Quote from tristancliffe :

Please, don't assume I don't know how a flywheel effects a car. And of course you could reduce the diameter of the flywheel, and use a smaller diameter clutch... And I'm not entirely sure you're right about a lightened flywheel increasing torque at the wheels - where does the extra torque come from?

I never said you dident. And a flywheel does not increase the tq that an engine makes, but the tq that reaches the wheels. Now that the flywheel is lighter, the engine is not using as much power to spin it as before, thus more power reaches the wheels of your car, thus the car will accelerate faster.

Bob, you could, but im saying there really is no room to do that. You could also get a multi plate carbon clutch... but then thats dealing with the clutch and not flywheel.

Im not saying anyone here is wrong!

Quote from cardriverx :

I never said you dident. And a flywheel does not increase the tq that an engine makes, but the tq that reaches the wheels. Now that the flywheel is lighter, the engine is not using as much power to spin it as before, thus more power reaches the wheels of your car, thus the car will accelerate faster.

Bob, you could, but im saying there really is no room to do that. You could also get a multi plate carbon clutch... but then thats dealing with the clutch and not flywheel.

Im not saying anyone here is wrong!

Not torque, inertia.
At constant rpm torque is still the same that comes from engine and goes to wheels, accelerating is faster only because less inertia as when you try to accelerate engine rpm less inertia in flywheel takes smaller part from engine torque/power, but that effects only in acceleration. Bit similar to if you put heavy wheels or light wheels on car, there is more masses to get going.

Of course during acceleration there is then less torque ending up to wheels because bigger inertia is taking part of it, but as it still is same amount as before at constant rpm. So what you say is perhaps not correct but of course it is general assumption. (compare to that you should not polish intake manifold to mirror like, with fuel injection you can with carbs you can't but still there are lot that believe that it can't be polished so)

Inertia dynamo meter is one that is very easy to fool with this, but some bit better dynamo meters can measure power from certain rpm increasing load so that you can't get more rpm at all and of course these can measure only power from wheels.
Real engine dynamo meters are then very nice as you don't have grip issues or transmission losses etc so you can actually measure engine power, in these you can too accelerate so slowly that inertias are not showing up in a results.

Well it is more or less word play really, at least for me lighter flywheel effected only to 1. and 2. gear as could not take enough material out from edges because of holes that ignition requires to be there, must do another operation when I'm rich again

I did some tests! I figured out that there is a correlation between flywheel inertia (not weight, INERTIA!), and acceleration. As the flywheel inertia increases, the 1/4mi time gets higher and higher. But, at a certain point, more inertia actually helps you accelerate. My theory is that more inertia helps you accelerate right off the line. Past another point, the inertia probally get so great that you cannot accelerate fast enough. Also, as the inertia decreases, it is harder to launch, because it is so damn easy for the flywheel to deccelerate. I don't understand why you would really want a lower inertia flywheel. Except that it is easier to stop with less inertia, but too little flywheel inertia makes it very difficult to accelerate.

Here is a chart!!!!! (The 1/4mi time is the offset from 14s BTW)

Because going after your thoughts, race/rally cars should have 10ton fly wheel on the roof. Before start you are reving it up for 3 hours and than get superb acceleration all the time while racing

Some people don't just drive straight, they have learned that cornering is much more fun

Rev matching is much better with light flywheel as engine response is more immediate without load.

wheel4hummer - where did you get that data from? And those results don't seem particularly consistent, you should do far more than 2 runs before taking the average.

Quote from wheel4hummer :

I did some tests! I figured out that there is a correlation between flywheel inertia (not weight, INERTIA!), and acceleration. As the flywheel inertia increases, the 1/4mi time gets higher and higher. But, at a certain point, more inertia actually helps you accelerate. My theory is that more inertia helps you accelerate right off the line. Past another point, the inertia probally get so great that you cannot accelerate fast enough. Also, as the inertia decreases, it is harder to launch, because it is so damn easy for the flywheel to deccelerate. I don't understand why you would really want a lower inertia flywheel. Except that it is easier to stop with less inertia, but too little flywheel inertia makes it very difficult to accelerate.

Here is a chart!!!!! (The 1/4mi time is the offset from 14s BTW)

So what you're saying is that you don't really understand how cars work, but thought a nice graph would make you look clever?

Quote from tristancliffe :

So what you're saying is that you don't really understand how cars work, but thought a nice graph would make you look clever?

I used a memory editor. I am not quite sure about the value that I changed in LFS, but I am pretty sure I was changing the flywheel inertia. I still don't understand inertia. I have tried reading my dad's physics book, but I cannot understand the math. I have only taken Algebra 1, and geometry. I don't understand a whole lot of algebra, I just haven't learned it yet. So, if you could explain inertia to me, it would be alot more helpful then what you just said.

