5" Gauge LNER A4 'Silverfox'

[oldnorton]

Yes, looks nice Adam. Replacing big hex nuts with a more scale fitting always helps and is worth the extra effort.

[mbrown]

I raised an eyebrow at your comment that 7.25" fittings look more in keeping than 5" ones - but you are absolutely right, they do.

"Scale" is a funny thing....

Best wishes

Malcolm

[pault]

Hi
I’m a little late to the party, but a few thoughts.

Have a look at modeleng.proboards.com/thread/7812/7-1-4-dyno-car, it does show that radiant superheaters do work. Unfortunately it doesn’t show how they fair against spear end superheaters.

People judge a lot about the steam circuit and superheating in particular by what comes out of the chimney. This is actually a poor indicator.

The main factors governing if you get fluffy white clouds out of the chimney are the ambient air temperature and the temperature of the steam/gases coming out of the chimney. If the ambient air temp is low enough to condense the steam quickly you will get fluffy white clouds.

As far as what comes out of the chimney, in the ideal world it would be relatively cool, with the bulk of the heat in the steam having been converted into power at the wheels and the combustion gases having given up most of their heat to produce steam.

Imagine a loco on an autumn morning which supplies steam with identical properties in two different scenarios.

Scenario 1, same amount of superheat, loco driven at on the regulator in full forward gear hauling a heavy load. The steam leaving the blast pipe will still have a lot of heat energy and a relatively high temperature. Because of the way the loco is being worked the exhaust gases are relatively hot. This may show as a clear exhaust on a cool day.

Scenario 2, same loco, same degree of superheat, same load, loco driven with the regulator wide open and speed controlled by the reverser which is wound well back. The draft on the fire will be far less as steam consumption is significantly lower which will result in cooler combustion gases at the chimney. The steam is being used far more expansively in the cylinders (removing more heat from the steam) and so the exhaust steam is at a much lower temperature. This can result in white fluffy clouds under the same ambient conditions as scenario 1.

I have made and fitted a number of radiant coaxial superheaters and they have all worked quite well. One thing I did was make the CSA of the out and back passages the same as much as possible, if that makes sense

A word of warning to those who let water carry over on a regular basis. I have on my desk the spear end of a 15” gauge superheater which failed. The lower element is ¾ blocked with solids from water carry over. When you carry the water over the dissolved solids come over in the water. Then the water evaporates leaving the solids behind. Over the years this can kill the efficiency and ultimately the elements of a superheater. If anyone wants to post a picture of this, I’ll email it to them if they send their address to me.

Regards

Paul

[Cro]

Hi Paul,

Thanks for sharing the great info, I did have a read of that when I was trying to decide and it was the only thing that spoke about them working but I decided that I felt there was a restriction in the current element tube Dia’s and the ‘dry’ steam was passing down the center which to me didn’t seem the correct way of doing it so I thought I might as well stick with what I know!

Malcolm, I fully agree and you know what I’m like but I think due to the nature of the boiler layout and gauge glasses it does lend itself to looking ok. If I were to look at photos they probably should be smaller but this just looks ‘right’. I’m not going for full on scale with this, just a good looking model that I can use and enjoy.

Adam

[Cro]

Little update on the superheaters I dropped off with the welder before Christmas.

All done and leak tight, he said he found a couple tricky to get right and the forming of them wasn't easy so if we did it again a tool would be needed to help close the gap. I think I would change the angle to give them a bit more space to work as well. They said £5.00 a spearhead but I gave them 10 as it seemed too little to me.

Untitled by Adam Cro, on Flickr
Untitled by Adam Cro, on Flickr

Time to make the jointing pieces for the ends and get them made up for soldering.
Adam

[Cro]

A little bit of progress here with the superheaters, the main assembly work is complete just leaving the dry header ends to be made and soldered in place but need to pop the boiler back in the frames and align things with the steam pipes in the smokebox. The main header needs to come off the boiler for the final assembly but all looking as planned so far.

Untitled by Adam Cro, on Flickr

Adam

[Cro]

Little progress has been made over the last few months in the workshop as all my spare time is at work or with family but I did manage to do some more work on the superheaters late in June.

I decided to make life easier and get the smokebox off and out the way but that was easier said than done as the steam pipes into the cylinders pass through the streamlined platework so it was a bit of a fiddle but it has made the whole job easier. It also allowed me to fit the piston valves and valve gear at the front now i could see what I was doing. They feel a good fit but a think a few thou down so I plan to do what I did to the Brit last year with the flourosint when time allows.

IMG_1918 by Adam Cro, on Flickr

The current state of play is the outer two elements are in place and all connected, only small mods to the existing pipework to allow this to fit but the design does allow some adjustment in length which is very helpful.
IMG_1919 by Adam Cro, on Flickr

Quite tight when the smokebox is back on.
IMG_1722 by Adam Cro, on Flickr

Lastly I put the blast pipe and Klychap setup in place to see how it all looks, no idea what adjustments this will need once up and running to get the steaming right but we'll learn about that when the time is right, need to get it all cleaned up first.
IMG_1908 by Adam Cro, on Flickr

Adam