Soldering/brazing a boiler.

Having tried the small torch today for the first time, I would quite agree ...it is useless !

This is the torch I now intend to use :

**LINK**

I was worried that it would be too hot for the smaller parts but I will have to try it and see.

That may still give to local a flame, with silver soldering you want to bring the whole job upto heat and then the solder will flow, the risk of using a small flame is that you will just melt solder onto the surface where the heat is and not get a proper joint.

What would you suggest ?

The instructions for this boiler kit warn that this type of torch produces too much heat and recommend caution that the metal is not overheated.

I'd be looking at a torch with interchangable nozzels that runs of a large propane bottle, not sure what you can get down under but something along these lines would do

**LINK**

**LINK**

Or a better quality Sievert one

**LINK**

Leave the cookery torches in the kitchen for the creme brulee or skinning tomatoes! We want to braze.

All the above kit is likely to create too much heat and melt the unknown parent metals. Check with the Machinemart  salesman.

It looks like you need a fine, focused, low heat output burner. Suggest a Sievert 3938 burner fitted onto something like the Sievert PMPX or 2197 kit..

All products readily available. For more information. **LINK**

Keith

Edited By CuP Alloys 1 on 10/11/2014 16:56:45

Keith (assuming its you) is the advice of the small burner related to the 3" dia boiler at the start of the thread or as you mentioned "unknown parent material)" are you refering to the little oscillators plumbing?

J

Hello Jason

In the post I take it up from the "plumbing"

Taking it from the start ....

If the decision is to use soft solders then the 3938 burner should cope. If not put on a slightly larger burner eg 3939.

Use soft solders with different melting ranges if it helps. Alloys available with temperatures between 145 and 305 degC

If the decision is to use silver solder the 3938 will struggle.

As I understand it. the jury is out on the filler metals to be used. One of the considerations of burner selection is the melting point of the materials.

Keith

Brian Can you let us know what silversolder & flux you have bought so Keith can suggest a burner size and also what diameter the boiler is, looks about 3" to me.

Keith, Brian finds it hard to get hold of some things where he is, could you also suggest the KW rating of the burner so he can look for alternate makes if needed.

J

The boiler is 2'' in diameter

Flux is EZI-WELD 602 flux.

I purchased two solders : 8338 silver solder 245 grade 1.6mm diameter X 750mm

8339 silver solder 245 grade .8mm diameter X 1 meter

Hi Brian,

See email.

Keith

Looking through some of the other forum threads on this (mainly American) and remembering the old Mamod boilers, these appear to be soft soldered (probably plumbers solder )

As you may have limited resources, cleaning to the required standard for silver soldering would be quite a difficult task.

Perhaps a mail to [email protected] may be beneficial.

1. I have already sent an email to Midwest Products and it bounced back so I have no idea what is going on there ! Their instruction do say to hard solder it though.

2. I am curious about low, medium and high temperature silver solders. I am familiar with the process as I have put together some white metal train kits in the past using soft solder. But that was using a temperature controlled iron so I could set the temperature on my soldering iron and choose a solder to suit ie. start with high temp solder on the large parts then medium and finish with low temperature for the smallest parts.

But how does that work with silver solder/hard solder where a blow torch is used ? How can you tell the temperature of the flame ?

Disaster : As suggested above, the propane torch did not get the metal hot enough. I decided to start off with something small and easy : I tried to solder the piston rod to the piston and the cylinder to the the brass spacer as per the instruction. The flux did not turn to glass as advised, instead it turned pink. The solder would not melt when I touched the metal parts ; there is just not enough heat. I did end up with blobs of solder over many of the parts including the piston !

Oddly enough I cannot get the parts apart ! I know they are not soldered correctly as the solder did not run into the fluxed joins.

The propane torch kept flaming out when I pointed it downwards. Do they have to be kept in an upright position ?

With the equipment I have I might have to consider soft soldering the boiler. Can I use 15% silver plumbers solder from the hardware store for that ?

NOTE : The parts are sitting  in a glass of citric acid now. I will post some photos later.

Edited By Brian John on 16/11/2014 05:00:12

Hi Brian,

If you use the propane burner you link to in your 10/11/2014 07:45:49 post, you should not point it downwards. The propane container contains liquid and if turned upside down you get liquid propane out the torch end.

I use a Sievert Promatic system for silver soldering and pack firebricks around to keep the heat on the work being soldered.

Thor

I have had another go today. This time I changed things, I fluxed the joints then placed pieces of solder wire on this flux. I then applied the torch to the metal until it was as hot as I could get. The solder was almost starting to melt so then I applied the flame directly to the solder. I know this is not how it is supposed to be done but I decided to give it a try anyway. It seems to have worked but I doubt that I could use this method for soldering the boiler.

Problems :

1. I have managed to solder up the steam hole so I will have to drill that out.

2. I have dipped it in citric acid for a few minutes then worked on it with the Dremel tool fitted with a wire brush. I will put it back in the citric acid overnight. Should all the pink colour be removed from the brass ?

3. I may have stuffed up the piston. There was some solder on it and I removed it by placing the piston rod in a drill and applying 400 grit sandpaper to the surface of the piston. The piston may not be a tight enough fit in the cylinder now. I will have to try it and see. I should have used 800 grit which is what I usually use for this sort of job.

I cleaned it up and put it together and it runs like the clappers. The piston probably could have been a better fit but it does not seems to make much difference.

Edited By Brian John on 19/11/2014 06:50:09

Now back to the boiler : my supplier has advised me that the silver solder I am using is 45% silver with a melting point of approximately 650 degrees Celsius.

I'll stick by my earlier suggestion particularly as you are likely to want to make larger boilers than this one in the future to run your larger engines.

One thing to check is as you are in an appartment are there any restrictions on the size and type of gas you can keep in the building?

Yes the number gives away the silver content and its also a cadmium free one.

I did ask the hardware store and MAPP gas is not much hotter than propane gas (2020 degrees C compared to 1995 degrees C for propane).

Should the torch be removed from the propane cylinder after use (which is what I am doing) or can the torch be left attached ?

I will buy a handle and a hose for the propane torch this weekend so that I can hold the torch at any angle.

Edited By Brian John on 19/11/2014 08:09:08

Brian the temperature the gas burns at has very little to do with it. The amount of heat you get is governed by the size of the burner (bit the flame comes out of) this is usually measured in BTU or KW.

A small needle point burner may only put out 0.25kw where as something around 20mm dia will be putting out say 3kw so you can see that a larger burner will give 12 times the heat of a small one using teh same gas.

I do 99% of my silver soldering using a 22mm dia burner on a 3.9kg propane bottle. that will do small fabrications on 1/16" dia rod right upto 6" dia steel and brass fabrications.

Although mine is a Bullfinch handle and burners have a look at the data for sievert ones such as this and this