Why Do Rotaries Suck?

[ylwgtr2]

no he said this century.....2000 onwards

[jame88]

Alright ill reply to a few more things, but i seriously can't reply to every point you have raised or else each post in just going to get longer and longer till it gets ridiculous and noone will even bother read it (probably already has) maybe just tell me what you disagree with the most.

“Angular speed”, of course, that’s far more meaningful than rpm or cpm. Do you really want to get into apex seal speed versus piston ring speed discussion? Because it’s not very supportive of your case, in fact it contradicts it completely. But I’m up for it if you are.

Sorry if i have confused anything by using "Angular speed", it just means how fast something is rotating. Rpm is a measure of angular speed. I just don't like using rpm to refer to how fast something is rotating, its like saying "What's the degrees today?" or "What's the meters from here to over there?" and so on. Sorry if thats being a bit pedantic. I agree noone cares about piston speed vs apex seal speed.

So now we are multiplying the torque output by the step up ratio.

Yes, if you were to take the speed before your imaginary step up ratio, the power will not change no matter what the ratio is, if the speed is decreased, the torque is increased, pretty simple stuff there.

Power = Torque x Speed

This is of course irrelevant, as there is no gear ratio between the rotor and eccentric shaft.

Plenty have tried, have you read Phil Irving's engineering paper on rotary engines? But Mazda's marketing muscle has suppressed it, rather viscously in some cases. But I like a good joust, especially when I know my point of view is correct and I have plenty of evidence to support the view.

Ill try to have a read of that as soon as i can. The viscosity of Mazda's marketting department is irrelevant.

I like a good joust too, and im willing to try to explain my argument as long as people are actually going to listen. Please try to keep this as a technical discussion, not a flame war, as attempting to personally offend me doesn't make you correct.

[GT-R32]

I give up. You win Gary. I underestimated your ability to sustain an argument. I wasn't seeking this, only seeking whole and relative truth, to increase understanding of operation out there. I don't agree with you as time relative and combustion is missing. But you made some valid points with regard to displacement and operation and that's good.

[jame88]

Hang on, so the outside of the rotor does 3,000 rpm but the inside does 9,000 rpm, That's a good trick, but I some how doubt it. The fact is the whole rotorr is doing 3,000 rpm, and the rotor is the combustion medium, it's what makes the power, somewhat like a piston in a piston engine in that regard. So comparing it to a water pump is pretty stupid, they don't produce any power. Nice try on muddying the water with the camshaft rpm, but that's a 4 stroke. How about we compare it with a 2 stroke piston engine with no valves (like a rotary) and no camshafts (also like a rotary). Bingo, everything is doing 9,000 rpm (or cpm if you prefer) but in a rotary, oops the main parts, the bits that make the power, the rotors, are only doing 3,000 rpm (or opm if you prefer).

*facepalm

The cycle of a Wankel is a much more complex motion than the simple sliding crank of a piston engine. The rotors are rotating about two different points, think of the earth rotating around its axis while orbitting the sun.

Do you at least now understand the pinion gear in a rotary is fixed and there is no gear ratio between the rotor and eccentric shaft?

I don't mean to offend but how do you manage to reply in this thread so much? You write a very impressive amount in this thread, i don't know how you find the time.

[Parag0n]

Gary hates rotaries and mazdas LIES

Edited September 29, 2009 by Parag0n

[mad082]

OK well i'll start with the speed argument.

Heres the animation posted earlier in this thread, also on wikipedia

I can see where many of you may how got confused here. There is indeed a ring/pinion gearset which has a 3:1 ratio in the Wankel engine. The ring gear is attached to the inside of the rotor, but where you seem to have misunderstood is the pinion gear is FIXED to the rotor housing. NO POWER is transmitted through this gearset. This gearset's only purpose is to force the rotor to move in a Wankel cycle.

All power is transmitted from the rotor to the eccentric shaft via bearings on the lobes of the eccentric shaft (the white circle in the center of the rotor in the animation).

You are correct in that the rotor is rotating about its center (point A rotating about point B) at 3000rpm when the engine speed is 9000rpm. This is however about as relevant as the speed in rpm of the camshaft, timing chain, water pump etc in a piston engine, as no power is produced at the output shaft of the engine from this rotation.

Power is produced in a Wankel from the rotation of the center of the rotor (point B) about the centre of the output shaft. This rotation is at 9000rpm and should be where the speed of the rotors in taken from.

This is an eccentric shaft for a 13b engine, notice the offset lobes which the rotor rotates on, and the lack of gears of the shaft.

Hopefully i have explained this better and those of you who care to learn will benefit.

