Back to the Trevithick Dredger Engine Model – the lagging.
The only surviving Trevithick dredger engine, in the London Science Museum, shows no signs of ever having been lagged. I know this, because I examined it closely, recently, during my UK trip.
No lagging, no marks in the paintwork, which would indicate wooden lagging strips ever having been attached.
But, we know that Trevithick readily adopted ANY improvements to his designs, and lagging was appearing on engines at about the epoch of the dredger engine design. Plus, his engines were in use as late as mid 19th century, and lagging was well established as a normal feature by that time.
And, my model definitely needs some efficiency improvement. Using a 40kW burner to power an engine of this size is ridiculous. So I Have added some lagging.
I used about 48 strips of wood with some spares. These were cut and sanded in advance. 5mm x12mm x 130mm.
The Super glue is used to hold the wood strips in place temporarily, until the brass boiler bands are installed.
I started at the top, and worked my way down on both sides. Most effort is made in fitting around pipes and boiler bosses. Unsatisfactory strips are levered off and scrapped.
Super glue does not provide a permanent bond to copper for some reason. And it certainly will not survive the heat from steaming. But it is fine for a quick and temporary bond.
I chose olive oil to seal the grain openings of the jarrah. I know from previous firings that the temperature of the boiler shell does not exceed 100ºc. Olive oil will not smoke or flame until the temperature exceeds 200ºc, which is higher than any other common oil. Also, as a failed olive farmer, I have plenty of old olive oil. At worst, my engine steamings might smell like a fish and chip shop. And refreshing the oily surface will be quick, cheap and easy. And the olive oil will not form a skin which might peel or flake. Anyway, this is “model and experimental” engineering. If it does not work, I will make some new lagging, alright!.
And I took some more photos with my Panasonic Lumix 100-2 camera…….
Even SWMBO has relented… “It can go with the other engines”. It will, when it is finished. Still requires more painting.