I'll keep the heavier flywheel thanks. The inertia it produces suits my riding style and the terrain I ride.

 

It does if it is rotational mass, my statement that I was wrong, was well wrong...lol.

Bigger/heavier tires do reduce hp output to the dirt/asphalt...so the flywheel will too....hp is an odd measurement.

link to dyno test on car with different tires...your turn Brian.

http://www.turbomagazine.com/tech/01...wer/index.html

 

Bingo!
but mmmm can't 100% agree.
lightening a piston has the same effect on hp output.

rotating , reciprocating, linear, it's all about wasted energy.
To move mass takes energy.

What's the difference between energy and power?
Time.

Question?
Does reducing the weight of a bike increase top speed?
If you think yes, then you think lightening the flywheel will increase hp.
If you think no, then you think lightening the flywheel will not increase hp.

I think everyone would agree that reducing the over all weight of the bike would increase top speed.
Energy consumed v work done.
Power to weight. (minus time)

In very simple theoretical speak, the power required to move 10lbs at 10 rpm is the same as the power to move 20lbs at 10rpm.
It just takes longer to get there.
But in reality it take more power to rotate 20lbs at 10 rpm than 10lbs at 10 rpm.
And that power is not available to the rear wheel.

Simple theory discounts reality.
Simple theory states that energy in is only required to change the current state.
No energy is required to maintain the current state.

Yep, can't wait for the easter bunny.

The discussion here should be about power delivery.
And that is a personal thing.

 

Just checking in nice discussion. It is my flywheel that was lightened, but I also have a stock one to change back and forth between. This mod isn't for woods riding my riding is all sand, street and supermoto. I think alot of you would be disappointed with it as my goals are vastly different then most of your riding, as for the dyno it makes no difference in my pulls it just gets there faster but not higher. I've done alot to the motor and this was just a experiment on my part and really isn't a mod for most guys.


Kevin

 

Now I know what to get you for Christmas.
________
****TUB.COM

 

Reducing the mass doesn't change power. It just shifts the available power somewhere else. You get more at the rear wheel at the expense of rotational inertia at the flywheel / crank. Robbing Peter to pay Paul.

Again, if power was actually increased by reducing the mass of the flywheel, then there would be no downside, i.e., it would not become more prone to stalling due to less rotational inertia (momentum) which keeps the piston pumping over those rocks and logs. So instead, the energy isn't there to keep it moving, so it stops dead and stalls. Heavy flywheel has more stored energy which keeps it moving and is far less prone to that. Again, robbing Peter to pay Paul. Note this is NOT an issue on the MX track, not many rocks and logs there, it's all wide open full throttle. The quick burst is more important for that application.

I can't make it any more clear. You either choose to believe it or not. If you don't believe me, then at least work out the equations and apply the principles for yourself. It's all basic physics. How can the result be otherwise?

So you are still wrong. But I won't belabor this. Some may find it counter intuitive, but there's a lot of people out there that believe the world is flat, what can you do?

So let's do another thought experiment, one last try to get the point across - lets say you run a 1/4 mile in 10 seconds, the trap speed was 80 MPH, and the bike+rider = 400 lbs. That's a HP of 47 HP.

Now let's change the mass of the bike only, reduce by 50 lbs. What will the results be? Did HP increase?

In case you don't want to go to the effort, HP does not increase. But the 1/4 mile time goes down to 9.5 seconds. Still 47 HP output from the engine.

Rotational mass makes the problem a little harder to solve because not only does it take energy to accelerate it linearly, but it also takes energy to spin it. But the net result is exactly the same. The available HP us unchanged, but you will see an effect on how fast you can accelerate, etc. So change in mass does not change HP.

 

Neil, I think you are missing the fundamentals. Power is a rate. So when you say the it takes the same power to rotate 20lbs at 10rpms as it does 10lbs at 10rpms, "it just takes longer to get there" - that is the whole point of power - greater power will get it there more quickly. You are completely wrong in saying they are the same.

Power is defined as the rate of doing work. Once the mass is in motion at 10rpms it does not take any power to keep it spinning (assuming no friction). But spinning up the mass, takes power and if one motor can spin it up in 1 second where another takes 10 seconds, the first motor is outputting 10 times the power of the first.

Going back to the flywheel - same HP is working on the flywheel. By reducing its mass, you are spinning it faster because it takes less effort to spin up a smaller mass than a larger one. But the downside comes in that there is less stored energy in the flywheel now and thus the motor is more prone to stalling, blah blah blah.

And I would not necessarily agree that reducing the weight of a bike will increase its top speed. The bike will accelerate faster, but speed is limited by air resistance and gearing, not the weight of the bike. As I posted above, the 1/4 mile time will be faster for sure. But that was achieved by reducing the mass, not increasing the HP.

 

I know the KTM must have a quite light flywheel. It gives the characteristics of what you guys are talking about. stalls easily.. Very annoying.

It would be neat to have a 1/4 mile and 1/8 mile time with a heavy and light flywheel on the KLX.

 

I so want to multi quote here.
Running 5 PSI more in your tyres will have a similar effect as lightening the flywheel.
Like finger said, "inertia (momentum)" is the whole point of a flywheel. You could tripple the weight of the flywheel without any loss in HP. This engine has a gearbox. The outcome would be more time to spin it up to a given RPM (given the same gearbox) but the force required to slow it down would be much higher. The rear wheel on the bike is technically a flywheel too. See the effect of a 130 section rear tyre Vs a 110 section rear tyre! I like my "heavy" flywheel and my 110-100 18 AC10.
FMX. I'll take the spare flywheel for Xmas if it's not wanted. Nice paperweight.

 

Something I wasn't aware off.

"Now the idea is being revived and a flywheel-hybrid, or what’s called a flybrid, will appear on several Formula One cars next year. The organizers for the Le Mans 24 hour race, and the American Le Mans Series are interested in allowing them in 2010.

As automakers around the world race to come up with advanced batteries for hybrid systems, it’s fascinating to see that the flywheel could turn out to be a competitive energy storage device."

Quote from here. http://www.autolinedetroit.tv/journal/?p=545