Boiler Questions

[russell]

Hi all,

Made a start on the boiler yesterday: Trimmed the ends of the barrel, marked it out, and drilled and bored the holes for the bushes along the top.

However, reading the drawings and the articles, I realised that I don't understand it all:
1. The upper water-gauge bush is shown with a 5/16 32 thread on the bit that goes in the boiler. Obviously the alignment of this part is important and if the boiler is tapped it is unlikely that it will tighten up in the correct alignment. How should this be fitted.
2. The details of the blower tube assembly are sketchy. The front tubeplate is show to be tapped directly and I presume that the "Blower union for smokebox tubeplate" screws into this. Is it just screwed in (poor practice in copper?) or should it be silver soldered? If it is silver soldered then there is no need for the thread? At the other end the blower valve screws into a bush in the backhead. How is the tube itself fitted? Is it just threaded 1/4 40 at each end and hope for a reasonable seal? Assembling it after completing the boiler looks tricky!

Any advice gratefully received.
Regards,
Russell.

[baggo]

Hi Russell,

To get the water gauge fitting to tighten in the right position you can use copper washers (which you can get in various thicknesses) between the fitting and the boiler. What I do then is seal it with Comsol (high melting point soft solder).

The blower tube is threaded at both ends. One end screws into the blower valve and the other into the tubeplate blower union. The idea is that you screw the blower tube into the blower valve and then screw the blower valve into the backhead. At the other end the blower union is then screwed into the tubeplate and onto the blower tube at the same time.
There is no problem screwing the blower union directly into the copper tube plate but I fit a bronze bush as on the backhead.

You do need to seal the threads on the blower tube to stop steam leaking into the tube directly from the boiler. Any suitable gasket goo will do the job.

John

[russell]

Thanks John,

It makes sense now. I think I'll fit a bronze bush to the tubeplate as you do. I don't like the idea of the blower union being screwed directly into copper.

I presume the water gauge elbow goes into a hole tapped directly in the boiler. I guess this is not a problem as it will be a once and for all fitting (hopefully!)

Russell.

[baggo]

Hi Russell,

One thing I forgot to mention is that the blower valve as drawn does not have a captive spindle and could be unscrewed all the way out of the body. The same applies to the blowdown valve on the water gauge and the injector steam valve.

In the UK so far as I am aware all valve spindles now have to be captive so they cannot come out completely (makes sense really). I don't know if this will affect you or not but I think it's a good idea for safety reasons. The way I do it is to turn down the end of the valve spindle to a smaller diameter than the threaded part and then drill the hole in the gland nut to suit the spindle. The gland nut then prevents the spindle unscrewing completely.

John

[Shawki Shlemon]

Hi Russell
Baggo has given you some very good advice ,but if you are interested in some good information even if it is not mandatory in your country buy a boiler code from www.aals.asn.au/ which is very cheap and will answer all your questions and help you build a safe boiler .

[russell]

Hi Shawki,

The contents list of the Oz code looks interesting. I'll try and get hold of a copy.

There are no special requirements for home built and run boilers in France unless they are big enough to be covered by the Pressure Vessels Directive. There are some recommendations made by the national club, the CAV, but they are very basic and we are allowed to certify our own boilers if the pressure test is done in the company of one other club member.

Russell.

[bonsia500]

Hi Russell,
Does your boiler drawing show a 5/16 x 32 inlet bush on the left or right side at the front of the boiler? If is doesn't it is well worth putting one in, it makes for piping up the axle pump much easier than using the back head bushes, you can then use the back head bushes for the emergency side tank pump and injector as it is not easy to run the pump discharge under the chassis past the drop down door in the ash pan. I have run the bypass under the foot plate to the connection on the back of the left side tank

[russell]

Hi Bonsai,

No, my boiler drawing doesn't show this. Sounds like a good idea though.

I've been building Simplex for four years now. I hope it doesn't take me 30 years, I may be too old to drive it!

Regards,
Russell.

[baggo]

I'd already decided to feed both the hand pump and the axle pump into clacks at the front of the boiler and reserve the backhead bushes for the injectors. That way you're feeding the cold water into the coolest part of the boiler. It doesn't seem a good idea to feed cold water into the 'hot end' with the resultant rapid temperature change. At least the water from the injectors will be about 60°C so won't cause as much cooling around the firebox.

John

[ron]

Hi John
That's what I've done it as well. I was also going to silver solder the top gauge glass elbow rather than thread it, do you see any problems?
Ron

[spug103]

Hi all could someone please give me some dimensions for the simplex boiler, for now all i need is the overall height, barell dia, and external firebox dimensions.
regards
Ben

[baggo]

Hi Ben,

The boiler is approx 18" long, barrel diameter is 4.75". The firebox (outside) is 4" wide by 7" long. The firebox is round top of course as its made from the barrel tube with the usual side extensions. The overall height of the boiler is 7.5" at the throatplate although the backhead is only 6.25" high due to the slope of the grate.

John

[spug103]

thanks alot
ben

[ron]

As a matter of interest the boiler I bought from Western Steam recently has quite a few major design alterations to the original;
The boiler barrel and wrapper are separate, the wrapper being in one piece and joined to the barrel with an inner ring, the firebox crown stays are traditional, ie they are attached to the outer wrapper as well, there are an extra row of side stays and they are all 3/16" rather than the top row being 1/4" plus other minor changes.
Ron

[baggo]

Hi Ron,

Are the side stays closer spacing than the original or have they just fitted in another row?

John

[ron]

Hi John they're closer spaced, but the position of the top and bottom row is roughly the same.
Ron

[warthog1950]

Greetings, I cannot source 7/16" diameter copper tubing out here in South Africa for the boiler tubes. Can anyone advise on using 1/2" diameter pipes?
I will be able to get them in provided I move the top 3 tubes on the smoke box side up by approximately 1/8, they would then line up with the top of the super heater tube, and nolonger have the 3/16" slope towards the smoke box.
Regards, Kevin

[Shawki Shlemon]

I can't see any problem with using 1/2" tubes . You will need less number of tubes than 7/16" tubes , you may have to rearrange the tubes and keep everything else unchanged , but before doing that you should be talking to your boiler inspector about it.