But, while I am making a post, I will explain my understanding of inertia. Newtons law states that an object will remain in motion until a force acts upon it. So, my understanding is that inertia is resistance to a change of motion. So, the more inertia a flywheel has, the more resistant the flywheel is to acceleration. When I spool up a really high inertia flywheel in LFS, and let go of the clutch in 6th gear, energy/force is being transfered from the flywheel, through the clutch, and into the tires. So, if F=ma, then what is inertia? I know, rotational inertia is alot different. I figure I should learn about (linear?) inertia before reading about rotational inertia.

Having a flywheel with more inertia may help you perform a clean pull away by keeping tyres at their optimal slip ratio. However, ultimately, especially if you perform a clean pull away using the clutch, a lighter flywheel will always be faster, although you may not be able to measure this too much. Don't forget the rotational intertia from the wheels, once combined, is almost definately going to produce more angular momentum torque than the flywheel, and I remember when I first added rotational inertia to the wheels in my model, and it only increased 0-60 times by a few tenths. I haven't even bothered modelling the flywheel (or other engine components for that matter), unless you want to rev the engine with no load on it you can forget about them entirely and still get accurate results.

I was going to write about bi-mass fly wheels in some modern cars, but it seems to do completely another function. I thought that in low revs fly wheels is heavier to get more constant and lighter driving, and it drops the mass to achieve better acceleration.

But I read that this used too lower engine shaking and transmission wearing out.

Really confused now

Inertia is simple, it is resistance of changes to speed. Speed of 0 is speed too here.

Object that rotates and has high inertia is less likely to slow down or accelerate rotation speed than object with less inertia.

Every object has inertia, mass and specially location of mass defines inertia. Inertia is not single value, but three values one for each of three axis, you have to think 3-dimensional here.

I don't even know if inertia is force or not, but it does not really matter as I know what are basics and formulas can give me more or less useful numbers

Quote from JTbo :

Inertia is simple, it is resistance of changes to speed. Speed of 0 is speed too here.

Yes, but what is rotational inertia derived from?

What do you mean? It's a natural phenomenon. If you want to fit it into F=ma, then when you change the angular velocity of an object, it creates angular momentum torque around the axis, which in the case of the car is converted to a linear force by the wheels. So it can be thought to reduce the torque output from an engine when accelerating, it's not really doing that, but that's the apparent effect that will occur.

Quote from tristancliffe :

The mass makes no difference - it's the inertia that counts. If you had say a 10kg flywheel with x moment of inertia, and replaced it with a 100kg flywheel with x-1 moment of inertia you'd find the engine would actually rev as quickly as a 10kg, x-1 flywheel.

Confusing weight (mass) with moment of inertia is a mistake and an inaccuracy. Just nit picking, and I'm surprised one of you didn't realise what I was getting at

Edit: I realise that reducing the mass will almost certainly reduce the moment of inertia, but it remains incorrect to say low flywheel weight is wanted.

MMm you claim the mass makes no difference its the inertia that counts, yet momment of inertia is derived from mass(along with some other stuff). so reducing the mass should reduce moment of inertia.

this dosent necessarily mean that the lightest will be better as you could move and shift mass around the flywheel the inertia

Do you read threads, or do you just post in them to make yourself look stupid?

Take mass from the outside of the flywheel, and put it in the middle - the flywheel will weigh the same (mass) but have reduced inertia (resistance to change of acceleration).

At no point have I ever stated that mass, or the location of that mass with respect to the axis of rotation (radius of gyration), has no effect upon inertia, I've just stated that reducing the mass is not the benefit of a 'lightened flywheel', and that therefore the term 'lightened flywheel' is actually a misnomer.

Partly I wish I hadn't said anything, because it's caused too much discussion about it, but partly I'm glad because it's shown just how foolish some people are (not necessarily directed at the previous poster )

Quote from lalathegreat :

MMm you claim the mass makes no difference its the inertia that counts, yet momment of inertia is derived from mass(along with some other stuff). so reducing the mass should reduce moment of inertia.

this dosent necessarily mean that the lightest will be better as you could move and shift mass around the flywheel the inertia

What is your point really?

Inertia is what counts and that comes from mass and location of mass, mass alone does not make difference is what he means.

Reducing mass can reduce inertia, but is not necessarily reducing inertia or is reducing inertia lot less than hoped. That is common problem actually, people tend to think that it is mass that matters and they take 3kg off from centre of flywheel, instead of edges where it should be taken.

This is how flywheel is made to have least inertia possible, that is quite, ehm, light too

edit: I write too slow, lot too slow, maybe inertia of my fingers has increased

Quote from JTbo :

What is your point really?

