The flywheel toy is almost the exact opposite of an inertia only chassis dyno where you absorb power by spinning up the flywheel instead of expending power by accelerating the toy car from the inertia stored in the spining flywheel.

A flywheel when reved up, stores the energy it took to accelerate it. When you dump the clutch, or put the drive wheels of the inertia toy on the floor, that stored energy is released to launch the vehicle. Release of energy over time is often called power. I suppose you could measure the toy's acceleration and mass and calculate the rwhp it produced. From that and the gearing(or flywheel rpm) you could calculate torque. Again, that's how an inertia dyno (Dynojet) works.

FWIW, what's the "JET" connecton in Dynojet? Olther than a neat name I never got it.

Some drag racers use fairly heavy flywheels and high rpms before they "unfoot" the clutch. With nearly perfect bite they get a good launch of a heavy car and maybe some air under the fronts. That's the good news. The down side is that that heavy flywheel needs to be accelerated in each gear which reduces the hp to the wheels. That's rotating inertia. Watching Jeggie's in-car Pro Stock shots, his 500 inch engine accelerates a couple thousand rpm in a fraction of a second in some of the lower gears. I'll bet they have low inertia everything...except for those huge "tars".

Does anyone know it they went a little bigger on PS tires this season? I heard they might.

 

Here's a quote from Warren Johnson from a by-lined sidebar in the May 2004 issue of Drag Racing Action, pg. 71:

"The goal in drag racing is to apply as much engine torque as possible to the track surface to maximize acceleration up to the point when spin occurs."

WJ does a pretty good job doing just that. They call him "The Professor".

 

I want someone to compare the inertia toy car using more mass to produce "power" vs. a die grinder that spins at 40,000 to 50,000 rpms that relies on the speed to accomplish the "power" to get the job done...and apply those forces to explain "torque" vs. "horsepower" ...if that is possible...

 

Maybe... Here's my take.

Die grinder: Assume a 1 hp @ 52,520 grinder. Since HP= Torque x rpm/5252, T=HPx5252/rpm or about .1 lb-ft or 1.2 lb-in. The reason for the high rpm is that abrasives (grinding wheels) operate efficiently at a surface speed of 6000-6500 ft/min or about 65-70 mph. (I won't bore you with the math). FWIW, that's the reason a piece of steel dragging under a car on the road doesn't spark until it gets to maybe 30+ mph, and around 60-70 the sparks are very bright. If you are good, you can tell a lot about the metal being "ground" off (pun intended) by the color and shape of the sparks.

This grinder would be most efficient with a wheel about 1/2 inch diameter. If you pushed very hard with the spinning wheel on the part you were grinding, you could stall the wheel: only .1 lb-ft remember, or about 4.8 lbs of force at the .25 inch radius. However, by applying light pressure to make the abrasives in the wheel cut efficiently, the amount of metal you could remove per minute would be proportional to the horsepower the wheel put into the part.

The reason for using an abrasive wheel might be because the metal was hard or you wanted a shape you could only get by hand manipulation of the cutter (sculpting or maybe porting), unless you were really bucks-up and could afford a CNC mill and all the digitizing, programming, etc. that's involved.

Let's assume you have a small CNC mill with only 1.0 hp (some Bridgeports have only about that much power). We'll use a 1 inch diameter milling cutter that makes much bigger chips than the grinder, and cuts efficiently at a surface speed of 600-650 ft/min, or in this case 2300-2500 rpm. Now the 1 hp produces 2.1-2.3 lb-ft. of torque or 50-55 lbs of force at the cutter tip, which is what's required to remove the metal.

What system will remove more metal per minute? Well it's soft enought to mill (aluminum for example), the milling cutter is much more efficient and will remove more metal. If the metal is hard (like a roller bearing or piston pin), the milling cutter won't even touch it, but the grinder will. It might take a human 20 hours to do 16 ports on a pair of heads, but the CNC mill might do them in 4 hours. That doesn't mean the CNC is 5x as efficient, because the porter is stopping to flow the ports, take short breaks, etc. . Those may not be real numbers, but the ratio might be close. If the "head shop" charges $50/hr. for hand porter labor and $150/hr for CNC time, the CNC heads represent $600 and the hand-ported ones $1000. My point is that the efficient milling cutter is keeping that 1 hp working most of the time at it's point of best cutting. I equate that to excellent traction on the drag strip. The hand porter with the grinding wheel has lots of wheel spin (again pun intended) but eventually gets down the 1/4 mile. Rough analogy I admit.

