Picking up where I left off: Bruce, Pelton wheels and electricity

I have nothing but admiration for Bruce Comfort, engineer, historian and (in his own words) ‘general non-typical Kiwi bloke’.

Bruce wants everyone to know the story of Oamaru’s breakwater, which was built from concrete blocks laid by Moa, possibly the largest full-slewing rail-mounted travelling steam crane in the world at that time. Oh, and the blocks were made using what Bruce believes was the first large concrete mixer put into continuous work anywhere, ever.

Bruce also wants everyone to know about the borough race, which not only supplied water to the town, but played a vital part in powering commerce and industry in 19th century Oamaru.

And as I explained in my last blog, there’s now a new chapter: the centenary of mains electricity in Oamaru. Helped by a handful of experts and volunteers – and a grant from the Mayor’s Discretionary Fund – Bruce is restoring a double Pelton wheel almost identical to the one which first generated electricity in September 1918. When it’s finished, it will go on permanent display adjacent to the original power house in Chelmer Street.

Inspired by Bruce’s efforts, I decided to look into the story of Oamaru’s first electricity supply.

First, the story so far: the borough race was completed in 1880 after a whole series of setbacks. It supplied the town with fresh water, which travelled 40 kilometres from the River Waitaki to a reservoir above Oamaru, passing over nineteen aqueducts and through six tunnels along the way.

The borough race provided a consistent and mostly clean supply of water for human consumption and fighting fires. Just as importantly, it powered the local economy. Part of the design brief was to provide at least 300 horsepower of energy by delivering water under high pressure to local mills, hotels and other businesses. At the start, reciprocating engines were used: they resembled steam engines, except that pistons were pushed back by the force of water, not steam.

However, the real breakthrough came when the Pelton wheel was introduced. This was at the heart of one of the earliest forms of turbine: water injected through a nozzle collided with shallow cups (‘impulse blades’) arranged round the rim of the wheel ('runner'), turning it faster and faster. Pelton wheels were far more efficient than earlier types of water engine and were used to power anything and everything: flour mills, freezing plants, bottle washers, you name it.

Thomas Meek took the idea one step further. Realising that he could run Crown Mills 24 hours a day if he installed lighting, he used a Pelton wheel to generate his own supply of electricity.

That sparked an even bigger idea. If Pelton wheels could light a mill, maybe they could light the whole town.

Oamaru Borough Council first looked into this as early as 1898, but nothing happened until 1912 when Councillor Paterson estimated that a power station could light the streets for an initial outlay of only £12,000. Hmm, said the council, that sounds interesting: let’s set up a committee.[1]

The committee came up with a bold plan. By doubling the investment, enough electricity could be generated to power not just street lights, but also households, the hospital and businesses throughout the town.

Yes, it was bold, but the council wasn’t about to risk public money without the backing of expert opinion. They were still paying for the borough race, which cost well over double the original estimate and contributed to the council’s humiliation in 1892 when it ran out of money and defaulted on its loans. With that in mind, the council commissioned no fewer than three independent reports on the proposed electricity scheme before finally putting plans to the vote in 1914. By a margin of 510 votes to 129, ratepayers approved plans to borrow £30,000: £24,000 for the electricity scheme and £6,000 to extend the water supply to a new power house in Chelmer Street.

Then war broke out in Europe: what became known as the Great War, and later as the First World War. At first, the council – like everyone else – thought it would all be over by Christmas and that it would be sensible to delay the electricity scheme until then.

A year later, it was painfully clear that the war would not end any time soon. The council decided to go ahead anyway, raising the first part of the loan and inviting tenders to build the power house, supply equipment, extend the water supply, install cables, and so on.

Messrs Turnbull and Jones Ltd won the contract to supply equipment for the power station. They proposed to obtain Pelton wheels from Gilbert Gilkes and Co of Kendal, England, and two generators from the British Westinghouse Company.[2] All the other contracts were agreed at around the same time, and by mid-1916 it looked as if mains electricity would soon be a reality. Indeed, Turnbull and Jones said it would take just seven and a half months to complete their part of the works.

Then they hit a snag. The British government refused to license the export of the Westinghouse generators, because they might be needed for the war effort.

Telegrams flew back and forth around the world. But while the government gave approval for the Pelton wheels to be exported, they refused to alter their position on the generators.

The borough council was really worried. They were already paying interest on the loan and needed to generate revenue from the electricity scheme.