As for the other debates (combustion cycle, capacity etc) i will explain these further when i have a chance, as there is only so many hours in a day.

you have me confused there (and i see gary has posted up about the same thing). so it is true that the rotor is spinning 1/3 the speed of the shaft it is on, point b), but then the centre of the rotor is spinning at the same speed as the shaft? umm, how can that be? i know that with my car the wheels don't move at a different speed to hubs, and that is basically how i read what you are saying

edit: i should add that i am by no means a rotary expect and have very little knowledge of the actual works and would actually like to know what you mean by this post

another edit: i think i understand what you mean now

[Jez13]

I give up. You win Gary. I underestimated your ability to sustain an argument. I wasn't seeking this, only seeking whole and relative truth, to increase understanding of operation out there. I don't agree with you as time relative and combustion is missing. But you made some valid points with regard to displacement and operation and that's good.

Aw dont give up! We are so close to a conclusion. Why cant we measure the cpm speed by the e/shaft?

[Sydneykid]

Gary hates rotaries and mazdas LIES

Almost got it, I don't hate rotary engines, after all I am about to spend 4 days trying to win a national championship with one. But you're right in that I can't stand Mazda's lies and the efect that those lies have had.

Cheers

Gary

[Jez13]

Gary - in the voice of the kid who said - why cant we have a flat bottom on a taco:

why cant we measure cpm from the crankshaft? dadadddaaadda ddaaddda

[Birds]

[jame88]

you have me confused there (and i see gary has posted up about the same thing). so it is true that the rotor is spinning 1/3 the speed of the shaft it is on, point b), but then the centre of the rotor is spinning at the same speed as the shaft? umm, how can that be? i know that with my car the wheels don't move at a different speed to hubs, and that is basically how i read what you are saying

edit: i should add that i am by no means a rotary expect and have very little knowledge of the actual works and would actually like to know what you mean by this post

another edit: i think i understand what you mean now

Im glad someone is actually trying to understand. I know Sydneykid will never back down after this long but hopefully i'm getting through to someone.

To explain the kind of motion im talking about here think about a amusement park ride. Im no artist but hopefully this will get the point across.

People are in a cart which is rotating about point B on the end of a large boom, which is in turn rotating at point A in its center, held in place by a frame.

The cart is rotating around point B at rpm 1 and is also rotating around point A at rpm 2.

Hopefully this has cleared this up.

The simple truth is what the eccentric shaft lobes do is to convert the 2 styles of kinetic energy of a rotor, the rotate and the orbit, into one style of kynetic energy, the round and round rotation of the eccentric shaft itself. There is no magic here, it's much like the the throw of a crankshaft converts the up and the down of a piston into the round and round rotation of the crankshaft itself.

Getting there.

Anyway i have a life to live away from my computer for the rest of this day. Ill make an effort to explain a few other things in the near future.

[Sydneykid]

Alright ill reply to a few more things, but i seriously can't reply to every point you have raised or else each post in just going to get longer and longer till it gets ridiculous and noone will even bother read it (probably already has) maybe just tell me what you disagree with the most.

Sorry if i have confused anything by using "Angular speed", it just means how fast something is rotating. Rpm is a measure of angular speed. I just don't like using rpm to refer to how fast something is rotating, its like saying "What's the degrees today?" or "What's the meters from here to over there?" and so on. Sorry if thats being a bit pedantic. I agree noone cares about piston speed vs apex seal speed.

Yes, if you were to take the speed before your imaginary step up ratio, the power will not change no matter what the ratio is, if the speed is decreased, the torque is increased, pretty simple stuff there.

Power = Torque x Speed

This is of course irrelevant, as there is no gear ratio between the rotor and eccentric shaft.

Ill try to have a read of that as soon as i can. The viscosity of Mazda's marketting department is irrelevant.

I like a good joust too, and im willing to try to explain my argument as long as people are actually going to listen. Please try to keep this as a technical discussion, not a flame war, as attempting to personally offend me doesn't make you correct.

I’m sorry if I come across as flaming you, it’s not intentional I can assure you Perhaps you need to go back to the start of this thread and follow the flavour. From the start I put forward an opinion and supported it with facts. A few guys tried to convince me that I was wrong, but they failed. Some guys completely misunderstood what I was saying and took it as a biased rotary attack. So they popped over to the rotary forum and got one of the big guns over to have a go. He resorted to the personal insults when he couldn’t support his stance as well as I could mine and then eventually he agreed with me and left.

A few of the more regular contributors to this forum have kept the dialogue open, but one by one and point by point they can see where I am coming from. They don‘t necessarily agree with me, but what started out as dismissive, “this guys doesn’t know what he is talking about” has turned into “maybe he does know something about how a rotary works and he might just be right”.

