Is IC Piston Engine Really Less Than 1% Efficient?

During my days as a race engineer with a major and successful race team, our engines were consistently 25 to 45 horsepower shy of our competition, who we consistently beat (and won a major national racing championship) because our engines generated the torque needed at the engine speeds needed to win.

In two otherwise equivalent cars with equal drivers: Top speed is related only to engine HP. (The gearing of a low rpm high torque engine has to be taller than that of a high rpm, low torque engine, of course.) Acceleration is related only to hp/weight. (In practical terms, making two cars identical in other respects is difficult -- a peaky high hp engine has its power spread over a narrow range of rpm, so needs more speeds in the transmission to compensate -- thus 12 speed 50cc motorcycle racers).

If you increase torque and can maintain that increase at a higher rpm, then you have increased HP. But in your example, the top speed of a your car (if it were geared for top speed) was less than the top speed of one with 25-45 additional HP (assuming both HPs -- or wattage outputs -- were measured on the same dyno under the same conditions). Drivability is a different issue, and it is in that regard that your cars probably had an advantage. Further, your drivers were quiet possibly better.

I managed (and rode) for race teams also, and our bikes were often down on HP and torque, but we beat bikes with double the hp and more than double the torque (in endurance races where all classes would run together.) Handling, drivability, avoiding crashes, power spread vs number of available ratios... loads of things come into play that have nothing to do with the specifics of torque and hp at the flywheel.

I don't hold Smokey in the high regard that you do, because many of the things he did were just plain cheating. His statement is not unlike the stuff he wrote in "Ask Smokey": grossly oversimplified, sometimes completely incorrect, and based on anecdotal evidence and small sample size. (My own racing experience would indicate that both hp and torque should be very low to win -- our 350cc Honda beat every 500cc, 750cc and open class bike.) "Son, horsepower gets the headlines, but torque wins the race"* is generally technically incorrect (ask any Formula One team -- the average road going V8 has more torque) and is only vaguely correct in the colloquial sense that "torquey" engines have broader power bands and are therefore easier to drive and can accelerate out of corners better if they are not in precisely the right gear. (That, however has nothing to do with the current thread.)

My 50cc motor scooter has the same engine torque as a 50cc grand prix class bike (5 lb-ft) The GP bike produces this torque at 22,000 rpm, therefore producing about 4 times the hp of my scooter. The GP bike has better than twice the top speed, and is far faster in acceleration: at 45 mph my scooter can no longer accelerate and the GP bike is rocketing past.

In the matter of top speed, there is one meaningful determinant (with other variables held constant): HP. In acceleration , the same is true (although gear spacing makes holding all other variables difficult). If we assume appropriate CVTs in both cases, HP wins in acceleration: thus the ability to predict acceleration from hp/weight, whereas it is impossible to predict acceleration based on engine torque.

* In the motorcycle world, an obvious example is the Buell (1200) vs Honda (etc) 600's. The bikes are comparable in weight, but the Buell has much more torque, and the 600s have considerable more HP. When equally prepared for racing, the torquey Buell is already far behind at the first turn, and is hundreds of yard behind at the end of the first lap.

Again, I respect your comments. I am afraid we must agree to disagree.

With regard to my comment regarding our racing success, our advantage was being to out-accelerate our competition exiting turns, as our superior torque generated at the engine speeds exiting was, in combination with our gear train allowed us to pull away from the competition. Even though they could run us down at the end of straights, we maintained the lead position and could gradually extend our lead. All of the theoretical factors are important, but the point is we won...and they didn't. Also, we had a journeyman driver who was not considered one of the best. But, all of our performance factors combined to allow us success.

Our cars were relatively equal, our drivers were not.

I again will agree to disagree about your opinion of Smokey. Most of the public is unaware of his engineering innovations. The drinking, the public behavior and yes the cheating gathered the attention of the public. It is sad that his his contributions in engine design and chassis dynamics is largely obscured by the publicized activity. Having had an opportunity to study the historical documentation within two of America's major auto manufacturers, much of the technical innovation claimed by others was generated within his shops.

Again, my response was to the issue of horsepower vs. torque. The argument is made by another poster that mathematically, each can be a function of the other. True enough. I am a mathematician as well as an engineer. But, from the physical aspect of how the world works, the engine generates torque, which we measure on the dyno, we record the engine speed and calculate horsepower. Certainly, any interrelated physical parameters can be mathematical functions of each other. But in the real world, that is often irrelevant, as the mathematical analysis is pointless in certain instances as it does not support a physical reality.

Thank you for your comments.

standared,

I don't know?? But I get the feeling that you respect too much and stand up for yourself too little ! Although what exactly you are standing up for beats me !