The solution was to buy a generator that was already in New Zealand. It was not made by Westinghouse and its specifications were substantially different. One engineer said it simply would not work when connected to the Gilbert Gilkes Pelton wheels. Another said, well, it might – but we’d need to modify the Pelton wheels. ‘Let’s do that, then!’ said the council. An extra loan was secured to pay for the generator.[3]

And so it was that on the evening of 30th September 1918, the mayor, Mr Robert Milligan, presided over a small ceremony at the power house in Chelmer Street. After the inevitable speeches, Mrs Mitchell turned the tap, allowing water to enter the Pelton wheel casing. A few moments later, the master switch was thrown and electricity circulated round Oamaru for the first time.[4]

Hurrah! Perfect!

Except it wasn’t. There was a problem with water pressure.

The electrical engineer, Mr Dalmer, blamed the hydraulic engineer, Mr Beal, for not properly testing the water pressure before the system was installed. For his part, Mr Beal said it wasn’t his fault that the Pelton wheels had been connected to an unsuitable generator: wheels designed to turn at 330 revolutions per minute had been coupled to a generator designed to turn at 500 rpm.[5] The two men not only fell out; they fell out very, very publicly.

Further investigations showed that pipes carrying water from the reservoir were at the root of the problem. Gratings, junctions and joints had become clogged with scrub, silt and corrosion, greatly reducing the flow of water, to the extent that it provided only 175 horsepower – a long way short of the 350 horsepower assumed when devising the electricity scheme. Mr Beal said there wasn’t much he could do about it now, short of renewing much of the pipework at huge expense. Mr Dalmer said – and Mr Beal agreed – that the best solution would be to install generators capable of running at the same speed as the Pelton wheels.[6]

In the end, the council spent a further £7000 on a suction gas engine and a new generator, to complement - not replace - the Pelton wheel set up. The net cost was reduced by cancelling the order for the Westinghouse generators, which had still not received an export licence from the British government.[7] The council also endorsed plans for the first major hydro-electricity scheme on the River Waitaki, which came into operation a few years later.

Engineers also applied some creative thinking to the Pelton wheels, improving their performance and reliability. They remained in use for nearly 40 years, providing electricity from water supplied by the borough race. After the major hydro-electricity scheme came into operation, the Pelton wheels were used as a back-up system which could be brought into use at times of peak demand or when the hydro scheme was offline. They were finally decommissioned and broken up for scrap in the 1950s.

Incidentally, while it was the borough council that initiated the electricity scheme (and took out the loan), the assets were later transferred to the Oamaru Electric Power Board.

Bruce Comfort spends a lot of time researching the history of Pelton wheels, lime kilns, cement mixers, cranes and goodness knows what else. He was naturally delighted to hear about a Pelton wheel almost identical to the one installed in Chelmer Street in 1918. After investigating further, he was even more delighted when the owner, Bede McGrath, decided to donate it to the town of Oamaru.

It was no easy task to free it from its resting place in Hari Hari, on the west coast of the South Island, but with a lot of help and the loan of a truck and driver, Bruce recovered it. It was rusty.

But now it isn’t: it’s almost completely restored.

I can’t wait to see it in situ in Chelmer Street: a grand monument to Oamaru’s pioneers and a tribute to Bruce’s passion and determination.

 

[1] Municipal History of Oamaru, published by Oamaru Borough Council in 1936

[2] North Otago Times, 9 September 1916: https://paperspast.natlib.govt.nz/newspapers/NOT19160909.2.7

[3] Oamaru Mail, 8 June 1918: https://paperspast.natlib.govt.nz/newspapers/OAM19180608.2.14

[4] Oamaru Mail, 1 October 1918: https://paperspast.natlib.govt.nz/newspapers/OAM19181001.2.37

[5] Oamaru Mail, 1 February 1919: https://paperspast.natlib.govt.nz/newspapers/OAM19190201.2.7

[6] Oamaru Mail, 1 February 1919: https://paperspast.natlib.govt.nz/newspapers/OAM19190201.2.7

[7] Oamaru Mail, 13 October 1919: https://paperspast.natlib.govt.nz/newspapers/OAM19191013.2.24

The Pelton wheel, looking soooo much better. Photo by Bruce Comfort.

The Pelton wheel, looking soooo much better. Photo by Bruce Comfort.

And by the way: the District Archive was recently given all the leather bound ledgers, minute books and logs of the power station, starting from day 1. Photo by Bruce Comfort.

And by the way: the District Archive was recently given all the leather bound ledgers, minute books and logs of the power station, starting from day 1. Photo by Bruce Comfort.