1″ Minnie boiler stays

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1″ Minnie boiler stays

This topic has 14 replies, 7 voices, and was last updated 18 November 2020 at 15:33 by Mark B.

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11 September 2020 at 10:07 #495225
Mark B
Participant
@markb43031
Continuing with my Minnie traction engine boiler, I am now at the stage where I have complete boiler with passes the initial 10psi air under water test.

The next stage is to make up the bronze boiler stays which go around the firebox. They are threaded through the boiler front back and sides into the firebox and the book describes the process as soldering / sweating them into position. My question is what is the best solder flux for this process?

I have 60/40 tin/lead solder and bakers fluid but also have lead free plumbers solder and paste for copper pipes.
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11 September 2020 at 10:07 #2953
Mark B
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@markb43031
11 September 2020 at 10:57 #495235
Simon Collier
Participant
@simoncollier74340
Are you determined to use this old fashioned method? If so, use the normal solder, not the lead free stuff. I would silver solder plain copper stays. No one I know would dream of soft soldering stays these days. Oh, and best not to use Bakers fluid in the workshop as the HCl fumes will rust nearby items overnight. Do it outside (how do I know this…).
11 September 2020 at 11:16 #495241
roy entwistle
Participant
@royentwistle24699
If I remember rightly the firebox stays also hold the hornplates so I would suggest that they must be silver soldered

Roy
11 September 2020 at 11:38 #495244
Clive Brown 1
Participant
@clivebrown1
Before condemning soft soldering of firebox stays, don't forget that hundreds, nay, thousands of traction engine boilers have been made like that, with complete satisfaction. The stays are usually different from those of loco bollers in that they are larger diameter, screwed and nutted to allow through riveting for the hornplates so are very secure.

The "traditional" soft solder is Comsol, still easily available.

If the OP has already fitted the backplate, silver-soldering wouldn't be the easiest job.
11 September 2020 at 12:08 #495254
Dave Halford
Participant
@davehalford22513
Posted by Clive Brown 1 on 11/09/2020 11:38:28:

If the OP has already fitted the backplate, silver-soldering wouldn't be the easiest job.

Why is that Clive? Torch breathing trouble?
11 September 2020 at 12:37 #495257
Clive Brown 1
Participant
@clivebrown1
Posted by Dave Halford on 11/09/2020 12:08:14:

Posted by Clive Brown 1 on 11/09/2020 11:38:28:

If the OP has already fitted the backplate, silver-soldering wouldn't be the easiest job.

Why is that Clive? Torch breathing trouble?

Yes, I realise that equipment is available toget around this this, but I suggest that it can be seen as an avoidable problem for the OPs job.
11 September 2020 at 13:21 #495265
JasonB
Moderator
@jasonb
The Minnie like most other traction engines has two types of stay around the firebox. Firstly the plain stays that are simply there to stop the two plates spreading apart and used front & back and the current method is to use plain copper rivits, even my Minnie boiler that is getting on to 35yrs old has rivits as stays not threaded and rutted rods. Thes erivit starys are silver soldered. All nine of the side stays do not need to be used for mounting the hornplates so 5 of these can also be rivits leaving a pattern of 4 for the hornplates.

Again the current method is to use solid stays, 3/8" bronze would be OK on the Minnie and there are just slipped into 3/8" holes and silver soldered in place. After testing the boiler the excess length of these 5 stays can be milled off true to the barrel and then the hornplates offered up and holes spotted before drilling and tapping for bolts, screws or studs to hold the hornplates in place.

Once you have started caulking stays with soft solder you may contaminate the boiler making it hard to rectify any leaks that are found at higher test pressures.

As with all things boiler related talk with your boiler inspector first.

Edited By JasonB on 11/09/2020 13:22:42
11 September 2020 at 18:48 #495316
Mark B
Participant
@markb43031
In answer to the first question (am I determined to use this old fashioned method?), I'd say I'm just after the best solution. My reason for considering soft soldering is because this is the method described in the book which must have worked for quite a lot of builders…

I do agree that silver soldering would be a better approach as everything else so far is silver soldered. I am also aware that cooking this thing up now it is almost complete takes a lot of heating to melt the silver solder. The final back-plate and foundation ring required a lot of heating.

