Instruction for making a Wankel engine

[NC Cams]

To ITSME: I've learned from my voluminous exchanges with Ken to date that his concepts randomly go from classically unproven but "Ken proven" technologies to merely "Ken's instructions for everybody/anybody ELSE to use/try/perfect".

I can't wait to see his response to the very serious technological and dynamics realated challenges (I'd contend deficiencies) that you've uncovered in his latest claims.

An ECCENTRICLY MOUNTED PROPELLAR??? Interesting albeit dangerous idea. I think it has less than vacuous merit but to be fair, why not try it???

BTW, you DON'T want to put a concentrated imbalanced load into a ball or roller bearing. They simply won't live under that sort of loading environment. As a former bearing engineer for a major bearing supplier, I can say this with MUCH more authority and expertise than Ken can ever hope to muster via his SWAG's (God, how I hated doing unbalanced load life calculations), unbalance load applications are such a PITA to do and the load/life calc answer is NEVER good enough for the person to use the bearing they made room for!!!!.

To those folks who think this is 'viable' idea (I don't, so I refuse to waste time trying it), go to a model plane supplier and find the biggest, heaviest model air plane prop you can find - no matter how heavy of a one you'll find, it will weight less than a real one.

Bore the hole eccentrically - how much?? I dunno, ask Ken for his recommendation.

Then mount the prop to a motor. Make sure you can throttle it electrically. To be fair, be sure it is mounted the EXACT amount of eccentricity that Ken says to do. Now, run said motor at the speed Ken is claiming is viable for his latest wankel modification.

CAUTION: hang on and raise the RPM slowly because it will probably shake and shake pretty darn HARD and I suspect that the thrust will be irregular as well. Now imagine these or MORE shaking forces and irregular thrust forcees being applied to the nose of a light aircraft or an ultralight experimental airframe that YOU will be riding on.

At that point, please report on your findings... hopefully you'll be able to do it with all your digits still attached. In the mean time, I"d be interested to hear what other light/ultralight aircraft enthusiasts think of this eccentric prop idea...

Ken: has or have any REAL airplanes ACTUALLY flown with this concept? Yes or no.

Or is this another intuitively obvious 'Ken idea' that 'will work, trust me' that you're proposing for someone ELSE to try???

Ken, if your "sandpaper roll" cavity finisher concept works so well and so inexpensive to incorporate, you should EASILY be able to gain interest in a cost sensitive OEM buying the technology. This is especially true if it reduces the costs of capital tooling from $800K to a small fraction thereof. With the "cost down" philosophy in vogue at ANY OEM today, you should be welcomed wth open arms.

Lets say the the concept ultimately is production feasible and does perform as you claim (I am NOT saying it won't), OOPS, WAIT A MINUTE!!! You have a small problem.

For ANY OEM to incorporate a new, "advanced manufacturing technology" (oscilliting sanding rolls are not new nor advanced nor high volume production suited but I digess), you would have to -

guess what.......

PROVIDE A DYNO TEST TO PROVE VIABILITY OF YOUR CONCEPT. Isn't it strange how that small hurdle keeps cropping up??? Do you think that there is a reason why??? Can you or anyone guess what that reason might be??? Try rereading post 150, especially the closing paragraphs.

In light of the fact that Ken can't or won't do the dyno testing needed to prove his concept works, he merely seems to be hoping/expecting/waiting for someone else to do it. In such instances, the chances for Ken's concept EVER being implemented by an OEM or even other wankel afficianados are two (2) - slim and none.

Ken, keep one think in mind WHENEVER you start thinking about doing avante garde things to/with small aircraft:

Airplanes have a ruthlessly efficient and usually violent ways of proving that unproven, poorly engineered (perhaps stupid) concepts don't/won't/can't work.

Tinker all you want on "ground planes" and "bench motors". But when it comes to planes that will have a person's life at stake when it gets in the air, make DARN SURE you concept is dyno proven and engineering sound before you let it get off the ground.

SWAG's and "tinker engineered" concepts have NO PLACE WHATSOEVER in potentially life threatening useage applications.

Hmmmm. Eccentric propellars. Wait until the Experimental Aircraft Association and the FAA Inspectors hear about that one....

If there are any FAA folks or experimental aircraft plane builders in the viewing audience, I'd love to hear your input...

[fyffe555]

Ok, decided I wasn't going to contribute anymore but this is plain silly. Is this a troll? I have no trouble with new ideas but let us present them as such, not the suggestion or argue these are factual, proven and reasonable.

the best Wankel 'improvement' I've seen on the 'zone is Warren's (Itsme) model wankel, math for shapes almost identical to Kens drawing construction, made in a few weeks, openly shared here and I learnt some new stuff from it and he got it to fire if not run. great effort.

As to the sillyness;

Originally Posted by Ken McKenzie In the ultra light air craft the Wankel engine turns at a un desirable high speed.

Who said? This is rubbish. Assuming propellor propulsion here, the design speed of a prop is a function of tip speed, reynolds number, design parameters of the aircraft, thats it. An engine is chosen to meet the requirement. If the requirement is for the optimium torque of the motor to match a slower speed prop then gearing is used. Ask the Wright brothers, they figured it out.

