Aero 356 radial engine lined up with exhaust
“This is a fun engine. This isn’t a sensible engine.
“It’s just a crazy, visceral, good fun kind of thing and a real celebration of the engine. There’s just nothing cooler than a radial engine, ” enthuses Nick Mebberson, the Australian engineer behind the Radial Motion engine.
Speaking via phone from his 4000 m2 factory in the Adelaide suburb of Lonsdale, Mebberson is quick to point out that his radial also happens to be a very practical engine that’s simple and robust, with very high torque.
He explains that Radial Motion is the customer-facing brand for the engines produced by his business, Bespoke Engineering.
The ISO 9001–certified operation employs around 15 staff, including nine graduate engineers from a range of engineering disciplines including mechanical, aerospace, mechatronics, and electronics, as well as aerospace and CNC technicians.
Mebberson himself is trained as a mechanical engineer who has also developed a passion for aerospace and aviation engineering.
He has enjoyed a 20-year career in a successful family business that specialised in the design and manufacture of food grade thermoforming packaging machines.
He credits his time designing, building, and installing these machines as the key to his broad-based real-world engineering skill set.
“They were five-tonne, quarter-of-a-million-dollar high-speed packaging machines and we got a reputation for supplying the best of these machines all around the world,” says Mebberson.
“In hindsight, the skills that I learnt there, made [Radial Motion] all possible. It wasn’t just engineering skills, it was cash flow, people skills, all of the things you need to be able to do in a family business.”
After moving back to his hometown of Adelaide, Mebberson secured a million-dollar order from a former customer to design and make a new thermoforming packaging machine, which provided the funding to establish Bespoke Engineering in 2013.
“At that point I was cobbling together second-hand machines and getting together a bit of machine capability. But during this whole time, I was designing a small aircraft and it needed a particular engine that wasn’t available, so I started to look at, and learn about engines,” he says.
“I’m a recreational pilot and love aircraft, but also love aircraft design, so for the last 20 years my bedtime reading has been aircraft design books — I’ve got like a pallet of them,” he laughs.
Despite being self-taught when it comes to the topic, he explains that the concept for his aircraft engine started as a two-cylinder but quickly evolved into the three-cylinder radial.
It was four years ago, Mebberson met successful Adelaide engineer Loui Burke through Burke’s ownership of Harrop Casting Technology, a well-regarded Adelaide-based non-ferrous foundry, which he’d visited when searching for someone to cast his engine.
“Loui immediately recognised the [engine’s] potential and early on we both recognised the opportunity to stick these things in vehicles like Porsches or VW Kombis. Since then, we’ve invested the best part of three million dollars in developing the radial engine,” Mebberson says.
“It’s quite an unusual engine configuration, but the concept we had worked, and we first went from air cooled to water cooled, then continuously developed it and started to make patterns and casts, all the time being serious about low-volume production.”
Having built numerous prototypes, the company now has a batch of five pre-production engines and is halfway through a batch of 10 production engines.
“We’ve put them in and raced in a ‘72 Volkswagen Super Bug — which is a little scary as it’s got far too much power, but it’s good fun — as well as a Kombi and a 356 Porsche,” he says.
While most engines are vee or inline, Mebberson explains that his radial is what the Germans call a “stern” or star motor, with the cylinders arranged around the crankshaft, which makes for a short and torquey engine.
“What we’ve done that’s a little bit different to original radials is the originals didn’t have a conventional crankshaft and conrod, they had a master crank that was thrown off and then little slave rods that connected to it,” he says.
“We’ve got three conrods on a common journal, so it’s like a V-Twin with a single throw crank and two conrods. Having three conrods on a single throw crank is quite an unusual way of doing a radial engine and makes the diameter quite small.”
To ensure customers have ready easy access to parts, all the internal consumables, such as the pistons, conrods, valves, and valve springs are from a General Motors LS1 V8 engine.
“For that consumable stuff we’ve deliberately chosen one of the world’s most common engines, so that our customers can just go and get parts. We don’t have to machine or develop all that stuff either. We’re doing the unique, bespoke parts but the consumables are from the LS1,” Mebberson says.
Wen Soong, an Associate Professor in the School of Electrical Engineering at the University of Adelaide, confirms he and his colleagues are working with Mebberson to create an axial-flux electrical machine to couple to the radial engine, to produce a compact parallel-hybrid electric drive vehicle.
He said they hoped to have an early electric machine prototype ready by about April 2022, and a more optimised version by July.
“We are really pleased to see local development in this area. The fact that we’ve got a local company with outstanding mechanical expertise who have developed this innovative engine is great,” says Soong.
“For Mebberson’s engine, because of the fact he wants the overall traction system machine to be very compact, then the axial length of the electric machine must be very short, which really suits axial-flux machines.”
To date Mebberson’s radial engines have been fitted to VWs and Porsches, but Mebberson says the vehicles it can be fitted to are, “really only limited by your imagination”.
However, at a cost of around $35,000 for a base engine and going up from there, Mebberson agrees the engines are very much a discretionary purchase.
“The whole thing about this engine is that it’s not a disposable commodity,” he says.
“This engine’s all about being something you can keep. You can work on it, you can love it, you can understand it, and you can repair it.”
Brilliant! Is it fuel injected and does it have electronic engine management? Can it be adapted to run on hydrogen? A sound bite of it running would be great. All engine lovers want to hear what an engine sounds like.
I am a car fanatic (BMWs) love anything to do with IC engines – and some to do with EV vehicles. This is really interesting. Someday one of these ideas will tip the balance.
hello is there a video of the engine running would love to see it
Andy , great to see these tech developments here in Australia.
Great to see these tech developments here in Australia.
Great to see these tech developments here in Australia.
The pic shows the air cooled version, but Im interested in the crank. With 3 rods side by side on the one big end, I imagine there would be a rocking couple of sorts. Maybe revs are quite low do may not be an issue ….
How fuel-efficient is the engine? How is engine vibration? Love the concept.
I am currently in early stages of designing and building a light sports aircraft and working on a hybrid engine concept. Your work interests me and I would like to be kept informed. Best regards from an old engineer from another field.
C’mon, details ! 2.1 Litre ? HP and RPM ? Weight ?
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