Linear? Linear compared to what?

Relative to the power it puts out, that Atkins engine is significantly heavier than purpose built General Aviation (GA) and Light-Sport Aviation (LSA) engines, especially so given that (unless I'm missing something), the 220 pounds is dry. By the time one adds a radiator, necessary plumbing, oil, coolant, a gear-reduction mechanism and propellor mount hardware, the weight will be nearly 300 pounds.

Contrast the Atkins engine with the two most popular LSA engines:

• The conventional Continental O-200, an engine with a redundant ignition system, an engine with a higher power rating (both peak and continous), and an engine that, even when "wet" will only weigh in at less than 210 pounds. One of the nice things about this engine is that it puts its power out in the 2,300 to 2,700 rpm range, eliminating the need for a reduction system.
• The Rotax 912, a purpose built LSA engine that goes about its work in a more "modern" way (compared to the Continental). This engine carries a peak power of 100 HP, runs on auto gas, and like a Wankle, requires a radiator, coolant and a gear-reduction system. Dry this engine weighs in at 125 pounds with the gear-reduction box in place, and installed and wet it tips the scales at a bit over 170 pounds.

 

Considering that the whole motor turns the same direction, rather than having an upper rotating assembly that moves in one direction in order to turn the bottom end another direction; the motor is linear. The only rotational differences of a turbine and rotary is that the rotor wobbles while spinning, but a turbine only spins from a fixed location.

Linear isn't the most perfect way to describe it, but it definitely shouldn't be classified the same as piston engines

 

I would like to get one of the motors to see what kind of power I could make for a little kart. I would bridgeport the motor, build a sheet metal intake, turbo it, and program a custom ecu. Then I would have a belt drive built to adapt up to a motorcycle trans and run a solid rear axle like my shifter kart has.

Probably won't ever get around to it, but it's a fun idea. It may be heavy for an aviation motor, but it is light for a full scale kart.

 

Within the aviation community there are two classes of engines, IC and CC, the former stands for Intermittent Combustion and Continuous Combustion. Needless to say, Piston and Wankle engines are in the IC class, and turbines are in the CC class. Long story short, the Wankle still adheres to the old "Suck-Squeeze-Bang-Blow" and is still very much akin to a piston engine.

 

Fellows thank you all so very much for your input, since I’m in Seattle I will have to make some time to run down to Atkins rotary and see what they have.

Now got tell you I’m not engineer or a pilot, I’m a lay man, but I have had some good ideas, and my dream of flying is just a dream but you never know I might just get it off the ground.

Without getting real deep in to the workings of a vertical engine, (pistons going up and down ) to the workings of a circular engine, (Wankel as the rotors spin in a semi circular manner) if you have ever worked on a vertical engine you know that lots of things need to happen in harmony for the engine to work, I have a 5.9L diesel, I just adjusted the valves and could not hope to notice how many things can go wrong, I can suck a valve down and jam the engine, a push rod can work its way lose come through the block, Crank can break, cam can wear, piston can come loose, piston engines have the potential for lost of problems .
Now before I say this be forewarned that I have no real benefit on one engine over the other , my life won’t be on the balance if I was going to fly tomm, I won’t make a dime working on this engines (Wankel) . the circular engine came to my attention as I have been cruising the internet, looking at LSA kits, and low and behold people are recommending the wankel engine, people who fly, they are saying that no accident has been found associated with mechanical failure of the rotary, where as lots of accidents have been attributed not to pilot error but to broken push rods, pistons, etc.. this is what I’m reading, so I did some research and looked at the rotary and I was just amazed at the capacity of this engine, ok so Is not real fuel efficient, but what really caught my eye was the capacity of the engine to wind up, it reminds me of a tornado, naturally it just winds so delightfully, and with no valves, no pushrods, no bolt pistons, the possibility of this engine to fail is far lesser then the geriatric vertical engines, I never want be too close to a vertical engine when high rpm's are turning as I’m nervous it could blow up,.
I know the Cessna is a good plane but I really don’t feel that safe in them, they are so slow to respond, heavy, good track record but that plane is almost 50 years old, some tricks that old dog won’t do.
With things like composites, newer metals, newer lighter more power full engines, we can really built a far superior craft then the recreational planes that are still flying, soon they will be really cars in the sky, like our domestic car companies, if you don’t make a better vehicle for less money someone will, do you own a Honda ? If we don’t get a new superior recreational aircraft built soon, foreign competion will, and most likely will have the Wankel engine in it.
The ideas are different, maybe I’m crazy, but I like to encourage you to think on this things as I think we are going to see the investment the Asians have made on the Rotary experiment pay off for them, no Is not a turbine, but is most likely going to be in the middle from vertical to turbine, but if you really think about it, does a turbine not suck compress re compress ignite and then exhaust, uses the same fuel dead dinosaurs, and yes they too have a form of spark plug, kind of a cousin of the vertical engine, till we have hydrogen engines and True hybrids, we won’t see any real change, and did not someone say that Wankel’s can run on Hydrogen ?? We can only speculate… time will tell, but I think people on the other side of the globe might be thinking along a different route…

 

Properly maintained, none of the above worst case scenarios will happen to a piston engine, the flip side of course is that if you don't properly maintain a rotary engine then it too will fail.

Bear in mind that less than 1% (probably way less) of the engines flying these days are of the rotary design, and on a weighted scale, I believe that you'll find that they have no better safety statistics than piston engines.


Here again, you need to keep things in perspective; the crusing RPM range for a typical air cooled piston engine is somewhere between 2,000 and 2,300, meanwhile a rotary engine will be operating at two to three times that.

The Cessna 172 and the Cessna 170 before it were designed by WWII aircraft designers who knew a thing or three about aircraft design. So, what tricks are you needing that these planes won't do?

As I wrote before, the rotary engine, regardless of which version, will be significantly heavier than a piston engine of similary output, that and it will most likely require twice as many rebuilds for any given number of hours. Given the above combined with the lousy fuel consumption rates, rotary engines are NOT a good alternative to piston engines from an economic perspective.

As for composite aircraft, believe it or not they are typically heavier for any given capacity or size. Take the Cessna 172 (aluminum) compared to the Cirrus Design SR-20 (composite) as an example. Both planes are of a similar size and yet when both planes are empty, the Cirrus weighs nearly 400 pounds more than the 172.

I have no idea what you just wrote vis-a-vis comparing the two engines, however, I will lay odds and cash money that Wankle derived engines will never become widely accepted engines in the General Aviation community. So, what do I believe will replace the tried and true air cooled boxer engine found in most GA aircraft these days? Diesels (with good old fashioned pistons).

http://www.centurion-engines.com/
http://www.deltahawkengines.com/