Inertia is what counts and that comes from mass and location of mass, mass alone does not make difference is what he means.

Reducing mass can reduce inertia, but is not necessarily reducing inertia or is reducing inertia lot less than hoped. That is common problem actually, people tend to think that it is mass that matters and they take 3kg off from centre of flywheel, instead of edges where it should be taken.

This is how flywheel is made to have least inertia possible, that is quite, ehm, light too

edit: I write too slow, lot too slow, maybe inertia of my fingers has increased

Nice pic. I assume that flywheel doesn't have a ring gear on it for a starter motor? I can't imagine the 'spokes' would be strong enough to cope with starting torque, especially as it appears to be an aluminium alloy. And the clutch friction face also appears to be aluminium, which wouldn't be a good idea, so either the picture is over-exposed (making it look ally) or there is a cast iron insert for the clutch...

Not that it matters - it gets the point of low inertia across I think, so maybe (just maybe) we won't get a new poster claiming mass is the influencing factor in a 'lightened flywheel'.

Quote from tristancliffe :

Nice pic. I assume that flywheel doesn't have a ring gear on it for a starter motor? I can't imagine the 'spokes' would be strong enough to cope with starting torque, especially as it appears to be an aluminium alloy. And the clutch friction face also appears to be aluminium, which wouldn't be a good idea, so either the picture is over-exposed (making it look ally) or there is a cast iron insert for the clutch...

Not that it matters - it gets the point of low inertia across I think, so maybe (just maybe) we won't get a new poster claiming mass is the influencing factor in a 'lightened flywheel'.

That is from some S14 race stuff, don't really know how they have made starting or how long it will last really.

It is surprisingly common to see companies sell full aluminium flywheels and I guess some even by them too, well some buy magnets to fuel lines to line up fuel atoms so that they will get more power too, so nothing new.
But that pic should show principle, could not find proper pic and those that I have here I can't show

No, I'm pretty sure there will be yet another poster and then after him another and all this will happen quite many times before we see next patch, but that is just because how things go.

Quote :

The mass makes no difference - it's the inertia that counts

Quote :

At no point have I ever stated that mass, or the location of that mass with respect to the axis of rotation (radius of gyration), has no effect upon inertia,

you didn't say it but u sort of implied it, maybe accidentally idk. you said the mass makes no difference on the engine behavior, that it is the inertia; but mass contributes in determining the inertia. So indirectly mass does make a difference.

Eg. to flywheels with same distribution of mass except one is made out of dence steel and the other titanium or something very light in this particular situation the one with the less mass is going rev faster.

of course this only works in that example as the distribution of the mass can change the inertia. 9lbs flywheel vs a 10lbs flywheel with weight in the center.

Only responded to this thread cause it seems you went out of the way to make him look stupid

Quote :

If you think it does then you are a COMPLETE FOOL.

maybe it would of been better if your first post stated something like mass isn't the only factor to a cars performance.

Again these discussions about making love with little dots. I already said it is Nm, not nm!!!

Quote from lalathegreat :

...

My goodness. It was half-joking tounge-in-cheek nitpick. Time to get over it.


Also

Quote from lalathegreat :

would of

:gnasher:

I still maintain the mass of the flywheel makes no difference - a 10kg flywheel with X inertia will be the same (from a vehicle performance point of view) as a 100kg flywheel with X inertia (albeit the heavy flywheel will be harder to accelerate down the track, but assume the mass difference is taken up by ballast, so the kerb-weight remains the same).

You see, if you take what I said in the context of the rest of the sentence/paragraph, you'll see that I'm right. Quoting small parts of a sentence or paragraph doesn't make me wrong.

Also, Titanium isn't that light really - about 60% of the density of steel, and near 200% the density of aluminum. It does, however, have a high strength for a given mass (assuming the design is sound), which is where it's benefits lie.

If you're after light-weight, use aluminium, wood, GRP, CFRP, CFRC etc etc.
For ultimate strength, use steel or something like that
For high-strength when weight is still an issue then Titanium becomes an option.

You'd rarely bother to make a titanium flywheel, unless you either love marketing (selling 'flashy' things to morons) or you are a moron yourself. An exception might be if you are trying to mount a ring-gear to the flywheel, but still want lightweight, and have calculated that the aluminium flywheel (with cast-iron friction insert [or maybe CFRC] for the clutch) wouldn't take the stress caused by the high torque...

I blow my nose in your general direction...

Quote from Hyperactive :

Again these discussions about making love with little dots. I already said it is Nm, not nm!!!

But my shift key is broken, what can i DO!?

C'mon, what's so bad about a few nanometer of torque?

ROFL @ this thread

Good to have you back TC