Inertia car: As was mentioned before, spinning flywheels store energy. The heavier (more massive) the flywheel and the faster it turns, the more energy it stores. Think of the energy stored in the spinning flywheel like gasoline with energy stored in it. When the energy is released and work is done over a period of time we have (by definition) power. With the toy car, you expended your energy to spin up the flywheel, so in fact, you are the primary sourch of power. The faster you can rev it, the more stored energy it has, and the quicker and farther it will go when launched. One inertia car I had as a kid had a big enough flywheel and rubber tires so that we could actually leave rubber marks on the sidewalk. I think when we wore the tread off and discovered the "slicks" we had a quicker car. Of course we raced them. I don't remember ever figuring the gear ratioio between the flywheel and the tires, but it was high. I do remember that to get more distance you had to rev the flywheel higher to store more energy. Actually distance travelled was a good measure of how much power actually got to the ground.

To "hop up" an inertia car, replace the flywheel with a more massive one. Mallory metal ("heavy metal" used in crank balancing) comes to mind for a "cheater", if you can machine it. We tried gluing 2 flywheels together, but that was before epoxy and we had some flywheel "explosions". The plastic bodies were pretty good scattershields.

Some of my friends restore and drive 1 and 2-cylinder cars from the 1905-1910 era. These engines turn slowly and have very little power, but they have flywheels that weight maybe 100-130 lbs.! That's not just to keep the power coming smoothly from a 2 cylinder turning 1000 rpm. The engine spins up the flywheel and stores lots of energy. When you engage the clutch (or planetary trans), the flywheel slows down as it releases that energy to the driveline and, along with the help of the engine, slowly accelerates the car up to it's 20-25 mph cruising speed. On flat ground you get it to 25 (if you can) because almost any hill bleeds off speed as the flywheel gives back the stored energy, much like the inertia toy. Even in low gear, there are some hills you can't climb. My friends refer to their cars a being powered by a flywheel which is assisted by an engine. That's only a slight exaggeration.

After reading this long ramble, I'm not sure whether I've answered you question or just muddied the waters or just wasted more bandwidth.

My $.02

 

hello everyone, this is my first post and i just want to share what i thing about hp vs torque.
everyone agrees that the best combination of torque and horsepower is gonna make the car faster. and the faster the et is, the higher the trap speed will be. but the original question was "Which one will get you to through the traps fastest...and why?..."
My answer is neither one(because you wanna hear only one). just making your 1/4 mile time faster is gonna make your trap speed faster. take off has a lot to do determining trap speed too. my friends eclipse gsx runs 14.3-4 at only 91mph, a mustang with a few bold ons ran 14.4 at 95 or 96mph. most stock lt1 i've seen run close to 100mph. the gsx has the best take off of those three, then the mustang and then lt1 would be last to get off the line. But the lt1-with more HP/TORQUE-is gonna past them and get a better et=better trap speed.

or maybe i'm totally wrong, but it's what i think.

 

Welcome to the zoo!

As you said, launch helps a lot in the ET, but many sources credit hp and weight with determining trap speed. If you look at your 1/8 mile and 1/4 mile speeds, you'll see that most of your 1/4 mile speed is gained in the first 1/8. Usually the second 1/8 speed gain is very consistant. A 325 mph Top Fueler gets to about 270-275 in the 1/8. That's about 85%.

I've smoked the tires bad enough on my Vette to drop my 13.5 to 15.5 and only lost 2 mph in the traps. In fact, the slower the car (trap speed), the less the trap speed is effected by bad/good ET.

My son's LS1 Camaro gets about 12.9 with drag radials, 13.1 or 13.2 with stock tires, but trap speeds are within 1 mph, with speed not relating to ET.

Not intending to rip on you, and don't let me scare you away. The ET/trap speeds you referenced are typical for cars with those power/weight ratios.

"or maybe i'm totally wrong, but it's what i think. " I feel the same way about my beliefs.

Stick around.

 

...thanks for all the replies...not that it really "cleared" anything up for me. Tonight I see a commercial with a Volkswagon doing some mid-speed passing...the salesman tells her that at the lower speed, torque gets the car passing then the hp takes her through the ropes (paraphrased)....She then sees another vehicle and he says "go ahead" and she does...he gets eyeball to eyeball with the driver and it's a trooper...
Guess it's just not meant to be....
Thanks oldSStroker for all the info...

 

Ride a multispeed bicycle.

TQ can be compared to the pressure you put on the pedal.

RPM/engine speed is how fast you can move your feet on the pedals.

HP = TQ * RPMS * constant, so its the combination of how hard you can push against the pedal and how fast you can move the pedals.

