I've got a soft spot for portables, I like the idea of a design that was pretty much sorted out by 1850 still being built by the thousand eighty years later with only the most minor of changes along the way. When I go to our local builders merchants, Jackson's at Lincoln, you get a very real idea of the size this industry once was - their premises are the old Robey works, across the road is Siemens where once were Clayton & Shuttleworth. Both were huge concerns - Clayton's had a comprehensive set of railway sidings running into the works to ship out the engines they built, Robey built everything from ploughs through portable engines, innovative steam rollers right up to naval guns (indeed the building where I collect cement from is still known as the "gun shop", where they made barrels).
This engine is built to 4 1/2 inch scale, based on a Foden boiler and cylinder block. The builder is an accomplished engineer with many fine engines to his name, including a Fowler B6 Showmans, Clayton roller and Foden overtype wagon all in 4 or 4 1/2 inch scale. He currently has two Fosters and is working on a Price scarifier for the Clayton roller, itself a very rare and beautifully-built engine. In years gone by, he owned a ten ton Marshall roller.
Steel boiler, expanded steel tubes, working pressure 100psi, feed by mechanical pump and injector. Cast iron cylinder block, twin cylinder, simple expansion with mechanical lubricator. As far as specification goes, that's about it - the model, like its full-size forebears, is a simple machine intended to do a job of work with minimal amounts of fuel and maintenance. It is very well put together and runs beautifully.
The video shows the engine running in the yard, as you may be able to make out it was a filthy afternoon with rain coming down in intermittent squalls. It sat outside running for an hour, gently making pressure as it ran until the safety valves lifted - shutting down the damper a notch let it run just on working pressure with next to no attention while we warmed up inside with a mug of tea.
Despite the originals being made in their thousands and sold all over the world, portable engines are very rarely modelled. Bill Hughes did a nice design for a 1 1/2 inch scale Marshall - I had a good one in some years ago, but never since - and there are a couple of other designs available which I've never seen rendered into metal.
Length 34 inches
Height 32 inches to safety valves, 60 inches to top of chimney
Flywheel 12 1/2 inch diameter
Weight 3 cwt