I’m not here to win anything and I’m sure as hell not right all the time. So I will apologise in advance if what I post seems dismissive or insulting. But until you read the whole thread and gain some understanding of what I’m on about you really might misunderstand the strength of my convictions and my willingness and ability to support them.

Cheers

Gary

[jase-r34]

just out of interest....whats sort of 1/4 mile times do guys running honda engines do?

I believe Honda quote something like 11.1 off the showroom floor for my vehicle with a 0.6L piston engine in it.

Yes that's because it is a bike, but yes it is relevant because the arguments I've seen on here are saying that a rotary can run 6's so why can't an RB. What a load of shit. An engine doesn't run anything down the 1/4. The whole package does. So in my case, a very light vehicle, very small yet high revving and quite powerful engine delivers a pretty impressive 1/4 mile time without modification.

And if you get a 1L or 1.2L version they can run 9's out of the factory with next to no modification. Where's the rotary that can do that?

So this "Rotatries run 6's" crap i just that, crap.

[Sydneykid]

Gary - in the voice of the kid who said - why cant we have a flat bottom on a taco:

why cant we measure cpm from the crankshaft? dadadddaaadda ddaaddda

You can and in fact Mazda does. But is it correct to state that "a rotary engine does 9,000 rpm"? You will say, "well of course it is correct because the eccentric shaft does 9,000 rpm". Whereas I will say "no it isn't correct because the rotors are only doing 3,000 rpm". When we say "an engine does 9,000 rpm" the natural assumption is that all of the engine is doing 9,000 rpm". Now in a 2 stroke piston engine that is 100% correct, all of the engine is in fact doing 9,000 rpm. But in a rotary engine only the eccentric shaft is doing 9,000 rpm, nothing else. The rotors are only doing 3,000 rpm.

Keeping the above in mind, that means 100% of a 2 stroke piston engine is doing 9,000 rpm, but only 33% of a rotary engine is doing 9,000 rpm. In other words the vast majority of a rotary engine (ie; 67%) is only doing 3,000 rpm. So when someone says "a rotary engine does 9,000 rpm" I say rubbish because the whole engine is not doing 9,000 rpm. In fact I say double rubbish, because most of the engijne is only doing 3,000 rpm.

But wait, let me add even more weight to my argument. We are talking about an internal combustion engine here, so surely it is logical to count the rpm of the part that actualy carries out the combustion process. In a rotary engine that's the rotors and, like it or not, the fact is they are only doing 3,000 rpm.

This is usually the point at which the rotary huggers, start throwing in cycles not revolutions, orbits instead of rotations, no strokes in a rotary engine, elliptical motion, not up and down etc etc. But to me that's just being pedantic and deliberately narrowing the meaning of common use words, in some vane attempt to escape the truth. But the truth is right here, it's not out there.

Cheers

Gary

[ylwgtr2]

I believe Honda quote something like 11.1 off the showroom floor for my vehicle with a 0.6L piston engine in it.

Yes that's because it is a bike, but yes it is relevant because the arguments I've seen on here are saying that a rotary can run 6's so why can't an RB. What a load of shit. An engine doesn't run anything down the 1/4. The whole package does. So in my case, a very light vehicle, very small yet high revving and quite powerful engine delivers a pretty impressive 1/4 mile time without modification.

And if you get a 1L or 1.2L version they can run 9's out of the factory with next to no modification. Where's the rotary that can do that?

So this "Rotatries run 6's" crap i just that, crap.

Thanks for that....but you know i was asking about cars......I'm well aware of a motorcycles capabilities....concidering i have atleast 10 or so smashed sports bikes at work for repairs constantly

[jase-r34]

Bikes or cars it is irrelevant. The point was it is not the engine that runs the 1/4. It is the complete package. So sorry if you didn't like my comparison of a stock 0.6L piston engine to a 3.9L wankel, or just have some problem with bikes, but my point is valid.

[jase-r34]

Oh, and LOL at that!

[Birds]

Knew I couldn't stay out of this one...I tried my best ladies and gents.

A few of the more regular contributors to this forum have kept the dialogue open, but one by one and point by point they can see where I am coming from. They don‘t necessarily agree with me, but what started out as dismissive, “this guys doesn’t know what he is talking about” has turned into “maybe he does know something about how a rotary works and he might just be right”.

I’m not here to win anything and I’m sure as hell not right all the time. So I will apologise in advance if what I post seems dismissive or insulting. But until you read the whole thread and gain some understanding of what I’m on about you really might misunderstand the strength of my convictions and my willingness and ability to support them.

