Finishing the boiler, testing and first steam run.

October 16th, 2010

As promised last time here is a picture of the throttle valve parts. It’s very simple but does the trick.

IMG_8859_1 Throttle valve parts.

After leaving the boiler to pickle I took it out and gave it a rub down with a 3m scouring pad. It came out really well.

IMG_8857_1 Boiler after pickling in Citric acid solution.

Next I had to work out how to make the threaded boiler bushes that the safety valve and other plug bolts would screw into. Some people make these from brass but you shouldn’t use brass fittings in a copper boiler.  The zinc will eventually leach out the brass eventually making it brittle. This is cause by having two dissimilar metals, brass and copper, in contact in a hot and wet environment. To be honest, for a small boiler like this it probably isn’t a problem in the short term. But I like to do things properly so I decided to get some bronze which is the preferred material to use.

Bronze is available in rods but I didn’t want to have to pay a lot of money for a 300mm piece of stock when I only needed  three small bushes. Instead I went to the local ships chandlery and for a few dollars got some bronze nuts. These I then machined down on the lathe into bushes. I used 1/4 inch ones for the end holes and a 5/16ths one for the safety valve. Below you can see the 5/16ths one machined already. The end plugs were similarly machined although I left the hex end on them.

IMG_8861_1 Boiler bushes from bronze nuts.

The boiler bushes were silvered soldered into the boiler and the boiler was pickled again. I then soft soldered in the copper outlet pipe.

IMG_8873_1_1 Steed puppet holding the finished boiler.

Once the boiler was complete I needed to test it before trying to boil water in it. One way to do this would be to connect it to the air compressor and pressurise it. This is a very bad thing to do! You should never test a boiler in this way as even a small boiler like this can be quite dangerous when filled with compressed air. The correct way to do it is to hydro-statically test the boiler. You fill the boiler up completely with water then test it. To pressurise it the best way is to use a water feed pump of the same kind the model steam locomotive people use to pump water into a boiler. Not being a model steam locomotive person I had to do the next best thing. You still completely fill the boiler with water but then you use an air compressor and air hose attached to a small manifold to pressure the boiler though the outlet pipe. The compressor and hose is safe at pressure obviously. The boiler is full of incompressible water. If there is any flaw in the boiler that would cause it to burst all that happens is the water blows out.

IMG_8886_1 Boiler testing manifold and gauge.

I made the manifold from brass pipe fittings and attached a pressure gauge and a small brass outlet pipe. I soldered the boiler outlet to this and after completely filling with water I plugged the end holes and safety valve hole with bolts and fibre washers. I then carefully increased the pressure on my compressor a little at a time and checked the boiler for leaks. Eventually ti reached 60 PSI, the maximum on my gauge, so I left it to sit for 30 minutes.

IMG_8888_1 Boiler at pressure.

After 30 minutes I released the pressure at the compressor and checked the boiler. It was still exactly the same with no leaks. Next I removed the gauge and plugged the hole in the manifold and carefully took the pressure up to 100 PSI, the most my compressor would do.  Again after leaving it for some time the boiler was fine so I considered the test a success. My running pressure will only be about 20 PSI so with the boiler tested to 100 PSI I have a large safety factor there.

After the test I tipped out half the water and rigged up a simple test stand. Since I have no safety valve yet I used a piece of chainsaw fuel hose, kindly given to me for free at the local saw repair shop, to connect the boiler to the engine.  If the pressure gets too high the fuel hose simply slides off the engine inlet pipe. I used the meths burner from my Mamod traction engine. After a few minutes I had water showing in the fuel line and a few minutes steam! The engine fired up with a quick spin of the flywheel and ran!

IMG_8890_1 Nigel running on steam for the first time!

I made a small film which is up on YouTube of course.

There are some things to note. My single sided bearing design is a bit wobbly. The bearings aren’t actually that good! I did invest in some better quality but still cheap bearings (Bones Reds for those into skateboarding) and that did help. I think you really need a bearing each side of the crank to be stable though. Also the seal between the cylinder and the port face isn’t the best as evidenced by the large puddle of water that forms there! But it does run and the throttle does work so it should be fine for the plans I am making for Nigel.

On a side note I also this week rescued a dead scanner/printer someone had dumped at the bottom of my road. I walked past if for a week and finally decided if no one else was going to clean it away I would take it and recycle what I could.  So a quick zip down the road in Vicky the MGB and I nabbed it.

IMG_8863_1 HP scanner/printer.

It was a bit soggy, having been in the rain a few nights, but I pulled it apart in half an hour or so. I separated out the useful junk from the rubbish and also stripped out everything that be sent for recycling. This was a much nicer fate than the last printer I ‘fixed’!

IMG_8867_1 IMG_8868_1 Stripped and sorted.

From this I got a nice sheet of glass, three front surface mirrors, a nice little lens unit, three DC motors and one stepper motor, two very nice precision steel shafts and two others that can be cut up for steel stock, about five different opto-sensors, various cogs and gears and a very nice 12 volt CCFL power supply and white lamp.

I also found out why it had been thrown out.

IMG_8864_1 Faulty mouse!

Explained why the bottom of the printer was full of seeds too. Some of these parts will be used in Nigel.

Not the mouse.

2 Responses to “Finishing the boiler, testing and first steam run.”

  1. Asciimation » Blog Archives » A steampunk record player. Says:

    […] from some copper water pipe. After making the boiler and a small throttle valve I was able to test the engine running on steam. Now I knew the engine ran I started on the next part of my scheme – to use it to turn a […]

  2. Bob Field Says:

    How wonderfully inventive. Takes me back to steam radio days. I have fwd link to my friends in the Melbourne Audio Club.