"Voiding the Warranty" - Mol's experiments in 21mm gauge

[Horsetan]

On 17/4/2026 at 5:06 PM, Mol_PMB said:

As per attached spreadsheet.

CSB_calcs.xlsx 21.45 kB · 8 downloads

Interesting. I used a slightly different CSB spreadsheet and tweaked your measurements a touch....

J26_CSB.pdf

[Mol_PMB]

Slow progress today but I’m gradually populating the details.

 

 

 

I need to get some short Ross Pop safety valves for this loco, but can’t find any for sale. Might have to make my own from bits of brass rod, tube and tiny washers. 
I have a couple of sets of Markits tall ones, but I want to save those for the G2 and J15 for which they are correct. 
 

I have a very busy week ahead so there won’t be much modelling time. 

[GSR 800]

Lovely work Mol!

[Tullygrainey]

Very tidy Paul and great attention to detail. Ross pop valves do seem to be hard to come by. I had a small collection pillaged from second hand Hornby 0-4-0 Smokey Joes and the like but I've used them all up now. 

These from A Gibson aren't quite right but might be usable with work though it might be just as easy to make some from scratch as you suggest!

[Mol_PMB]

8 minutes ago, Tullygrainey said:

Very tidy Paul and great attention to detail. Ross pop valves do seem to be hard to come by. I had a small collection pillaged from second hand Hornby 0-4-0 Smokey Joes and the like but I've used them all up now. 

These from A Gibson aren't quite right but might be usable with work though it might be just as easy to make some from scratch as you suggest!

Many thanks, that's a good tip. 557 and 560 had tall Ross Pops, but my prototype 559 had short ones. In fact I think there were several types used on the class, and their appearance also varied according to which type of bonnet was fitted.

Having made the fittings for the vacuum ejector exhaust pipe from bits of rod, tube and M1 brass washers, I think I could have a go at making a couple of short safety valves the same way. 

 

[Galteemore]

That’s really nice work and neatly done. Wish my 7mm version looked as good !

[Mol_PMB]

9 hours ago, Galteemore said:

That’s really nice work and neatly done. Wish my 7mm version looked as good !

Thanks! I’m sure your larger one will look even better when it’s detailed up. 

[Mol_PMB]

I managed to find a couple of hours yesterday to use my friend's lathe to modify the axles for my J26, and to prepare a few more for other projects too.

Axles cut in half were set up in a collet and the end turned down in diameter using a homemade go/no-go gauge. There was a bit of slack in the lathe and I didn't have 100% success rate but my process improved through the batch. 

Back home this morning I prepared the brass tube sleeves and then assembled 6 axles. Four of these use the turned-down axle halves into a 1/8" OD tube to give an axle that's nominally 1/8" all along. The other two use the simpler approach of leaving the axle halves full diameter and fitting a 4mm OD tube over the halves. 

In both cases I was able to achieve a press fit and used my assembly jig to push the parts together. 

I drilled small holes in the tubes, and after the axles had been pressed together I fed some Loctite 290 into these holes. This is a very low-viscosity Loctite that seeps into the gaps by capillary action and takes 24 hours or more to set fully. So for now, I'm waiting! 

I have another busy week this week, including a flying visit to the IRRS archives in Dublin. So not much modelling time but hopefully some more research.

This week's eBay success has been the negative of this image, which will hopefully arrive in the next few days. It's good to have a clear photo of this side of the loco I'm modelling, most show the other side.

[Tullygrainey]

Excellent. Your little jig is a fine bit of work. Beautifully made and it seems to do the job well. A useful addition to your tool kit.

[Galteemore]

Excellent work all round. Photos are great - got to model that loose boiler cladding !