A simple Stuart 500 style Babcock boiler

[coniston]

That looks a pretty damn fine job you're doing there Lennart

Chris D

[JonL]

Looks great, nice work.

[lennart]

Thank you. I hope that the boiler won't only look good but also to be an improvement to the current pot boiler.

There has been some more progress. Yesterday I soldered all the bushes into the barrel and into the end cap. The barrel bushes were secured with the blanking plugs and some pieces of wire.

I applied some correction fluid to keep the solder away from the threads and the front faces.

Babcock boiler plant (20) by Technikfreak L, auf Flickr

Since the method of putting rings of solder on the inside onte the parts worked out perfectly with the tubes, I went that way with the bushes,too. This also eliminated the chance of getting the wobbly stick of solder into places where I didn't want it to get.

Yesterday's achievements:

Babcock boiler plant (21) by Technikfreak L, auf Flickr

Today the first big heat up was done - the barrel to front end cap joint.

As I had planned some days ago, I fitted the end cap with three rivets and soldered with 55% solder. One bush joint might have remelted but I checked afterwards that all their front faces stayed parallel.

The solder formed a nice large fillet on the inside except the 2 o'clock area. It did fully penetrate though. That shouldn't be a problem I would guess.

Babcock boiler plant (22) by Technikfreak L, auf Flickr

And an outside impression:

Babcock boiler plant (23) by Technikfreak L, auf Flickr

[coniston]

You've done a nice job of the silver soldering, don't worry about the fillet not being there, it adds nothing to the strength. All the strength of the joint is between the mating parts where the joint is in shear. Actually a fillet can hide poor penetration so as long as you have a continuous silver solder line both sides of the joint and all the way round you really should be ok.

Chris D

[David]

Yes, you can see the solder is there and has come all the way along the mating surfaces.

Really neat work, looks great!

[lennart]

That is a good thing to read, that the joint should be ok.

I did the last bit of solderig yesterday evening. Just like with the front end cap joint, I assembled the parts with flux and three rivets and laid pieces of bent solder on top of the gap.

To make sure that I will get a more uniform fillet all around, I fed some more solder into the joint during the heat up.

Babcock boiler plant (24) by Technikfreak L, auf Flickr

After a first half an hour in the pickle bath, I rinsed the boiler in a pot of hot water to flush out the last remainders of flux.

Babcock boiler plant (25) by Technikfreak L, auf Flickr

To test the condition of the threads I screwed a blanking plug into one of the bushes. The thread might have gotten a little bit looser compared with when I made them, but still a pretty good fit.

I am not sure if I should pickle the boiler for another few hours to get rid of the black scale or if I should better do it by hand with scotch brite and emery paper. This would not do anything on the inside of course.

Do the threads get looser in the pickle bath, too? Or is it only the heat, that might burn them away, so that I don't need to worry about some more hours in the pickle?

This is how it looks right now. Not too pretty.

Babcock boiler plant (26) by Technikfreak L, auf Flickr

[mbrown]

Excellent soldering!

I find that a short time in the pickle cleans off all that discolouration - then a rinse in cold running water and it's a uniform pink-ish colour. I only polish it when the boiler is finished and use a fairly mild Scotchbrite pad. I wouldn't use emery as it erodes the copper more than milder abrasive. My pickle is dilute sulphuric acid.

I don't know if the pickle is likely to erode the threads - if it does, I think it would only be a little. I only tap the first couple of threads in my bushes when making them, then finish the tapping when the boiler is completed - that way the thread is started truly and the main part of the thread is unaffected by the brazing and pickling.

You are doing a very neat job indeed.

Malcolm

[lennart]

Feb 20, 2021 21:22:56 GMT mbrown said:

Excellent soldering!

I find that a short time in the pickle cleans off all that discolouration - then a rinse in cold running water and it's a uniform pink-ish colour. I only polish it when the boiler is finished and use a fairly mild Scotchbrite pad. I wouldn't use emery as it erodes the copper more than milder abrasive. My pickle is dilute sulphuric acid.

I don't know if the pickle is likely to erode the threads - if it does, I think it would only be a little. I only tap the first couple of threads in my bushes when making them, then finish the tapping when the boiler is completed - that way the thread is started truly and the main part of the thread is unaffected by the brazing and pickling.

You are doing a very neat job indeed.

Malcolm

I use citric acid for safety reasons. Maybe it is not as strong as sulpuhric. The boiler was pickeled for another two hours or so. The areas that were already pretty clean came out in the pink colour but it didn't make much difference on the dark spots. I will check, if the condition of the threads has changed during the pickling. If not, it will be pickled again.

Now to the important part: I made a set up for the hydraulic test. Since the only feed pump that I have is the one on the boiler plant, I just soldered up a pipe with two unions and connected the new boiler to the plant. The clack valve had also been made but that was nothing special that i need to show here, I think.

Babcock boiler plant (27) by Technikfreak L, auf Flickr

I reached twice the working pressure with now problem. Nothing came off and everything stayed tight - well sort of. All the solder joints did but the gasket (copper) under the large blanking plug on the right was leaking a little. Nevertheless I would call this a success.

[JonL]

I do my pickling in a cheap Tesco kettle which I bought for the purpose; it seems to clean things up very well in citric acid with a bit of heat.

Sounds like a good success, congratulations!

[David]

Very tidy job.

If you don't care about the inside of the boiler put blanking plugs in all the threaded bushes. That will keep the pickle off the threads. It's probably not necessary but you have them from the pressure test anyway.

For the inside you could fill it with hot citric acid and leave it for a few hours.

[lennart]

There has been some progress since my last post.

I gave the pickling another try but with the acid heated to about 70°C. This speeded things up a little bit but the last remaining discoloured areas were cleaed with some scotch brite.

With the basic boiler completed I made a start on the fittings.

The pressure gauge and the water gage will be commercial items which should arrive next week.

The other fittings were / will be made by myself. The safety valve was the next part to be made after the clack valve. It is of the Gordon Smith mild-pop-type, although some dimensions had to be altered to suit metric balls and springs. The 3/16" ball was replaced by a 5mm one. The dimensions around it were scaled up respectively, so hopefully the pop-effect will still be there after those modifications.

The working pressure was roughly set with compressed air and the large pressure gauge that has been used for the hydralic test.

Babcock boiler plant (28) by Technikfreak L, auf Flickr

My air line valve should probably be replaced by something more elaborate with a proper gland and spindle. The nozzle which is usually connected to the valve was an oxy-acetylene tip in its first life.

It is ideal for blowing into small holes and other confioned spaces.

A close up of the safety valve:

Babcock boiler plant (29) by Technikfreak L, auf Flickr

The main steam valve will be the next fitting to make. Maybe I will reuse the old one from the previous boiler. We will see.

I also made a start on the housing. Nothing special there. The round cut-outs for the boiler barrel were bored with a boring head. Everything else was done by hand with a hacksaw and files.

Babcock boiler plant (30) by Technikfreak L, auf Flickr

The protective film on the side panels will have to be come off before the first steaming but I will leave it on there for now.

[JonL]

That safety valve looks fantastic, artwork!