Fiddle with the gears in differnet scenarios. Carry a bookbag full of books to add on weight. It will all become clear.

 

You brought back early gearhead memories I had almost forgotten. Thank YOU!

 

Easiest way to say this...
Torque gets the mass moving. Horsepower keeps the mass moving...
It's not so much of a question of how much of this and how much of that. It's a question of when.
Making sure your shifting before your torque drops off too much. Making sure your gearing is enough to keep you accelerating up to the lights.

As far as the formulas posted above. This vary based on your setup.
If it is N/A, Nitrous, Turbo, or a blower motor. Also changes on size of motor and the cam shaft.
There is no real solid way of calculating HP against your torque and rpm.

For instance some Corvette setups run slightly less torque then horsepower. Meanwhile with a blower motor we produce over 100 ft. lbs of torque then HP.

So after figuring in all these, think of the weight of your vehicle. If you have a heavy vehicle like a pick up you'll need lots of torque, however if your running a gutted out f-body you'll need a good equal balance.

 

Just showing how hard an engine can push doesn't show how much work it can do.

According to the torque theory, if an engine produces the same amount of torque at 2000 rpms and at 4000 rpms, the acceleration would be equal.

And it may be torque that accelerates your vehicle down the road, but it's horsepower that shows how fast you're going to accelerate.

 

BTW, those little quick fix "carries the wall", "starts/keeps it moving" replies just muddy the water on this subject even more...

 

what will make you go down the DragStrip the fastest has always been => Torque times RPM

its the greatest average amount of Torque times RPM
in the required/desired RPM range that will get you down DragStrip fastest

Torque times RPM = HorsePower

HP = TQ * RPM * .0001904

========================================

Find out at what RPM your engine makes its Peak Torque

then go to DragStrip at shift your engine at that peak torque point


then make another run..this time shifting at peak HP point


report back here in this Forum
which method produced fastest ET down 1/4 mile DragStrip pass

 

Damn...

I followed this post since the beginning, but I never responded because
I knew my scientific explanations would be weak at best.

After five pages and thousands of views, it has all settled with the
last statement.

I guess we can sum that up as, what would hurt more:


a.) 400 punches, 2000 times per minute = some pain

or

b.) 200 punches, 7000 times per minute = much more pain

Torque * RPM = Lots of black eyes.


I'm picking Horsepower peak!



EDIT - as it has been explained to me and through my theory:

Torque is a function of mechanical leverage. The assembly of the
connecting rods and crank stroke, etc. are going to determine
the amount of mechanical torque.

Cylinder pressure and combustion pressure (on the piston face)
is going to determine how much torque is translated from the
force on the piston out to the crankshaft.

Cylinder pressure will vary based on engine efficiency across RPM
and that may be the root factor of why the torque output changes
over RPM.

The torque generated from cylinder pressure at the crankshaft in
one instant (one combustion cycle) may be xxx.xx ft./lbs.

If I can make my motor apply xxx.xx ft./lbs. of force to the tires, many
times per minute, it has done work.

If I can make my motor spin faster applying less torque, but more
torque cycles per minute, it has done more work and therefore moved
my car faster.

IE: You can move 5lbs of dirt from the pile 10 times per minute,
or you can move 1 lbs of dirt 100 times per minute.

Same amount of time, more work done.

Again, I pick HP peak!

 

No, this is not the case. No chance in that happening. why? because to go the same vehicle speed, the engine at 4000rpms needs to have a 2:1 gear reduction. That means the engine with the same torque at 4000 is putting TWICE the torque to the wheels as the engine at 2000 rpms is. (suspiciously, that engine is also rated for TWICE the hp of it's 1/2 speed sibling )

ENGINE torque is pointless, it's rw torque that matters. Unfortunately it's a PITA to figure out the total forces to the wheels for every gear, and in every tire/final drive ratio. Hense the very REASON that horsepower is used... to combine the variable values of torque and rpm. By determining the total work done at any rpm, you can easily determine what gears to run... so that you can maximize HORSEPOWER at each rpm you'll be driving in. Regardless of tranny gear, rear gear, or wheel size... the MOST torque you can put to the ground occurs at peak hp.

Yes, torque is the force that moves and accelerates you, but ENGINE torque is NOT directly related to this value. If it was the determining factor to look at, it would be pointless to rev past 2500 or even use a gasoline engine.

Quote:

and it may be torque that accelerates your vehicle down the road, but it's horsepower that shows how fast you're going to accelerate.

ABSOLUTELY!