Awwrite,, you physics guys, re,,,angular momentum.
Now, take a metal disc, say, diameter, ten inches, thickness, three.
So. If you take the weight off of the perimeter, how different would that be from taking the same weight off, but just as close to the center as possible?
IOW,
Well, should we see the Flywheel Effect of every cubic millimeter of the flywheel change as we progress outward from the axis and if we do,would it look anything like the Calculate Perimeter of a Circle formula?
And,if so,can we figure how much to take AND where to take it?

The Polar Moment of Inertia can be calculated for the circle and the material removed.  For the crankshaft and rotor this would be difficult to do - as they are not common circles and they are made up of different materials.  For the flywheel it would be pretty easy to do as it basically a flat disc.

Let's assume the disc is the 10" diameter that JOG wanted.  The Polar moment of inertia is PI/2 x the radius cubed.......981.

If we were to reduce the flywheel to 9"....the Polar moment of inertia would be reduced to......644.

If we were to take 1" of material out of the middle (which is impossible as the connection to the crankshaft would be gone).....the Polar moment of inertia of a 1" diameter disc is 1.57 (small because 1 cubed is still 1).  So if you took the 10" sphere that has a Polar moment of inertia of 981, and took the 1" out of the middle which has a polar moment of inertia of 1.57....the result is a polar moment of inertia of 981 - 1.57 = 979.43.

Taking 1" off the outside reduces the polar moment of inertia by 34%, while taking 1" out of the middle reduces the polar moment of inertia by only 0.16%.  This is why driveshafts, columns, handlebars etc. are all made hollow....it reduces weight and has a very small effect on the strength (and/or energy stored the rotating mass).  Have you ever noticed that most flywheels have most of the mass located on the outer circle?  This allows the flywheel to be as light as possible - while storing the most amount of energy possible.

The bottom line is - you want to take as much weight as possible off the outside of the flywheel if you goal is to improve acceleration....and take off as much weight as possible from the center of the flywheel if your goal is to reduce weight and keep the polar moment of inertia high.  As an example...if you were to remove the center 8" from the disc, the Polar moment of inertia would be 981 - 402 = 579(59%) - while the area (and weight) would have been reduced from 78.5 - 50.2 = 28.3 (36%).  So you would get bit less than 59% the inertia at 36% of the weight.

On the Savage engine - I would not recommend taking weight off the rotor.  You will get far more effect by taking material off the outside of the flywheel.

I was never the great answer guy, OHHH, but if someone could answer the questions,,, we could make stuff Happen..


I STILL wanna see the graph of a dot on a wheel ( both speed and position, one above the other).

The dot, ( The theoretical dot, uz it is on the surface that touches the road)
and it stops when its on the road and is going twice the speed of the car on top.

Yes,, I have an active imagination..


Ohh,, and thank you Dave,, I know my old lab partner in Chemistry coulda sat me down and explained it.. I did the labs, the hands on stuff,, he did the paperwork, we smoked it,, good grades, out early if not first,, dang that dude was SHMAAAAART..


Ohh, yea,, and I told a guy who used to be here a lot about this,, he mumbled something as he hung up to go get steaks on the grill,,,,

Then,, after he ate, he called back,, RARELY do we speak twice in a day,,  So,, he musta had sumthin to say..


He was a hot rodder as a teen and young man,, and pointed out that Yes, this will work, but that working on the reciprocating elements will also increase top RPM AND decrease spin up lag,, so, yea, lighten rotating mass,, and dont thknk the clutch isnt a drag,,, if you can get a lighter clutch pack in it, and, of course, the crank, piston and rod and counterbalance all come into play in a Big Way..

That said,, high RPM on a Long Stroke equals Crazy piston speeds,, and on the exhaust stroke, the piston is ONLY held down by the rod , so, when the crank throw gets to its end and is heading back down,, the rod is suffering. So, a lighter piston on a rod thats designed for that kinda punishment,, yea,, you do the math..

How many miles have ya got on the thing since you went to the Wiseco?
What rear tire ya runnin?
How much time do you spend at highway speeds?

The way Im readin ya,, YOur goal isnt to jack up ythe high end RPM, but to just unburden the engine so it can rap up TO its max quicker,, as in,

I wanna a little street sleeper, dont look scary quick,, BUT,, will come off the line like a Warthog goin at a Lion thats just crossed the line.. leaving any Harleys in the immediate vicinity in the dust..

Dave wrote on 01/21/15 at 04:58:14:

This was a very hard video to follow sorry  . How ever I did pick up near the start where he said about 1.20 min into it, " It didn't matter how thick the ring was this way and I'm assuming its pretty thin this way" So in layman"s terms my understanding is it doesn't matter how wide it is but does matter how thick it is?

That's good news. Go get them,dude.. . Bummer about the Can't prove improvements... ohh well...


Dave, my lab partner did the math, mmmmkay? I'm not gonna track well, I need someone to talk to,ask questions, and then MAYBE I'll get it.

I'd get it running, get some miles on it, break it in, run some time trials, then step into the flywheel..

I'm old... 😉


Keep notes on performance as you work the flywheel. Keep up with Exactly what is coming off the flywheel. You make a cut and see a problem, you can cut the other flywheel to the best performance specs..

Glad to be some help...