After reading a lot of the drivel in tha last few posts, I have to weigh in on the side of the OP, what do you say to his claims?? Apart from blathering about wrong units etc., ?? The fact remains that an initial force of 2861 some pounds force results in a torque of only 40 ft lbs approx., while it could result in a torque of in excess of 2816 ft lbs if the lever was long enough. Stick to the point don't get bogged down in what is possible or not! I DO AGREE 40/2816 x 100 = 1.5 % approx!! Get around that if you can, stop spouting about wrong units if you please. If you take the trouble to look throught this post most of it is giobberish about wrong units!! Open your eyes try to see what he is saying!

You can have as much torque as you want if you make your lever long enough - but it's not going to do you any good unless it produces a useful angular velocity at the output shaft.

Torque and angular velocity are almost synonomous!

NO WAY!

There are zillions of places where significant torque being applied results in zero angular velocity. A person standing at rest on a diving board would be a good example, as would any overhanging structure, like a marquee.

I thinkmaybe what guest meant in his post was that in an engine torque and angular velocity are almost synonomous since without the applied torque there would be no angular velocity.

So what is the angular velocity of a torque wrench socket when a mechanic tightens a bolt to a specified torque? Well the angular velocity is zero, for the wrench socket stops moving. But the torque being applied is certainly not zero because the mechanic is applying a force. When the mechanic stops applying the force the socket's angular velocity is still zero but now the torque is also zero.

Do you think before responding?

To add to Redfred's comment....what about when the bolt is just getting started and the torque is near zero....but the mechanic is spinning the wrench as fast as he can...angular velocity will be high.

Heh! , Here's an idea !! How about if there is some type of ratchet mechanism in the wrench that prevents it from engaging, so you can turn all you want nothing happens. Brain wave right !!!

RUBBISH!

Look it up!

http://en.wikipedia.org/wiki/Torque

http://en.wikipedia.org/wiki/Angular_Velocity

They are different physical quantities.

John, the link to torque you had posted was very useful.

You say "I DO AGREE 40/2816 x 100 = 1.5 % approx!!"

The reason for being picky about units is that units matter. The value of 40 in your equation is in units of torque (ft lbs), while the value of 2861 is in units of force (lbs). If you divide 'ft lbs' by 'lbs', you are left with units of feet, and multiplying that by 100 does not give you %, it still leaves you with units of feet. How about if we convert the 40 ft lbs to in lbs...so it would be 480 in lbs....then poof!!! 480/2816 X 100 = 17%....how's that? I just increased the efficiency by a factor of 12.

JB,

If you apply that unit of force (2681 lbsf) through an angle of 90 degrees at the end of a 12 foot lever it gets translated into 2681 ft lbs torque. The point I am trying to make is that even with such a relatively large (2681 lbsf) force available it translates into only 40 ft lbs torque. Do you see what I am getting at ? I am certainly not suggesting anything close to lbsf/ft lbs!

I do not know if JB grasps what you are saying but I certainly don't. I hate to be dense but I don't understand what the unit "lbsf" stands for. An acronym Google search on lbsf gives me useless terms that have nothing to do with force, like the Local Back Surface Field and Lehman Brothers Special Finance. If you mean instead the non-standard pressure unit of pounds per square foot then we're not talking about force but pressure. So one cannot directly convert pressure to torque without knowing the lever arm length and the area that the pressure is being applied on. To obtain only 40 ft lbs of torque with a 2681 lbs/ft² the pressure must be applied on only 40 ft lbs /(1 ft * 2681 lbs / ft²)≈ 0.0149 ft² → 0.0149 ft² * 144 in² / ft²≈ 2.15 in²

If you mean instead pounds of force then why does a this not become 2681 ft lbs since the lever arm is one foot. What reduces this to 40 ft lbs?

JB,

As far as I can see the torque does not become 2861 ft lbs, simply because your lever is only 0.11 inches long! This is exactly the problem although the area of 5.7 sq ins (diameter of piston = 2.6 ins) is adequate to result in a pressure of 500 psi resulting in a total force of 2861 ft lbs torque, both the length of the lever and the angle at which the force is applied result in a torque of 40 odd ft lbs torque.

Firstly, I think you mean at the end of a 12 inch (1 foot) lever.

Secondly, your example is based on an assumption about an engine design that doesn't exist. Using your logic, if I have a lever that is 11 feet long with a fulcrum (pivot point) at 1 foot to the left of the right most end, and I apply 1 pound to the right most end, I would only get a force of 0.1 pounds at the left most end and you would claim it is only 10% efficient.

