Where to position the steam outlet on a horizontal boiler ?

[Ian S CParticipant @iansc]

The paint used for engine exhaust manafolds might do, I tried bbq paint, the black looks nice when new, but soon goes grey.

My last little boiler, the fire box is extended so that the sides go right up, and over the top of the boiler, leaving a 1/4" gap, the filler, and saftey valve, bushes are about 3/8" high, the steam dome is 1/2" high, and the 1/8" bore steam pipe goes a short distance to a little V twin, single acting wobbler, 1/2" stroke, 1/4" bore.

There is a useful little steamengine, and boiler in no 4509/4511 of Model Engineer

Ian S C

Edited By Ian S C on 07/08/2015 13:13:44

[Brian JohnParticipant @brianjohn93961]

No, the exhaust manifold paint sold here says that it must not come in contact with direct flame. I have looked at many different products. Pot Belly Black is for the outside of stoves and it is not meant for naked flames either which surprised me..

[Brian JohnParticipant @brianjohn93961]

The boilers never look finished until the boiler bands go on . I have raised the steam outlet a bit higher than I usually do : I am hoping that this might eliminate the problem of water coming from the steam outlet (priming ?) when the boiler is firing up.

Soft soldering is very easy when you have the right flux. I am using a plumbers solder from Bunnings which is a white paste. It is very similar in appearance to the white paste I use for silver soldering but obviously it is chemically different. I never did get on with those liquid fluxes when soft soldering. I used 243 degree solder used for building model trains.

Edited By Brian John on 20/08/2015 07:38:41

Edited By Brian John on 20/08/2015 07:40:36

[Brian JohnParticipant @brianjohn93961]

Finished boiler on its stand and ready for testing :

[Brian JohnParticipant @brianjohn93961]

With the lathe out of operation I had plenty of time test the new boiler. It works very well with the both the double wick meths burner and even the single wick meths burner. As you can see there is still a bit of a gap between the boiler and the sides of the firebox ; some heat is being lost there. I was thinking of building another one and soft soldering some brass strip in there to completely seal it. I am not sure it would make much difference as this one runs great with plenty of steam.

 

 

Edited By Brian John on 01/09/2015 08:03:03

Edited By Brian John on 01/09/2015 08:04:00

[Neil WyattModerator @neilwyatt]

I wouldn't bother sealing those gaps – they let the residual hat flow up and around the outside of a boiler and allow a good flow of hot flame around the underside of the boiler, it does no harm when boiling a saucepan…

If you block them the only place for the hot air to go is up the chimney, where it won't heat the boiler at all.

Most pot boiler designs like this have a narrow gap and no chimney.

Neil

[Brian JohnParticipant @brianjohn93961]

Yes, I noticed that there was not much heat going up this chimney compared to the vertical boilers I have built.

No chimney the horror ! …you must have a chimney even if only for the sake of appearance.

Edited By Brian John on 01/09/2015 09:34:26

[David Clark 13Participant @davidclark13]

The easy way to assemble would be to use brass angle rather than bending tabs up.

[Neil WyattModerator @neilwyatt]

is there an echo in here?

Neil

[Brian JohnParticipant @brianjohn93961]

Brass angle : this is what I intend to do next time. I had no idea bending 0.6mm brass would be so difficult.

[AjohnwParticipant @ajohnw51620]

It's possible to make a decent job of folding metal with maybe in your case a small engineers vice and 2 pieces of thick bright drawn angle iron and something long to fold it with. If brass is too hard it will split so I'd guess you may have half hard.

According to my law fully annealing brass involves heating to red heat and quenching in water. That's all I have ever done with it. For that I will stick to that too. Some reckon that the heat it's raised to determines the degree of softening. This might be true. It might be worth trying an extended period in a domestic oven running flat out. From a uni educational paper.

John

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[Brian JohnParticipant @brianjohn93961]

I tried heating the brass but the results were not good : the brass sheet buckled and bent to the point that it was useless. There was no way I could flatten it out again.

There is much argument on the internet as to whether annealing is necessary or if the brass stays soft without it.

[JasonBModerator @jasonb]

A lot will depend on what grade of brass you bought. If CZ120 engraving brass it will not bend well, if a softer brass like CZ108 or even CZ106 it will bend quite easily

[Brian JohnParticipant @brianjohn93961]

That would explain the different experiences people have had in bending/heating their brass. I must have bought the hard brass (online from China). I will just use brass or aluminium angle next time so no bending required.

