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Flywheel weight,power and torque 
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#1
Sep2207, 03:58 PM

#2
Sep2207, 08:45 PM

P: 45

hi The_Trainee
well,thats agood point what u opened to discuss here. your mathematical formula for the Power=torque*w(angular velocity)is correct. But do u know how many hps are considered when u want to design an engine? 1theoretical hp and thats what u showed in ur formula 2Bhp and thats what showed in the graph. 3friction hp. 4Indicated hp which equals=Bhp+friction hp 5Rated hp,and this is what the manufacturer tells how much hp the car would give at a certain RPm. now,what the engineer was telling u about is the Bhp which is the power generetaed by the flywheel,so,it hase an effect on the power,when u use a light flywheel or heavyto see the difference jus read this(http://www.thumperfaq.com/mxa_flywheel.htm). so,the graph wasnt showing the theoretical hp which u could calculate from ur formula,if it was theoretical then ur right,about ur answer u give to the engineer,when the torque decreased cuase the Rpm increased then it would keep the power increasing. thanks in advance,and please let me know if im wrong:) Gaber 


#3
Sep2307, 06:17 AM

Engineering
Sci Advisor
HW Helper
Thanks
P: 6,953

Some people can't tell the difference between
(1) engine power and torque (2) vehicle performance and "driveability". The OP's graph is about (1) and the understanding about the relation between power and torque are correct. If you read the numbers off the graph and convert one to the other, the two curves are exactly equivalent. Machinest's link is about (2)  and some of it (e.g. using nonsense terminology like "gyroscopic reverberation", and the garbled description of how to measure inertia) is BS. 


#4
Sep2307, 02:46 PM

Sci Advisor
P: 674

Flywheel weight,power and torque



#5
Sep2307, 03:59 PM

P: 3

Thanks for the answers!
I told him that it can't be like he said but he continued to say that I was wrong. I can't believe that someone that spend so much time at the university could be so wrong about something that is thaught in school.That's why I had so many doubts. I do have 2 more questions (could you please answer it?): If that engine (the one of my example) had a lighter flywheel,would the torque curve drop much quicker after 4000 rpm? Can a flywheel store enough energy to be able to accelerate an engine? (for example,when you're going at full throttle and then lift the throttle just a little bit) Thanks again! 


#6
Sep2407, 06:36 AM

Sci Advisor
P: 5,095

Trainee,
Just to echo what was already said, this guy is a tool. His own plot proves him wrong. Tell him to take two minutes to do a couple of quick calculations to see that your answer matches exactly with the plots. I cringe whenever I hear anyone come out with that famous line "I'm the engineer. I must be right." 


#7
Sep2707, 01:23 PM

P: 9




#8
Oct707, 04:18 PM

P: 3

Can a flywheel store enough energy to be able to accelerate an engine? (for example,when you're going at full throttle and then lift the throttle just a little bit) Yup. Flywheels are made from strong chromoly metals, or cast iron. If the HP is increased on a motor(for example via forced induction  turbo/supercharge), the clutch and flywheel must be upgraded to handle all that power, or energy  for all sorts of applications. :D 


#9
Oct707, 04:51 PM

P: 3

Oh and looking at the dyno sheet, im really semiimpressed on how much that 2 liter pumps out HP, even with the turbo. It looks like that motor is starving for more air :P
oh and to back up Cornellians response, that 2 liter motor is equipped with balancer shafts and probably an engine dampener. 


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