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Dollars to donuts the rotary will be easier to manufacture and maintain than the diesel. It's got fewer parts and the parts themselves are way simpler. Lubric

Dollars to donuts the rotary will be easier to manufacture and maintain than the diesel. It's got fewer parts and the parts themselves are way simpler. Lubrication's easy if you don't care about efficiency or emissions, which the military doesn't.

nine_k 4y ago
The military does care about efficiency: higher efficiency means longer range, as we seem to be talking about aircraft / rotocraft applications. Higher wear is what they care less about: at peacetime, parts can be replaced more often, and at wartime, many will be destroyed before spending up the spec-dictated operation hours.
- inferiorhuman 4y ago
  Right - they care about range, fuel efficiency is secondary at best. WRT this engine, it's too small for anything but a small-mid sized drone. In that context the specific fuel consumption is likely less of an issue as there's some pretty hefty weight and size savings over the comparable piston engine (and they're claiming better fuel efficiency). The issue with the parts isn't higher wear, it's simplicity. Look at the strain that Ukraine has put on military supply chains. Now take a look at what's involved in building a diesel engine versus a rotary. The rotary engine is a few relatively simple castings*, a piston engine has a ton of small, complex parts. There's no mention if they comparable diesels are two or four stroke, but take a look at a four stroke injection pump and how complex they are (inline pumps are basically mini piston engines). Then take a look at the LiquidPiston motor – at least on one variant they're using the crankshaft for fuel and air delivery. Pretty much everything about it is simpler than a comparable piston engine, and when you've gotta scale up wartime production simpler is better. * okay so it looks like LiquidPiston is milling everything for the time being.
  - nine_k 4y ago
    This is right; the simpler, the cheaper and faster to make, and often the harder to break. Very important in the military. Delivering fuel and lubrication via the crankshaft is not uncommon in aircraft motors, or was at times of WWII at least. Delivering air this way is indeed novel and impressive.
    - inferiorhuman 4y ago
      https://www.liquidpiston.com/how-its-made https://www.liquidpiston.com/how-its-made If I'm not mistaken there are no apex seals in there – so there's one major weakness eliminated. Regardless of military applications there is some real interesting engineering there.
- pkphilip 4y ago
  Since this engine is so much lighter and smaller, you can just have a larger capacity fuel tank and drastically increase the range

nine_k 4y ago

The military does care about efficiency: higher efficiency means longer range, as we seem to be talking about aircraft / rotocraft applications. Higher wear is what they care less about: at peacetime, parts can be replaced more often, and at wartime, many will be destroyed before spending up the spec-dictated operation hours.

inferiorhuman 4y ago
Right - they care about range, fuel efficiency is secondary at best. WRT this engine, it's too small for anything but a small-mid sized drone. In that context the specific fuel consumption is likely less of an issue as there's some pretty hefty weight and size savings over the comparable piston engine (and they're claiming better fuel efficiency). The issue with the parts isn't higher wear, it's simplicity. Look at the strain that Ukraine has put on military supply chains. Now take a look at what's involved in building a diesel engine versus a rotary. The rotary engine is a few relatively simple castings*, a piston engine has a ton of small, complex parts. There's no mention if they comparable diesels are two or four stroke, but take a look at a four stroke injection pump and how complex they are (inline pumps are basically mini piston engines). Then take a look at the LiquidPiston motor – at least on one variant they're using the crankshaft for fuel and air delivery. Pretty much everything about it is simpler than a comparable piston engine, and when you've gotta scale up wartime production simpler is better. * okay so it looks like LiquidPiston is milling everything for the time being.
- nine_k 4y ago
  This is right; the simpler, the cheaper and faster to make, and often the harder to break. Very important in the military. Delivering fuel and lubrication via the crankshaft is not uncommon in aircraft motors, or was at times of WWII at least. Delivering air this way is indeed novel and impressive.
  - inferiorhuman 4y ago
    https://www.liquidpiston.com/how-its-made https://www.liquidpiston.com/how-its-made If I'm not mistaken there are no apex seals in there – so there's one major weakness eliminated. Regardless of military applications there is some real interesting engineering there.
pkphilip 4y ago
Since this engine is so much lighter and smaller, you can just have a larger capacity fuel tank and drastically increase the range