Yeah I did that accidental lever arm translation in my head, too. 2681 lbs with a 12 ft lever will produce about 30,000 ft lbs of torque. I still don't see where 40 ft lbs comes from though.

redfred, I think the 40 ft lbs torque comes from the manufacturers figures for this particular engine 59 Nm torque = 40ft lb torque approx. (It should be 43.7 ft lbs ) approx.

Ah, but this is where we talk about the revolutionary [pun intended] new engine design. We switch to measuring distance traveled, and because the leftmost end goes 11 times as far as the right, it's 1100% efficient! It isn't perpetual motion, "merely" over-unity.

Does this approach remind anyone of a physics-law-defying gearbox thread?

This thread is not going anywhere . And I am surprised why 275 posts have come up.

If you traverse through this I feel the nobel prize belongs to the OP and few others.

Force = torque = angular velocity

Are we moving quickly towards GUT ? After all if all the fundamental qualtities can be expressed as a single fundamental quantity will it not be even beyond GUT ? After all nobody yet has unified time, mass, length,.. into a single quantity.

Keep it up, Nobel prize is yours for taking.

THE NEW GREEN ENGINE

I would like to draw your attention to the following points:-

1) A Fuel/pre-compressed air mixture is fed into the combustion chambers and ignited, the exhaust is then opened allowing the gases of combustion to escape at velocity, the rotor then moves in the opposite direction in keeping with Newton's Third Law, for every action there is an equal and opposite reaction, turning the main shaft to which it is attached..

2) There are two combustion chambers both synchronized to fire at the same time lending a wonderful balance to the whole system, and creating a force couple that acts on the main shaft to give a smooth and powerful output.

3) Note, the distance between the centers of the two combustion chambers is (in this model) 18 ins.

4) The thrust is exerted at right angles , resulting in maximum use of the long lever arm.

5) Using the same diameter for the base of the combustion chamber as in the piston diameter in the Maruti 800 example it is possible to generate 3000 ft lbs torque.

6) If the engine is running at 3000rpm this would result in a horsepower of 3000 x 3000/5252 = 1713 hp approx.

7) This extra power generated is not wasted it is used to impart kinetic energy to a 50 Kg, 40 cms diameter flywheel spinning at 30000 rpm . The kinetic energy developed by the flywheel would be in the region of 9 MJ, enough power to keep a car weighing 1000 Kg running at 12 hp for 16minutes.

8) It will take the engine when running at 3000 rpm only 0.5 seconds to bring a 40 cm. diameter 50 Kg flywheel to 30000 rpm

9) The engine would thus run for just a few seconds or so in every 16 minutes running time of the car.

10) Is this a green car or what????

May I say that this engine is all the things that many claimed was impossible. It has a huge ( compared to the IC piston engine ) lever arm. It is compact, It is beautifully balanced. It exerts force at right angles and not at some continuously varying angle. It uses all of the power that it generates by offloading power to a flywheel storage system. It saves fuel by running for only a few seconds in every ten minute period or so. It is therefore extremely energy efficient and clean. What's wrong with it. I don't want exaggerated, aggressive or hyperbolic comments, I just want some sensible well phrased comments/questions that I will then address.

What an ego you must have.

You start this entire thread proclaiming that a working existing engine, the now maligned Mauruti 800, is a grossly inefficient engine with the worst mechanical analysis I have ever seen. You would certainly fail any Physics class with the methods you use. You then insult the people here who try to politely correct you. Now you come up with what looks like a Photo-shop edited clip-art drawing and proclaim you have a more efficient engine.

First, none of the numbers you have fabricated for this contraption can be believed. We already have here written proof how badly you can calculate the simplest of equations.

Second, clearly this machine does not exist. At the very least it has not been built by you, nor tested by you. This is all a fantasy.

I'm tempted to bring up several of the technical difficulties I see in trying to realize this engine approach, but that would be granting you some credence I am convinced you do not deserve.

I wish you the best in your realm but it is not engineering. You have no grasp of the requirements for good engineering. You should not be here.

Please, go away.

No Comment!!!

P.S. Try not to forget that I am also one of the "people" here !!!

P.P.S. In case there are any "people" here with a more moderate approach, I am willing to validate the design.

I shouldn't really do this. But Redfred, why don't you go away before your blood pressure gets the better of you. At least try to stay on the side lines, while the discussion goes on??

Did you get this idea from the design of the helicopter with ramjets on the ends of the rotor blades? S.

No Steve, I got the idea frm thinking about how to overcome the linear to rotary conversion problem in an IC piston engine. Does this helicopter you are talking about really work. However I think if they do work theymust be continuous combustion types like a turbine and not the intermittent combustion that I have in mind.

