At some point in 2013, it occurred to me to build a radial engine. The decision was inspired by the engines on two Stearman biplanes which are resident at the airfeld where I keep my microlight.
So, I started considering how I would make the major parts and what the aim of the engine was to be.
While I have no objection to 'display' engines, that would not satisfy me. My engine had to have a purpose. I fly model aircraft, but not with the skill to warrant sending many hundereds of hours work into the sky at the risk of destroying it at first go. Certification requirement precluded making a radial for my microlight, so the application would have to be ground based.
Another of my passions is motorcycles. I have seen bikes built around the Australian Rotec radials, but they are frankly ridiculous.
I came to the conclusion that I should build a manageable size engine of 50 to 100 BHP and think about the specific application later.
I elected to design my engine around easily available, low cost motorcycle cylinder heads and barrels, with the option to produce my own heads at a later date. I selected Dnepr parts for their simplicity and layout appropriate to a radial.
The engine was designed in CAD and spreadsheets created to calculate stress in critical areas (con rods, bearings, valve train). Other parts were simply over-engineered, leaving many opportunities for future mass reduction.
The resulting design is 2.3 litres, weighs 120kg and is expected to produce upwards of 80BHP at 3500 rpm.
Then there's a supercharger...
The blower is a bit of a shot in the dark. It started with the realisation that the single carb setup creates a lot of 'dead' space between the carb and the intake valves, which will be a problem with fuel falling out of suspension at low rpm and when starting. To address this issue, I first drew up a simple 'stirrer' which would keep the induction mixture moving. The stirrer soon evolved into an impeller and gained a 2 speed drive from the crank.
All the major parts are done. I'm now working on details of the lubrication, ignition and exhaust systems. First run might be this year. Or it might not.
I now have an application designed specifically for this engine. It is for a road going vehicle, but it's not a bike and the engine will assume pride of place. More of that another time.
So, I started considering how I would make the major parts and what the aim of the engine was to be.
While I have no objection to 'display' engines, that would not satisfy me. My engine had to have a purpose. I fly model aircraft, but not with the skill to warrant sending many hundereds of hours work into the sky at the risk of destroying it at first go. Certification requirement precluded making a radial for my microlight, so the application would have to be ground based.
Another of my passions is motorcycles. I have seen bikes built around the Australian Rotec radials, but they are frankly ridiculous.
I came to the conclusion that I should build a manageable size engine of 50 to 100 BHP and think about the specific application later.
I elected to design my engine around easily available, low cost motorcycle cylinder heads and barrels, with the option to produce my own heads at a later date. I selected Dnepr parts for their simplicity and layout appropriate to a radial.
The engine was designed in CAD and spreadsheets created to calculate stress in critical areas (con rods, bearings, valve train). Other parts were simply over-engineered, leaving many opportunities for future mass reduction.
The resulting design is 2.3 litres, weighs 120kg and is expected to produce upwards of 80BHP at 3500 rpm.
Then there's a supercharger...
The blower is a bit of a shot in the dark. It started with the realisation that the single carb setup creates a lot of 'dead' space between the carb and the intake valves, which will be a problem with fuel falling out of suspension at low rpm and when starting. To address this issue, I first drew up a simple 'stirrer' which would keep the induction mixture moving. The stirrer soon evolved into an impeller and gained a 2 speed drive from the crank.
All the major parts are done. I'm now working on details of the lubrication, ignition and exhaust systems. First run might be this year. Or it might not.
I now have an application designed specifically for this engine. It is for a road going vehicle, but it's not a bike and the engine will assume pride of place. More of that another time.
