lewisracing00
New member
Im looking to get an adjustable timing flywheel. Should I try the small diameter or go with the full size? Im running small bullring style tracks. Will the small one help or hurt?
Small diameter flywheel?
- Thread starter lewisracing00
- Start date
jack burroughs
member
A lighter F/W will accelerate quicker , but will also be pulled down quicker too, a heavier F/W will make inertia racing much easier.
sCREamnClones
New member
Small Bull-ring(?)....less-is-Best!
Depending on how small your bullring is, i would either go with the smallest one you can find, possibly the ultralite flywheel, or one of the billet ones which are not much heavier but still alot lighter than stock. The reason is, you can have the advantage of a lighter flywheel if you choose one of the heavier billet aluminum ones, while not sacraficing to much like if you were to go with the smallest and lightest you can find. I believe the Ultralight is the lightest one you can get that is actually same size in diameter as the other billet flywheels, but am not sure on this as i have not seen one in person. You want a medium weight one if you arent having to completely lift out of the throttle alot or on and off the throttle alot. Some bullrings have sweeping turns to where you can actually get some momentum going without having to lift alot, just depends on how small your talking. If thats the case, the smaller and lighter one would hurt more than help. If your in and out of the gas ALOT and dont really have much chance to really get to full throttle before having to lift, then the lightest and smallest one you can find should help.
sneaks12303
Member
I have tried and tested the smaller diameter wheels. You have to relocate the coil with a bracket that is usually supplied. I tried the Arc . The theory is the smaller dia. would bring the centrifugal rotating mass closer to center line making a heavier wheel feel lighter to the motor...The difference is very small if any on the dyno...
Sneaks always has to get in the discussion using facts.
A smaller diameter flywheel that has the same mass as a larger diameter f/w will have less inertia and will accelerate faster.
More horsepower? Maybe not.
Will the motor rev/accelerate quicker? I would say yes.
modifiedman
Member
It will rev up faster and will slow down just as fast.Jmo but on a small track it helps on a large track not so much BUT
you could go smaller diameter with a little more weight and works well for both again jmo.
you could go smaller diameter with a little more weight and works well for both again jmo.
Can I say thanks to a post twice? Just because the dyno doesn't show it doesn't mean the advantage isn't there. I've tested this on the track with great results proving that less rotating mass equals kart seperation!!!!Sneaks always has to get in the discussion using facts.
A smaller diameter flywheel that has the same mass as a larger diameter f/w will have less inertia and will accelerate faster.
More horsepower? Maybe not.
Will the motor rev/accelerate quicker? I would say yes.
jsstump#70
Member
The light flywheel craze come from other forms of racing that use multi-cylinder engines. A v8 will typically rev much quicker with light flywheels and clutches. A single cylinder may or may not rev quicker. It doesnt have another cylinder firing keeping it spinning for the 2 revolutions it needs to get back to the firing stroke. In some cases , singles actually rev a little slower because the flywheel is so light that there is very little "momentum" keeping it spinning till it can get back around to fire again. There has to be limit to how light is too light. I know Sneaks did the battle of the flywheels. Maybe a retest measuring the time to go from say 2500 to 7000rpm? May be very telling. I would suspect any difference is increadibly slight. I will add that even if multiple tests prove no advantage to light wheels exists, I would still run one. You got to admit the ARC and Raceseng and Slipstream LOOK awesome. They are very fast looking. LOL. Keep testing and questioning. As soon as you dont, you will be passed by those who do. Good luck
sCREamnClones
New member
sneaks12303
Member
Something to think about...The flywheel is the heaviest piece of rotating mass in the motor. A smaller flywheel spins slower cause it covers less distance in 360*. This is a good thing coming out of the corners and braking . This is a bad thing for top end and momentum tracks...I found the larger diameter wheels got a wee bit more rpms at top end. The difference between diameter/same weight is not nearly as much as an ultra lite vs an AKRA legal steely..Now heres the tricky part...3 pounds rotated to 6000rpms should require the same amount of energy no matter what the diameter...So whats going on ?
lewisracing00
New member
The wheels I'm looking at are the arc 6607 weight is 2.85lb small diameter and the arc 6618 weight is 4.9 lb full size. And it will only be ran on short tight corner tracks no long tracks around here really. I get in and out of the throttle alot.
Not true ... the torque (energy) required to accelerate a rotating mass (flywheel) is dependent on the mass (flywheel weight), the distribution of that mass, and the radius of gyration of that mass (radius or diameter of flywheel). Assuming a homogenous distribution of mass between two flywheels of equal weight, the flywheel with the larger diameter (radius of gyration) will require more torque to accelerate and decelerate at a given rpm.
If the mass of the flywheel is expressed as M and the radius of gyration is expressed as R then the formula for determining the moment of inertia is (M)(R)(R) = I
So you can see from the formula that the torque required to accelerate the flywheel increases by the square of the radius of the flywheel .. as an example, for a given mass, a flywheel with a 12" diameter would require 4 times the torque to accelerate as a flywheel with a 6" diameter.
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alvin l nunley
Site Supporter
When I was dragracing, and we switch to a aluminum flywheel, the 1st thing you notice is the engine will rev much faster with the clutch disengaged, but once you get off the line and you're accelerating, as far as I can remember it pretty much accelerated the same as with the steel wheel. One big difference was, off the line, you didn't spin the wheels nearly as far.
Once the wheels stop spinning, and you're accelerating the whole car, which was 3500 pounds, the difference in weight between the steel and aluminum flywheel and the effects it has on acceleration, was hardly noticeable.
So if you're in the shop, and your flapping the throttle, you will see a difference in the acceleration of the engine, but on the track, coming out of a corner with the clutch fully engaged, that lighter flywheel, and the power it takes to accelerated it, has got to be nearly insignificant compared to accelerating the whole kart.
Comments compliments criticisms and questions always welcome.
Once the wheels stop spinning, and you're accelerating the whole car, which was 3500 pounds, the difference in weight between the steel and aluminum flywheel and the effects it has on acceleration, was hardly noticeable.
So if you're in the shop, and your flapping the throttle, you will see a difference in the acceleration of the engine, but on the track, coming out of a corner with the clutch fully engaged, that lighter flywheel, and the power it takes to accelerated it, has got to be nearly insignificant compared to accelerating the whole kart.
Comments compliments criticisms and questions always welcome.
sCREamnClones
New member
Allow me to say this about that...."It has something too do w/ physics and the spinning of the globe!" (I assure you!!)
I think i'll go get the pretzels and beer now....Carry on Troops!
I think i'll go get the pretzels and beer now....Carry on Troops!
sneaks12303
Member
Here's the problem , Flywheels are not homogenous, They are different shapes with different friction values while spinning and I believe your formula is only true in a zero gravity environment.
Actually the flywheels used in our application are fairly homogenous in terms of the distribution of the mass. Also there is very little frictional losses associated with the flywheels in our application ... only air and magnetic resistance, and those are fairly constant between the various flywheels, regardless of their mass or weight. Most of the frictional losses are attributed to those generated internally within the engine and are a not affected by flywheel selection or design.
Neither zero gravity, nor earth gravity, have any effect on the formula ... The laws of mass and inertia are not affected by gravity. Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object.
While the weight of a object is a function of the strength of gravity, the mass of an object is constant for any location, and not an associated function of gravity.
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sneaks12303
Member
Hhhmmm, Try a finless flywheel vs a finned flywheel and get back to us..
sneaks12303
Member
But I think my real problem here is one formula does not cover everything that's happening.
youngengines
Member
It never does, does it? LOL