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This is more hype than performance. When I worked on a hybrid-power multirotor drone about eight years ago, I was checking out Wankel engines for their power-w

by toss1 4y ago

This is more hype than performance. When I worked on a hybrid-power multirotor drone about eight years ago, I was checking out Wankel engines for their power-weight ratio, and also came across this Liquid Piston crew. They were supposedly ready to ship Real Soon Now. But worse, their power-weight just didn't compare to Wankel options available then. Liquid Piston still do not compare on their headline power-weight ratios. They make a lot of claims about 25 HP (18.6kW) and light weight, but don't actually mention the weight, which is down in their spec sheet - 21.2kg dry [0], which is about 0.877kW/kg. By comparison, just a quick search of small Wankels turns up these: -- AIE model 225CS outputting 40 bhp / 30kW weighing 10kg = 3.0 kW/kg[1] -- AIE model 80S outputting 15 bhp / 11.2kW weighing 5kg = 2.24 kW/kg [2] -- Sorrel Hiperlight Wankel outputting 75 hp / 56 kW weighing 52kg (fully wet with all electric start, reduction drive, and exhaust system, etc. = 1.07 kW/kg [3] -- Crighton CR700W motorcycle engine puts out 220 hp / 164 kW weighing 43kg = 3.8 kW/kg. [4] -- Small Nitto NR20-EP puts out 2.24kW / ~3hp weighing 1.466 kg = 1.53 kW/kg. [5] In short, this is a lot of marketing hype for low pefrofrmance, and they've been working on it since 2003 according to their website. The sole advantage this engine might have is running on a broader range of fuels including JP-8, but I've seen Wankels setup for a wide fuel range also. If I had a funded task to develop a high power-weight engine, I'd start with the Wankel design, not this one. It is already WAAAY ahead, and there's still a lot of performance left on the table. [0] https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/6427fdcf5c4c4c3d073e9bc4_LPI%20Brochure%2020230331.pdf https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/642... [1] https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ [2] https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ [3] http://www.ultralightnews.com/sunfun99/hiperlight.html http://www.ultralightnews.com/sunfun99/hiperlight.html [4] https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w-motorcycle/ https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w... [5] https://barnardmicrosystems.com/UAV/engines/wankel.html https://barnardmicrosystems.com/UAV/engines/wankel.html

majou 4y ago
How much does that metric matter? Especially in the context of hybrids with regenerative braking. For comparison a Model S weighs over 4,500 lbs.
- toss1 4y ago
  Power/Weight ratio matters for pretty much everything more than one initially thinks. People usually think first of adding power as adding performance. But power affects only one parameter - acceleration. In contrast, reducing weight similarly improves acceleration, but also improves turning, and braking performance, and reduces the loads and wear on every other component (the opposite of adding power). And that is just in automotive performance. As soon as you go to anything that flies, the same effects are just multiplied. Every gram of weight saved is either a 1:1 increase in available payload, or an increase in range and/or fuel that can extend range, and of course still improved performance across the entire envelope. And the only reason that e-Vehicles get away with such absurd weights is that all that weight can be put low and centered in the suspension so the fundamentals of chassis dynamics is acceptable. They still massively abuse the tires, but with a higher weight distribution would be absolute pigs if no virtually un-driveable. Of course, any vehicle choosing between a Wankel and this LP thing is not likely an overweight battery-heavy vehicle, so it'll count more. Obviously a 1% saving of 45 pounds on a 4500Lb EV is not going to do a lot, but ... yeah, it's still a key issue. And this is especially an issue because LP is making it the central claim of their pitch, and it is so easily beaten by much older technology. Makes it seem more like a basis for fleecing investors than a serious entry to improve the state of the art.

by toss1 4y ago

majou 4y ago

How much does that metric matter? Especially in the context of hybrids with regenerative braking. For comparison a Model S weighs over 4,500 lbs.

toss1 4y ago
Power/Weight ratio matters for pretty much everything more than one initially thinks. People usually think first of adding power as adding performance. But power affects only one parameter - acceleration. In contrast, reducing weight similarly improves acceleration, but also improves turning, and braking performance, and reduces the loads and wear on every other component (the opposite of adding power). And that is just in automotive performance. As soon as you go to anything that flies, the same effects are just multiplied. Every gram of weight saved is either a 1:1 increase in available payload, or an increase in range and/or fuel that can extend range, and of course still improved performance across the entire envelope. And the only reason that e-Vehicles get away with such absurd weights is that all that weight can be put low and centered in the suspension so the fundamentals of chassis dynamics is acceptable. They still massively abuse the tires, but with a higher weight distribution would be absolute pigs if no virtually un-driveable. Of course, any vehicle choosing between a Wankel and this LP thing is not likely an overweight battery-heavy vehicle, so it'll count more. Obviously a 1% saving of 45 pounds on a 4500Lb EV is not going to do a lot, but ... yeah, it's still a key issue. And this is especially an issue because LP is making it the central claim of their pitch, and it is so easily beaten by much older technology. Makes it seem more like a basis for fleecing investors than a serious entry to improve the state of the art.