bending the ends of the slidebars. The desired clearance only has to be a tiny, so sometimes only a tweak is needed to get it all running smoothly. In this case I added a slight bend and then filed the backs of the skidebars - but really only minimal work.

 

What's the white thing at the front? It was pointed out on Wright Writes that the ride height appeared to be somewhat high. So I made a jig set for the 8'6" boiler pitch, and the lower edge of the horizontal bit should line up with the midline of the boiler -- which is doesn't! After some discussion, it appeared to be the case that the Comet frames make life a bit difficult in this regard, so some modification needed to be done to lower the cylinders a smidge and get the body sitting as low as possible.

 

Over the next couple of days I worked to reduce the body height as much as possible, within my means, while also plugging on with the rest of the valve gear:

 

 

 

The valve gear is now complete and working. No hitches were encountered, but as always, the last major bit - fixing the return crank. rod and associated gubbins to the motion bracket, was a pain! It's not hard, just fiddly and swear-inducing. At least with this loco, the return crank doesn't get anywhere near the other moving parts, so no further tweaking was required and I was pleased with how smoothly the valve gear worked as assembled.

 

 

And finally, a coat of paint begins to help it all look a bit better:

 

 

However, we're not done! Work now turns to the body. When I upgraded this model to late LMS/BR condition about 25 years ago, I didn't do a great job of filling in the rear cab cutout

or of applying the lining, so some remedial work is needed. Whether it will amount to a complete repaint and relining--job is up for grabs but at the moment I'm hoping to do some patch

repairs, as the BR black is nicely applied. Compared to the earlier photos, you'll notice how the entire outer layer of varnish and weathering has been largely removed - mostly because it

was coming away anyway, just by handling! I removed the rest with a cotton bud and alcohol. I've no idea which varnish brand I used at the time, but it obviously wasn't very durable. Hiwever,

no bad thing in the long run...

 

Hope this has been of interest so far and I'll aim to post an update on the body mods in due course.

 

Cheers!

 

Footnote: regarding rivets versus pins, I couldn't get pins to work for the following reason. I was thinking of forming the joint between two moving parts in an analogous manner to a rivet, which retains the two pieces but isn't fixed to either of them. What i didn't realise was that a pinned joint can (and must!) be soldered to one of the two moving parts. As soon as as I got my head around that, and stopped trying to form a soldered blob onto the pin without it being attached to either moving part, it all became a lot easier! Just use a paper space between the two bits of valve gear, plenty of flux, a hot iron, a dab of solder, and get in and out fast, and it works! The pins need to be genuine brass dressmaker's pins - I got a lifetime's supply from ebay for a few quid.