You mistake peoples' willingness to get on with the rest of their lives...for agreeance. It's simply not the case Gary. A long time ago I used to be a very argumentative person, and just like you I thought I'd won all my arguments just because the other person stopped arguing their point. But it wasn't a case of me being right all the time or simply assuming so, it was actually a case of them not having the patience to deal with me not letting go of a tired point that could be argued back and forth for eternity. So don't assume that because people have come and gone or closed dialogue with you means that they concede their side of the argument...don't rule out the possibility they simply can't be bothered wasting their energy on people like you and petty arguments after making the realisation that no matter what they put forward they'll never be able to change your mind. You are your own worst enemy.

You can and in fact Mazda does. But is it correct to state that "a rotary engine does 9,000 rpm"? You will say, "well of course it is correct because the eccentric shaft does 9,000 rpm". Whereas I will say "no it isn't correct because the rotors are only doing 3,000 rpm". When we say "an engine does 9,000 rpm" the natural assumption is that all of the engine is doing 9,000 rpm". Now in a 2 stroke piston engine that is 100% correct, all of the engine is in fact doing 9,000 rpm. But in a rotary engine only the eccentric shaft is doing 9,000 rpm, nothing else. The rotors are only doing 3,000 rpm.

Keeping the above in mind, that means 100% of a 2 stroke piston engine is doing 9,000 rpm, but only 33% of a rotary engine is doing 9,000 rpm. In other words the vast majority of a rotary engine (ie; 67%) is only doing 3,000 rpm. So when someone says "a rotary engine does 9,000 rpm" I say rubbish because the whole engine is not doing 9,000 rpm. In fact I say double rubbish, because most of the engijne is only doing 3,000 rpm.

But wait, let me add even more weight to my argument. We are talking about an internal combustion engine here, so surely it is logical to count the rpm of the part that actualy carries out the combustion process. In a rotary engine that's the rotors and, like it or not, the fact is they are only doing 3,000 rpm.

This is usually the point at which the rotary huggers, start throwing in cycles not revolutions, orbits instead of rotations, no strokes in a rotary engine, elliptical motion, not up and down etc etc. But to me that's just being pedantic and deliberately narrowing the meaning of common use words, in some vane attempt to escape the truth. But the truth is right here, it's not out there.

That's your assumption and it's a very shitty one at that. It's also based on people knowing next to nothing about how the engine works? Why are you basing a technical term like RPM on a lamen assumption, i.e. that all rotary components move at the same speed? Given engine RPM is and forever will be a direct reference to crankshaft speed, irrespective of what actually drives the crankshaft, it is very correct to say that a rotary engine revs to 9000rpm. Perhaps you would like to take a look at the hypothetical case that if crankshafts didn't exist in engines and instead motion relied on something other than "the wheel", your piston engine without a crankshaft would have no use for the term "revolution". It would instead be called strokes per minute or termed according to whatever motion an engine happened to rely on. Case in point, and reality has it, that piston engines do rely on crankshafts...hence the term revolutions per minute and use of this term outside of a rotating component is ridiculous. We're allowed to be specific and pedantic with terms here...this is engineering...not year 12 literature open for interpretation.

And while I'm at it, how can you call it pedantic to narrow the meaning of so called "common words" like RPM...when you yourself are being so pedantic about the meaning of the much more common and ambiguous word "displacement"? This sounds somewhat hypocritical to me.

[ylwgtr2]

Bikes or cars it is irrelevant. The point was it is not the engine that runs the 1/4. It is the complete package. So sorry if you didn't like my comparison of a stock 0.6L piston engine to a 3.9L wankel, or just have some problem with bikes, but my point is valid.

Not really dude....you and everyone else knew what the question was(and the fact that we were talking about cars)....gary answered it which i thank him very much i might add....Its like me trying to compare a jump jet to a wankel powered car or to your CBR600 or my brothers prostock drag bike ....well they all have engines dont they????

Edited September 29, 2009 by ylwgtr2

[jase-r34]

Not really dude....you and everyone else knew what the question was(and the fact that we were talking about cars)....gary answered it which i thank him very much i might add....Its like me trying to compare a jump jet to a wankel or to your CBR600 or my brothers prostock drag bike ....well they all have engines dont they????

No it isn't. My cbr is a road going registered vehicle. How is that like comparing to a jump jet or a pro drag bike?

I was only debating the "rotaries can do 6's and RB's can't" statement. Neither of them can, its the entire vehicle that does the time.

I fairly compared a stock 0.6L piston engine to a stock 3.9L rotary, so what's wrong with that comparison to make my point?