Finally I'm making that small boiler, this is the first boiler I've made. Although it's very small and below the size that requires independent testing (less than 3 bar litre) my plan is to hydraulically test it and do all of the normal sign-off testing that is required.
Would be good to hear from people who have experience making boilers and testing them.
chainsawd (Mar 17, 2021)
This boiler is just 117mm high and you can see it here alongside the traction engine:
I have now hydraulically tested this to 2x working pressure
I used a simple garden sprayer - a small modification to the nozzle to fit a pipe. This easily gets to 100psi and I think it would get to 200psi - need a gauge.
I've written a brief article on making the boiler.
I will share more on testing as I need to ensure no issues under steam.
A simple modification to the sprayer nozzle and you have a pump that can pressurize a water volume at over 100psi - perfect for hydraulic testing
the fixed nozzle of the sprayer seals against the rear flange of the new brass fitting
I had to use cable ties to keep the pipe secure on the nozzle with the pressure
I needed a grate for the fire, but cannot cast iron and so made one from solid. This meant I needed a jig to hold the disc:
The jig was made from aluminium and it meant I could flip the part over and so machine both sides without damaging it. There were a few steps to making a cast iron grate, but it was very enjoyable. I think the finished part looks good even though you will only ever get a glimpse of this in reality.
I'm in the process of making two fireboxes, one for methylated spirit and the other for coal. I know, why?
In all honesty I just wanted to have a play and see. This way I can learn about firing with coal and see how hard it is with a tiny boiler. The boiler with the firebox and chimney is just 105mm tall (~4 inches). Air, coal mass, thermal mass, air draft etc is all going to be an issue. I will go through this and share my pains.
This small boiler is driving me a bit mad, I'm struggling to get the heat into it. It gets to temperature and pressure, but it takes ages considering the meths burner I'm using.
So I decided to instrument the boiler with thermocouples and to then do some measurements.
I'm using a Pico Technology measurement board and software, very easy to use. I will share the data and my analysis.
Jon (Apr 5, 2021)
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