Is this a green car or what????

No! S.

At Last, we see the concept for a new engine... enough to bring me back, I suspect for a short while...

Your points 1 through 4 are valid.

You fail at point 5. It appears that you are assuming that the force on your combustor will be the same as the force on the piston of the Maruti 800. That is definitely NOT so! In a piston engine, the closed cylinder causes the burning gasses to exert a large pressure on the cylinder walls and on the piston. You yourself say "allowing the gases of combustion to escape at velocity". If the gasses are allowed to escape at velocity, then there is no chance for them to build up pressure, so the force exerted on the combustor is nothing more than the force of a small rocket acting on each side of your rotor.

Please investigate the amount of fuel required to power a rocket, and the resulting thrust.

The concepts of using a longer lever arm and a force exerted perpendicular to that lever are quite valid. Now if you can figure out how to exert a force anywhere near to that exerted on a comparable piston in a piston engine over a comparable distance of travel, THEN you'll have something worth promoting.

Since point 5 is clearly mistaken, all subsequent points have no meaning.

Hi dkwarner,

Yes now we come to the nub off it. I have too much respect for this forum and for members like yourself, blink, mcb the list goes on, who at least retain some sort of objectivity, to have come back to the forum without taking your advice and trying to validate the design. Yes, I have built a working model that shows, the validity of the design or I wouldn't have posted on a subject that has already been posted.

Did your 'working model' include that massive flywheel and some sort of load, or was it just the pulsating rocket pinwheel?

Probably the most fundamental equation of physics is F=MA. For a rocket engine, that becomes F=M(∆V/T), where F= thrust, M=the mass of fuel plus oxidizer, ∆V is essentially the velocity of the exiting gasses, and T is time during which that fuel/oxidizer is ejected. The one thing that is difficult here is to know the velocity of the exiting gasses, which mostly depends on the temperature of combustion, the size and shape of the combustion nozzle, and the back pressure exerted by previously spent fuel/oxidizer.

Noise limitations tell us that your exit velocity must be less than the speed of sound, so use that as a starting point for calculations.

Even though you may develop some pretty good pressure, that pressure is only able to push on the area of the nozzle, which must be orders of magnitude smaller than the area of the top of a piston.

dkwarner,

Forget about rockets for the moment, or rather keep them in mind, for a later date. Start of with an open mind to the concept. In the design being detailed here for the new engine design, instead of using a piston to compress air, pre-compressed air is used from an external tank. Thus if you have an external tank of compressed air with air at about 125 psi this works out to a compression ratio of about 9:1 in the combustion chamber. Once this pre-compressed air and fuel enters the combustion chamber, the inlet valve is closed creating a completely sealed environment. Next this compressed fuel air mixture is ignited causing a rise in pressure to about 500 psi and a rise in temperature to about 2000- degrees Fahrenheit. So far this process closely follows the combustion process in an IC piston engine. Next the exhaust valve is opened causing these gases under pressure to exit at velocity propelling the rotor forward. The difference between this process and a rocket is that the air/fuel mixture is ignited and put under pressure BEFORE exiting the combustion chamber.

I have studied both of your drawings (#320 and #331) rather carefully. I know it is very difficult to post high resolution pictures here, but I fail to discern any valves, or any mechanism to actuate valves. I appreciate that since your air is already compressed (using significant energy, by the way) you can use relatively small intake valves, which would be difficult to show in such a small drawing.

The exhaust valves, on the other hand, must be large. In your drawing #320, you clearly show the exhaust exiting through large openings. If you temporarily close those openings in order to build up pressure, that pressure will push on ALL the walls of the combustion chamber, exerting both clockwise AND counterclockwise torques on the rotor, which essentially cancel each other. Unless you have figured out some very special valve mechanism that forces the gasses to exert pressure on the left side of the upper chamber and not on the right side, this remains essentially a rocket pinwheel.

So, you've come up with a more-complex pulse-jet engine than normal ones - and MUCH more complicated than ram-jets, as described in the February 1951 issue of Popular Mechanics (yes, that's the pair of jets on helicopter blades design - and it was actually being flown and demonstrated to passengers already). Fundamentally, this is still Hero's aeolipile. It also used rotating unions [whoopee]. You've also added a new set of failure modes, beginning with what happens if the exhaust doesn't open exactly on schedule for ANY reason.

Hi mjb!

Ignoring for the moment the rather unpleasant allegations about coming to this forum in order to cheat everyone here including yourself, I am sure you can look out for yourself as can the others. Coming instead to your calculations, it does seem to me a rather weird way to go about calculating the amount of power that would be required to bring a 40 cm diameter, 50Kg flywheel up to a rotational speed of 30000 rpm.

