41–50 of 56 posts
Engines can be prototyped on the time scale of months not decades.
Now they are soliciting the public to "invest" in their business.
Haven't rotary (Wankel?) engines proven to be unreliable? I love the RX-7 (my dream is to own a FD one day), but IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. I think Mazda has a rotary acting as a range extender in their MX-30 EV. I wonder how that will fare.
The second generation NA 13b engine was probably the most reliable / longest lasting wankel. Easily could go 200k miles without a rebuild. The Rx-8 rarely makes it past 150k due to insufficient lubrication which was required to meet ~2010 emissions standards.
Source: Experience. I've owned five rx-7s and two rx-8s, maintained them myself for the past 23 years.
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 ra…
For comparison a Model S weighs over 4,500 lbs.
Haven't rotary (Wankel?) engines proven to be unreliable? I love the RX-7 (my dream is to own a FD one day), but IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. I think Mazda has a rotary acting as a range extender in their MX-30 EV. I wonder how that will fare.
Kinda, kinda not, they have been proven to be vulnerable to mishandling. They have few quirks and require a bit different handling than normal engine, which means that someone treating it as any other car. But at some point it will need to have engine out job and replace apex seals. In motorsports it proven to be very reliable for example. > IIRC even the more refined Renesis engine on the RX-8 seems to have been pro…
Haven't rotary (Wankel?) engines proven to be unreliable? I love the RX-7 (my dream is to own a FD one day), but IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. I think Mazda has a rotary acting as a range extender in their MX-30 EV. I wonder how that will fare.
What killed the rx-8 is emissions. Wankel engines are very similar to 2-cycle piston engines. Both 2-cycle and Wankel burn oil in order to lubricate their seals. Very difficult to do that and also meet current emissions standards. The second generation NA 13b engine was probably the most reliable / longest lasting wankel. Easily could go 200k miles without a rebuild. The Rx-8 rarely makes it past 150k due to insuffic…
Would you describe the past 23 years as self torture or did you actually enjoy the process?
The only rotary I'd want is some ridiculous 4 router putting down enough horsepower to make me wet myself, and even then I'd probably sell it before I'd need to do maintenance on it.
Earlier quoted context omitted.
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.
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.
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.
Earlier quoted context omitted.
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.
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 t…
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.
This is a pretty cool engine. 25hp is about 18.75 kW so a really good fit for a 15kW generator (sometimes marketed as "whole house" generators) its high RPM (typical of rotary engines) makes it a good match foundation for a turboprop engine. A pair of these driving ducted fan turboprop engines would give you an excellent long duration drone platform with good payload capacity. My guess is the Army might be considerin…
Earlier quoted context omitted.
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 t…
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.
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.
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 ra…
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.
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.