Rebuilding a 2½" Gauge LBSC Green Arrow

[John Baguley]

Thanks Pete,

I'll probably find out later today!

John

[John Baguley]

Well, I tested the boiler yesterday and it went much better than I was expecting. There are a few tiny pin hole leaks but nothing serious. The stays are all water tight and the inner firebox and combustion chamber are fine. There is a pin hole leak around the solid stay on the front tubeplate, one at the top of the firehole tube on the backhead and a couple of really tiny leaks around the blower valve. They have been previously 'repaired' with soft solder but obviously not well enough so will need to be redone.

The bad leak on the front tubeplate when I first tested the boiler must have been the superheater header joint leaking as I suspected and I was obviously mistaken when I thought that some of the stays inside the firebox were leaking.

I would guess that all the previous soft soldering has been done with plumbers solder rather than Comsol so I will have to use that to do the repairs. Trying to use the higher melting point Comsol will no doubt cause more problems than it will solve.

I'll try and modify the superheater header joint to use an O ring seal rather than a gasket.

John

[stevendavis]

Hey John,
I think I have a handle on the super heater. I think it starts at the hot head and travels into one of the larger firebox tubes twords the the fire box for a little over 8", then returns to the cylinder inlet T bushing. Is this correct? And the hollow longitudinal stay tube goes from the blast nozzle on the exhaust dome to the backhead of the boiler, is this also correct? Thanks again for all the help.

[John Baguley]

Hi Steve,

Yes, you've sussed it.

Here's a photo of my superheater and the blower pipe that connects to the smokebox end of the hollow stay

And one with them in position

In my case, the blower pipe is formed into a ring with three small holes in it to act as jets. This ring fits over the blast nozzle.

The backhead end of the hollow stay has the valve attached to it that operates the blower.

I'm glad you mentioned this as I have just spent ages trying to find the superheater etc. I thought it was with the rest of the bits in the workshop but I eventually found it in the house with the old boiler cladding. Shows why it's important to keep all the bits together in one place!

The Southern Maid is now finished, or as finished as it is ever going to be, so hopefully I will be back on Green Arrow very shortly. First job will be to get some small leaks on the boiler fixed and then get the boiler tested.

John

[stevendavis]

Thanks John!!! That helps out a bunch! Can't wait for the updates. 

[John Baguley]

Well, I have spent the last week on and off trying to sort out the boiler. It was worse than I thought with quite a few pinhole leaks. The boiler is silver soldered with threaded and caulked stays but some of the original silver soldered joints, although basically sound, seem to have a few pinholes in them which the builder had obviously tried to seal with soft solder. 

The front tubeplate was the worst and a bit of a mess and covered in soft solder so I cleaned all that off and started again. This produced even more leaks! I ended up having to reapply soft solder to a lot of the joints to cure the leaks. None of the leaks were bad, just tiny pinholes, but it was a devil of a job to get everything clean enough to properly take the solder. I ended up using a small rotary stainless steel wire brush in the Dremel and scratching the surfaces clean with a scriber and small screwdriver. Eventually I got everything on the tubeplate water tight.

The backhead had a few leaks as well. The blower valve was sealed to the backhead with soft solder and it took a few attempts to get that water tight. Again the problem was getting it all clean enough. There was also a small leak at the top of the firehole ring and one of the stays underneath the firehole was leaking from the nut. It turns out that it had been drilled to take a steel screw which had rusted away but had been drilled and tapped off centre and the hole had broken through the side of the stay into the water space. I actually managed to get the old stay out by heating it up to melt the solder and unscrewing it. I made a new stay from hex bronze, threaded it 4BA (the original was 5BA), retapped the bolier and refitted it with a bronze nut. It was then soft soldered. There were a couple of other very small leaks but they were resealed with soft solder.

I was slowly winning the battle of the leaks but as I got the pressure higher a few of the stay nuts in the firebox were weeping and a couple of rivets that had been used to hold the crownstays. The rivet heads were easy to clean up and resolder so I did all of them to be on the safe side. I thought I might struggle to reseal the stay nuts as the inside of the firebox was very dirty but after a thorough clean I managed it quite easily.

Just when I thought the end was in sight I noticed water dripping from the combustion chamber  This could be a disaster and the end of the boiler  I haven't manged to trace where the leak actually is yet but it could be very difficult or even impossible to get at to fix it. Once again, it is only a tiny leak that has only appeared once I got the pressure to hold at 160psi. Radweld anyone?

I will persevere with it for a bit longer but if it's impossible to fix then this project will be going on the back burner. I just don't want to spend the time and the money at the moment to make a new boiler. I would sooner move onto the Canadian Switcher and get that finished. At least the boiler on that is ok. If I do eventually decide to go ahead with a new boiler then I will redesign it without a combustion chamber and larger tubes.

John

[waggy]

Morning John,

Have you given thought to using Radweld or similar? Your boiler appears sound enough, just a few tiny leaks as you’ve said.

Surely worth a shot, as long as your inspector agrees.

Best regards,

Dave.

[John Baguley]

Hi Dave,

If I can get at the leaks and clean them up I think I will try putting a vacuum on the boiler and applying some Loctite 290 first and see if that sorts it. I have used that method successfully before on pin hole leaks.

I did have another quick look last night and one leak is on one of the water tube joints on the bottom of the combustion chamber nearest the firebox and I can just about get to that. The second leak is further in and not easy to get at.

I had thought about Radweld as a last resort but I presume that it coats every surface? I could be wrong. Just wondering if it would affect the heat transfer? Some people recommend waterglass and even ginger!

John

[JonL]

I've heard the waterglass one before. It worked on the boiler I saw, but I have no idea if it assists in structural integrity or just fills leaks.

[millman]

Water glass will just fill leaks, Radweld is to be avoided because it will block all the boiler fittings up, how do I know? Bloke in our club many years ago had a couple of weeping tubes in smokebox and decided he knew best and tipped a can of Radweld in, stopped the leak and stopped everything else working, totally blocked injector, blower regulator and safety valves. Loctite will work providing you can get a vacuum on the boiler to pull the Loctite into the joint.

[stevendavis]

Hey John,
I've gotten started on my Green Arrow and some of the driving wheels were already machined. They were machined to a 3.24 running surface diameter instead of a 3.375" diameter. I've also looked over the frame and it has the same issue that your does, as the side frames were machined flat at the rear, instead of having the 5/16" drop down. Does the smaller wheel size compensate for the frame? And is the current wheel size of 3.24" running surface diameter ok to run? Thanks.

Steve

[John Baguley]

Hi Steve,

Although the mainframes didn't have the 5/16" drop at the back it is added as a separate piece so the trailing frames are still at the correct height. I think the builder did it like that to avoid using a wider piece of steel for the frames and perhaps make them easier to cut out.

I don't think your smaller driving wheels will be a problem but the pony and trailing wheels may have to be reduced in diameter as well to compensate as the whole chassis will be about 1/16" lower than it should be. The height of the tender relative to the locomotive will also be affected.

My driving wheels are the correct diameter but have what my friend calls 'steamroller rims' i.e. the rims are way too thick and look a bit ugly. I'm not going to change them though as that would be even more work!

John

[stevendavis]

Thanks John!
I've debated making new frames but I'm going to try and make these work first. Looks like I'll probably need to take some measurements and make sure these are going to work out. I don't mind reducing the trailing and pony wheels if needed, but the frames are giving me pause at the moment now. I'll try and figure out how to post a pic or two.

[stevendavis]

Woops, I misspoke! I double checked the frames today and they do have 5/16 drop in the rear for the back frame. I must have looked at it with my bad eyes last time.