[AjohnwParticipant @ajohnw51620]

The problem with annealing and buckling is failing to apply and even heat all over – hence suggesting a domestic oven but pass if it will achieve anything. However some control can be exorcised by heating slowly and moving the flame around all over the sheet – just like when aluminium is annealed with a torch.

Brass can only be hardened via cold working as far as I am aware and softened via heat.

John

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[Howard LewisParticipant @howardlewis46836]

Not being a steam man, am probably treading where angels would not.

Taking steam directly above the boiling water risks picking up water droplets? (G J Churchward went to lot of trouble on his loco boilers to minimise this. Admittedly, being on a loco everything did get shaken about)

Also, to help dry the outgoing steam, how about doing what Mamod did on their boilers? Which was to run the steam offtake pipe down under the boiler, through the flame and up again on the other side. Presumably this helped to dry the steam a little (Although, MANY years ago, despite this, my engine used to dribble hot water out the cylinder quite liberally!) Trouble with this is hat the, hopefully, higher steam temperature will soften the flexible tubing even more!

Howard

[Brian JohnParticipant @brianjohn93961]

I have tried to bend some 3/16 copper pipe into a ''toaster'' arrangement ie. sharp U bends but it is very difficult to get tight bends like this without crimping. I will order some more copper pipe to give it another try now that I have a proper 3/16 pipe bender. I found that the bending springs were useless for sharp bends.

[Paul LousickParticipant @paullousick59116]

Hi Howard, (I drive full size steam engines and have never been called an angel)

Most traction engines and portable engines (full size and miniatures) take the steam from the top of the boiler. The steam chest is often mounted directly on top of the boiler and takes steam thru a hole in the boiler barrel under it. Locomotives have a steam dome on top of the boiler and steam is taken from here. Traction engines are the worst for getting water in the steam because they go up and down hills and the water is not level. Also a lot of sloshing of water inside the boiler because of the movement. Water only gets into the steam outlet if the boiler is overfull or if the boiler is tilted when going down hill and it covers the steam outlet. (this causes priming and can damage an engine). The other way water can get into the steam supply is when you try and use steam at a higher rate than it can produce and water droplets are drawn into the steam instead of turning to vapor (called forcing the boiler), This should not be a problem with the small boiler in this post.

Paul

[HopperParticipant @hopper]

Another reason you can get water in the steam is an uninsulated pipe from boiler to engine. Steam condenses as it hits the cooler copper pipe. One way around this is to fit a throttling valve at the boiler outlet to "wire draw" the steam. This allows only a small amount of steam through so pressure in the pipe is sliightly lower than that in the boiler. But the steam remains at basically the same temperature so can cool down in the pipe a few degrees before it will condense.

[Brian JohnParticipant @brianjohn93961]

So perhaps I should fit a globe valve very close to the steam outlet ?

But my other problem is that I am not producing enough steam to run this engine for more than 60 seconds ; it runs out of puff. I tried my usual trick of inserting a piece of 1/8 brass tube inside the 3/16 steam pipe outlet but it did not help much that I could see. I assume that the reversing link mechanism is the reason for this as I have no problem running my other PMR engines using this boiler ie. more friction hence more energy required.

I am going to have to find way to get more heat to the boiler. This may also solve the steam condensation problem. I was going to build a three wick burner for this boiler then put the job on hold as unnecessary. I think I may go back to this idea.

[JasonBModerator @jasonb]

Brian, have a look at the boiler in this thread, It should not be too hard to add a "U" shaped tube or two under the boiler like it has which will help get the most out of your existing burners.

Another reason you may be getting water carried over to the engine is that on a new boiler the residue left from flux etc can cause the water to throth, how well did you clean out the boiler?

Are you running the engine at full notch? as its not under any load you should be able to use a notch mid way along the quadrant which will make the engine use less steam

J

[Brian JohnParticipant @brianjohn93961]

It is hard to know how well the inside is cleaned. I soaked it overnight in citric acid solution which cleaned the outside so I assume the inside was clean as well.

The engine has three speeds for each direction : slow, medium and fast. Just running on air I can get it to run on slow and medium but the ''fast'' speed seems slower than the medium speed and it does not run well on this top notch. The medium speed is its best.. No amount of fiddling seems to change this.

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