Here is how I calculated the problem:

The problem here is how much torque would it require to accelerate a 50Kg , 40 cm diameter disk to 30,000 rpm. in 0.5 seconds

Mass = 50 Kg ,

Diameter = 40 cms.

30,000 rpm

Initial angular velocity = 0 .

The final angular velocity: w = 30000/60 x 2 pi = 3140 rad/s

Acceleration = w 2 – w 1/t = 3140 – 0 / 0.5 = 6280 rad/s^^2

Inertial mass of disk = M R^^2 = 50 x 0.2 ^^2 = 2 Kg .m^^2

Torque needed = Inertial mass x angular acceleration = 2 x 6280 = 12560 Nm. (12560J/s)

The K.E of this flywheel spinning at this rpm would be : 9.87 MJ.

According to your calculations 1.27 MJ/s are available if the engine produces as much HP as predicted, so that the engine running according to the figures I have given actually produces more than enough power to accelerate the 50 Kg, 40 cm diameter flywheel to 30,000 rpm in the given time of 0.5 seconds.

As to your calculations regarding what mileage might be got from a car from 9.7 MJ, I can only state that the 11,000 Kg gyrobuses, used to manage quite well for minutes at a time using just 6.1MJ. Those buses were in service for more than 8 years at various places around the world.

Lastly I note with interest that you completely ignore what dkwarner at least has the decency to admit, namely that a longer lever arm (by a factor of 10) and the application of the force at right angles might result in greater power. I think your mistake is in not seeing that there are too many variables in that 33 MJ/l of energy you keep referring to, this energy can be released fast it can be released slowly, do you get what I am saying?

Mr. DDjames Sir,

This is precisely the lack of recognition of a correction I referred to earlier. I will put your text in italics.

The K.E of this flywheel spinning at this rpm would be : 9.87 MJ.

According to your calculations 1.27 MJ/s are available if the engine produces as much HP as predicted, so that the engine running according to the figures I have given actually produces more than enough power to accelerate the 50 Kg, 40 cm diameter flywheel to 30,000 rpm in the given time of 0.5 seconds.

So all of the kinetic energy stored in this flywheel comes from this engine in 0.5 seconds. The engine produces only 1.27 MJ/s so in one half of a second the engine produces 0.635MJ of energy. This is an order of magnitude less energy than the 9.87MJ you claim gets transferred from the engine into the flywheel that started at zero kinetic energy.

You simultaneously recognize and ignore this correction offered to you.

I know, I know, but you have the crystal ball.

I will admit that you have some very creative ideas, sir. But if you refuse to listen....

Help I'm a rock !

You have the initial flywheel energy calculation basically correct, which is why I am surprised you are having trouble with the next steps.

Engine supplies 1700 [hp] = 1.27 [MJ/s] and you want to pump 10 [MJ] into a flywheel energy storage system.

10 [MJ] / 1.27 [MJ/s] = 7.87 [s]

As a double check...

10 [MJ] / 0.5 [s] = 20 [MJ/s] = 20 [MW]
20 [MW] x 1/745.7 [hp/W] = 26,820 [hp] <this violates your initial assumptions so 0.5 seconds is NOT possible as initially proposed>

If you cannot understand and correctly execute such simple calculations, your design concepts will never work and no one will ever take you seriously.

The amount of energy in the fuel, ~33[MJ/liter], doesn't change. Whether you burn the fuel slowly and continuously or in huge infrequent bursts is IRRELEVANT!

12 [hp] x 18.6 [minutes] = 10 [MJ]
1700 [hp] x 7.87 [s] = 10 [MJ]
26820 [hp] x 0.5 [s] = 10 [MJ]

ALL cases need the same amount of fuel-energy-work to get from point A to point B. All you have done is increased the complexity of one system by creating a 1700 [hp] pulse engine, which will undergo HUGE stresses, and ADDED a flywheel energy storage system, which could kill everyone within 5 meters when it fails.

Just for a side reference, 5 deep-discharge batteries contain about 10 [MJ] of energy.

*************

Did you read this? http://en.wikipedia.org/wiki/Gyrobus
Gyrobuses were an interesting technology experiment, but they failed to take over because of functional, technical, and cost issues. Research in flywheel energy storage is ongoing and many improvements have been made in materials, safety, and electronics. Even with these improvements, the technology is STILL not significantly or economically better that other energy storage systems.

*************

A lever is a FORCE multiplier, NOT an energy or power multiplier!!
WORK (energy) is equal to FORCE times DISTANCE or

W = F x D.

