Gear lightening

[Bill Edgeworth]

The math is not all that simple buy you can work out exactly how any particular part can/will affect the acceleration of your car. Hear is a couple of links briefly explaining some of the math involved;
http://hyperphysics.phy-astr.gsu.edu/Hbase/rke.html

http://www.ac.wwu.edu/~vawter/Physic...FormsofME.html

Where it gets complicated is that to get a truly accurate picture of how a part will affect the acceleration of your car (to accurately calculate the energy or work required to accelerate the part to a certain RPM) you don’t need to know its weight you need to know the moment of inertia. Also what I talk about below is only part of the bigger picture you have the whole car to accelerate not just the rotational speed of the part.

To put it all into laymen’s terms not all light parts are created equal. I will use light wheels as an example; two different 10 pound wheels can take significantly different amounts of energy to accelerate through the ¼ mile;
Brand X with a heavier center and super light outer rim will take much less energy to accelerate than brand Y with a super light center and heavier outer rim.
Again keeping it simple and not getting into center of mass and moment of inertia calculations;
Speed = 2*pi*r and kinetic energy = ½ *velocity^2

So comparing the kinetic energy of two identical weights but one twice as far out from the center as the other both rotating at the same RPM the one twice as far out will have 4 times the energy or will have taken 4 times the energy to get it up to that speed.

So the benefit of lightening rotating parts diminishes the closer you get to the rotational center.
Gun drilling axles; almost no benefit, only unsprung weight
Aluminum spool is less effective than the same weight savings by turning the outside of the ring gear.
AND all light wheels are not created equally.
Most people see ET improvement with light wheels because there is such a significant savings in rotational weight compared to any other thing you can do.
Also what this all shows is that rotational weight savings prior to the rear end is very important. Taking rotational weight out of your transmission and engine is far more beneficial as it has to wind up to 5 or 6 times the RPM of your rear tires.
I think the Yak touched on this in another thread talking about the two different diameter clutches and flywheels. Just because two parts weigh the same does not mean they accelerate the same.

[Fred Popov]

Originally Posted by Bill Edgeworth

kinetic energy = ½ *velocity^2

Just a minor correction to the equation... Linear Kinetic Energy = 1/2*mass*velocity^2

[Jeff Lee]

I have a dana 60 with all the good parts from MW; MW disk brakes, 40 spline gun-drilled axles, back-cut ring gear, CM axle tubes. What I do not have is an aluminum spool. I have a MW lightened steel spool. So for all my light parts that was one area I did not want to push. The bonus is every time a change a R&P for ratio it always looks new.
I'm still of the opinion these light parts are worth it however I have no back-to-back data to prove it.
I am looking at going from a 168 tooth flywheel to a 142 tooth flywheel. I guess that falls into that "center of inertia" theory Bill was talking about. From what I have read and heard, it will be worth the effort.
I hope...

[Mike Fuller]

I can perform ring gear machining if anyone isinterested. 313-792-4288

[Bill Edgeworth]

Originally Posted by Fred Popov

Just a minor correction to the equation... Linear Kinetic Energy = 1/2*mass*velocity^2

Hey, I’m just trying to keep it in the realm of the crowd that does not have a Hewlett Packard calculator hanging from their belt and a pocket protector, were not all nerds!
Er didn’t mean to say I wasn’t a nerd.

[Bill Edgeworth]

Originally Posted by Jeff Lee

I have a dana 60 with all the good parts from MW; MW disk brakes, 40 spline gun-drilled axles, back-cut ring gear, CM axle tubes. What I do not have is an aluminum spool. I have a MW lightened steel spool. So for all my light parts that was one area I did not want to push. The bonus is every time a change a R&P for ratio it always looks new.
I'm still of the opinion these light parts are worth it however I have no back-to-back data to prove it.
I am looking at going from a 168 tooth flywheel to a 142 tooth flywheel. I guess that falls into that "center of inertia" theory Bill was talking about. From what I have read and heard, it will be worth the effort.
I hope...

I think the aluminum spools are real source of controversy exactly because of your observation of gear condition; is the very small advantage of the aluminum spool negated by the extra friction created by all the distortion that takes place with an aluminum spool?
I guess if someone really wants that extra 0.005 they can drop a few grand on a titanium spool.

I think your flywheel will be money well spent; it is any time you can lighten things up prior to any gear reduction. One of the other factors is that the flywheel gets accelerated 4 times in your stick car the spool only once. You should see it in your 60’ it’s a diminishing return thing through the gears. It takes way more energy to accelerate a part at 2000 rpm/second in first gear than at 600 rpm/second down track. It will be a little different animal though. With the same clutch setting your motor will pull down faster due to the reduction in rotating inertia.

I think even the tech department at NHRA has clued in on the center of inertia thing. I noticed with all the recent crankshaft chatter the rules state you can only add enough heavy metal to do a normal balance job. Not sure if that’s exactly how they worded it.
But if you were to turn a bunch of weight off of your crank counterweights and then add heavy metal to get the assembly to balance it’s going to be a faster piece. It won’t show up on the dyno but the motor will accelerate quicker.

[Dave Goob Cook]

When it comes to ET reduction from the rear end, I think the best money and time is spent on de-burring and polishing the gear sets, getting the lash and depth perfect for low drag on the load side, and careful attention to the details of the lubricants, and control of it, bearing loads, and bearing fit.

For the lighter vehicles, especially stick shifted ones with lot of ratio and operating RPM, it changes the priorities some.