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4 stroke engine..
#11
Yeah, every last 4 stroke I can personally think of either weighs more than the entire aircraft put together, or doesn't have nearly enough power output to be effective. Out of curiosity, have you looked into any of the cut down VW style 2 cylinders? I know the 4 cylinders will be way to heavy, but I don't know about the cut down versions.
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#12
I don't remember ever seeing ANY 4-stroke that even gets close to producing 1 HP per pound of engine weight, like 2-strokes and turbines!
ARE THERE ANY?
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#13
bryancobb - 10/28/2011 3:49 AM

I don't remember ever seeing ANY 4-stroke that even gets close to producing 1 HP per pound of engine weight, like 2-strokes and turbines!
ARE THERE ANY?

Yes, formula one race engines output 1 hp for each pound (can, but this is not always the case). There are a few others, but not many.

James
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#14
I would like to see the MZ get injected. Almost all 2 stroke reliability issues are related to jetting and mixture issues. 2 strokes have so few moving parts compared to 4 strokes. I feel better with a 2 stroke turning 6000rpm than a 4 stroke turning 4500 (however subaru and rotary engines seem to have a decent track record). Some of the new marine 2 stroke engines that are injected have better reliability than their 4 stroke competitors. The light weight of the mosquito coupled with the MZ are a perfect match. Instead of worrying about the 2 stroke phobia, let's focus on making the MZ a bullet proof package with injection. The MZ runs a lower rpm compared with many other 2 stroke engines (closer to a marine engine minus water cooling) adding to its potential reliability. Less moving parts, lighter weight, lower rpm and (hopefully) fuel injection makes it hard to consider any other option in my book.

Just my 2 cents,

Bryan

( My 2 stroke Mercury marine engine runs year after year with no maintenance on my part, I don't even drain the fuel at the end of the season..horrible, I know but its a beater boat....yet, despite this it runs flawlessly year after year with not even a sputter of the engine..This is typical of marine 2 stroke outboard engines..lower rpm and good cooling help make this happen. The MZ has the potential to get there..)
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#15
I would like to know what the feelings are on a rotary engine. A rotary can be brought to near 1 to 1 power to weight, are perfectly smooth aside from torque pulses and have consumption about midway between 2 and 4 strokes. They add some complexity with an oil system and water cooling but can be very reliable. Cost would be in the order of the current XE3 maybe slightly more.

Thoughts??
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#16
I think a rotary has a lot of potential and they are very smooth with good torque and power bands - - maybe a start point
http://www.renntechkarting.com/produc...
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#17
I just spoke to the guys at the rotary engine shop and here is the link to the new web page
http://www.renntechmercedes.com/www/c...
It looks like there aviation engine is a little low on power for our mosquito application.
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#18
mosquito - 10/28/2011 3:52 PM

I would like to know what the feelings are on a rotary engine. A rotary can be brought to near 1 to 1 power to weight, are perfectly smooth aside from torque pulses and have consumption about midway between 2 and 4 strokes. They add some complexity with an oil system and water cooling but can be very reliable. Cost would be in the order of the current XE3 maybe slightly more.

Thoughts??

I have a friend who but a Mazda rotary in a Hughes 269 and it was THE SMOOTHEST HELICOPTER I EVER SAW. It had power to spare. Well .....The FAA wouldn't give him an airworthiness certificate, so it's a boat anchor.
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#19
John: As I told you at OSH'11, I'm v. interested in the rotary. I want its desirable characteristics of smothness, reliability & acceptable FF. If cost is 1/2 way between MZ202 & turbine, I'll take the rotary. How far out is REALISTIC delivery date? I would even hold off delivery of my MZ if rotary is within 1 year!!
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#20
I am going with two rotary's. Their is a ton of info on turning those engines into aviation motors. The big problem with them isn't their APEX seals, It is the cooling in a very tight cowling. The engines Exaust gases pass next to the water jackets heating up the water hotter than it needs to get. Now it has to cool water that is starting at a higher temp. Some people use heater cores from cars to cool it since it has a higher transfer of heat. You could cut the engine in half. One rotary stage next to another so you would have a single engine failure as opposed to complete power loss. for almost the same weight. One guy who wrote a book about his rotarys in his planes had originally used two seperate carbs for his engine. This was clever because if one carb failed supplying fual/air to each rotor housing, he had the other carb supplied the fuel/air to the other side of each rotor housing. He like the redundancy of it, but hated the "no adjustment" in the air ant the large altitudes. So he did away with the carbs and went fuel injected. He got his hot temp under control and has a ton of reliable hrs on his airplane engine.

The rotary operates under very low G-loads relative to piston engines. There was a great article written about this in Kitplane Mag about eight months ago. To look at how a piston engine works will scare you mathmatically as well as from an engineering standpoint. A piston must accelerate its mass (equal to the sum of piston, pins, rings, pushrods, and rod bearings) up at an incredible rate only to stop it at a high rate (all at once). This G-load makes the weight of a piston at TDC and BDC an unbelievable weights. It will do this thousands of times a minute. The engineering on all of these components must withstand this torture for long periods of time to avoid fatigue. So when looking at the weight it must endure for the number of cycles per minute added up in flight hours on the engine, piston engines are designed to destroy themselves unless engineered to overcompensate for it. That carries a weight penalty. Rotary's only have three moveing parts. And yes they do suffer from centrifugal force loads or weight, it is not the high G-load start stop start motions. It is mostly under the same stress all of the time. It is so smooth because of this. Everyone says it is as smooth as a turbine. When looking at how it operates relative to a piston engine, i would agree, though i have not been around one yet. With less vibrations from the engines, comes less fatigue for the mounts on the airframe which i read is why rotorway did away with the evinrude of the old days and made their own. I dont think the new ETAC evinrudes have the high vibrations anymore according to their advertisments. But i have not read anywhere that someone has tried the new ETEC's on a helicopter. For a small helicopter, i would seriously look into the ETEC's also. Those engins produce and enormous amount of power for being so small. They are also designed (engineered) to operate most of their life at high RPM's. They would be another cooling problem maybe. Maybe not.

I am going with two wankle (13B or 20B). You should look at rotarys or ETECs.
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