17 hours ago, 34theletterbetweenB&D said:

The nylon used to make the plastic insulating muffs and gears, (and also whatever compound is used for the cosmetic wheelface inserts on many of the breed) has proven very apt to degrade from contact with lubricants and solvents.

That is a myth.

Nylon and all normal engineering plastics are _not_ damaged by conventional mineral oils or silicone type lubricants.

The commonest cause of failure of nylon gears is dehydration. 

Nylon 6 contains about 2.5 - 3.5% water under ideal conditions. If it dries out over time due a hot and low humidity environment, it both becomes brittle and shrinks, which can cause cracking.

Lubricant compatibility info; see page 5 for the table:

https://www.ecllube.com/resources-for-engineers/tutorials/ECL_Tips on Lubricating Plastics.pdf

A couple of examples relating brittleness to moisture content:

http://www.atlanticfasteners.com/simple-remedy-for-dry-brittle-nylon-parts/

https://onlinelibrary.wiley.com/doi/abs/10.1002/adv.1989.060090206

I've now been able to add the gas pipes to the roof to complete the model. Those who have read my blog will know that I'm quite obsessive about roof detail. It always surprises me that people spend so much time detailing the underframe which is hardly seen whilst ignoring the roof which is always visible. We don't look at models like you look at the prototype.

Having said that I'm not sure of the exact layout of the piping. I recollect a photo of what may be a Siphon C on the Highworth branch taken from above but can I find it? As the model represents the later 1920's period, I've added the thinner acetylene pipes. For bedtime reading I've been re-discovering my old BRJ magazines and an article in one of them about gas lighting showed that remarkably few Siphons actually had any form of lighting. The Siphon C certainly did though.

The plastic rod came from a model shop discovered whilst visiting my mother in a home in Axminster, Devon. Buffers is in the middle of fields but is an excellent shop with a far wider range of goods than I expected. I'm sure those in the area already know of it but if you are in the vicinity it's worth looking in.

Back to the Siphon. as so often with me, things go well until I pick up a paintbrush. I wanted to do some weathering using Humbrol washes but, stupidly, picked up the dark brown which for me dries to a high gloss finish. I consequently had to use "dust"wash to cover the gloss finish which means the model is rather dirtier than I wanted. Photographic evidence shows that like all wagons they were not cleaned and therefore the level of dirt is typical. I like the dust colour as I know when washing the car the "dirt" is light but whether that holds good for a steam railway is questionable. I do like the way that weathering picks out the fine detail. Incidentally, when it comes to weathering in the aforementioned BRJ there was an advert for a book by John Hayes, "The 4mm Coal Wagon." Look at the photos and weep.

The Siphon C was one part completed project that I wanted to finish. Another was a kit for a GWR 64xx pannier tank. Those of you of a certain vintage may remember a range of kits by a manufacturer, Stephen Poole. The 64Xxx was one of those and had, as all kits did in those days, a crude brass chassis. I rebuilt this to EM gauge using Romford wheels but it still looked crude. I probably wouldn't have bothered with it but it had been painted by Larry Goddard (brass safety valve cover?) so I thought it deserved a little attention.

Below is a photo taken in 2015 before I tried improving it.

I wanted a better chassis but the only one I could trace was the one from the Westward Models (I think) kit. This unfortunately was etched in one piece as an inverted "U" for OO gauge of course. In a fit of enthusiasm I split the chassis down the middle and using  brass spacers set the sides wider for EM gauge. There was no provision for compensation so it was fixed bearings aligned using lengths of 1/8th inch OD brass tube. I didn't want to spend much (any?) money on this so raided my spares drawers for a Mashima motor, Comet 38:1 gears and a motor mount of indeterminate origin. I had a number of Alan Gibson wheel sets and this was where the problem arose. The wheels I found were a tightish fit on the axles but not tight enough. Trying to quarter the wheels I found they slipped on the axles and even cyano would not cure the problem. If I wanted to make a proper job of this I would get a High Level gearbox and a new set of wheels. The moral of this story is if ever using wheels that are a push fit on the axle don't expect them to be a tight fit if taken on and off more than a couple of times. I had some old Romford wheels of the right size but the oversized flange and fixed balance weights were too much even for me. Incidentally these defects have been cured in the "Romford" wheels marketed by Markits.

As any layout I do is likely to be in the "uncoloured" category the 64xx won't find any use which is why I'm reluctant to spend too much cash on it. A Bachmann body too would would be better detailed. As ever though this is the modellers quandry, what to do with those efforts from earlier days when the products; look at those handrail knobs; and your personal skill level were of a lower standard than now. I think though it is worth updating, maybe a job for the next modelling season.

The other kit I mentioned in a previous blog was a GWR 2021 kit. This is being re-introduced by SE Finecast (the same range as the 517) so will wait for that to appear as it seems they are doing the chassis separately.

What you really need for accurate axle and coupling hole matching/checking is a set (3) of these.  I wouldn't know where to get them as I've had them for years.