The long end of a lever arm has the smaller force, but travels a larger distance.
The short end has the larger force, but travels a smaller distance.

In a simple lever system, the FORCE and DISTANCE are inversely proportional to each other and the net WORK stays the SAME!

This is a fundamental concept behind simple levers and torque arms. It is critical that you try to develop a better understanding of these simple machines and the basic physics that describe how they work.

This is in response to #340 and #341

What you say may seem to be correct on an energy in energy out basis, ALL that I know is that the amount of Torque necessary to accelerate a 50 Kg , 40 cms diameter flywheel to 30,000 rpm is equal to the inertial mass x angular acceleration.Here is a site that clarifies what I am trying to say. In other words to accelerate a flywheel of mass 50 Kg and diameter 40 cms from rest to a speed of 30,000 rpm in 0.5 seconds needs a torque of 12560 Nm .

That's roughly equivalent to the torque of a Locomotive diesel.

How the hell are you going to manage that?

Your ram jets are going to need the thrust of an interconinental missile on a hell of a long lever. And the lever has to be accelerated from rest itself, using valuable energy.

I hope you haven't lost sight of the fact that all 'jets' are reactionary (rockets too). There's none of this piston-top stuff, enclosed in a cylinder.

Redo your thrust calcs again, in pounds force so we can all understand. S.

Please give an example of a 10:1 multiplier gearbox, output rated 12.5 kNm @ 30,000 rpm. I can't seem for find anything in that range.

How about CVT's ?? Just a thought.

Mr. DDJames

I appreciate that you are now quoting external sources for your equations. This lends credence to anyone's proposal. I also appreciate that you at least imply an error in your calculation. If you recognize other's criticisms of your work then your criticisms of others work will be consided. If you work with me, you'll find that despite my earlier brusque responses I can be very helpful. I'm not always perfectly correct. Sometimes this is from poor writing, and sometimes I'm just wrong.

In the spirit of showing where errors in calculation can be made by anyone, I also originally calculated like you and mjb did that this flywheel would have 9.8 MJ of stored mechanical energy at 30,000 rpm. But this was based on the moment of inertia calculated by all of the mass at the end of the lever arm of rotation, I=MR². This is not the moment of inertia for a uniformly distributed mass of a disc which is I=0.5*MR². So the actual energy required to be stored in this fly wheel when spinning at 30,000rpm will be about 4.9 MJ. Still to large of an energy for your engine with 100% transfer to produce in a half second, but we all make mistakes.

Not wishing to muddy the water, but to get the most advantageous compromise of mass, size & energy stored, the flywheel would probably have as much of the mass as possible concentrated towards the rim (leaving enough strength to keep itself intact at full speed), so the moment of inertia would be somewhere between 0.5*MR² and 1*MR².

... although very high speed flywheels (if we were to accept Mr James's contention) often have their mass distributed more envenly, or even more toward the center.

I agree with your theoretical number and you appear to understand this particular calculation.
However, you fail to carry through to see what this 12560 [N-m] of torque at 30,000 rpm MEANS in real life.

horsepower = torque x angular_velocity = 12560 [N-m] x 3140 [1/s] = 39,438,400 [W] = 52,889 [hp]

Over 50,000 [hp] ??
Didn't we start with a generous 1700 [hp] ?
Do you not see a problem here?

You still have a fundamental misunderstanding that torque is the primary factor. It is NOT!
Please go back and re-learn some basic physics to understand that ENERGY is the primary factor.
Torque and rotation are dependent on the available ENERGY.

Hi mjb go back to school !! What kind of post is that 3,000,000 odd hp ??? At least consult someone before posting things like that. You can do better if you try.

The calculations are pretty clear for anyone to verify. The cowardly and plainly incorrect sniping is a nice emotional touch, but it doesn't help your argument.

The equations and math are very simple. The absurd numbers arise because the OP is assuming he only needs to consider a constant torque. His assumption neglects the fact that he does not have an UNLIMITED ENERGY source!

To meet his 0 - 30,000 rpm in 1/2 second requirement, he would need to apply his constant torque all the way up to full flywheel rotation. This would require a ramped power input of 0 - 52,000 [hp] over the 1/2 second time period. A 0 - 52,000 [hp] ramp is an average 26,000 [hp], which applied for 1/2 second equals the 10 [MJ] of energy stored in the proposed flywheel.

There is no problem with the math. There IS a problem assuming unlimited energy is available, especially when the discussion is supposed to be about trying to build a practical and more efficient engine. I'm not the one who needs to go back to school.

