We're talking about the London boats, correct? I believe they did steam trials on at least one on the Thames. Which leads to the question of whether they were shipped from London and in what condition (knocked down for reassembly)? The British were already experimenting with steel shields for their light field artillery and I wonder if this feature was incorporated in the steel TB's to protect the crew from airbursts. I'm also wondering what they were using for engines. There were 20- 40- and 80- hp (multiply these numbers by about 3 to get output horsepower as we know it) horizontal trunk gunboat engines that were built in large numbers in groups of 20 to 60 at a time and assembled by two different engine manufacturers. Also, at least 16 of these engines should have been available "war surplus" from gunboats built with green wood that had deteriorated by 1862-63 (sound familiar?). They would have been available with driveshafts, propellers, engines and boilers. As a number of these vessels had never been commissioned, the boilers should still have been in good shape. They were high pressure engines, however, without condenser and had a reputation for needing careful maintenance. Add a scotch boiler and a condenser and you had a winner - the Brits did just that by recycling pairs of these powerplants in later, larger gunboats with great success.