Saving Onehunga’s port
Asteam engine, Auckland’s Wayne Larsen will tell you, is a relatively simple piece of technology, with far fewer moving parts than any internal combustion engine. But, he will add, it’s also a wonderfully elegant invention, a fluid song of shining metal, rotating with grace. A movement he never tires of watching.
Scores of steam-powered launches operate around New Zealand today – and a number of them are fitted with engines Wayne has built. These are not restored engines – they are built from the ground up, starting with design, casting and machining, through to assembly and fine-tuning. All from a backyard garage.
Though a trained automotive engineer, Wayne has always been fascinated by steam engines. His love affair began, he says, as a boy watching the synchronised movement of the engine in the ferry that took his family on outings to Motuihe Island in the 1960s.
The steam expertise and precision machining skills were largely self-taught, though he learnt a “helluva lot” from the old-timer engineers who tackled the 1980 restoration of the William C Daldy – the historic tug that steams around Auckland’s Waitemata Harbour as a tourist attraction.
“I volunteered to help with the restoration. Many of the chaps who’d operated her engines over the years were also involved, and one them – Graham Wilkinson – taught me most of what I know today.”
Since then Wayne has gained a formal steam qualification, and is often the old tug’s chief engineer for her trips around the harbour – a mantle he’s happy to have ‘inherited’ from his teachers.
“She’s a fascinating vessel. Her twin, triple-expansion engines – rated at around 900hp each – are the largest in any New Zealand steam vessel today. They sound small by modern standards, but bear in mind the torque they develop is astronomical – and maximum power is available instantly. The engines are very slow revving – they swing 11-foot 6-inch diameter props, with an 11-foot pitch.” [3.5m by 3.3m.] BUILDING A STEAM ENGINE
As his experience and knowledge developed, so Wayne’s interest expanded and eventually embraced the notion of building steam engines rather than simply operating them.
He began – 22 years ago – with an engine for his own boat – the 20-foot Victoria. “I bought the hull third-hand and I’m afraid I still don’t have a clue who built her or how old she is. But she was perfect for my engine.”
Wayne initially considered importing the various engine components from Britain but decided against this because they were over-priced and also clashed with his notions of what constituted good design. Instead, he elected to design and build the engine from scratch – engine bed, flywheel, crankshaft, cylinders, pistons, piston rings, conrods, bearings, valves, condenser pump – every single piece.
“The process involves making wooden patterns for each of the different parts, which I send to Papakura’s South Auckland Foundry. I tell them what the castings are for, and leave it to the metallurgists to make sure the quality of the cast-iron is suitable for building an engine.”
While the engine’s major components are cast-iron, items such as the crankshaft and conrods are machined from high-tensile steel. The condenser pump, bearings and valves are machined from phosphor bronze, and there is plenty of copper tubing.
Wayne’s garage is equipped with two lathes, a milling machine and a 13-tonne hydraulic press – and there’s an impressive selection of
micrometers and Verniers in attendance. He operates each of these with the finesse and delicacy of a neuro-surgeon, working to tolerances of a “few thou”.
Victoria’s engine is a twin-cylinder model. It looks surprisingly small for a 20-foot timber launch, but at its maximum 350rpm it powers her to a comfortable six knots – her displacement speed. And even though it appears to be a fairly basic engine, with the revolving crankshaft and conrods clearly visible, there are intriguing features.
It’s direct drive, for example, with the prop shaft attached to the flywheel. “Because maximum torque is available instantly,” says Wayne, “there is no need for a reduction gearbox. You advance the throttle to introduce the steam into the cylinders and away she goes.”
And, um…..reversing? Well, it’s just a matter of shifting a lever – steam enthusiasts know it as a Stephenson Link – from ahead to astern. It quickly and smoothly reverses the direction of the engine’s rotation.
The crankshaft is another unusual piece of design. Unlike many twin-cylinder petrol/diesel engines where the pistons fire 180o apart – the interval between the pistons on Wayne’s engine is only 90o. Because…?
“It ensures that one of the pistons will always be on a downward or upward stroke, which makes for immediate operation and effectively delivers two power pulses in each
revolution. If they were 180o apart, one at top-dead-centre and the other at bottom-deadcentre, the engine may struggle to turn over.”
THE BOILER
The only part of the power train that Wayne doesn’t build is the boiler. “In New Zealand, recreational steam boats are governed by various boiler codes and they’re limited to an operating pressure of 100psi. Boilers have to be fabricated by a certified boilermaker – it’s not a DIY project.”
Victoria’s boiler is fired by coal. Many steam boat owners prefer to run their boilers on used cooking oil, which Wayne concedes is probably more efficient and a little cleaner. “But I prefer coal because it’s more traditional.”
He is very particular about the coal he feeds into the boiler. “It usually comes from Huntly and it’s generally pretty good, but occasionally it’s contaminated with stones, and I carefully pick them out before feeding the boiler.”
Steam engines have reasonable efficiency, says Wayne. “Victoria’s engine uses a small amount of coal, and almost zero water because the water’s continuously recirculated. It’s a closed-loop design, with the steam condensing back into water. The only time I really need to top up the water is when my passengers use Victoria’s steam whistle with too much enthusiasm.”
You advance the throttle to introduce the steam into the cylinders and away she goes...