Gemini Diesel

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Gemini Diesel

Postby R Rinker » Thu Aug 27, 2015 1:16 am

The 'opposed piston' technology has been licensed to several very credible developers that are currently developing an engine for several of the big markets. Automotive being one of the biggest. Superior Air is developing the Gemini Diesel for aircraft, and their first model is a 100 horse, and a 125 horse diesel that is a Rotax replacement. All I can say is that many of us have been waiting for many years for this to happen, but as Abe Lincoln said, "The hen is the wisest of all birds because it doesn't cackle until 'after' it lays it's egg." We've been disappointed with so many engines, and especially for homebuilts. This one has really got my attention. There's one prototype mounted on a Legend Cub. There is a huge list of positives and almost nothing negative I know of. There's no carbs, valves, camshaft. The 100 horse is supercharged and the 125 is turbocharged. Huge ports going all the way around the cylinder, so there's little restriction or backpressue. Six pistons and only 3 cylinders that are slide in sleeves that are easily replaced at overhaul. Touted as very smooth running. Geared but not exactly a 'gearbox'..evidently a solid thrust bearing. Get this..the prop turns at 2100 rpm, because with it being diesel there's lots of torque and ideal for a 'big long prop'.
It's a very clean installation without a rats nest of hoses, clamps, and junk hanging all over. Smaller than Rotax, so the cowl could be trimmed a little lower (Badly needed on the S.S.) Three exhaust and three intake points, which are not even visible exactly. It uses an off the shelf starter and alternator with lots of juice. Runs diesel, Jet A, even bio-diesel. and on & on...
This design was used as far back as 1930 in some huge, record setting gas engines in Germany (Junkers). Don't have a clue why it disappeared, unless it was just the usual contract preference game between industrialists. I think it had an emissions issue, but with supercharging and the redesigned induction system with the swirling mixture it meets today's emission standards.
I'm watching this one. If all goes well there will be larger versions to replace most Continental & Lyc's.
For a discussion and graphics showing how it works...https://www.youtube.com/watch?v=2kehHbZ5DTU&feature=youtu.be
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Re: Gemini Diesel

Postby FlyerChief » Thu Aug 27, 2015 2:06 pm

Hi Roger,
I have been watching the Gemini 100 for over 5 years now. The website sat dormant for over 3 years while they were developing it and trying to get funding. Hopefully it has passed the point where funding is no longer the issue and they can finally start production. It sure holds a lot of promise for the GA market.
Dan
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. ~Henry Ford
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Re: Gemini Diesel

Postby R Rinker » Thu Aug 27, 2015 2:16 pm

How long has Superior Air been involved with it??
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Re: Gemini Diesel

Postby R Rinker » Tue Sep 08, 2015 10:29 pm

I totally understand the loyalty and attachment of so many Just builders to Rotax. The involvement in getting through the learning curve to get them operational has been extensive for many, and you don't want to start over on something else. But I haven't got my engine yet, so I'm free to chase the dream. So many of the red flags don't exist with the Gemini diesel Rotax replacement. Tens of thousands of hours on it's type, and thousands of hours on this basic engine in airships. A strong, established aviation engine company behind it...I have to believe Superior Air has better management than to be 'gambling on a potential flop'. Yes, we all know there will undoubtedly be some things to work out..( a number of people lost the summer flying to Rotax still having things to work out also.) The more I understand about this engine the more I'm sold that when it is available, (and they do have a timetable for that,) it is what I want. So I was interested in seeing what others that are knowledgeable about it have to say, and links to how the proving phase is progressing. Here is a photo of it installed...http://www.ainonline.com/sites/default/files/uploads/webgemini-legend-cub.jpg You can enlarge the image by clicking on the plus.
I was trying to figure it out. The low end torque will drive a hefty alternator for all the electrical you'll ever need. Looks like a serious oil cooler to say the least. But what is the big aluminum or stainless tank behind and between the engine mounts? Looks like the blue hose is the air/fuel intake (it is supercharged, not turbo'ed). Be really interesting to have someone who knows something about it to explain it...
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Re: Gemini Diesel

Postby Av8r3400 » Wed Sep 09, 2015 12:12 am

A very intriguing engine to say the least. Being a diesel fan, I'd love to see this engine (or another small diesel) succeed.

The induction on this engine looks to me to be very much like the old Detroit 2-stroke diesels. The roots type blower is not a "supercharger" but a "scavenging" air pump. It provides scavenging flow into the cylinders to clear the exhaust and induce air, but not to provide much (if any) boost pressure over atmospheric. Boost would be supplied by the turbo option.

There's a million explanations on YouTube for the Detroit diesels.

Here's one example of the two stroke Detroit explanation: Link
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Re: Gemini Diesel

Postby R Rinker » Wed Sep 09, 2015 5:07 pm

Ok...So they have a lot of experience to draw from. I believe they have gone with the best options. I really like the no valves or cam design. Some of the Detroit two strokes had exhaust valves, but the Gemini uses ports for intake and exhaust. I like the bolt on alternator & starter. I could go on and on. With the right team and commitment this could be a winner. It looks like a design that was just waiting to happen. I wonder if there is anything in the fuel supply line that would be different for diesel fuel. Probably a special filter before the injection system, but the tanks, lines, valves, vents, etc. should be the same? The lift or supply pump before the injector pump would be special....
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Re: Gemini Diesel

Postby Syd » Wed Sep 09, 2015 7:45 pm

If the sound, vibrations levels/smoothness, weight, reliability are all sorted.... then the 20% less consumption and in my case absence of petrol excise tax making $1/litre vs $2/litre approx should make it a pretty good choice......

