Where to position the steam outlet on a horizontal boiler ?

The fire box for the boiler for the "Popular Mechanics" steam engine is made from aluminium sheet lined with sheets of asbestos. Another wick would not go amiss, although the two will boil the boiler, the extra heat will help it keep up once it has an engine to supply.

Ian S C

I did intend to build another burner with three wicks but this one with two wicks seems to be running the engine okay.

The tricky thing about the fire box is to make sure there are no gaps between the top of the sides of the firebox and the boiler itself. A lot of heat can be lost here. I am considering soft soldering the boiler to the firebox to achieve this. I will decide once the firebox is constructed.

Soot : I was wondering if raising the boiler another one centimeter above the flame might improve things ? But once the firebox is built and the boiler painted then who is to know

Edited By Brian John on 06/07/2015 12:44:49

Edited By Brian John on 06/07/2015 12:45:24

The .6mm brass sheet arrived a few days ago and I have been attempting to build the firbeox for this horizontal boiler. I thought the main problem would be cutting out the curves on the ends for the boiler but this turned out to be very easy with tin snips and a Dremel tool to clean up. The big problem is bending up the tabs on the sides.

I thought I could use a hold and fold tool for this but the brass is too thick. So then I tried the sheet metal bending pliers but I still was not getting nice sharp right angle. Some online sites suggest heating the brass to anneal it but this simply made the brass wobbly and impossible to straighten out again. It did not seem any easier to bend anyway !

I have had most success with scoring along the bend line with a large scalpel blade then bending with the sheet metal pliers then bashing it into shape over the edge of a piece of timber. This all seems quite primitive. Is there a better way ? How would you have done it ? I should have used some brass angle as internal supports and soft soldered the whole thing together but I thought this would be easier

NOTE : I had ordered a few extra pieces in case I ran into problems

Edited By Brian John on 05/08/2015 08:08:21

This is the completed firebox : it's even square It just needs two boiler bands now. I am waiting for my dies from the UK to tap the brass to do this. That ''heat resistant paint'' on the boiler is not all that heat resistant and I am thinking of burning it all off. There is no genuine heat resistant paint available in Australia ; nothing that will withstand contact with direct flame.

Edited By Brian John on 07/08/2015 07:23:04

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

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..

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

Finished boiler on its stand and ready for testing :

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

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

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

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

is there an echo in here?

Neil

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

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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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.

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

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.

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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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