Hi mjb,

I was not sniping and I was not kidding, you really have to go back to school OR get those figures verified by an impartial observer. I will say it again IF you are so OBTUSE K.E. of a flywheel increases by 10 ^^4 with rotational speed. Get with it man, whats wrong with you ???

mjb,

that link really proves my point go back tp school!! Learn something there AND THEN if you still think this forum is good enough. Come back. OK!

Where did you see "3,000,000 odd hp"?

mjb did leave out the conversions: 30,000 RPM/(60sec/min)=500RPS

and 500RPS* 2pi radians/revolution = 3,140 radians/sec = 3,140 (1/s),

but anyone pretending to be able to verify these calculations should know that well.

If you were referring to the "39,438,400 [W]" then you left off a zero (not a trivial error), but this value is in Watts, NOT horsepower.

It seems YOU are the one who needs to go back to school!

Get with it dkwarner, mjb is not the mathematical genius he claims to be, angular velocity is already taken into account when figuring the torque, why do you need to square it!

In his absurd calculations where else??? OK, I mistook his watts number for HP but everything he has posted is equally ridiculous!

Ask anyone who knows high school physics well (or maybe passed first year engineering physics with a decent grade)! The results are absurd because the OP's original statement (using a small engine to accelerate a 50kg flywheel from 0 to 30,000 RPM in 0.5 sec ) was absurd. THAT is the point mjb was trying to show!

If you see one or more errors in his math, please post the corrections. Any reasonable person will admit mistakes - we all make them at least occasionally, but don't criticize unless you can offer something better.

Reading the last para of the above comment #334 reminds me once more of that helicopter with jets on the tips of the rotors, they must have to move a huge distance, considering that each rotormust be about 3m - 4m in diameter, also to move fuel that distance ( along each rotor) through a rapidly spinning axle must also be quite an achievement, the torque delivered must be quite impressive, as is shown by the problems they have with the auto gyro. So, why exactly can't the combustion chambers move the rotor over the relatively smaller distances that DD james quotes?

http://en.wikipedia.org/wiki/Dynamite

A stick of dynamite is about 2 [MJ]. Shoving the equivalent of 5 sticks of dynamite,10 [MJ], into a kinetic energy storage system in 0.5 seconds would be pretty scary! I would not want to be anywhere near this special event.

While dynamite releases its energy much faster, the energy comparison is a good reality check!

One of the larger concerns with flywheel energy storage is catastrophic failure from high stress. If this flywheel fails at full rotation, that 10 [MJ] will launch some very unpleasant shrapnel.

What about having a whole set of smaller less 'explosive' flywheels. The dimensions would be quite small and compact. Energy could be drawn off serially.

What about all thoe race cars going at 20000 rpm plus !! There is no symmetry at all in those engines and compared to a flywheel little balance or cohesion , parts are flying back and forth in all directions !

Is this another tongue-in-cheak post?

The motion of pistons rod's etc in piston engines are all based on circular functions, so that the accelerations are very gentle near the top and bottom of the stoke. Obviously, if diesel engines can go 250,000, 300,000 or more miles between rebuilds, dealing with these forces is not challengining.

Hi Mr James,

Presenting this is a positive step.

Number 5 is completely wrong by far more than an order of magnitude, so nothing thereafter makes sense.

If you recalculate thrust, based on the air mass to be expelled, the average internal pressure and the nozzle size, you will come up with a very small value. (By guesstimate, a pound or two for a fraction of a second?) After you have done that calculation, come back with the number, and we can fine tune it.

By the way, the area at the "back" end of your rocket pod combustion chamber has almost nothing to to with the thrust force. By reshaping the chamber, you could double or halve that area, and not change thrust measurably.

Blink,

The sheer verbiage of your posts makes them obfuscating but also very interesting, because you tend to go into things in depth, or at least use more words to describe your ideas, which is good. However, there are a few points I would like to take up with you. Firstly whatever facts and conclusions, all the manpower hours spent on analysing the IC piston engine may have resulted in. One can't get away from the fact that OP is right when he states that an initial pressure/force on the piston head of 2618 Lbf or whatever results in a torque of only about 40 ft lbs being generated ! This is a fact it is not somethig he has dreamt up. Whatever, the frequency that this torque is later used at to create HP, he is undeniably right. Equally undeniable is the fact that with a slightly different configuration using a longer lever arm, moving at the same frequency or speed would result in an increase in power by a factor of ten. So why condemn him on those grounds. Secondly, the example of the helicopter with jets on its tips quoted by Stuey, actually works!! You don't seem to have got your head around that fact. The supply of fuel through a rotary union works, the ability to spin such huge rotors using tiny jets at the tips works, the fact that this provides enough power for the helicopter to actually fly, works, at least for me. Now regardless of whatever else you might have in mind take a more considerate view of the OP. Stop using epithets like, scam, fraud et al!