Silver soldering anything to the outside of the boiler around the firebox I don't think is going to be an issue. I do worry about being able to do much inside the firebox. I tried an experiment this afternoon with my torch to see how it works when pointed inside the firebox… poorly I think is the best description. Breathing as described by Clive is very much an issue.

Although I have my throat plate and backhead stays made up I'm going to consult my boiler inspector for guidance.
13 September 2020 at 19:45 #495634
Mark B
Participant
@markb43031
I have become aware of this post from a few years ago which ended up in a scrap lump of copper and silver solder at about the same stage I am at now: PGK's 1" Minnie

Its a remarkably similar story of someone following the book in the same way as I have so far. I'm a little concerned I'm following the same route at this point.

At this point I'm at the stage of having a low pressure vessel which passes the 10psi test looking for bubbles under water. The foundation ring did take a couple of cookings up with additional copper "fillings" in the hard to fill triangles around joints of the fire box.

The next stage is to add boiler stays and I'm a little concerned that the order I'm following in the book isn't a good one. I agree that silver soldering everywhere is the way to go, but I've got difficulties applying head inside the firebox. If I stick my Sievert 2941 7.7Kw burner inside the firebox it lacks air and goes out!

What if I get a bigger burner such as the Sievert 2942 26Kw. Would that allow me to melt the silver solder on the inside purely from heating from the outside?

I have tried an experiment where I use a heat gun blowing air into the firebox whilst trying to use my torch, but this isn't really helping the breathing issue…

This is my story so far: progress

Edited By Mark B on 13/09/2020 19:52:22
13 September 2020 at 19:58 #495636
JasonB
Moderator
@jasonb
Have a look at their "cyclone" burners, these have a longer neck and draw their air in from a lot further away so you won't be sucking in burn gas.

Edited By JasonB on 13/09/2020 20:04:21
19 September 2020 at 17:18 #496733
Mark B
Participant
@markb43031
I've gone down the route of getting a cycle burner as suggested and it makes a massive difference. With the burner going out all the time I've never have been able to use soft solder even.

Now I can heat inside the firebox and having chatted to by boiler inspector (who has since discovered my post) I'm going to silver solder plain stays. These will mostly be 5/32" copper rivets. For the hornplates mounting stays I'll use 4 x 3/8" PB120 stays on each side which can be drilled through for the mountings.

For the bronze bushes I've been using material which came with the boiler kit of materials. I'm not sure what bronze it is, but it works for silver soldering. For my alternative horn plate mounting stays, is PB120 okay like this: pb120 okay?
18 November 2020 at 14:50 #508229
Mark B
Participant
@markb43031
I just wanted to update on this. The cyclone burner I purchased was a huge success and enabled me to apply good heat to the inside of the firebox. This in turn has allowed me to deviate from Mason's soft soldering approach to boiler stays to silver soldered ones. My boiler inspector was fine with this alteration as it was a clear improvement.

The end result is that last week my boiler passed its initial pressure test of twice working pressure. It held 100psi for several minutes without any drop in pressure. Very pleased with that result so I can not proceed with rest of the project.

Thanks for all points on this!
18 November 2020 at 15:10 #508237
Brian H
Participant
@brianh50089
Glad that worked well for you Mark and many thanks for reporting back on the use of a 'Cyclone' burner, and thanks to Jason for the reminder about them. Something else for my Christmas list.

Mark, did you mean PB120? or did you mean PB102? which is excellent for that purpose but can be a little difficult to turn unless you tools are newly sharpened.

Brian

Edited By Brian H on 18/11/2020 15:13:45
18 November 2020 at 15:33 #508246
Mark B
Participant
@markb43031
Yes BP102 – typo in my post! It is what I used and it cuts okay with sharp HSS tools.
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