Rotating weight.....crankshaft....bobweight

[maxracesoftware]

Ok, I get what you're describing with your math now.

Going back to the "stored energy polar inertia (or momentum)", there has to be some merit of that somewhere. To light, can't be good for power?

What was with the aluminum flywheel in EMC?

Too light, can't be good for power?
someone "passed Tech" with it
...yes, on the EMC Series, the lighter the Flywheel the better
or other words, the higher Avg HP and TQ Number + Score will be


on the Dyno,
there's no Mass to Launch
and no recovery aspects on gear changes to consider
i

i just re-edited my Post above with a Pic........ take a look

[maxracesoftware]

look at 55 feet distance ET and MPH
that equates to exactly = 920.225 Peak HP
out of 1450 Peak HP i inputed

920.225 Peak HP @ 55 Ft
plus things like Tire Growth, Tire Traction,
Rotational Inertia Losses of all rotating components
accounts for whats leftover

[williamsmotowerx]

I understand about tire weight, dia... all that.

But let's just focus on engine itself.

Let's say we have a titanium crank and flywheel, identical dimensions to steel parts.

Would the Ti motor make more HP? How about on a single cylinder engine? What keeps the motor spinning between cycles?

[maxracesoftware]

I understand about tire weight, dia... all that.

But let's just focus on engine itself.

Let's say we have a titanium crank and flywheel, identical dimensions to steel parts.

Would the Ti motor make more HP? How about on a single cylinder engine? What keeps the motor spinning between cycles?

PMI or MOI
is not ONLY about mass
but where that mass is concentrated
and especially at what distance AWAY from the centerline axis
and this has substantial effect on Losses

you can't directly compare
2 given 14.000" dia Flywheels even at the same Weight Lbs

one might have the majority of its mass located at a greater distance
away from the axis...so it will loose more TQ or HP
the faster you try and accelerate it

its possible a Titanium Crank would loose more HP than a
steel crank depending on where's the majority of its Mass is located
away from rotational axis
(its counterweight shape / or mass distribution )

[williamsmotowerx]

Ok, see now we're getting somewhere.

Yes I understand where the weight is has the greatest effect. We're both on the same page, but just getting a few posts to clarify.

My point that I'm trying to get to is this I guess, and let's just talk about cranks for the moment... I think that's where this original topic was headed...

Lightening the crank throws will take less HP to spin, but, if lightened to much it can actually cost you HP overall.

[maxracesoftware]

Ok, see now we're getting somewhere.

Yes I understand where the weight is has the greatest effect. We're both on the same page, but just getting a few posts to clarify.

My point that I'm trying to get to is this I guess, and let's just talk about cranks for the moment... I think that's where this original topic was headed...

Lightening the crank throws will take less HP to spin, but, if lightened to much it can actually cost you HP overall.

reducing component rotational inertia should always increase HP+TQ
output


Looking at this as Flywheel (instead of Crank Throw )..
easier in my Mind to make a point->

if you would have a relatively low Power to Weight Ratio RaceCar ? ,
that might need Flywheel Weight to benefit launch,
....but then at a certain Track distance + RPM,
the heavier Flywheel will subtract HP + TQ
until you changed gears again,
and the stored flywheel energy would VERY BRIEFLY help,
then at some next point, it would again start to hurt HP and TQ
...it just depends on your application.

if your application is highly geared ( Trans Ratio + Rear Gear Ratio)
and the power -to- weight ratio is high,
you can free up substantial amounts of HP and go faster
the lighter all the rotational components are

[David Redszus]

Lightening the crank throws will take less HP to spin, but, if lightened to much it can actually cost you HP overall.

Let us ask why counter weights and thick webs were used on a crank in the first place.

Crank shaft weight is used for torsional balance and for engine smoothness. An ultra light crank, while easily twisted, is subject to rough runnning, imbalance and, in some cases have been known to break.

Typically, crank throws masses are not too far from centerline and little is to be gained or lost with weight removal. Flywheels, clutch pressure plates and friction discs are another matter entirely. Here every ounce removed, especially at the outer perimeter, means a gain in power.

[2xmod]

My heads goin crazy trying to follow.... LOL

[panic]

.

[williamsmotowerx]

Lightening the crank throws will take less HP to spin

No. Steady-state power doesn't change with inertia, only transient power.

Taking in context, "HP to spin", does that not mean a transient state?

[maxracesoftware]

Video on Rotational Inertia


a DragRace between a hollow Ring and a solid Disc

2 Objects of the same Mass and Diameter and Width

Flash Video
http://www.mediafire.com/file/qimmmndh4 ... 25_001.flv

in the Video, similar results as->
PMI or MOI
is not ONLY about mass
but where that mass is concentrated
and especially at what distance AWAY from the centerline axis
and this has substantial effect on Losses

you can't directly compare
2 given 14.000" dia Flywheels even at the same Weight Lbs

one might have the majority of its mass located at a greater distance
away from the axis...so it will loose more TQ or HP
the faster you try and accelerate it

"HP to spin"

another example would be an Inertia Dyno
like testing a single cylinder engine as it tries to accelerate a large Flywheel

[williamsmotowerx]

There is roughly 580 degrees of crank rotation that is basically stored energy or momentum by the crank, flywheel that keeps that piston moving until the next ignition cycle. (won't get into chasis, just a dyno or bench run).

So if there is not enough stored energy, how can it make it's full cycle?

That's why I've mentioned that too light can be detrimental to HP. How much is optimum? Good luck!

[janus]

wow, this thread was quite interesting! however i'd also like to see that last question by williamsmotowerx resolved.. maybe anyone can shed some more light on this?
thanks for everyone who shared their expertise.

[MadBill]

The only time 'too light' could reduce steady-state power would be in a engine running extremely slowly with ultra-light components, in which case yes, it perhaps wouldn't have enough momentum (the 'moving' form of inertia) to carry it through the non-power strokes and continue running. In fact, if it's turning slow enough, it would stop immediately when the starter disengaged. No matter how light in terms of real-world materials though, there would be enough momentum at some reasonably low RPM to maintain operation.

There is an undercurrent of belief in most threads like this that somehow, apart from friction, it takes power just to maintain a steady-speed rotation, so the heavier the parts, the more power lost to overcoming it. NOT SO! A fat kid on a tricycle could spin an inertia dyno roller up to pedal float, given enough time and cheeseburgers.

[In-Tech]

There is an undercurrent of belief in most threads like this that somehow, apart from friction, it takes power just to maintain a steady-speed rotation, so the heavier the parts, the more power lost to overcoming it. NOT SO! A fat kid on a tricycle could spin an inertia dyno roller up to pedal float, given enough time and cheeseburgers.

Why can I see that in my head now?