Take a look here. Read to the end! The reason you don't see tip jets today is mostly due to poor efficiency!

Attempting to put them in a car engine does NOT make them more efficient.

dkwarner, Are you from another planet or can't you measure ? Seems to me that there is a hell of a lot of difference in what DDjames is proposing and your rotor jet tip helcopter.

This is a drawing of an exploded view of the engine. Pre-compressed air is mixed with fuel and delivered to the combustion chambers through the main shaft using a rotary union. The main tank of compressed air is replenished by a small compressor run off the engine output. The use of rotary unions to isolate a stationary element from a rotating element has been known in Industry for many years. In this case the stationary fuel supply line is isolated from the rotating main shaft by use of a rotary union. Below is an illustration of a rotary union as used in Industry.

Today rotary unions have become extremely efficient and are capable of dealing with upwards of 20000 rpm shaft speed and 1000 bars pressure. Hopwever it is an accepoted fact that all rotary unions leak to a lesser or greater extent. This deficiency has been remedied. The output from the engine is fed to a flywheel, this kind of setup, (i.e., a mechanically driven flywheel) from which energy can be stored and retrieved through regenrative braking using a flywheel storage system has already been demonstrated in Formula 1 racing in 2009 by the flybrid systems company of the UK.

Ladies and Gentlemen,

I think that this farce has gone on more than long enough. DDjames and the multiple incarnations of "guest" have clearly demonstrated both their poor engineering skills and their inability to learn from our corrections. (I'm certain that I'm not the only one who thinks that many of these "guests" are DDjames, himself.) While at times it was useful as a teaching exercise for us to sculpt our replies in as simple and as informative a fashion as possible to try and correct the poor analysis, it has now degraded to childish insults.

DDjames refuses to learn anything that disagrees with his already established opinions. The two times anyone has gotten him close to admitting an error, he responded only that maybe our analysis was right. He has yet to acknowledge any error even a typographical error on his part. This individual refuses to engage in any useful discourse.

I propose that this thread be should closed from discussion. But I don't want the administration to just review the abusive language here and declare this thread dead. For just because I have grown weary of DDjames and the faceless clones that agree with him, doesn't mean everyone has. So what I'm asking for is a vote to close this thread. The vote to be held by giving this post a GA for closing the thread and an OT for continuing it. Since "guests" cannot vote and named individuals can only vote once per name, this seems like a fair proposal to me.

If by 10:00PM EDT this Friday March 19 2010, there's an overwhelming OT vote here, I will ask the administration to remove this post to retain the dignity and integrity of this thread. If instead by Friday an overwhelming GA vote is here, I'll ask administration to close this thread and cite the poll of this post. For anything in between, I will simply drop my subscription to this thread and leave.

As I hope many of you should know by now, I enjoy trying to teach people many of the skills I have learned over the years here at this blog. But I cannot tolerate those who actively refuse to learn. It saddens me to see this blog tarnished by this childish activity.

Redfred

This caused me to laugh almost to the point of tears: to retain the dignity and integrity of this thread.

For me, the first several words of the thread title seemed OK: "Is the IC piston engine really less than". The "1%" destroyed any sense of dignity or integrity. It is a huge stretch to say that such a contention is anything but ludicrous.

If one were to jump over the content of the original post (which is gibberish) and read the first three responses, the rational part of the thread ends before post #4: you either agree with Berlin (the basis for which can be found in thousands of places, easily) or you can go a step further and calculate the efficiency of a given engine along the lines of John's post #3. Doing so only takes a second, and if you are familiar with engines you can go directly from BSFC (real dyno values) to % efficiency without so much as lifting a pencil.

I think that DDJames (who could be a bright 7th grader here for fun, a hardened criminal, someone with twisted thought processes that cannot be untwisted, a psych ward patient, or someone who (for some unexplained reason) seems intelligent but cannot come to grips with the simplest physics) should be given the chance to present his thrust calculations showing that his little rockets would produce not the expected pound or two of thrust, but a couple thousand times more than that.

I think he has generally refrained from outright insults, and is perhaps unaware that any of the borderline ones have the reverse of the intended effect -- we are not silently laughing with him, we are laughing at him.

So my vote is OT. I think this stuff is a hoot.

Let's be honest... we are here because we like to watch the car crash.

Although I said back at #288 that I was "out", there is definitely a kind of morbid fascination about what will be the next strange claim or factual contortion.

So I'll be hanging around for as long as it remains entertaining - it's an OT from me.