Dargaville & Districts
There are shades of Bert Munroe in Allan Fillery – and it's not that some people thought the Invercargill genius was a bit mad.
The Watitiri-based member of the Northern Wairoa Aero Club has poured much of the same do it yourself and make it better attitude into building what he believes is the first computer-managed seven cylinder side valve radial aircraft engine.
The four-litre engine, which was fired up for aero club members on May 30, is the result of thousands of hours research, discussion and reading plus probably a similar amount of building and experimentation.
Allan is a plumber by trade but also a self-taught engineer who can turn his hand to most things, including building much of his own home.
"Don't be afraid to step outside the square," he says.
On learning to fly he built a tiny 78cc nine-cylinder overhead valve radial engine which spurred him to want something bigger.
"But a bigger model is a bit useless so I decided to build something as big as my machines would allow."
This turned out to be four litres and capable of hauling a real aircraft around.
He opted for a side valve engine because of its smaller frontal area, then aimed to overcome its disadvantages – including poor power output at higher revs – by using technology like computer management. Seven cylinders were chosen instead of the more usual six as he says this gives a smoother power pulse.
"I've done nothing new," he says modestly.
"It is really an assembly of other people's ideas and the way I have put them together."
Ignition components, pistons, bearings and valves were purchased but most of the rest was built by Allan, including cutting the crankshaft out of a heavy steel block with an electric drill.
At times he was dealing with tolerances as minute as .02 of a millimetre.
Wax replicas – 32 in total – had to be created to make moulds for casting the cylinders.
Allan says there were worrying moments.
"There were stages where if an operation had failed it would have killed the project because of the cost.
"I held my breath shrink fitting liners to the cylinders and when assembling the crankshaft into the crank case. It was a huge relief to have it turn smoothly."
While modern car engines are computer managed Allan says few aircraft motors are.
"There seems to be a fear factor with computers but the advantages far outweigh any risk factors. They are very reliable in cars and, anyway, most computers fail on start-up."
Although he uses automotive computer technology, only two companies made systems able to handle seven cylinders.
Alan opted for a Hungarian one but post-purchase problems saw him change to a more expensive Kiwi version which produced excellent results.
However, he says programming the computer to configure with his motor was still a major exercise.
The engine has been successfully run and when fired up it created enough draft to make standing difficult several metres behind the prop.
Allan is happy with its performance but plans further fine tuning.
He says public response has ranged from interest to polite scepticism. And, yes, he does see some resemblance to Bert Munroe of World's Fastest Indian fame.
"Some people thought he was crazy too."
Currently he is two-thirds through building a plane to use the motor. But unlike his innovative engine, this is a standard design.
Alan hopes to have this project finished in about two years and has Brian Taylor lined up as test pilot.
Before this happens the motor will be run for at least 10 hours, five of them at full throttle. Then the plane must clock up 40 hours before passengers can be carried. Normally this is 25 but extra is needed because of the prototype engine.
Allan admits it would have been cheaper to have purchased a ready built engine.
"But there would have been no satisfaction in that. I have wanted to build something like this since I was 16."
He concedes that the fear of failure and the cost were scary at times. "I had to keep positive or I would have defeated myself."
- © Fairfax NZ News