quote Originally posted by Patrick: You guys are arguing the complicated stuff, yet nobody questions this?

I didn't comment because I had previously done the math and found the claim to be reasonable. It's a pretty amazing fact.

quote Originally posted by Lambo nut: 9000 divided by 60 gets the revs per second, or 150 150 times the 4.5 seconds is only 675 revolutions.

quote Originally posted by TennT: Elementary, my dear Patrick, 9000 rpm /60sec = 150 rev/sec 150 rps x 4.4 sec = 660 revolutions

You're both on the right track, but unfortunately your methodology is wrong. It assumes that the whole run is done at 9000 rpm.

Here's the correct calculation: Assume 9000 rpm at 330 mph through the traps. 330 mph is 5.5 miles per minute (mpm). 9000 rpm divided by 5.5 mpm => 1636 revs per mile => 409 revs in the quarter mile. The actual figure from a rev counter would be somewhat higher due to clutch slip and tire hysteresis.

[This message has been edited by Marvin McInnis (edited 01-29-2008).]

Yeah, well, I just gave the highest value since I didn't know, right off the cuff, what rpm
they dump the clutch. Still seems low, doesn't it?
And besides, he isn't going 330 mph for the whole run, or did I miss something?

tg

[This message has been edited by TennT (edited 01-29-2008).]

quote Originally posted by ray b: they inject so much nitro into the motors that Cylinders run on the verge of hydraulic lock at full throttle. not the air being compressed to a solid/liquid form just there is so much fuel in there

If the claim in the original scenario of a 7:1 air/fuel ratio is correct, you may be right. I had originally considered this possibility but dismissed it. (Engineers and engineering students will be familiar with the drill: "This term is too complex to solve, but its value is so small that we can just ignore it in these calculations." )

The Handbook of Chemistry and Physics gives the following physical properties for nitromethane: molecular weight = 61, density = 1.14, Critical Temperature = 315 C, Critical Pressure = 62.3 atmospheres. A cursory Internet search did not turn up an accessible phase diagram for nitromethane, but the values for the Critical Point raise some interesting possibilities.

Even if the 7:1 air/fuel figure is correct, remember that this ratio is normally stated by weight rather than by volume.

Feel free to do some research and report back to us. I'm always willing to learn something new. But I'm done here for a while. I have other work to do.

[This message has been edited by Marvin McInnis (edited 01-29-2008).]

quote Originally posted by Marvin McInnis: You're both on the right track, but unfortunately your methodology is wrong. It assumes that the whole run is done at 9000 rpm. Here's the correct calculation: Assume 9000 rpm at 330 mph through the traps. 330 mph is 5.5 miles per minute (mpm). 9000 rpm divided by 5.5 mpm => 1636 revs per mile => 409 revs in the quarter mile. The actual figure from a rev counter would be somewhat higher due to clutch slip and tire hysteresis.

Aren't you assuming that his average velocity is 5.5 mpm when in fact it would be less?

quote Originally posted by TennT: Aren't you assuming that his average velocity is 5.5 mpm when in fact it would be less?

No. See above. I'm only assuming that the engine is turning 9000 rpm at 330 mph.

they run a hi slip multi plate clutch
with added clamping ''finger'' as speed goes up
controled by a ''majic'' box

also tyres slip some but not tooo much
and grow ''expand'' at hi wheel RPM
so RPM vs speed is not linear
and very hard to pin to an exact number

but the whole point is the motors do not live long

------------------
Question wonder and be wierd
are you kind?

quote Originally posted by ray b: but the whole point is the motors do not live long

And don't turn very many revs in the quarted mile.
At least not as much as some would have thought.

Kevin

quote Originally posted by Lambo nut: I never assumed such. I only pointed out, that if they hit 9000 rpm, they would only be turning 150 rps. 4.5 seconds at 9000 rpm, would net 675 revolutions.

Thanks for the clarification. So you are saying that the total crankshaft revolutions in a quarter mile would be less than 675, and I am saying that that they would be "somewhat higher" than 409. Then we are both correct, and both figures together neatly validate the number ("approximately 540") stated in the original piece.

[This message has been edited by Marvin McInnis (edited 01-29-2008).]

.

[This message has been edited by JazzMan (edited 12-08-2008).]

Makes me feel warm all over to know that my thread has stimulated such an elevated intellectual discussion. Thanks.
Either that or I should have taken that bathroom break earlier.
Well, at least folks are playing nice.
------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

[This message has been edited by blackrams (edited 01-29-2008).]

I'm glad to see that the number of engine revolutions has been clarified, now it remains to be seen whether it will fly.

quote Originally posted by JazzMan: I just remembered that from an article I read a few years back in Smithsonian Air & Space Magazine about the Hindenburg. The article's author posited that the visible flames from the dirigible where actually from the aluminum powder w/ nitrocellulose binder (a mixture remarkably similar to shuttle solid rocket fuel) rather than the H, and also determined that there wasn't enough free O available within the fireball to actually combust the H with. He determined that the H actually drifted up through the flames and then burned far above the flames where there was enough free O to reach critical. Since H burns in UV they would have been essentially invisible to the cameras and instruments of the day. That was a good article. When I get my library unpacked I need to dig it back up for a reread. JazzMan

I seem to recall hearing that there was also iron oxide in the paint: yeah, the Hindenberg was painted with freakin' THERMITE...

It was some show on Discovery or Science Channel or History Channel, but I can't remember which channel or what show. (This was in like 2002.) Oh well.

Ed

quote Originally posted by Marvin McInnis: But have you ever tried sex in a top-fuel dragster? It would probably be even more physically challenging than in a Fiero, and I agree that the 4.441 second E.T. would definitely be a downer.

4.441 seconds is all the time i need for sex!

Ed

[This message has been edited by ED's85GT (edited 01-29-2008).]

quote Originally posted by ED's85GT: 4.441 seconds is all the time i need for sex! Ed

Nope, not going there.

------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

quote Originally posted by Marvin McInnis: The correct calculation only assumes 330 mph at 9000 rpm through the traps and that the relationship of speed vs. rpm is linear (e.g. 165 mph at 4500 rpm, etc.). Here's another way of looking at it. Your calculation and mine produce different answers. Both of them can't be right, which means that one of us has done something wrong. There's an good lesson here: Never trust anybody's data (even your own) unless you have independently verified it. (Some of my work involves human health and safety, where this is especially important.) A corollary is that if you don't fully understand where the answer comes from, then you don't really understand the system being analyzed.

How can a "correct" calculation "assume" a value?
Perhaps the "calculation" doesn't really understand the system being analyzed?

The "GOOD LESSON"?
If you have independently verified you own data, then you can't trust it?

Unusual choice of words.
Difference in values boils down to interesting point of view.
You assumed a 1:1 relationship between speed and rpms, relationship being a key word
not 1:1 ratio, obviously the tires are not going to go far at 9 grand! AND obviously the
engine is not turning at 0 rpm at launch (0 MPH).
My calculation assumed a 9k rpm start at 0 mph WITH tire slip allowed for by using the
time of travel (from my understanding, a dragsters tire slips for some 75-80% of the run).

I don't know about the trans. I thought they were direct hookup with clutch, but I never could find out
what top fuel uses, 2sp or direct drive. I plan to call today and find out, just for curiosities sake,
Google was no help this time, too much superficial info.

You understand that I am taking this as a discussion and not an affront, I hope.
G'Day,
TG