Soldering/brazing a boiler.

[Keith HaleParticipant @keithhale68713]

Hi Brian,

See email.

Keith

[FMESParticipant @fmes]

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 info@midwestproducts.com may be beneficial.

[Brian JohnParticipant @brianjohn93961]

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 ?

[Brian JohnParticipant @brianjohn93961]

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

[Thor 🇳🇴Participant @thor]

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

[Brian JohnParticipant @brianjohn93961]

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.

[Brian JohnParticipant @brianjohn93961]

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

[Brian JohnParticipant @brianjohn93961]

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.

[JasonBModerator @jasonb]

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.

[Brian JohnParticipant @brianjohn93961]

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

[JasonBModerator @jasonb]

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

[Brian JohnParticipant @brianjohn93961]

Okay, I will check what burners are available from the hardware store but it is difficult to find anybody in these places who knows anything about what they are selling. Sometimes I get lucky if it is an ex-tradesman, but usually any questions are met with blank stares !

Is 3/8'' BSP standard for all brands ?

Edited By Brian John on 19/11/2014 09:30:45

[Ian S CParticipant @iansc]

If the piston on your little wobbler is a bit loose, take it out and turn a bit of a groove just a bit below the crown of the piston, and wrap a twisted bit of Teflon plumbers tape in the grove, put it all back together, it probably won't go faster, but it will have more power.

In the 4 or 5 wobblers that I'v built, the cylinders have been built up using tin lead solder. The pistons made by drilling, and tapping, and the con rod screwed in, except for the little one where the piston/con rod are one piece stainless steel.

Ian S C

[JasonBModerator @jasonb]

Ian, Brian does not have a lateh yet.

The Sievert stuff is not 3/8" BSP nore is my Bullfinch so no and I doubt your Mapp gas torch has 3/8" BSP on it, probably 7/16x28tpi

[Brian JohnParticipant @brianjohn93961]

I have ordered some more brass rod 7/32''  to have a go at making my own piston but without a lathe it could be difficult. How do you find the EXACT centre of the piston in order to drill it for the con rod ? I have tried doing it by eye but do not even get close. There must a be a trick or a tool to do this ?

The other problem is damaging the outside of the piston when you hold it in a vice prior to drilling and tapping.

Edited By Brian John on 19/11/2014 10:26:40

Edited By Brian John on 19/11/2014 10:27:28

[pgk pgkParticipant @pgkpgk17461]

<<How do you find the EXACT centre of the piston in order to drill it for the con rod ? I have tried doing it by eye but do not even get close. There must a be a trick or a tool to do this ?>>

Measuring for the centre of a circle the manual way is a centre finder.. a tool that is simply an angle around 90degs with a ruler edge that bisects that angle. Mark from several points around the circumference to allow for inaccuracies of the tool. Woodturners use a cheap plastic device or an engineers combination square set.

I needed to make some simple thumbscrews recently without access to lathe but I do have a bench pillar drill of dubious accuracy. To bypass marking for a centre – The solution I came up with was to drill a hole in a scrap of timber clamped to the drill shelf the diameter of the large end, drop a piece of stock into the hole and drill the centre hole without adjusting anything but the drill bit change. My fit was tight enough to get away with it or you may need to glue the stock in to stop it spinning. Most glues will soften with heat.

[Ian S CParticipant @iansc]

Jason, yes he does, as far as the grove in the piston, even if he only has a hand drill, if you can Brian fit the piston in the drill chuck, and get to work with a file, whole models have been built this way, just a bit difficult mounting a hand drill in a fixed position so you can crank with one hand, and file with the other. Must try it in practice.

Ian S C

[Brian JohnParticipant @brianjohn93961]

There are no grooves or piston rings on this cylinder. I will turn the piston down in the drill until it fits the cylinder as you described. I have already done such things a few times. Who would have thought there were so many uses for a cordless drill ?

Yes, the hole in the timber should work. I was also think of putting the piston in a piece of 1/4 inch tubing (or the closest fit) then drilling down into that with a close fitting drill bit until I made a mark dead centre.

[Brian JohnParticipant @brianjohn93961]

I have spent all morning at the hardware store and  BOC Gas talking about torches and burners. Here is what I intend to buy to solder the boiler :

handle BK2119

hose BK8179

neck tube and full flame burner BJ2146

ultra pin point burner (for small fittings) BJ8842

Plus an LPG 1.25 kg gas cylinder as used for camping.

**LINK**

All up it is about $140.

 

 

Edited By Brian John on 20/11/2014 12:55:14

Edited By Brian John on 20/11/2014 12:59:35

[FMESParticipant @fmes]

Hi BJ,

I emailed Midwest as you had some difficulty and they advise that the boiler is SOFT SOLDERED, hope this helps

Info

To

me info

Nov 20 at 6:22 PM

Good afternoon,

The boiler is soft soldered.

Thank you,

Traci Gregory

Customer Service Manager

400 South Indiana St/ PO BOX 564

Hobart, IN 46342

Phone: 219-942-1134 ext 316 Fax: 219-947-2347

E-mail:tgregory@midwestproducts.com

Website: http://www.midwestproducts.com

"When Precision Matters"

[JasonBModerator @jasonb]

Lofty, if you look back through the thread somewhere you will see that Brian wants to use the boiler to practice his silver soldering, that is why he is doing it that way.

[FMESParticipant @fmes]

Really jason? I also saw that he tried to contact Midwest without success.

Only trying to be proactive.

[Brian JohnParticipant @brianjohn93961]

Thank you for that email address ; that will be useful.

Yes, I need to practise my silver soldering/hard soldering. I assume that Midwest mean for the boiler to be soft soldered because they recommend cleaning the metal thoroughly before fluxing and soldering. I gather from recent advice that there is no point to cleaning the metal prior to hard soldering as the large amount of heat involved oxidises the metal anyway so cleaning it is a waste of time.

NOTE : I will clean the metal anyway

[JasonBModerator @jasonb]

Brian, don't know where you got that idea but you do need the metal to be clean. The areas covered by the flux which is applied before you start heating will be protected and not oxidise.

Have a read of CuP's best practice and see what it says about cleaning

[Gordon WParticipant @gordonw]

What ever you finally decide, don't forget that you cannot silver solder if there is any trace of soft solder near the joint.Soft solder, ie lead/tin, can be used after silver solder.

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