Geared and direct drive wankel engines are very successfully in use and readily available for Ultralight and heavier Aircraft fully certified and have been for many years. All with conventional props or ducted fans. Wankels produce torque at higher speeds so they have to turn faster but correct prop or gearing is the solution.

Originally Posted by Ken McKenzie In a previous experience I found excessive torque produced when I created a direct link between the rotor and drive shaft.

IC engines produce torque - Hp is a function of torque, which is just a function of pressure in the engine. More Hp and efficiency is desirable so how can you have too much torque??? Or do we mean there's too much for your 'direct link' modification. That's an engineering problem, not excessive torque.

Originally Posted by Ken McKenzie What we have is an air cooled engine that turns the propeller slightly eccentrically at one third the speed.

OK this is where it gets real silly. Find someone who actually understands Props suggest your idea, stand WELL back if they happen to be drinking.

Prop balance is critical to such an extent that the prop is usually dynamically balanced, often to less than 0.1in/sec and depending upon engine the engine/prop assembly might be balanced too.

What do you think the balance might be on an eccentric prop? Did you even consider it? Exercise for the student; calculate the mechanical forces on a simple 2 blade 6' prop at ~1500-2000 rpm with a 1/2" eccentric. Now do the same for 3 blade. Now calculate the aerodynamic loads caused by running these props eccentric. Hint the aero loads on an eccentric prop will act to rock the blade forward and back or wobble in its plane as well as in the plane of the blade.

As a further clue, typical pager vibrator motors rotate around 6krpm and have an eccentric of 1/2mm and diameter or 3mm. Ignoring aero loads you're proposing a 100hp pager vibrator six feet in diameter and around 20-50lbs. In a microlight weighing under 254lbs empty?

Believe it or not Aero loads can exceed the mechanical loads, just ask someone with an Aeronautical education, oh wait, you just did..

Vibration shortens the flight hours of airframe, engine, electronics, avionics and aircrew. It's a major factor in calculating airframe life and when the switch to jet occured airframes doubled or more thier airframe hours even though the actual in flight loads increased simply because vibration was reduced.

My example of the 6' prop above would take the prop outside the 0.4 in/s balance requirement for FAA certified aircraft by many ORDERS of magnitude, and that entirely ignores the increase in stress failure risk.

At a simpler level, as I understand it you're mechanically connecting the prop, or in this case a massive vibration maker, vibrating in all three planes to the rotor and not the original output shaft? What do you think that's going to do to your bearing assemblies, let alone rotor clearances or seals?

Finally you suggest connecting to the rotor will ' reduce the speed' by a 1/3rd? really ? because in post #7 you say thats not true? Whateveryou are removing the gearing implicit in the engines original design and expect to turn a prop at rotor speed without gearing ? where do you think thats going to put the prop speed in the engines torque curve?

Apologies to 'zone members, not trying to rag on anyone but this is too much.

Andrew

[fyffe555]

Eason; 'Highly schooled engineers are limited by their lack of fantasy'

Originally Posted by balsaman Could not have said it better myself.

A good question but I'm not sure about that. Engineers are limited by requirements of money, production costs, employers demands, peer review and inconveniant things like physics. That doesn't mean they don't image a better bridge or what ever fantasy they have, they are human after all!

However, wether they personally actually do anything about it is another issue and that's often down to human nature, Ken's an 'inventor' and tries, that's more than a lot of 'engineers' would do and he should be applauded for that. Especially since he's been doing the same thing since 1978.

He shouldn't be applauded for suggesting as fact ideas that are dubious or unproven. Like the idea that Mazda's housings are not 'precision'. The fact that so many are running for profit suggests that Mazda's are precise, they couldn't run consistantly otherwise, and they are precise to Mazda's spec. The issue is with definition and assertion that one is better than the other - and Kens not told us why his are more precise and what the benefit is, percieved or measured - other than quotes from one specific book. The idea that Mazda in their thousands if not millions of engines might know a thing or two isn't reasonable apparently.

Back to engineers, most successful engineering companies are sucessful why? because they're slow, unimaginative or behind the ball? Or because they are better, and if so what's better? Frequently it's because they DO put their imagination, fantasy or exciting product into fact. The fantasy does go on - it's just not visible, next time you go buy the newest technology; TV, ipod, hot sports car think that somewhere someones imagination came into play - and an engineer turned it into actual reliable fact.

To be a 'highly educated engineer' you have to graduate, if not post grad graduate. Most schools, if not all require some final thesis on a subject not previously covered or with a unique aspect. You don't get to do that without some imagination and fantasy. In good schools the pressure is to learn the skills AND how to apply it with imagination required. Lack of imagination means poor grades and thats where Eason's observation comes true.

At the end of the day we expect society to advance, in engineering thats means imagination and fantasy AND the ability to turn it into fact.

Most can identify a new problem, it's much harder to produce the solution, and it usually doesn't come from copying a book.

Andrew

[balsaman]

I agree that running a propeller on a slight eccentric is suicide.

We need to remember that all Ken's ideas are just that. Ideas. Food for thought. I do not believe he is suggesting you should try them. Perhaps he is suggesting that he would like to try them, and obviously he believes that his ideas will work without a doubt.

We can agree the we don't all believe that this is so.

I wish this thread would have turned out differently. As it is, I believe that it is no longer constructive, nor is it all that informative at this point. I have decided to close it for the time being. Perhaps, after a time, I will open it again.

Eric