Small Boiler

[editor@glue-it.com]

I wrapped the boiler and electrically heated it so I could estimate the heat loss. This way I could then compare unclad to maximum cladding.



At the designed operating point of 40psi and 140°C bulk water temperature the heat loss unclad is ~35W and with maximum cladding it is around 12W.


The cladding is a lightweight fleece, then a aluminium coated bubblewrap.

This has made me realise that I could make a low voltage miniature immersion heater - I will post something on this.

[editor@glue-it.com]

I think I now have most of the parameters for an optimised design of the firebox for the small vertical boiler. At last I can finish it and get back to the traction engine. So, I ordered a bar of 2" mild steel hex. However, when it turned up I just couldn't turn it into swarf....



So I thought I could make the firebox from sheet metal, trouble is my sheet metal skills are not that great.



However, I'm quite happy with this, now to add a door for the meths burner and some louvres for air.

[editor@glue-it.com]

I've been struggling to get heat into the boiler. So I instrumented it to understand the heat losses and to optimise the burner location.

Then I made two types of steam raising blowers.

Left: compressed air jet Right: electric suction fan

What is interesting is that both give a similar performance. Below is my calculated heat input to the boiler versus time for the two blowers and you can see them switched on, off, on and then finally off.


The heat input to the boiler using the simple methylated spirit burner increases from ~50W to ~350W with either blower on.

[editor@glue-it.com]

A video describing the blowers and the data

[editor@glue-it.com]

Finally I'm back to the 1/20th scale Burrell traction engine. My new problem to solve and design is the cylinder block.

I have an idea for creating a plate that is silver soldered to the boiler and forms the joint. The cylinder is then mounted one side and the boiler the other.



Me offering up the Stuart 10V that is 1.5x too big at 3/4" bore and stroke. The Burrell will be 12mm bore and stroke.



This bracket would be easiest made from brass, however, it's best to avoid using brass due to dezincification.

[editor@glue-it.com]

Back onto the traction engine and whilst waiting for material for the cylinder block I roughed out a steering wheel.



This is 22mm in diameter (~7/8")

[editor@glue-it.com]

I turned the other side, filed the spokes and then tumbled it for an hour.



It's not perfect, might have to make another one, but were traction engine steering wheels perfect anyway?

[editor@glue-it.com]

I've now added a fast handle to the wheel. A complete steering wheel for the Burrell, around 6 hours of work

[editor@glue-it.com]

The cylinder block has taken some thought. The single cast iron block bolted to the boiler forming a seal felt difficult to achieve at this scale.

My solution is to create a saddle with an upright backbone that becomes the mounting plate. This part can then be silver soldered to the boiler.

This saddle part is shown with the green cross-hatching, the boiler shell with orange cross-hatching.

This is the roughed out part sat on the traction engine

[rendoman]

That project is wonderful!