Other manufacturers could take a few lessons from the clean design as well... :D
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Re: Gemini Diesel

Postby Av8r3400 » Wed Sep 09, 2015 10:21 pm

R Rinker wrote:... Some of the Detroit two strokes had exhaust valves…
... Probably a special filter before the injection system, but the tanks, lines, valves, vents, etc. should be the same? The lift or supply pump before the injector pump would be special....



All of the Detroit two strokes used exhaust valves. The cam was required because it also ran the fuel injectors.

Filter grades or size may be different in the fuel system, but the rest would mostly be the same. Remember this engine is designed to run on Jet A, not diesel. Therefore the fuel is far more quality controlled for filtration before it even gets into the tank.
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Re: Gemini Diesel

Postby R Rinker » Thu Sep 10, 2015 2:13 pm

True as to the the quality control on Jet A...but they are advertising it as acceptable to use diesel, and I'd like to design a fuel system for that option. I remember from my A&P school days that Jet A had the ability to 'hold' water in suspension, and there is also an issue with the potential for microbe growth. Usually only under certain conditions, (probably your warmer climates) but with those conditions possible, so the filter system would probably take that in consideration. Also if my memory is correct, Jet A weights 8 lbs. per gal. to gasoline's 6 lb., so the weight would be about the same per hour of fuel burn, but the volume would be less....Progressive already has Canadian companies in place for their products, long established in that regard...
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Re: Gemini Diesel

Postby Fresnoredneck » Thu Sep 10, 2015 2:59 pm

The Gemini is designed in the UK, development continues in the UK, and is a long way from being near testing let alone sales. If you want an interesting conversation ask Superior to see their complete engine, they haven't got one!!

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Re: Gemini Diesel

Postby R Rinker » Thu Sep 10, 2015 4:15 pm

Rich...interesting...if that's so, then Superior's claim of having several running on test stands proving beyond expectations, and this one http://www.ainonline.com/sites/default/ ... nd-cub.jpg is just a fake?
I talked to Darren at Legend Cub, and they do indeed have this engine on the airplane, Superior does have them running in test cells, and they are working with Bosch to finalize the supercharger that will be on the production models. I'm just searching for facts and wish them all the best. One thing that's evident is it should be a more robust design for the prop stresses and not as susceptible to the MMOI issues as the Rotax gear box. Lycoming has had a geared engine for years and I've never heard of any MMOI issues with it. Six pistons also have historically not had harmonic issues like the four cylinders.
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Re: Gemini Diesel

Postby Fresnoredneck » Thu Sep 10, 2015 5:30 pm

Beyond expectation, no, a mistruth yes, ring Superior and ask what management changes have happened in last couple of weeks and why, you won't get the full story I am sure but you might draw a sensible conclusion from what you are told.

If Legend or Superior have one running, simply ask for 10 seconds of video installed and making power not a still jpg something honest, something actual a close up of a Gemini running .........

The only working Gemini is indeed on a test bed still in development in the UK and as late as last week was having component failures.

Ask for 10 second of video footage, quite happy to eat my words......but I don't think I will
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Re: Gemini Diesel

Postby R Rinker » Thu Sep 10, 2015 7:43 pm

If the Gemini turns out to be a bust due to incompetence and exploitation I think it will really hurt Superior. The time has come for this technology to move forward and if they mess up with the opportunity they stand to lose a lot. North America is still tied to gasoline burning, old design,but the rest of the world needs, wants, must have Jet A burning engines. When I was in Russia, there was no avgas available, and the car gas was so bad it would destroy any engine, let alone a Lyc. or Continental. Believe me, you wouldn't use car gas in Providenya in a Rotax, and try to fly home! We had to carry enough fuel to get back to Alaska, and could only go as far as how much fuel we could take with us. The homebuilt market may be fairly small, but around the world there is a huge developing market for drones, and generators, pumps, etc. that use this type of engine. Is your source of inside information something you can't reveal Rich, or can we follow along also?
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Re: Gemini Diesel

Postby Fresnoredneck » Fri Sep 11, 2015 3:16 am

No I think the engine is right, it is heavy and needs to go on a diet, its also one of the directions aviation should be heading but only one there are others. My point is that the followers of the industry are being fed a line of bull**** typical US marketing bull. Give them a call and ask for the video, then post back, I am really interested not so much in Superior as they cant help their lips flapping but more Legend Cub, it they say they have one then fire that puppy up just for 10 seconds and lets see, shouldn't be a problem should it?? I really detest people who tell the public they have something when really they dont?? Wasn't that what Bernie Maddof did???

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Re: Gemini Diesel

Postby R Rinker » Fri Sep 11, 2015 2:19 pm

But it's lighter than an 0-200. Their saying about 200 lbs. I'd rather see it 200 lbs and 'work' trouble free than super light and problematic. But I'm only 140 lbs. That gives me the luxury of offsetting the weight and still be lighter than the average build. Real world takeoff weight normally includes a pilot.
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