Was looking at Hirth 2 stroke engines in another thread. Hirth also makes 2 stroke “diesel”. Or rather 2 stroke engines running on heavy fuel (diesel, Jet A1 etc). Technically they are not diesel engines, they just runs happily on diesel fuel. They make engines for drones manufactured by SAAB, Northrop Grumman and several others.
A 62 hp 3503 hf
A 40 HP s1204
The 3503 hf is obviously a modified 3503. The s1204 is a heavily modified F 23 with carbon pistons and watercooling and a 1.5 kW generator weighing only 24 kg total weight. If diesel is ever to be popular, it is engines like these that will make it, or more “ordinary” two stroke diesel. A s1204 type engine as a range extender in a hybrid diesel/electric aircraft for instance.
Well, that would make an easier comparison: a complex geared Rotax vs. a complex geared diesel
I thought the Weslake was direct drive? I’ll have to re-read the article in the LAA mag.
Actually, the Weslake is the opposed piston diesel, like the WWII JUMO concept. Each cylinder has two pistons and the engine has two crankshafts.
The power is then transferred from both crankshafts by sprocket wheels to the propeller.
About complexity – Weslake claims the engine has one third of components compared to Rotax.
I can’t be too sure either – the company website is not abundantly clear, as said. Still, I see a mention of “fitting the crank covers and gear case cover” next to an image showing a bell-shaped case that might well house epicyclic gear. Perhaps they’ve not yet decided themselves?
http://www.weslake.eu/news/newspages/opposedpistonengine.html
@Pavel: If it does follow the Jumo concept then it must be a two stroke, doing away with valves, cams, and everything thereto pertaining… but putting in some stout yet delicate gears. Also it needs to sport a turbo, again adding to complexity.
it is engines like these that will make it, or more “ordinary” two stroke diesel. A s1204 type engine as a range extender in a hybrid diesel/electric aircraft for instance.
Have you any idea how much the S1204 would be likely to cost? Weightwise it might fit some of the SSDR aircraft (e.g. Luciole, Spacek designs).
The range extender concept appears to be a rather silly one when applied to aircraft. It is already hugely inefficient in electric cars (the BMW i3 when run on the range extender has an extraordinarily bad MPG compared to all petrol cars) and in an airplane application, the weight penalty kills the concept completely.
The only smart variant of that concept is the Zoche diesel where the generator is part of the diesel engine which drives the propeller but also charges batteries that are available for additional takeoff power. Aircraft engines are dimensioned for the required takeoff power, not the require enroute power so an electric boost engine makes sense. Even more so for seaplanes where takeoff power requirements are significantly higher than for land planes.
Think of the DA40 which has a great engine for cruise but it has terrible takeoff and initial climb characteristics.
Aircraft engines are dimensioned for the required takeoff power, not the require enroute power
That’s not intentional though, is it? It is a fait accompli, given the available technology. You can make an engine which delivers max rated power in cruise but it needs a turbo (unless you are crop spraying 
) and if you fly it like that you will shag it fairly rapidly. Car engines last as long as they do because most of the time they aren’t doing any work.
The range extender concept appears to be a rather silly one when applied to aircraft. It is already hugely inefficient in electric cars (the BMW i3 when run on the range extender has an extraordinarily bad MPG compared to all petrol cars) and in an airplane application, the weight penalty kills the concept completely.
The only smart variant of that concept is the Zoche diesel where the generator is part of the diesel engine which drives the propeller but also charges batteries that are available for additional takeoff power. Aircraft engines are dimensioned for the required takeoff power, not the require enroute power so an electric boost engine makes sense. Even more so for seaplanes where takeoff power requirements are significantly higher than for land planes.
Think of the DA40 which has a great engine for cruise but it has terrible takeoff and initial climb characteristics.
I don’t know how the i3 works,but it depends how you look at it. A so called “plug in hybrid” have an ordinary gas/diesel engine and a battery capacity of approximately 50 km or so. The idea is to charge it over night, then use the battery in combination with the engine to achieve a fuel consumption of typically 2 liters per 100 km (gasoline). When the battery is depleted, it works as a normal hybrid, like the Prius. This concept can easily be extended to mean primarily electric and a small engine to charge the batteries, with the downside that the smaller the engine is, the poorer it works when the batteries are depleted because the engine is not dimensioned to power the car alone. If it also charges the batteries, the perceived efficiency will of course be very poor. Still you wont end up stranded IF you should run out of batteries. Another concept is to use hybrid technology to increase short time power needed for acceleration for instance, like they do in F1. There really are infinite possibilities for how to combine electric power and gasoline/diesel engine with lots of goals, efficiency, power etc.
The Prius technology is primarily a technology that fixes the two main deficiency of the gasoline engine. It is very inefficient except in a narrow power band, and it has no way of storing/absorbing energy for later use. The result is an engine that is as powerful as a much larger engine, while being as efficient as a much smaller/weaker engine. A range extender is something that “fixes” the main deficiency of a battery; low power density and low energy storage capacity. The good part with electric power is it can deliver an insane amount of power at high efficiency, and it can absorb energy and store it for later use.
An aircraft demands high power over long periods, and even higher over short periods (take off). Obviously an aircraft engine is designed to run efficient at cruise condition. During take off, the primary objective is to achieve high power output, not necessarily high efficiency. A hybrid solution would theoretically increase the efficiency during take off, and would allow smaller engines to be used. For an electric powered aircraft, power during take off is no problem. The problem is to have enough energy stored for more than some minutes of flight. A range extender would therefore increase the endurance.
But, with better battery technology, the need for hybrid solutions will disappear.
Car = full power for acceleration, 25% power for cruise, little weight sensitivity
Aircraft = full power for acceleration, 65-75% for cruise, high weight sensitivity.
Simple works better for aircraft.
