Edward Adams's 2½" Gauge 'Monstrous'
With the Winson Britannia out of the way it's time to get back to the Monster!
I decided to buy the loco after all so I am happier now about doing work on it and making a few improvements.
I've had a really good look at the boiler and decided that it's going to be too much work to make it right. Apart from the hole through the water tube in the combustion chamber, the firebox crown has bulged in the middle as has the outer firebox wrapper. It looks to me as though the boiler has suffered too much pressure at some point and been over stressed. I doubt that it would pass a modern boiler exam. Also, quite a few of the firebox stays were found to leak when I tried to pressure test it initially and sealing them would be pretty difficult as the inner firebox is thick with carbon and I doubt if I could get the surfaces clean enough to even use Comsol to recaulk the stays.
So, I've decided to scrap the original boiler and build a new one to the same dimensions. I will be keeping the old one so it stays with the loco. However, I will not be fitting a combustion chamber this time but will go up a size in the tubes to help with the increased length that they will have to be. I've ordered the materials and am now £400 worse off. The price of copper etc. is ridiculous nowadays! Fortunately, I won't need to buy any silver solder as I've got a large stash of Silverflo 55 that I acquired some time ago plus some Silverflo 40.
Whilst waiting for the boiler materials to arrive I've stripped the chassis again to put a coat of paint on it and the wheels to keep future rust at bay.
Before doing that though I decided to investigate the slight leak from the exhaust when I last ran the chassis on air. By a process of elimination I pinned it down to the middle cylinder and I think that the valve was not sealing onto the portface very well allowing air to leak underneath it straight to the exhaust port. The outside valves seem to be fine.
After removing the cylinders from the chassis I rubbed the middle cylinder port face on some wet and dry on the surface plate and it did seem low around the ports. After a bit of work the port face now seemes flat and hopefully that will solve the problem. The valve itself was perfectly flat so it wasn't that that was the cause of the leakage.
Whilst I had the cylinders off I decided to drill and tap the middle cylinder for some drain cocks which it didn't have originally. I think it will need them as there is a large mass of metal in the cylinder and there will be a lot of condensation until the cylinders warm up. I'll probably fit some automatic cocks as the chassis does not have any means of manually operating ordinary ones. I'm not sure how those on the outer cylinders were meant to be operated as there was no linkage to them.
Anyway, back to my favourate job of painting (not!) but it will be nothing fancy. I'm just going to give the chassis a coat of etch primer and then use satin black paint. The rest of the loco was originally gloss black and that will stay the same.
I've got some photos of a full size NZR Kb class loco that is on display and it looks as though the whole loco has been painted matt black, motionwork and everything! I'm sure that's not how they were in real life?
Incidently, I'm picking up a part built NZR Kb at the Rugby rally in June so may finish up with another monster to keep this one company! At least the new boiler for Monstrous will be good practice for making one for the Kb. They are both very similar in size and design although Monstrous has a longer firebox.
To be continued