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Earlier quoted context omitted.
to me it still looks like its principally a wankel motor just with a few changes.
If you look at an image, you can see the three apex seals on the stator, which is shaped the same way as a wankel rotor. The rotor of the liquidpiston engine is shaped similarly to the wankel stator and has no seals. It's almost the same just turned inside-out.
hmmm.. still uses apex seals, would need seriously small tolerances to make it work effectively. Call me skeptical but I don't see how this is really any better than the traditional wankel/rotary design
It's effectively an inside-out wankel, so the seals are stationary. This is a much easier problem to solve, and now you don't need to throw oil in the combustion chamber to lubricate the moving seals.
Posts on Hacker News related to LiquidPiston go back 11(!) years. The most comments are on this post: https://news.ycombinator.com/item?id=25450477 If this was going to revolutionize anything, it would've happened by now.
Seven-ish years ago while working on a hybrid-powered UAV I was checking out high power/weight engine platforms. I found a significant variety of regular Wankel engines that had MUCH better power/weight ratios and were available for purchase (not "real soon now").
Since power/weight is Liquid Piston's main claim to fame, this is rather important.
Today, a quick DDG search similarly returns many Wankel-based engines that definitely have better powr-weight ratios than Liquid Piston. The primary markets seem to be lightweight aircraft and some motorbikes.
The first one is AIE 80S [0]. It puts out 15BHP/11.2kW at 5kg/11 Lbs.
AIE's 225CS puts out 40BHP/30kW at 10kg [1].
In contrast, Liquid Piston's XS-210 weighs 21kg/46.7 Lbs to produce 19kW/26HP (third page of PDF spec sheet in button on [2]).
The net power/weight for these Wankels is 2.24kW/kg and 3.0 kW/kg. Compare this to the Liquid Piston XS210 0.9kW/kg. Liquid Pistoin's main advertised performance is between 1/2 and 1/3 of an already available Wankel. And there are many more Wankel options.
Plus, despite power/weight being Liquid Piston's main claim to fame, I have to wade through multiple pages, multiple "Invest Now!" popups, to finally dig down to their PDF spec sheet to even find an actual weight figure. In contrast, whereas the Wankel's pages post it right up front.
It is quite obvious that the Liquid Piston people know that they are not even close on their main claim to fame, yet are willing to just act as if they are the best available and count on people not actually doing their due diligence.
They literally look like they are in the same position as 7-8 years ago, "ohh we have this great lightweight new technology, shipping real soon now -- get in on the ground floor!!" I used to look at it as "maybe they'll get better". But at this point, it is pretty clear that they know they have nothing groundbreaking and are just trying to ride it as long as possible.
TBF, they MAY have a possible market using JP-8 fuel which is widely used and available in military contexts. But Wankels have been adapted to many different fuels and it would only be a temporary advantage if someone wants to get into this market.
Don't be parted from your money here....
[0] https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/
This is basically a variant of the Wankel engine, and if you do a cursory view of the Wankel engine wikipeida page it paints a pretty clear picture of a theoretically better engine that ends up not performing as well as standard engines due to a 1000 little things like the seals, ignition and chamber shape that have been perfected over the century + of normal engine designs. This engine is going to have all those pro…
For example the apex seals being on "the outside" instead of on the rotating assembly means they could be made easier to replace and easier to oil too.
But yeah, improvements look not all that big, certainly not revolution
Unless they are getting some miraculous increase in efficiency compared to any other Wankel engine (see Mazda), I don't see the value add here. It's essentially just a different way to do what the Wankel does with a few differences (apex seal placement, rotor shape and function).
hmmm.. still uses apex seals, would need seriously small tolerances to make it work effectively. Call me skeptical but I don't see how this is really any better than the traditional wankel/rotary design
It is 2-4X WORSE on Liquid Piston's main advertised claim to fame "lightweight" "power/weight" than many available actual Wankel engines.
And the fact that this is still in development a decade+ later and 7-8 years after I was first vetting them for a hybrid multirotor drone company indicates that your suggestion is correct — they have many nagging and serious not-easily-solved problems.
On the one hand, it seems like they have an addressable market. On the other hand, it seems like a scam because they're trying to attract investors with a fancy web page and thin statements about where they're actually selling. The comparison to a 25HP Kholer on the main page is... something. Here's the 'brochure': https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/642... Less than half the torque at more than…
I mean if you double RPM you halve the torque at same power, dunno what's weird here ? It's smaller CC faster rotating engine.
> And very low compression, I don't see how this can run diesel.
I'm also on "show us the working engine" side but supercharger will also add some heat and pressure to the system it might work?
hmmm.. still uses apex seals, would need seriously small tolerances to make it work effectively. Call me skeptical but I don't see how this is really any better than the traditional wankel/rotary design
But the fact companies make normal wankel engines that are better at everything is worrying for them
Earlier quoted context omitted.
It's effectively an inside-out wankel, so the seals are stationary. This is a much easier problem to solve, and now you don't need to throw oil in the combustion chamber to lubricate the moving seals.
right, but any float in the main eccentric shaft is still going to wear them out